PLASTIC GEAR DESIGN 3

[june]

Hello,

I am looking for good references for plastic gear design. Can anyone recomend any books, articles, etc. that deal specifically with plastic gear design? Also, any references for plastic gear manufacutring, testing or inspection would also be greatly appreciated. Thanks.

June

 

[insideman]

I don't have details at my fingertips... The people that publish a terrific book on plastic gears are called ABT-- I think. Try for a web site---

 

[june]

insideman, do you have any more info? I tried to find ABT but did not have any luck.

 

[MCM]

June, try these site:

- moldedgear.com
-

http://www.agma.org

 

[Buhrmann]

June and Insideman, the best best information that I could find on the Web for the design of plastic gearing is a company called ABA-PGT at

http://www.ABAPGT.com.

With all the searches I have done, they seem to be the best... The new AGMA standards on plastic gearing has incorporated a lot of the ABA-PGT work as is.

AGMA has a few good introductory standards into the do's and dont's of plastic gearing, see AGMA 1106-A97 Tooth proportions, plastic gears. But AGMA does not seem to have a fully developed plastic gearing standard yet. I have been personally doing all my plastic gear design according to the ABA method.

I have come across a reference to another code VDI 2545 (probably german based), and a method by Niemann in a specialised gear design package called KISSSOFT

http://www.kisssoft.com.

This package (cost an arm, a leg and a finger) has implemented VDI to calculate plastic gears, but I dont know to what extent.

Hope it helps, since plastic gearing is still very new in terms of coverage by specifications.

I hope this helps,

Regards,
Teo Buhrmann

 

[Spurs]

Buhrmann

I have used several methods to design plastic gears.

Kissoft did some consulting work for me themselves using their software which was a total disaster. They used their software and the application miserably failed.

I have used the UTS package. In one of their packages they calculate a factor of safety for strength. I happened to have one application with a safety factor of 2.8 that failed within 100 cycles!

The ABA-PGT software is very limited in what it can do. AGMA has used some of the information developed by ABA-PGT in their standards.

The lesson I have learned is that you have to test your designs! Software is not always the magic solution. Testing is critical.

 

[diamondjim]

This was extracted from another site
dealing with lubing plastic parts and
looks interesting.

The website is

http://www.lnp.com/LNPSite.nsf

 

[Buhrmann]

Spurs,

It is scary that KISSOFT was so far out.... one would expect that what you pay for it should in some way relate to its accuracy! (In defence to the package it is accurate in the design of steel gears)

Besides KISSOFT.... (obviously), how do you rate your plasic gears. Especially moulded gears?

Regards,

 

[strokersix]

June,

I suggest akgears.com and kleissgears.com are a couple of good resources for plastic gear design.

 

[401K]

I know Maytag redesigned their washing machine transmission using plastic gears. You might be able to mine some information from their website. I read the article once and I think they listed resources that they used in the design process.

 

[Spurs]

I came across this site - they have software for plastic gear design and they consult on plastic gears.

http://members.rogers.com/webgear/home.htm

 

[israelkk]

http://www.sdp-si.com/D190/D190cat.htm

they have the technical part of their handbbook on this site. They sell plastic gears and their handbooks are excelent reference for gear design.

 

[Buhrmann]

Thanks a lot for the references.

The Maytag search gave me a lot of leads to follow up, and I am busy downloading the manual and a lot of other info.

I have a lot of reading to do!

Regards,

Teo

 

[strokersix]

I believe UFE Inc. worked on the Maytag gears.

 

[Gearhead]

Hi

The Maytag design was done by Ken Gitchel of UTS. Plastic Gear design software is avaialble from them at

http://www.uts.com

othe users of UTS Software include to name just a few.
UFE,ABA/PGT,Dupont,Intier,Delphi,Xerox,Winzler,DSM,Visteon,Kohler, and many more. They also offer a Plastic gear school, consulting and "Fundamentals Of Gearing" E-Learning course.

 

[patprimmer]

I have quite a bit of design data for plastic gears from various materials, and quite a lot on plastic bearings.

There are quite a few variables that make plastic gear design quite different to metal gears, such as you do not need to design out noise, but you need to give consideration to fatigue, PV factor, moisture conditioning if it is nylon, anisotropic effect if it is reinforced with fibres, degree of crystalisation, lubrication added to the plastic compound, thermoplastic creep under load, notch sensitivity, surface layer effect, effect of varying section thickness on properties, effect of gate position and flow direction on properties, effect of pigments on properties, effects of UV light, effects of ambient temperature, notable differences between machined prototypes and moulded parts, post moulded shrinkage and or swelling, environmental stress cracking, etc etc.

I doubt if any software package takes all these factors into account.

DSM and LNP both have some good literature on bearing properties of special compounds.

Polyplastics of Japan and probably Celenese had some good books on gear design with Acetal.

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Spurs]

Pat

On your list of the considerations for plastic gears, you left out the most fundamental issue.

Effect of surface temperature. Heavily loaded plastic gears will have the frictional losses create heat. This changes the properties of the plastic material. For example an unfilled acetal may have a tensile strength of 10,000 psi at room temperature, but with a material temperature of 180 degrees F (even in a room temperature environment), the tensile strength is approximately 3,000 psi.

To make matters worse, the plastic gearing industry is still in its infant stages and as such, there is not enough body of knowledge available to accurately calculate load capacities.

Then to make matters even more difficult, the material suppliers do not have testing data on their products in gearing applications to be used as engineering design data.

But

given all that - they certainly do have an important role in gearing, and are widely used.

 

[patprimmer]

The PV factor covers heat as that is the mode of failure if the combination of pressure and velocity exceeds the factor.

In my experience, raw materials suppliers data was more comprehensive in the 70's than now, so old books might be more valuable.

Experience has taught that the details are now withheld at the direction of the marketing experts, so as not to scare of potential customers with lots of complex data.

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Gearhead]

Hello

I wish to give a little history here. The use of plastic gears has increased dramaticaly in the last ten years. Part of the reason for this is better understanding of the material and the design of Plastic gears. UTS has been at the center of this developmen. They have partnered with companies such as Dupont,Ticona,DSM,LNP and molders UFE, ABA/PGT,Winzler and more. They also worked with the AGMA to produce a Plsatic Gear Standard.

Currently UTS offers Software,training, consulting and e-learning. They have presented seminars with ABA/PGT,Design News Dupont and TIcona.

They also offer a piece of Free Software "Preliminary Plastic Gear Design" at there web site

http://www.uts.com

The above person who had a question about the software should contact UTS about the results.

 

[patprimmer]

Gearhead

I just visited that site. Very interesting, but I had no luck getting any free software. From what I saw, I needed to spend well over US$ 1000.

June

If you post or send drawings with speeds and loads, I can spend a bit of time on it for free. If it gets to hard, and takes more time than I can afford, I would need to stop but I could then direct you to a number of professional design houses with extensive experience in designing with plastics under critical loads.

Most of the data I would refer to is of 70's vintage, but then again, whenever you use Pythagoras's therom, the technology is well over 2000 years old.


Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.