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drermer
04-21-2011, 11:54 AM
I need to make some prototype heat spreaders out of a thermally conductive polymer. I want 2.5" x 3.5" x 1.25" (or there about) blocks that I can then machine

The company that makes the material will sell a compression molded block at an outrageous price with a significant lead time. I get the impression that they don't want to do it. I'm also concerned that the compression molded material will be porous, which is unacceptable for my application.

I can get pellets shipped the next day at a resonable price.

Are there any companies that do this sort of thing, i.e. make standard sized injection molded blocks without the cost of having a mold made?

Any info would be appreciated.

mc_n_g
04-21-2011, 02:08 PM
Why will it be porous? I would worry more about the part warping and have potential heat sinks. I would also worry about the part warping because of the compressed stress in the material when you machine it.
Most likely their cost is manufacturing a mold and mounting it to their machine for a small run. You are paying for all the labor and material to get your blocks made.
For as many 'standard' sizes as you can come up with that is a lot of molds to have on hand. The other thing is you state this is a thermally conductive polymer. Is there a market for thermally conductive polymer blocks?
Can you do injection or compression molding yourself or can you only machine? Meaning your only have milling equipment and not plastics equipment.

jetski
07-05-2011, 09:59 PM
You can have large blocks molded in Scottsburg Indiana at Engineered Block sales. I can tell you like the previous M C ng lots of stress is molded in this way. I machined some glass filled Valox and about 1/2 the way through the part made a bang that sounded like a shot gun blast. We did not know where the sound came from untill the block was done and we had set up another one to cut and bang again. A crack in both parts due to stress. The Valox was 4" x 12" x 12" hope this helps. Good luck.