Change from bronze to plastic gear 1

[newteceng]

I am looking for some help in reducing cost of a product
that we have market but was designed in the late 1950's. One area we think we can save is in the gear train changing some of these from bronze to plastic gears.

The torque load and speed are low. I could use some advice
as to some one who could advise us in the change and get us in contact with some one to produce the gears we were
thinking molded parts as the volumes are in 100,000'S a year area.


Thank you,
NewTecEng

 

[TVP]

I suggest reviewing some of the companies and technical articles available from the Gear Technology website:

http://www.geartechnology.com/product.php?b=Injection Molded Plastic Gears

 

[SincoTC]

If silent operation is a prerequisite of your product, be aware that there are moulded gears and moulded gears, check that you're getting the required accuracy, especially at the cheapest end of the market and remeber that even good quality plastic gears don't have the sound damping characteristics of metal ones (at least that's been my experience).

 

[dinjin]

Undoubtedly you can change to plastic gears but you should hire someone with expertise in this area if you are going to commit to that number of gear production.

 

[Spurs]

Check out a consulting company who specializes in this type of work

Web Gear Services Ltd

http://www.webgearservices.com

 

[tbuelna]

newteceng,

A simple molded plastic gear would seem to be less expensive than a machined bronze gear, but your post presents lots of open questions.

A machined bronze gear will be much more accurate than a simple molded plastic gear. Also, depending upon the bronze alloy of your present gear, and the plastic material you propose to substitute for it, the gear strength may be better or worse, and the cost may also be higher or lower.

Some heat-treatable bronze alloys (like aluminum bronzes)have excellent mechanical properties, while other bronze alloys are not so good. As for plastics, some plastics (like Torlon or Vespel polyimides) have amazing mechanical properties, while others (like Delrin nylons) are not so good.

High performance polyimide resins would make an excellent molded gear material, but they are very expensive and would be much more costly than even the best bronze alloy.

If you have very high production rates, and can't use plastic for strength reasons, you might consider making metal blanks that are near net to reduce machining time and scrap. Sintered powdered metal blanks or near net forgings might be a cost-effective option.

Good luck,
Terry

 

[chicopee]

What's the horsepower rating on this gear train?

 

[strokersix]

Also be aware that polymer gearing in general is quite sensitive to operating temperature whether ambient or due to heat generated by the gears in operation.

Common gear materials such as acetal or nylon are roughly 1/2 as strong and 1/2 as stiff at, say 200F, compared to 70F.

Second the suggestion to consult an expert. Here is one I'm not affiliated with, just a satisfied customer.

http://kleissgears.com/

 

[plasgears]

When going from metal to plastic gears, expect to design for lower gear stress [read larger gears], larger gear box, etc. Things look different when you go from metal to plastic: webs and undercuts appear because of concerns for near const thickness design.

GE Plastics has great experience in this growing discipline.