http://www.ziddu.com/download/3418863/MachineDesign-Gear.pdf.html
http://www.ziddu.com/download/3418864/SpurGearDesign.pdf.html
http://www.ziddu.com/download/3418865/PrecisionEngineering.pdf.html
http://www.ziddu.com/download/3418866/MaterialAnalysis.pdf.html
http://www.ziddu.com/download/3418867/GearDesign.pdf.html
http://www.ziddu.com/download/3418868/Springs.ppt.html
http://www.ziddu.com/download/3418869/X-RayDiffraction.ppt.html
http://www.ziddu.com/download/3418870/Joining.pdf.html
http://www.ziddu.com/download/3418871/BevelGears.ppt.html
http://www.ziddu.com/download/3418872/MaterialScience.pdf.html
Thursday, February 5, 2009
Wednesday, February 4, 2009
Gear Design
Design - DSGN 215, 221 Gear Design Home Page.
Introduction.
When mating gear teeth are designed to produce a constant angular velocity ratio during meshing they are said to have 'conjugate action'. To provide this an 'involute' type profile is almost universally used for tooth forms.
There are two modes that are important causes of gear failures. Bending stresses (leading to tooth breakage) which are a maximum at the tooth root and compressive stresses (leading to pitting) that are a maximum on the tooth face. Because tooth loading is cyclic, both of these mechanisms are of a fatigue nature. The design of gears needs to counter both of these potential failure modes. An important part of providing the resistance to the high contact stresses is to use gears of appropriate hardness. The lower the levels of impurities in a material, the better it is normally able to resist fatigue.
Link to page showing some gear nomenclature.
Quite a bit of information is available about gears on the following sites:
DR Gears site.
Quality Transmission Components site, go to QTC Technical Library.
Loads on Teeth
The tangential force on the teeth can be found from:
Wt = 60H/(3.14159.d.n) where:
Wt = transmitted load, N
H = power, W
d = gear diameter, m
n = speed, rev/min.
Bending Stresses - The Lewis Formula
Although this was published in 1893, it is still very widely used for assessing bending stresses when designing gears. The method involves moving the tangential force and applying it to the tooth tip and assuming the load is uniformly distributed accross the tooth width with the tooth acting as a simple cantilever of constant rectangular cross section, the beam depth being put equal to the thickness of the tooth root (t) and the beam width being put equal to the tooth, or gear, width (bw).
The section modulus is I/c = bwt2/6 so the bending stress is given by:
sigmabending = M/(I/c) = 6WtL/(bwt2) eqn.1.
Assuming that the maximum bending stress is at point 'a'.
By similar triangles: 
or 
eqn.2
Rearranging eqn.1 gives:
Substitute the value for 'x' from eqn.2 and multiply the numerator and denominator by the circular pitch, 'p' gives:
let y=2x/3p then
This is the original Lewis equation and 'y' is called the Lewis form factor which may be determined graphically or by computation.
Engineers often now work with the 'diametral pitch', 'P', 
and 
or the 'module', 'm', which is 1/diametral pitch = 1/P
Then 
where Y = 2xP/3
Written in terms of the module:
The Lewis form factor considers only static loading, it is dimensionless, independent of tooth size and is a only a function of tooth shape. It does not take into account the stress concentration that exists in the tooth fillet.
The Lewis formula is generally limited to pitch line velocities up to 7.6 m/s and based on tests (in the 19th Century) on cast iron gears with cast teeth, C G Barth suggested a modification involving a velocity factor, KV.
For cut or milled teeth the Barth equation (in SI units) is often modified to:
sigmabending, allowable = Wt/bwmYKV
NB Recent Changes in Barth Equation
In about 2000 the AGMA (see below) re-defined the dynamic factor, KV, as the inverse of that originally proposed by Barth, above. Consequently it is greater than 1 (and called KV' here) and the expression for the allowable bending stress becomes:
sigmabending, allowable = WtKV'/bwmY
For a full depth tooth with a 20o pressure angle, Y varies between 0.245 for a gear with 12 teeth to 0.471 for a gear with 300 teeth. (0.485 for a rack).
It is common for spur gears to be designed with a face width of between 3 and 5 times the circular pitch.
American Gear Manufacturers Association (AGMA) Code
Some key points from the AGMA approach to gear design are shown below.
AGMA have published graphs of allowable bending stresses and allowable surface contact stresses as a function of the Brinell hardness for some grades of through hardened steel.
Grade 2 steels, that have higher allowable stresses, are more closely specified than grade 1 steels.
This is commonly used and contains further refinements compared to the approach above, it also includes detailed guidance about materials.
A number of modifying factors are normally included in the AGMA code:
Ka = application factor - depends on the type of power source
Ks = size factor - increases above 1 for a module, m, of 6 mm or greater.
Km = load distribution factor - depends mainly on face width.
Kv = dynamic factor - depending upon tooth accuracy, loads greater than the transmitted load may be generated.
Contact Stresses
These are determined by Hertzian contact stress analysis. The maximum pressure in the (rectangular) contact zone when two parallel cylinders are pressed together is given by:
where E' is the effective modulus of elasticity:
W' is the dimensionless load = w'/(E'/Rx)
w' is the load per unit width = normal load/gear width and
1/Rx = 2((1/pinion dia)+(1/gear dia))/sin(pressure angle)
The same modifying factors are again used with the contact stresses that were used with the bending stresses.
sigmacompressive = pH(Ka Ks Km/Kv)0.5
Link to example gear tooth strength calculation, note file size: 214 kB.
Forces on Helical Gear Teeth
As the teeth on helical gears are inclined to the axis of the gear, the tooth force generates an axial or thrust load in addition to the radial force and the tangential force (which is the only one that does useful work). The tooth load can be resolved in the three directions as shown in this diagram.
The forces and resulting bending moments on the shaft carrying a helical gear are illustrated in this note.
Stresses in helical gear teeth
When calculating the stresses in helical gear teeth, the Lewis form factor for the 'virtual number of teeth' needs to be used rather than that for the actual number of teeth. This is because on looking along a tooth on a helical gear the apparent radius of the gear is greater than that of the gear blank (the cross section is an ellipse). The 'virtual number of teeth' is found by:
Supplementary note on Stresses in Gears
It should be noted that using the simplified version of these methods (including only Kv) on gears in automotive gear boxes gives high stresses, particularly for 1st gear. Gears for car gear boxes are probably manufactured to a high degree of accuracy, to keep noise levels low. The velocity correction factor, Kv, from the Barth equation, is over 100 years old and probably gives a conservative factor compared to that appropriate for modern high quality gears. Using all the AGMA factors - and noting that 'Y' the Lewis form factor is NOT used but the geometry factors J or I, (for bending and compressive stresses) are included, should give a more useful answer.
Note that 1st gear may be designed for a limited life as it so rarely operates under maximum load.
Link to example on helical gear tooth strength calculation, 85kB file size.
Torque Acting on a Gearbox
As the input and output torques associated with a gearbox are normally not the same, some 'holding' torque will be needed to prevent the gearbox rotating. This can be determined as shown in this diagram
Lubrication
During operation the teeth are sliding against one another, so to prevent wear lubrication is normally essential for heavily loaded gears. Even though a gearbox may have an efficiency of 97%, where considerable power is being transmitted, 3% loss as heat generated within the gearbox, may necessitate the provision of some type of forced cooling.
Acceleration of a Geared System
- link to notes.
- example on a geared hoist, 56 kB file size
More detailed information about gears and some helpful animations can be seen in the chapter on 'Gears' at Mechanical Engineering Department pages at the University of Western Australia.
Useful information (albeit in imperial units) can be found on the 'Boston Gear' web site: click here
Further Reading: Shigley and Mischke, chapters 13, 14 and 15.
David J Grieve, 24th November 2005.
Spur Gear Design
The notes below relate to spur gears. Notes specific to helical gears are included on a separate page Helical Gears
Gears are machine elements used to transmit rotary motion between two shafts, normally with a constant ratio. The pinion is the smallest gear and the larger gear is called the gear wheel.. A rack is a rectangular prism with gear teeth machined along one side- it is in effect a gear wheel with an infinite pitch circle diameter. In practice the action of gears in transmitting motion is a cam action each pair of mating teeth acting as cams. Gear design has evolved to such a level that throughout the motion of each contacting pair of teeth the velocity ratio of the gears is maintained fixed and the velocity ratio is still fixed as each subsequent pair of teeth come into contact. When the teeth action is such that the driving tooth moving at constant angular velocity produces a proportional constant velocity of the driven tooth the action is termed a conjugate action. The teeth shape universally selected for the gear teeth is the involute profile.
Consider one end of a piece of string is fastened to the OD of one cylinder and the other end of the string is fastened to the OD of another cylinder parallel to the first and both cylinders are rotated in the opposite directions to tension the string(see figure below). The point on the string midway between the cylinder P is marked. As the left hand cylinder rotates CCW the point moves towards this cylinder as it wraps on . The point moves away from the right hand cylinder as the string unwraps. The point traces the involute form of the gear teeth.
The lines normal to the point of contact of the gears always intersects the centre line joining the gear centres at one point called the pitch point. For each gear the circle passing through the pitch point is called the pitch circle. The gear ratio is proportional to the diameters of the two pitch circles. For metric gears (as adopted by most of the worlds nations) the gear proportions are based on the module.
m = (Pitch Circle Diameter(mm)) / (Number of teeth on gear).
In the USA the module is not used and instead the Diametric Pitch d pis used
d p = (Number of Teeth) / Diametrical Pitch (inches)
Profile of a standard 1mm module gear teeth for a gear with Infinite radius (Rack ).
Other module teeth profiles are directly proportion . e.g. 2mm module teeth are 2 x this profile
Many gears trains are very low power applications with an object of transmitting motion with minium torque e.g. watch and clock mechanisms, instruments, toys, music boxes etc. These applications do not require detailed strength calculations.
Standards
|
If it is necessary to design a gearbox from scratch the design process in selecting the gear size is not complicated - the various design formulea have all been developed over time and are available in the relevant standards. However significant effort, judgement and expertise is required in designing the whole system including the gears, shafts , bearings, gearbox, lubrication. For the same duty many different gear options are available for the type of gear , the materials and the quality. It is always preferable to procure gearboxes from specialised gearbox manufacturers
Terminology - spur gears
|
Spur Gear Design
The spur gear is is simplest type of gear manufactured and is generally used for transmission of rotary motion between parallel shafts. The spur gear is the first choice option for gears except when high speeds, loads, and ratios direct towards other options. Other gear types may also be preferred to provide more silent low-vibration operation. A single spur gear is generally selected to have a ratio range of between 1:1 and 1:6 with a pitch line velocity up to 25 m/s. The spur gear has an operating efficiency of 98-99%. The pinion is made from a harder material than the wheel. A gear pair should be selected to have the highest number of teeth consistent with a suitable safety margin in strength and wear. The minimum number of teeth on a gear with a normal pressure angle of 20 desgrees is 18.
The preferred number of teeth are as follows
| 12 13 14 15 16 18 20 22 24 25 28 30 32 34 38 40 45 50 54 60 64 70 72 75 80 84 90 96 100 120 140 150 180 200 220 250 |
Materials used for gears
Mild steel is a poor material for gears as as it has poor resistance to surface loading. The carbon content for unhardened gears is generally 0.4%(min) with 0.55%(min) carbon for the pinions. Dissimilar materials should be used for the meshing gears - this particularly applies to alloy steels. Alloy steels have superior fatigue properties compared to carbon steels for comparable strengths. For extremely high gear loading case hardened steels are used the surface hardening method employed should be such to provide sufficient case depth for the final grinding process used.
| Material | Notes | applications |
| Ferrous metals | ||
| Cast Iron | Low Cost easy to machine with high damping | Large moderate power, commercial gears |
| Cast Steels | Low cost, reasonable strength | Power gears with medium rating to commercial quality |
| Plain-Carbon Steels | Good machining, can be heat treated | Power gears with medium rating to commercial/medium quality |
| Alloy Steels | Heat Treatable to provide highest strength and durability | Highest power requirement. For precision and high precisiont |
| Stainless Steels (Aust) | Good corrosion resistance. Non-magnetic | Corrosion resistance with low power ratings. Up to precision quality |
| Stainless Steels (Mart) | Hardenable, Reasonable corrosion resistance, magnetic | Low to medium power ratings Up to high precision levels of quality |
| Non-Ferrous metals | ||
| Aluminium alloys | Light weight, non-corrosive and good machinability | Light duty instrument gears up to high precision quality |
| Brass alloys | Low cost, non-corrosive, excellent machinability | low cost commercial quality gears. Quality up to medium precision |
| Bronze alloys | Excellent machinability, low friction and good compatability with steel | For use with steel power gears. Quality up to high precision |
| Magnesium alloys | Light weight with poor corrosion resistance | Ligh weight low load gears. Quality up to medium precision |
| Nickel alloys | Low coefficient of thermal expansion. Poor machinability | Special gears for thermal applications to commercial quality |
| Titanium alloys | High strength, for low weight, good corrosion resistance | Special light weight high strength gears to medium precision |
| Di-cast alloys | Low cost with low precision and strength | High production, low quality gears to commercial quality |
| Sintered powder alloys | Low cost, low quality, moderate strength | High production, low quality to moderate commercial quality |
| Non metals | ||
| Acetal (Delrin | Wear resistant, low water absorbtion | Long life , low load bearings to commercial quality |
| Phenolic laminates | Low cost, low quality, moderate strength | High production, low quality to moderate commercial quality |
| Nylons | No lubrication, no lubricant, absorbs water | Long life at low loads to commercial quality |
| PTFE | Low friction and no lubrication | Special low friction gears to commercial quality |
Equations for basic gear relationships
It is acceptable to marginally modify these relationships e.g to modify the addendum /dedendum to allow Centre Distance adjustments. Any changes modifications will affect the gear performance in good and bad ways...
| Addendum | h a = m = 0.3183 p |
| Base Circle diameter | Db = d.cos α |
| Centre distance | a = ( d g + d p) / 2 |
| Circular pitch | p = m.π |
| Circular tooth thickness | ctt = p/2 |
| Dedendum | h f = h - a = 1,25m = 0,3979 p |
| Module | m = d /n |
| Number of teeth | z = d / m |
| Outside diameter | D o = (z + 2) x m |
| Pitch circle diameter | d = n . m ... (d g = gear & d p = pinion ) |
| Whole depth(min) | h = 2.25 . m |
| Top land width(min) | t o = 0,25 . m |
Module (m)
The module is the ratio of the pitch diameter to the number of teeth. The unit of the module is milli-metres.Below is a diagram showing the relative size of teeth machined in a rack with module ranging from module values of 0,5 mm to 6 mm
0,5 0,8 1 1,25 1,5 2,5 3 4 5 6 8 10 12 16 20 25 32 40 50
Normal Pressure angle α
An important variable affecting the geometry of the gear teeth is the normal pressure angle. This is generally standardised at 20o. Other pressure angles should be used only for special reasons and using considered judgment. The following changes result from increasing the pressure angle
|
Contact Ratio
The gear design is such that when in mesh the rotating gears have more than one gear in contact and transferring the torque for some of the time. This property is called the contact ratio. This is a ratio of the length of the line-of-action to the base pitch. The higher the contact ratio the more the load is shared between teeth. It is good practice to maintain a contact ratio of 1.2 or greater. Under no circumstances should the ratio drop below 1.1.
A contact ratio between 1 and 2 means that part of the time two pairs of teeth are in contact and during the remaining time one pair is in contact. A ratio between 2 and 3 means 2 or 3 pairs of teeth are always in contact. Such as high contact ratio generally is not obtained with external spur gears, but can be developed in the meshing of an internal and external spur gear pair or specially designed non-standard external spur gears.
(Rgo2 - Rgb2 )1/2 + (Rpo2 - Rpb2 )1/2 - a sin α
contact ratio m =
p cos α R go = D go / 2..Radius of Outside Dia of Gear
R gb = D gb / 2..Radius of Base Dia of Gear
R po = D po / 2..Radius of Outside Dia of Pinion
R pb = D pb / 2..Radius of Base Dia of Pinion
p = circular pitch.
a = ( d g+ d p )/2 = center distance.
Spur gear Forces, torques, velocities & Powers
|
| Tangential force on gears F t = F cos α |
| Separating force on gears F s = F t tan α |
| Torque on driver gear T 1 = F t d 1 / 2 |
| Torque on driver gear T 2 = F t d 2 / 2 |
| Speed Ratio =ω 1 / ω 2 = d 2 / d 1 = z 2 /z 1 |
| Input Power P 1 = T1 .ω 1 |
| Output Power P 2 =η.T 1 .ω 2 |
Spur gear Strength and durability calculations
Designing spur gears is normally done in accordance with standards the two most popular series are listed under standards above:
The notes below relate to approximate methods for estimating gear strengths. The methods are really only useful for first approximations and/or selection of stock gears (ref links below). — Detailed design of spur and helical gears is best completed using the standards. Books are available providing the necessary guidance. Software is also available making the process very easy. A very reasonably priced and easy to use package is included in the links below (Mitcalc.com)
The determination of the capacity of gears to transfer the required torque for the desired operating life is completed by determining the strength of the gear teeth in bending and also the durability i.e of the teeth ( resistance to wearing/bearing/scuffing loads ) .. The equations below are based on methods used by Buckingham..
Bending
The basic bending stress for gear teeth is obtained by using the Lewis formula
σ = Ft / ( ba. m. Y )
- F t = Tangential force on tooth
- σ = Tooth Bending stress (MPa)
- b a = Face width (mm)
- Y = Lewis Form Factor
- m = Module (mm)
σ = Ft / ( ba. p. y )
Where y = Y/π and p = circular pitch
When a gear wheel is rotating the gear teeth come into contact with some degree of impact. To allow for this a velocity factor is introduced into the equation. This is given by the Barth equation for milled profile gears.
K v = 6,1 / (6,1 +V )
V = the pitch line velocity = d.ω/2
Note: This factor is different for different gear conditions i.e K v = ( 3.05 + V )/3.05 for cast iron, cast profile gears.
The Lewis formula is thus modified as follows
σ = K v.Ft / ( ba. m. Y )
Surface Durability
| This calculation involves determining the contact stress between the gear teeth and uses the Herz Formula σ w = 2.F / ( π .b .l ) σ w = largest surface pressureF = force pressing the two cylinders (gears) together l = length of the cylinders (gear) b = halfwidth = ν 1, ν 2 Poisson ratio for the two gear materials E 1 ,E 2 Are the Young's Modulus Values for the two gears To arrive at the formula used for gear calculations the following changes are made F is replaced by F t/ cos α d is replaced by 2.r l is replaced by W The velocity factor K v as described above is introduced. Also an elastic constant Z E is created
Note: Values for Allowable stress values Se and ZE for some materials are provided at Gear Table r1 = d1 sin α /2 r2 = d2 sin α /2 Important Note: The above equations do not take into account the various factors which are integral to calculations completed using the relevant standards. These equations therefore yield results suitable for first estimate design purposes only... |
Design Process To select gears from a stock gear catalogue or do a first approximation for a gear design select the gear material and obtain a safe working stress e.g Yield stress / Factor of Safety. /Safe fatigue stress
- Determine the input speed, output speed, ratio, torque to be transmitted
- Select materials for the gears (pinion is more highly loaded than gear)
- Determine safe working stresses (uts /factor of safety or yield stress/factor of safety or Fatigue strength / Factor of safety )
- Determine Allowable endurance Stress Se
- Select a module value and determine the resulting geometry of the gear
- Use the lewis formula and the endurance formula to establish the resulting face width
- If the gear proportions are reasonable then - proceed to more detailed evaluations
- If the resulting face width is excessive - change the module or material or both and start again
Internal Gears
Advantages:
- Geometry ideal for epicyclic gear design
- Allows compact design since the center distance is less than for external gears.
- A high contact ratio is possible.
- Good surface endurance due to a convex profile surface working against a concave surface.
- Housing and bearing supports are more complicated, because the external gear nests within the internal gear.
- Low ratios are unsuitable and in many cases impossible because of interferences.
- Fabrication is limited to the shaper generating process, and usually special tooling is required.
Lewis form factor.
Table of lewis form factors for different tooth forms and pressure angles
| No Teeth | | Load Near Tip of Teeth | Load at Near Middle of Teeth | ||||||||||
| 14 1/2 deg | 20 deg FD | 20 deg Stub | 25 deg | 14 1/2 deg | 20 deg FD | ||||||||
| | | Y | y | Y | y | Y | y | Y | y | Y | y | Y | y |
| 10 | | 0,176 | 0,056 | 0,201 | 0,064 | 0,261 | 0,083 | 0,238 | 0,076 | | | | |
| 11 | | 0,192 | 0,061 | 0,226 | 0,072 | 0,289 | 0,092 | 0,259 | 0,082 | | | | |
| 12 | | 0,21 | 0,067 | 0,245 | 0,078 | 0,311 | 0,099 | 0,277 | 0,088 | 0,355 | 0,113 | 0,415 | 0,132 |
| 13 | | 0,223 | 0,071 | 0,264 | 0,084 | 0,324 | 0,103 | 0,293 | 0,093 | 0,377 | 0,12 | 0,443 | 0,141 |
| 14 | | 0,236 | 0,075 | 0,276 | 0,088 | 0,339 | 0,108 | 0,307 | 0,098 | 0,399 | 0,127 | 0,468 | 0,149 |
| 15 | | 0,245 | 0,078 | 0,289 | 0,092 | 0,349 | 0,111 | 0,32 | 0,102 | 0,415 | 0,132 | 0,49 | 0,156 |
| 16 | | 0,255 | 0,081 | 0,295 | 0,094 | 0,36 | 0,115 | 0,332 | 0,106 | 0,43 | 0,137 | 0,503 | 0,16 |
| 17 | | 0,264 | 0,084 | 0,302 | 0,096 | 0,368 | 0,117 | 0,342 | 0,109 | 0,446 | 0,142 | 0,512 | 0,163 |
| 18 | | 0,27 | 0,086 | 0,308 | 0,098 | 0,377 | 0,12 | 0,352 | 0,112 | 0,459 | 0,146 | 0,522 | 0,166 |
| 19 | | 0,277 | 0,088 | 0,314 | 0,1 | 0,386 | 0,123 | 0,361 | 0,115 | 0,471 | 0,15 | 0,534 | 0,17 |
| 20 | | 0,283 | 0,09 | 0,32 | 0,102 | 0,393 | 0,125 | 0,369 | 0,117 | 0,481 | 0,153 | 0,544 | 0,173 |
| 21 | | 0,289 | 0,092 | 0,326 | 0,104 | 0,399 | 0,127 | 0,377 | 0,12 | 0,49 | 0,156 | 0,553 | 0,176 |
| 22 | | 0,292 | 0,093 | 0,33 | 0,105 | 0,404 | 0,129 | 0,384 | 0,122 | 0,496 | 0,158 | 0,559 | 0,178 |
| 23 | | 0,296 | 0,094 | 0,333 | 0,106 | 0,408 | 0,13 | 0,390 | 0,124 | 0,502 | 0,16 | 0,565 | 0,18 |
| 24 | | 0,302 | 0,096 | 0,337 | 0,107 | 0,411 | 0,131 | 0,396 | 0,126 | 0,509 | 0,162 | 0,572 | 0,182 |
| 25 | | 0,305 | 0,097 | 0,34 | 0,108 | 0,416 | 0,132 | 0,402 | 0,128 | 0,515 | 0,164 | 0,58 | 0,185 |
| 26 | | 0,308 | 0,098 | 0,344 | 0,109 | 0,421 | 0,134 | 0,407 | 0,13 | 0,522 | 0,166 | 0,584 | 0,186 |
| 27 | | 0,311 | 0,099 | 0,348 | 0,111 | 0,426 | 0,136 | 0,412 | 0,131 | 0,528 | 0,168 | 0,588 | 0,187 |
| 28 | | 0,314 | 0,1 | 0,352 | 0,112 | 0,43 | 0,137 | 0,417 | 0,133 | 0,534 | 0,17 | 0,592 | 0,188 |
| 29 | | 0,316 | 0,101 | 0,355 | 0,113 | 0,434 | 0,138 | 0,421 | 0,134 | 0,537 | 0,171 | 0,599 | 0,191 |
| 30 | | 0,318 | 0,101 | 0,358 | 0,114 | 0,437 | 0,139 | 0,425 | 0,135 | 0,54 | 0,172 | 0,606 | 0,193 |
| 31 | | 0,32 | 0,101 | 0,361 | 0,115 | 0,44 | 0,14 | 0,429 | 0,137 | 0,554 | 0,176 | 0,611 | 0,194 |
| 32 | | 0,322 | 0,101 | 0,364 | 0,116 | 0,443 | 0,141 | 0,433 | 0,138 | 0,547 | 0,174 | 0,617 | 0,196 |
| 33 | | 0,324 | 0,103 | 0,367 | 0,117 | 0,445 | 0,142 | 0,436 | 0,139 | 0,55 | 0,175 | 0,623 | 0,198 |
| 34 | | 0,326 | 0,104 | 0,371 | 0,118 | 0,447 | 0,142 | 0,44 | 0,14 | 0,553 | 0,176 | 0,628 | 0,2 |
| 35 | | 0,327 | 0,104 | 0,373 | 0,119 | 0,449 | 0,143 | 0,443 | 0,141 | 0,556 | 0,177 | 0,633 | 0,201 |
| 36 | | 0,329 | 0,105 | 0,377 | 0,12 | 0,451 | 0,144 | 0,446 | 0,142 | 0,559 | 0,178 | 0,639 | 0,203 |
| 37 | | 0,33 | 0,105 | 0,38 | 0,121 | 0,454 | 0,145 | 0,449 | 0,143 | 0,563 | 0,179 | 0,645 | 0,205 |
| 38 | | 0,333 | 0,106 | 0,384 | 0,122 | 0,455 | 0,145 | 0,452 | 0,144 | 0,565 | 0,18 | 0,65 | 0,207 |
| 39 | | 0,335 | 0,107 | 0,386 | 0,123 | 0,457 | 0,145 | 0,454 | 0,145 | 0,568 | 0,181 | 0,655 | 0,208 |
| 40 | | 0,336 | 0,107 | 0,389 | 0,124 | 0,459 | 0,146 | 0,457 | 0,145 | 0,57 | 0,181 | 0,659 | 0,21 |
| 43 | | 0,339 | 0,108 | 0,397 | 0,126 | 0,467 | 0,149 | 0,464 | 0,148 | 0,574 | 0,183 | 0,668 | 0,213 |
| 45 | | 0,34 | 0,108 | 0,399 | 0,127 | 0,468 | 0,149 | 0,468 | 0,149 | 0,579 | 0,184 | 0,678 | 0,216 |
| 50 | | 0,346 | 0,11 | 0,408 | 0,13 | 0,474 | 0,151 | 0,477 | 0,152 | 0,588 | 0,187 | 0,694 | 0,221 |
| 55 | | 0,352 | 0,112 | 0,415 | 0,132 | 0,48 | 0,153 | 0,484 | 0,154 | 0,596 | 0,19 | 0,704 | 0,224 |
| 60 | | 0,355 | 0,113 | 0,421 | 0,134 | 0,484 | 0,154 | 0,491 | 0,156 | 0,603 | 0,192 | 0,713 | 0,227 |
| 65 | | 0,358 | 0,114 | 0,425 | 0,135 | 0,488 | 0,155 | 0,496 | 0,158 | 0,607 | 0,193 | 0,721 | 0,23 |
| 70 | | 0,36 | 0,115 | 0,429 | 0,137 | 0,493 | 0,157 | 0,501 | 0,159 | 0,61 | 0,194 | 0,728 | 0,232 |
| 75 | | 0,361 | 0,115 | 0,433 | 0,138 | 0,496 | 0,158 | 0,506 | 0,161 | 0,613 | 0,195 | 0,735 | 0,234 |
| 80 | | 0,363 | 0,116 | 0,436 | 0,139 | 0,499 | 0,159 | 0,509 | 0,162 | 0,615 | 0,196 | 0,739 | 0,235 |
| 90 | | 0,366 | 0,117 | 0,442 | 0,141 | 0,503 | 0,16 | 0,516 | 0,164 | 0,619 | 0,197 | 0,747 | 0,238 |
| 100 | | 0,368 | 0,117 | 0,446 | 0,142 | 0,506 | 0,161 | 0,521 | 0,166 | 0,622 | 0,198 | 0,755 | 0,24 |
| 150 | | 0,375 | 0,119 | 0,458 | 0,146 | 0,518 | 0,165 | 0,537 | 0,171 | 0,635 | 0,202 | 0,778 | 0,248 |
| 200 | | 0,378 | 0,12 | 0,463 | 0,147 | 0,524 | 0,167 | 0,545 | 0,173 | 0,64 | 0,204 | 0,787 | 0,251 |
| 300 | | 0,38 | 0,122 | 0,471 | 0,15 | 0,534 | 0,17 | 0,554 | 0,176 | 0,65 | 0,207 | 0,801 | 0,255 |
| Rack | | 0,39 | 0,124 | 0,484 | 0,154 | 0,55 | 0,175 | 0,566 | 0,18 | 0,66 | 0,21 | 0,823 | 0,262 |
Gear
Gear Design
Gears have been around for hundreds of years and are as old as almost any machinery ever invented by mankind. Gears were first used in various construction jobs, water raising devices and for weapons like catapults.
Nowadays gears are used on a daily basis and can be found in most people’s everyday life from clocks to cars rolling mills to marine engines. Gears are the most common means of transmitting power in mechanical engineering.
Gears are used in almost all mechanical devices and they do several important jobs, but most important, they provide a gear reduction. This is vital to ensure that even though there is enough power there is also enough torque(is a movement of force).
This site is a valuable resource about gear and gear design.
Bevel Gears
Bevel gears are useful when the direction of a shaft's rotation needs to be changed. They are usually mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well.
A good working example of a bevel gear is the mechanism used in a hand drill. As you turn the handle of the drill in a vertical direction, the bevel gears change the rotation of the chuck to a horizontal rotation. The bevel gear also works to increase the speed of the chuck so that its possible for the drill to work on a range of surfaces.
There are four types of bevel gears:
Straight Bevel Gears: These gears have a conical pitch surface and straight teeth tapering towards an apex.
Zero Bevel Gears: Are very similar to straight bevel gears except the teeth are curved.
Spiral Bevel Gears: The teeth are curved at an angle which then allows the contact to be gradual and smooth.
Hypoid Bevel Gears: These gears are similar to spiral bevel except that the pitch surfaces are hyperboloids
Helical Gears
Helical gears are so called because the angle of the teeth are inclined to the axis of the shafts in the form of a helix.
Helical gears are generally seen and described as high speed gears as they can take higher loads than equally sized spur gears. Also with a helical gear the two teeth start to engage and gradually increase as the gears rotate this gradual movement makes helical gears operate much more smoothly and quietly that spur gears. Its because of this design that helical gears are used in the majority of car transmissions.
Rack & Pinion Gears
Rack and pinion gears are used to convert rotation into linear motion or linear motion into rotation. The rack is the flat toothed part and the pinion is the gear. The diameter of the gear determines the speed that the rack moves as the pinion turns.
A perfect example of a rack and pinion gear system is the steering system on many cars. The driver turns the steering wheel which rotates the gear which then engages the rack so as the gear turns it slides the rack to the right or the left depending on which way the steering wheel is turned.
Spur Gears
Spur gears are the most common type of gear they have straight teeth and are mounted on parallel shafts. The main reason for the popularity of spur gears is their simplicity in design, easy manufacturer and maintenance. However due to their design spur gears create large stress on the gear teeth.
Spur gears are known as slow speed gears. Spur gears are seen as noisy due to their design so if noise is not a problem spur gears can be used at almost any speed. Spur gears are noisy because every time a gear tooth engages a tooth on the other gear, the teeth collide, and this impact makes a noise.
Spur gears can be found in applications like washing machines and electric screwdrivers but due to the noise you will never find them in your car.
Worm Gears
A worm gear is used when there is a requirement to reduce speed. It’s very common to see worm gears with reductions like 20:1 and as high as 300:1 or even greater depending on the situation.
A worm gear consists of a cylinder with a spiral groove mounted on a shaft, this is generally referred to as the worm shaft and a gear which is normally referred to as the worm wheel. The gear then meshes with the spiral groove on the cylinder and so when the cylinder rotates it causes the gear to rotate as well. So for each complete turn of the worm shaft the gear shaft advances only one tooth of the gear. So a gear with 20 teeth will see the speed reduced by a factor of 20:1.
The worm always drives the worm wheel around it is not reversible so the worm wheel can’t drive the worm to increase the speed. If it’s attempted the system will normally jam or lock.
Gear Manufacture
The materials that are used for gear manufacturing depend massively on the conditions that the gears will be operating under, conditions like wear and noise etc. Gear manufacturers use metallic or non-metallic materials.
The Metallic materials used in gear manufacture are normally available in cast iron, steel and bronze. Steel is used when there is a need for a high strength design. But cast iron is mainly used because of its good wearing properties, excellent machineability and the ease that complicated shapes can be created due to the casting method.Castings are created by pouring molten metal into a mould and once the metal as cooled it takes the shape of the mould.
The non metallic, materials used are generally wood, rawhide, compressed paper and synthetic resins like nylon. These types of materials are generally used when there is a need for the reduction in noise from the gears.
Gear Design
Selection of Gear Type
Selection of Gear Materials
Formulae for gear forces
Gear Force Diagram
Spur Gear Design
DESIGN OF SPUR GEAR
Spur Gear Fundamental1. Determine HorsePower based on Lewis Formula
Metalic Spur Gears :
W = SFY . 600 / (P . [600 + V] )
where W = Tooth Load, Lbs
S = Safe Material Stress (static)Lbs per Sq.in
F = Face Width, In.
P = Diametral Pitch
D = Pitch Diameter
V = Pitch Line Velocity, Ft. per Min. = 0.262 . PD . RPM
For Non-Metalic Gears
W = S.F.Y. {(150 /[200 + V]) + 0.25} / P
Horse Power Rating (HP_L) = W . D. RPM / 126000
2. Calculate Design Horse Power
Design HP = HP_L * Service Load factor
3. Select the Gear / pinion with horse power capacity equal to or more than Design HP.
Ref :"Handbook of Gears" -Stock drive products
Table 1.15 Ratings for Steel Spur Gears
Helical Gear Design
HELICAL GEAR DESIGN
Helical Gear Fundamental
1. Determine HorsePower based on Lewis Formula
Same as Spur Gear Design except the inclusion of helix angle
HP_Helical = HP_Spur * cos(ψ)
2. Calculate Design Horse Power
Same as Spur Gear
3. Select the Gear / pinion with horse power capacity equal to or more than Design HP
From "Handbook of Gears" -Stock drive products
Table 1.18 Ratings for Hardened Steel Helical Gears
SolidWork PLANAR JOINTS
PLANAR JOINTS:
NOTE: if you are not familiar with the layout of SolidWorks, then click here to familiarize yourself with the layout. If you are unfamiliar with assemblies please see the assembly tutorial.
There are three types of Planar Joints: Pin Joint, Pin-in-Slot, and Sliding. Solidworks will allow us to study these joints in a way that a simple drawing or schematic would not allow. We will be able to actively move the joints and see the limitations of each joint type.
This tutorial uses files in the parts.zip package. Make sure you download and extract the files to your computer. The assemblies in this tutorial come from the "planar joints" directory. RED pins represent pins that are fixed from translating...each still allows rotation of the body connected to it.
The first Planar Joint is called a Pin Joint. It is one you are already familiar with since it can be seen in most mechanical systems.
It only permits two bodies to pivot relative to another.
As an example of a pin joint consider a scissors lift shown below. This mechanism, which serves to raise platform holding workers, has a series of links which are unfolded by several hydraulic cylinders. Each pair of links is connected by a pin joint which enables them to pivot with respect to each other:
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To examine a simple pin joint in solidworks, follow these steps:
1.) Goto File->Open and select "pinjoint.SLDASM" from the planar joints folder
2.) using the rotate component button 
and the move component button 
see how the pin joint moves in space. Notice the limitations of this joint:
You can see that there are actually two pin joints in this assembly. The pin in a pin-joint could be fixed in position, or it can join two parts, both of which can move.
The second Planar Joint is called a Pin-in-Slot joint. A pin-in-slot joint allows the joined bodies to pivot with respect to each other and to translate with respect to each other in one direction. However translation in the perpendicular direction is restricted.
As an example of a pin-in-slot joint, consider the motorized door opener shown. The end of one member has a pin with a roller, which rolls in a slot in the door:
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To examine a simple pin-in-slot joint in solidworks, follow these steps:
1.) Goto File->Open and select "pininslot.SLDASM" from the planar joints folder
2.) using the rotate component button and the move component button see how the pin-in-slot joint moves in space. Notice the limitations of this joint:
You can see that the link with a slot and a hole is pinned at its hole to some fixed body which is not shown, but that a second link is connected to the slot with a pin. The pin-in-slot joint is that connecting the two links.
ALSO: Notice that you can only translate the link with two holes, not rotate it. This is a limitation of Solidworks. A work around to this problem is to "fix" the link in space by right clicking on link3slide in the Feature Manager Design Tree and click "Fix":
You may get a message that the assembly cannot be solved with this mate. However, you will find that it probably works. Now the link with two holes can be both translated and rotated. You can return to the initial state in which the slotted link floats by right clicking on link3slide in the Feature Manager Design Tree and selecting "Float":
The third Planar Joint is called a sliding joint. A sliding joint prevents two bodies from rotating with respect to one other and permits the bodies to translate with respect to one another only in a single direction.
As an example of a sliding joint, consider the mechanism for adjusting the position of the back to the exercise machine. The black sleeve can only slide on the white member. Notice that the sleeve is locked into position by the spring loaded pin (with the black handle) which engages one of the holes in the white member. But when this pin is retracted, the sleeve can slide. Notice that another link is pinned to the sleeve:
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To examine a simple pin-in-slot joint in solidworks, follow these steps:
1.) Goto File->Open and select "slidingjoint.SLDASM" from the planar joints folder
2.) using the move component button see how the sliding joint moves in space. Notice the limitations of this joint:
You can see that a link with a slot and a hole is pinned at its hole to some fixed body which is not shown. A second member with a square peg engages the slot. While the link with the slot can pivot about its pin joint, the second member can only slide in one direction relative to the slotted link. The sliding joint is that connecting the two links.
Using Planar Joints to Form Mechanisms:
NOTE: if you are not familiar with the layout of SolidWorks, then click here to familiarize yourself with the layout. If you are unfamiliar with assemblies please see the assembly tutorial.
By connecting members of various shapes and sizes with planar joints, the motion (input) of one body brings about the desired (output) motion of another body. Two common input motions are: rotation of a shaft (by a motor) and translation of a body (by actuating a hydraulic or pneumatic cylinder). These are also two commonly desired output motions: pivoting a body about a point and translating a body along a line.
However, the input body often cannot be attached directly to the output body. Therefore, a mechanism converts the input motion to the output motion.
To illustrate this effect, we show three mechanisms which accomplish the same purpose: pivoting a member about a point. The member could be a door pivoting about its hinge:
This tutorial uses files in the parts.zip package. Make sure you download and extract the files to your computer. The assemblies in this tutorial come from the "pivot" directory. RED pins represent pins that are fixed from translating...each still allows rotation of the body connected to it.
Method 1 (Pivot1.SLDASM)
The pivoting member (top) is acted upon by a link (middle), which is in turn driven by a second link (bottom). The bottom link is pivoted by a motor. The motor is not shown, but the shaft of the motor (shown here as a fixed pin) would engage the link causing it to turn. Besides the hinge of the top green member (which is like the hinge of a door), this method involves two pin joints. The mechanism at work here is called a four bar linkage. The "fourth" link joins the two red dots. In the four bar linkage, one link always joins the two fixed pins.
Method 2 (Pivot2.SLDASM)
The pivoting member (top) has a slot in which a pin (blue) slides. The pin is connected to an L-shaped member. The L-shaped member would be pivoted by a motor just as the bottom link above is pivoted by a motor. Besides the hinge of the top member, this method involves a pin in slot joint.
Method 3 (Pivot3.SLDASM)
The pivoting member (top) is acted upon by the piston of a hydraulic (or pneumatic) cylinder. The hydraulic cylinder case is connected to a fixed pin about which it can pivot. The piston is moved back and forth in the case by the flow of compressed fluid or air. As the cylinder extends or contracts, the top member pivots about its pin. Besides the hinge of the top member, this method involves a sliding joint and two pin joints. (The piston and case are connected by a sliding joint.) The mechanism at work here is an inverted version of the crank and slider mechanism.
MATING:
NOTE: if you are not familiar with the layout of SolidWorks, then click here to familiarize yourself with the layout
SolidWorks has a simple, yet powerful mating feature. It is used for joining parts in an assembly and simulating how they fit together and move together. The picture of the engine above shows an intricate assembly. This tutorial will cover the most basic mates that we will use to simulate simple mechanical systems. To use mates we will be working with more than one part and therefore must be in the assembly mode of SolidWorks. To enter this mode follow these steps:
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Start SolidWorks and goto file->new
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Double click the "assembly" icon:
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you will notice a new toolbar appearing to the left of the screen. This is the only noticeable difference between part mode, and assembly mode:
This tutorial uses part files from the parts.zip archive. Make sure you download and extract the files to your computer before continuing...
Concentric Mate:
The most common mate is called a concentric mate, and as the name implies, it is a mate between two concentric features. Any time you want a pinned connection or a piston cylinder type connection you will use a concentric mate. We will mate a pin to a link in the following example:
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First you will add the pin to the assembly. Goto Insert->Component->From File
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Find the "Pins" folder and double click "pin2inch.SLDPRT"
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Click anywhere on the screen to place the part near to where you want it.
NOTE: In solidworks assembly mode ,the FIRST part you insert is automatically fixed in space. This means it can not rotate or translate. Every other part you add is "floated" in space which means it can rotate and translate. For more information about fixing and floating parts please see the Planar Joints Tutorial.
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To add the link follow the same steps for adding the pin. Add "link1.SLDPRT" from the "Links" folder
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Your screen should now look similar to this:
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Select the Mate icon
from the assembly toolbar and mate options will appear. Select the inside face of the hole on the link and the outside face (circumference) of the pin. Watch this animation for clarification:
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Your assembly should now look similar to this:
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To check that the mate worked try moving the link around the screen using the move component button
. The link will remain concentric with the pin, although it can move parallel to the pin (and even off it).
To further restrict our pin we will want to do a second mate:
Coincident Mate:
A coincident mate, like the name sounds, is a mate between two features that you want to coincide with each other. Generally we use it for making two planes parallel and coincident. In this tutorial we will use it to mount the link onto the pin so that it cannot fall off of it. When we do this, the link will spin around the pin, but it will not be able to slide up and down the pin. Follow these steps to achieve this mate:
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Click the mate button
on the assembly toolbar -
Select the top face of the link and the top face of the pin. If you can't easily select the surfaces, use the zoom
and move buttons 
to navigate around the object until you can clearly see the features. Watch the following animation for clarification:
[NOTE: you can also use the middle mouse scroll button to zoom and rotate]
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Your assembly should now look similar to this:
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To check that the mate worked try moving the link around the screen using the "Move Component" button
. The movement of the link movement should be restricted to be concentric with the pin and parallel with the top of the pin.
you are now ready to try mating exercise 1
Try to create the following assembly for more practice:
Troubleshooting:
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it is always a good idea to position the part close to its final mated position before you set up the mate. You can move the part using the move component button
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If you mess up badly, you can always edit->undo. Likewise, if you want to go back to a certain point, you can use the undo list
to see your undo options. If this does not work, Solidworks keeps a record of all mates in the Feature Manager Design Tree under 'MateGroup#' If you expand this list, you can manually delete any mates you have made by selecting the mate and then hitting Delete on the keyboard. Likewise, you can right click and select delete:
MODIFYING PARTS:
NOTE: if you are not familiar with the layout of SolidWorks, then click here to familiarize yourself with the layout
This tutorial will use "link3slide.SLDPRT" from the parts.zip file. You can use these techniques on any part though. The steps in this tutorial are similar to the steps in the dimensioning tutorial. The more you understand solidworks the more you realize that even the most complex parts are made and changed in a similar fashion to the steps in these tutorials.
1.) Use file->open and browse to the links folder. Select "link3slide.SLDPRT" and click open:
2.) You can only add features in sketch mode. To enter sketch mode you must first decide where you want to add the feature. You can add a feature to any plane. You can usually find the sketch under an "extrude" in the feature manager design tree. You will have to click the
to reveal the sketch:
3.) Right click on the sketch and select ‘edit sketch.’ You will notice that the rest of the part disappears or becomes transparent. Do not worry if some of the features of the part become transparent or disappear. They have NOT been deleted. They have simply been removed to simplify the screen and highlight the sketch you are currently working with. See the advanced dimensioning tutorial for an example of "disappearing" parts:
4.) You will now be in sketch mode and can use all the buttons on the right of the screen (picture rotated to save space):
5.) If your view of the part is skewed, click the front view on the standard view menu to rotate the sketch (view->toolbars->standard view):
6.) Your window should now look like this:
7.) To add another hole to the link select "draw circle" from the sketch toolbar:
8.) The cursor changes and you can now draw a circle on the link:
9.) to edit the radius of the circle either follow the steps in the dimensioning tutorial or modify the radius in the feature manager design tree:
10.) Exit sketch mode by clicking the purple arrow in the top, right hand corner:
11.) The new hole will be cut out of the link and your link should now look like this:
12.) To remove the hole you re-enter edit sketch mode. Do this by right clicking on the sketch and selecting edit sketch:
13.) Select the hole you just created by clicking on it with your mouse and hit the delete key on your keyboard. The hole will disappear. Exit sketch mode by clicking on the purple arrow:
You are now ready to try Modification Exercise 1
If you want to modify any extrusion follow this example:
1.) Use file->open and browse to the links folder. Select "link3slide.SLDPRT" and click open:
2.) Right click on "Base-Extrude" in the Feature Manager Design tree and click "Edit Definition":
3.) You will be presented with extrusion options. In this example change the Depth dimension from 1.00in to 3.00in and click the green check mark:
4.) The link will now be three times thicker:
You are now ready to try Modification Exercise 2
for more practice try adding a square hole to the same link:
starting with "linkwithsquareboss.SLDPRT" stretch the boss to 2 inches:
NOTE: make sure you are familiar with the dimensioning tutorial
Troubleshooting:
● If you mess up badly, you can always edit->undo. Likewise, if you want to go back to a certain point, you can use the undo list
CREATING A SIMPLE PART FROM SCRATCH:
The purpose of this tutorial is to create a simple bracket from scratch. Every new part in solidworks begins with a sketch. If you notice this bracket is just a 2d shape that has been extruded to create a 3d object. So to create this part we will create a 2d sketch and extrude it.
1.) Select 'File' -> 'New'' and double click 'Part':
2.) On the main toolbar click 'Sketch' to enter sketch mode. Then click the 'Sketch' button to the right to enter sketch mode:
A set of planes will now appear. Select the plane labeled Front to start your sketch on that plane:
3.) Draw a rectangle starting at the origin. [click once on the origin and a second time at any arbitrary point in the 1st quadrant] :
4.) Click 'Smart Dimension' on the main toolbar and then change the height to .08m and the length to .32m:
For help on dimensioning click here
5.) Now select the 'Circle Tool' and draw a circle similar to the one in the picture below:
6.) Click the circumference of the circle and enter the following values into the panel on the right side of the screen:
These numbers correspond to the absolute location of the circle's midpoint, and the radius of the circle. Namely, the midpoint of the circle is located at (0.25,0.04) and its radius is 0.03m.
7.) Click the little arrow next to the Features button on the main toolbar to bring up the following screen. Then click 'Extruded Boss/Base':
8.) In the pane that appears to the left, enter 0.01m in the box and click the green arrow:
9.) Your model will now look like this:
10.) To create the boss on the surface, you need to start a new sketch on the face of the model. To do this, select the face of the model and click the 'Sketch' button on the main toolbar:
11.) Change to a front view of the model and draw a rectangle using the Rectangle button:
12.) Dimension the rectangle using the 'Smart Dimension' button to be 0.06 m square:
13.) To locate the rectangle in the proper place, use the 'Smart Dimension' tool and select the left edge of the boss, and the left end of the goldish rectangle underneath. Enter 0.01m as the distance:
14.) Repeat this for the gap between the top edge of the boss, and the top edge of the goldish rectangle:
15.) Click the little arrow next to the Features button on the main toolbar to bring up the following screen. Then click 'Extruded Boss/Base':
16.) Enter 0.02m in the D1 box, click the green check mark, and you will get the following model:
CREATING A TRUSS STRUCTURE FROM SCRATCH:
The purpose of this tutorial is to create a truss-like bracket from scratch. Every new part in solidworks begins with a sketch. If you notice this bracket is just a 2d shape that has been extruded to create a 3d object. So to create this part we will create a 2d sketch and extrude it.
before you begin this tutorial make sure you have the 'sketch' , 'sketch tools' , and 'features' toolbars open. Make sure the base units are Meters. Optionally, you may want to turn on the drawing grid. Click here if you don't know how to add these options.
1.) Select 'File' -> 'New'' and double click 'Part':
2.) On the sketch toolbar click 'Sketch' to enter sketch mode. Then click the 'Rectangle' tool:
3.) Draw a rectangle starting at the origin. [click on the origin and drag the mouse to another point and click again] :
4.) Dimension the rectangle using the 'Dimension Tool' and by clicking on two edge's. Change the height to 0.08m and the length to 0.32m:
For more help on dimensioning click here
5.) Select the 'Line Tool' and draw a triangle on the part:
6.) In order to place the triangle exactly where you want it and make it the proper size you must use the 'Dimension Tool.' First you should line adjust the spacing around the triangle. In this example we will change the spacing to 0.01m:
For more help on dimensioning click here
7.) Next you should adjust the length of the triangle's base. Notice the height is already defined. In this example we will the base and height are 0.06m:
8.) Draw and dimension the upper triangle in the same way as the lower triangle. Notice the vertical and horizontal spacing between the two triangles is set to 0.005m:
9.) The sharp corners in the triangles will lead to very high stress concentrations. Fillets are used to lower the stresses in the corners. Use a fillet radius of 0.003m on each corner. To add a fillet, click the 'Fillet Tool,' enter the fillet radius, then click the two lines that create the corner you want to fillet:
10.) Instead of drawing each triangle again, you should use the 'Linear sketch and repeat tool' to add more triangles along the length of the bracket. Using this tool is simple. First select the 2 triangles you want to repeat. Then click the button, choose the number of copies you want, and the spacing between the copies. It will dynamically preview any changes you make. In this example we have 4 triangles, with a spacing of 0.08m.:
7.) Click the purple arrow
to exit sketch mode.
8.) Click the extrude button on the 'Features' toolbar and enter .01m in the d1 text box:
If you want to import this file into ANSYS for analysis, you must save it in the IGES file format. For instructions on how to do this, click here.
Before importing a SolidWorks part into ANSYS, while still in SolidWorks you must export the part in the IGES file format. Click here if you have not done that yet.
MODEL:
START ANSYS AND IMPORT FILE:
Open ANSYS: on cmu cluster machines its under math & stats:
From the file menu select Import>IGES... and select the following options:
Locate your IGS file using the browse button. When you find the file it should look something like this:
Your screen wll now look like this (notice the axis directions):
MATERIAL PROPERTIES:
In order for ansys to do a Fine Element Analysis [FEA] we need to specify what kind of element we want to use. For this 3d solid we will be using a 10 node tetrahedron shaped element[solid187]. To set this click on Preprocessor>Element Type>Add/Edit/Delete:
Click 'Add' on the next window(Elements Type) and then find 'Tet 10 node' under 'Structural Mass' -> 'Solids':
click OK and then click Close on the 'Elements Type' window
Now we must specify what type of material this solid is. The problem specifies the bracket is to be made of aluminum. To enter material data click on Preprocessor>Material Props>Material Models:
Select Structural>Elastic>Isotropic and enter the following numbers into the window that appears:
EX refers to Young Modulus, which is 7e10 Pa for aluminum
PRXY refers to poisson ratio, which is .33 for aluminum
click OK, then close the Define Material Model Behavior' window
MESHING:
To mesh the volume into individual elements, go to Proprocessor>Meshing>MeshTool:
The MeshTool window will pop-up on the right side of your screen. Select the following options and click 'Mesh':
Select the bracket and click ok:
NOTE: If ANSYS gives you an error about going over the maximum number of elements, you must adjust the Smart Size slider to a number higher than 6. The reason for this error is because the educational version limits the maximum number of elements.
Your mesh should look something like this:
While not necessary to solve the problem, for more accurate results it is often a good idea to add more elements in certain areas of interest. This is called Refining the Mesh and can be done by selecting Preprocessor>Meshing>Modify Mesh>Refine at>Areas:
We are concerned with stresses in the holes so add more elements around the holes by selecting the areas that makes up the 2 holes (4 areas in all).
in the next window select 3 and click ok:
Your mesh will now look like this. Notice there are approximatly three times the elements around the circles:
this picture better illustrates the new elements:
BOUNDARY CONDITIONS:
Now we have to apply the loadings to our meshed volume. This problem has 1 mounted area and 1 force.
Before we apply forces you should familiarize yourself with the pan/zoom/rotate tool. You can find it under PlotCtrls:
It has the basic engineering views as well as buttons for rotating about each axis, and buttons for zooming in and zooming out:
Once you are familiar with this tool, you can continue on to apply forces
Since the left side of the bracket is mounted it will not displace in any direction. To set this choose Preprocessor>Loads>Define Loads>Apply>Structural>Displacement>On Areas, select the mounted face and click OK (NOTE: you will have to rotate your view so you can easily select this area):
on the window that pops-up select All DOF and enter a Displacement of 0...the click OK:
To apply the force select Define Loads>Structural>Force/Moment>On Nodes:
You will apply the forces at the end of the bracket, at the two corners. This will make the loading symmetric about the center plane of the bracket. Select the two nodes near the end of the bar (NOTE: select 'iso' on the 'pan/zoom/rotate' tool and zoom in a little to easily select these nodes):
A window will appear asking for the force data. To have a net force of 1200 N, you will need to apply 600 N to each of the nodes you have chosen. Enter the values shown below: Notice a downward force is -600 because the positive y direction points up.
Your bracket should now look like this:
SOLVE:
To run the FEA on the bracket select Solution>Solve>Current LS:
and your bracket will look like this:
POSTPROCESSING:
To see the deformed shape of the bracket select General Postproc>Plot Results>Deformed Shape click OK on the window that appears and your bracket should look something like this:
To get various results for the bracket select General Postproc>Plot Results>Contour Plot>Nodal Solu:
To see the stress in the X direction select the following:
use the 'Pan/Zoom/Rotate' tool to see the 3d stresses. Notice MX and MN locate maximum and minimum stresses
or stress in the Y direction:
Introduction Solidwork
WORKING WITH PARTS IN SOLIDWORKS:
NOTE: if you are not familiar with the layout of SolidWorks, then click here to familiarize yourself with the layout
SolidWorks allows you to view 3d parts from all different angles. There are infinite ways to view an object, but engineers usually only concern themselves with 4 main views. You can see these views in the above picture of the green link. The main views are Side, Front, Top, and Isometric.
For this tutorial you can open up any part in Solidworks. The tutorial will use the green link above to demonstrate, but any 3d part will work just as well. This link can be found in the parts.zip archive
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Start SolidWorks and goto file>open
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Find your part and click open.
Viewing the Part:
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You can access the standard engineering views by clicking the Standard Views button on the main toolbar:
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Each small box on the "Standard View" menu corresponds to a view of the object. The best way to understand what each view means is to click each view and see what happens.
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Below is a front, back and isometric view of the link:
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You can select a non-shaded view using the "View" toolbar:
and by clicking on the non-shaded box(with hidden lines) 
. There is also an option for non-shaded without hidden lines, and non-shaded with solid hidden lines:
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What if we want to view the indent in more detail? The standard views do not give a good view of it. Sometimes the only way to get a better look of a part or feature is to control the view manually. Use the rotate
and zoom tools to get a better view of the indent. NOTE: if you have a mouse with a scroll wheel, you can rotate and zoom without these buttons. Push down on the wheel to rotate, and spin the wheel to zoom in and out:
Extracting Dimensions From the Part:
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The simplest method of extracting the dimensions of a part is to make the dimensions visible in the default view:
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Right click where it says annotations on the feature manager design tree, and click where it says 'Show Feature Dimensions':
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If there is a check mark next to 'Show Feature Dimensions,' all the defined dimensions will appear.
- Dimensions are easier to see if the part is viewed as shaded. Sometimes rotating the part will make some of the dimensions more readable.
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Another method of extracting the dimensions of a part is to use the Measure Tool:
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Go to the main file menu and select Tools>Measure. The cursor will change to a ruler and a dialog box will appear with the title 'Measure.' Switch to Isometric View and then click the circular hole. The Measure Tool window will display all the properties of this hole:
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Likewise, you can use the measure tool to measure the distance between any 2 lines. For example, the distance between the top and bottom of the link from the side is 1.50 inches (shading turned off for clarity):
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Another method to extract dimensions of the link is to use the sketch mode. This will be most useful later on when we are interested in changing dimensions:
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Goto the feature manager design tree and locate 'Base-Extrude.' Click the
to reveal the sketch.
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Right click on 'Sketch1' and select ‘edit sketch.’
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The view will change and you will now see a 2d drawing with all the dimensions:
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To exit sketch mode click the purple arrow in the top, right corner, or right click in the drawing area and select 'exit sketch':
Solving Problems with Solidworks:
Checklist for creating mechanisms:
1.) [ ] If your assembly has pins that should be located in specific locations.....Place them using the move component tool and FIX them in place
[ ] Concentric Mate your links to the fixed pins
[ ] Face mate the end of the pins to the side of the links
2.) [ ] If your assembly has objects that must be located in specific locations.....Place them using the move component tool and FIX them in place.
Measure Tool: The Measure Tool is used to get the distance between points, the angle between lines, the displacement of parts in an assembly, and anything else you would use a ruler or protractor for in real life. To open the Measure Tool you can select it from: Tools->Measure...
Or you can select the measure tool using the Tools Button on the main toolbar:
Using the tool is very simple. You can select points or lines and it gives you information regarding the two selected entities. Pay particular attention to delta x, y, and z values. It allows you to determine distance between points independently from the global origin:
To measure the angle between 2 parts you must select 2 intersecting lines or edges on those parts. Look at the following picture for clarification(the 2 red edges were selected):
To change the units for display, click the Options... button and use the drop down menu to select the units you want:
Move Component: It is often important to be able to move a part in an assembly by a specified displacement or angle or to a specific xyz coordinate. The move component tool can be used for this if you understand how to properly use the tool. It is located on the main toolbar:
The Move Component tool has the following options (they are explained in detail below):
1.) Free Drag option is the default and it allows you to drag the selected part wherever you want. It is useful for positioning parts for mates or for moving assemblies. It is not useful for accurate movement.
2.) Along Assembly XYZ is an inaccurate method of moving a part in exclusively the x y or z direction.
3.)Move to XYZ position: This is useful if you want to move a point on a part to a specific xyz coordinate. Consider the following link, which is located somewhere random in space.
To move the link to the origin, first select a point on the link. (Notice that the origin is below the selected point and to the right at the location 0,0,0)
Next click the Move Component button on the assembly toolbar and select 'To XYZ Position.'
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Now the the point on the link is at the origin of the assembly:
4.) Move by delta XYZ: This is useful when you want to move a part a specific distance relative to its current location. You can choose to move by any combination of x, y and z distances as long as the part is not fixed or restrained by a mate. In this example, move a pin in a slot by 10mm to the right. Note that since the pin is mated to the inside of the slot you cannot move it in the y or z directions.
The first step is to select a point on the pin, or the pin itself:
Next click the Move Component button on the assembly toolbar and select 'By delta XYZ.'
Change the value in deltaX to 10mm and hit apply:
Now the pin has moved 10mm to the right:
Rotate Component: It is often important to be able to rotate a component in an assembly by a specific angle about the x y or z axis. The rotate component tool can be used for this if you understand how to properly use the tool. It is located on the main toolbar:
In this example the green link will be rotated around the pin by 45 degrees in the positive z direction. To do this, click the Rotate Component button. In the window that appears to the left of the assembly, use the drop down list to select 'By Delta XYZ'
Enter 45 into the Z text box and click apply:
The link will rotate 45 degrees and stop:
Select 'Tools' -> 'Options.' On the 'Document Properties' window select 'Units' and change them to whatever you want:
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Exporting to ANSYS: ANSYS uses a different file format from SolidWorks but it can still read SolidWorks parts as long as you first convert them to the IGES[Initial Graphics Exchange Specification] format.
1.) After saving the file in SolidWorks as the usual .sldprt file, and while that file is still open in SolidWorks, select 'File' -> 'Save As...' and change 'Save as Type' to 'IGES File (*.igs)':
2.) Click Options in the 'Save As' window and change 'Surface Representation' to 'ANSYS':
3.) click 'OK' and then 'Save'
click here to import model into ANSYS
Printing: To print what you see on the screen you have to change a setting in page setup. 'File' -> 'Page Setup'.
Otherwise the printout will be the actual size of the part you are working with. In some cases this is larger than a piece of paper.
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