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Fasttrack
10-31-2014, 10:23 AM
I have two parts that are used to mount a 20 lb static load inside an enclosure. The enclosure may experience temperatures between -30*C and 65*C but most of the time, it will be maintained at 40*C using electrical heaters. One of the parts is pictured below. For sense of scale, the two large holes near the top are 1" in diameter. The original design called for 3/8" thick 6061 aluminum but we need these to be made from a material with low thermal conductivity.

Do you guys have any suggestions about a reasonably strong, rigid plastic that would perform well at temperatures up to 65*C and be reasonably good insulators? It also has to be machinable so I am hesitant to go with a glass filled plastic. Thoughts?

http://i108.photobucket.com/albums/n22/fasttrack237/DetectorMount_zps185463df.png (http://s108.photobucket.com/user/fasttrack237/media/DetectorMount_zps185463df.png.html)

Rich Carlstedt
10-31-2014, 10:53 AM
The temperature ranges narrow down the selection and the weight means no sagging allowed.
my vote is for 3/8 " thick phenolic sheet

Rich

Sample supply- no affiliation to me

http://www.highlandwoodworking.com/phenolicboard38x11x15.aspx

MaxHeadRoom
10-31-2014, 10:55 AM
+1 on Phenolic (Paxolin, Tufnol), has excellent thermal, electrical insulation and machining qualities.
Max.

Fasttrack
10-31-2014, 11:21 AM
Thanks guys - I wasn't sure how well phenolics machined but the thermal and mechanical properties are very appealing. If it is machinable, that is the material I will specify.

lakeside53
10-31-2014, 11:53 AM
Around here (Boeing land) there's a lot of GF plastic parts in production.

Glass filled "plastic"(many types) machines easily. Sure.. you use up tooling and you need to clean up...

LKeithR
10-31-2014, 12:06 PM
Another vote for the phenolic...

RichR
10-31-2014, 12:22 PM
Does it have to be plastic? Maybe 3/8 inch plywood.

Fasttrack
10-31-2014, 01:20 PM
Plywood is definitely out.

I have called out G-10 Garolite for now.

Rustybolt
10-31-2014, 08:02 PM
Glass filled garolite would be my choice

mooney1el
10-31-2014, 08:38 PM
Did you reject G11 Garolite?

Fasttrack
10-31-2014, 11:03 PM
Did you reject G11 Garolite?

It was actually my first choice but I rejected it because McMaster-Carr recommended diamond tipped tooling to machine it.

Tony Ennis
10-31-2014, 11:18 PM
Use a dust mask when machining glass-filled Garolite.

darryl
10-31-2014, 11:37 PM
Plastic laminate. GP, or general purpose, is about 1/16 thick- six layers would give you the thickness. It's a combination of phenolic and melamine resins, and kraft paper. It can stand considerable heat and is an insulator. Depending on how many parts you need, it might be worth laying up some thicknesses using epoxy. If you put the finished sides out it will have a finished look on both sides.

I do this often where I use just two layers- the final is about 1/8 thick. It's easy for me as I have access to scraps and can make up as much as I've ever needed. I've just finished machining up several pieces of this, using HSS. Where I need to use thicker I rough sand what would normally be the show surface, and it glues up just fine. Four layers makes a pretty tough board.

macona
11-01-2014, 03:49 AM
G10 is nasty stuff. You could always tell when they were running in the shop I worked at.

Delrin ought to work just fine. Also polysulphone, it is tough and even used as an insulator in capacitors, apparently.