Re: Custom rubber parts

I'm not sure why my cell phone camera does that... reminiscent of old Penthouse magazine layouts where they coated the lenses with Vasoline to blur the image a bit... or that's what I heard anyway... ahem...

Either 60A or 70A would work well, 70 being the stiffer of the two. Be aware there is a Shore "D" scale as well, where 60 and 70 are getting into the bowling ball range, so order carefully. Some manufacturers offer "Wet" and "Dry" varieties, the "Wet" version exudes a mold-release-like liquid that works well in some applications. For your purpose, I'd stick with the "Dry" variant if offered the choice, that way you can make the mold from the same material as the part. Be sure to purchase a compatible mold release.

Most polymers can be colored using either a dispersion pigment (my choice) or tints. In my experience it takes a lot of tint to obscure imbedded steel brackets (or screws in hole pockets), which is why we use the dispersion pigments. Those bumpers being where they are, direct sunlight could make them appear a translucent purple when using a tint. Colors are generally added to the hardener component before mixing with the resin.

Paul, yes, 3D techology is becoming affordable, but for the purpose of making soft molds the pattern has to have a good surface finish that won't grip the mold material - for this type of work the hand finishing required generally makes CNC a more logical choice. We have even seen the 3D printers that print metal, but that won't be affordable for a while, and current technology would still mean leaving some finishing stock for final polishing.

The suppliers that sell urethanes and silicones will also usually have mold board available. It's a hard plastic board that's great for short run tooling and suppliers will sometimes have samples or scraps that might work well to make this pattern. That said the pattern can be acrylic, wood, aluminum, most anything you can whittle into the desired form. Do check the data sheet for the polymer you choose for any material interaction or incompatibility before investing time in a pattern.

SC

On Friday, April 25, 2014 2:48:53 PM UTC-4, Plucked Chicken wrote:

Is there a two part urethane rubber compound to pour your own rubber parts? Or a company that could do it small quantity reasonable?

The rear seat back on my wagon has 5/8” x 1” x 3/4” rubber bumpers it rests on in the upright position. They are hard as rocks from age. Not something I will find reproduced most likely........ They have two counter-bored holes for mounting them and the seat release spring clip, with two #8 sheet metal screws.