Help with a polymer selection for my application (automotive bushing)

[stoltz23]

I am not that well versed on polymers so i am going to try to explain this as best i can.

i am looking for a polymer bushing to replace a rubber bushing in an automotive application. The material must have a very high durometer rating. I also need the material to be able to hold its properties from -30F to 250-300F. I would also like to be able to purchase this material as a liquid resin to keep my manufacturing costs as low as possible. I have looked into polyurethene but have not had any luck finding a resin that i can purchase that is hard enought, will hold up to my temperature requirements, and is not brittle. There are 3 pieces that i need to make. One is a 1" wide cylinder that is pressed inside a metal sleeve. A bolt is then inserted into a hole in the bushing. The other 2 are the same and are put onto a bolt with a washer on each side and a crossmember in between the bushings.


Any advice, links, or other information would be greatly appreciated. Thank you

 

[patprimmer]

What's wrong with maching it from brass or aluminium or even nylon 6.6 or PTFE barstock.

Epoxy may also work.

A lot also depends on duration of load and impact loads and amount of frictional heat generated and dirt contamination.



Regards
Pat
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[stoltz23]

I am trying to stay away from machining only because of the time that it will take per part. Casting these parts will reduce my costs a alot. That was where i started actually and i have some prototype pieces that have been machined but for the above reasons i am trying to find something that i can purchase and poor in my garage in to molds.

The duration of load will be constant as the compression bushings will always be under load. The bolts will be torqued at a max of 60 ft/lbs. When the vehicle is cornering this is when the most load will be placed on the buchings. There should very minimal impact loads if i understand what your asking right. Also there will be very minimal frictional heat. The bushings will not see movement like a control arm bushing does. I do want a material that will hold up to oil and typical road grime contamination.

 

[patprimmer]

It sounds like your pretty much stuck with epoxy then. I hope it works.

What numbers of each variant do you need to produce.

A company called Unasco Shamban (well that was their name a few years ago) make a special bush grade of PET in semi finished bushes. You still need to machine a bit to final size.

They may be prepared to slightly modify a mould if the volume was enough. Enough might be less than you think, but would be at least a few hundred (maybe 500) parts

Regards
Pat
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[mcgyvr]

Typical aftermarket suspension bushings are molded from polyurethane. (energy suspensions/prothane bushings are 2 manufacturers). They typically include a graphite filler to aid in lubrication. I have some and they require frequent (yearly) lubrication to prevent squeaking. I have also seen bushings/motor mounts made from delrin. You really need to decide on the durometer you want and find a suitable material. Polyurethane is typically available up to a durometer of 90 shore D

 

[patprimmer]

Da

Acetal is not up to the temperatures he states he needs.

I agree about the PU, but he claims he investigated and discarded it.

Vulcanised rubber is still the OEM material of choice even in exotic expensive cars and heavy trucks.

Talcum powder is a very good dry clean lube for bushes. It also works on door rubbers if they squeak on the bodywork.

Regards
Pat
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[plastx]

As Pat mentions, Shamban has products that include filled PTFE that will perform well though pricey. Shamban products are now part of Trelleborg at

http://tss.trelleborg.com/com/

http://www/en/products/Products.jsp

. They can be compression molded to your specs. Molding will depend on the amount of parts you need to offset the tooling costs. There are also products out there that have a layer of filled PTFE with a metal shell in standard sizes and then cut to length. You can check McMaster-Carr or other catalogs for these types.

 

[patprimmer]

Shambams partner in Aus actually injection moulds preforms for bushes in a custom brew of PET, glass fibre, Teflon and other fillers. They have moulds with removable inserts so they can cheaply adjust tooling to give a size that minimizes final machining, but it still depends on minimum numbers to be viable.

Regards
Pat
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[stoltz23]

Thanks for everyone’s input, I'll do some more research on some of the materials listed above.

For my application and the quantities that I need I would really like to stay away from machining because of the labor costs involved. I have spoke with Promotion and energy suspension about there polyurethane. That was my original plan but i am having a hard time finding a company that sells liquid resin polyurethane in a D-85 or 90. I have a solution if i decide to machine the parts but as stated above i am looking for a product that i can buy as a liquid, mix and poor into molds. This is how most of the polyurethane bushing companies make their bushings. i would have to think that they are doing this vs. machining for the same reason i am. Lower production costs.

There are a lot of companies that i have found that sell liquid polyurethane resin for arts and craft type molds but that is where their knowledge base stops. The companies that i have contacted don’t know much more than what is listed on their web sites which is not much

Thanks
Phil

 

[patprimmer]

Try BASF, Bayer Material Science, Merquinsa (spelling?), Noveon for starters.

Pouring is a slow process and is probably no more economical than turning.

Most common aftermarket bushes are actually injection moulded

Regards
Pat
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