Machinable Ceramic Materials

[biomech21]

I am designing a heat staking fixture (inserts brass

inserts into thermoplastic parts with the aid of heat) for

the injection molding industry. The staking procedure

requires temperatures of around 300 degrees F and the

machine can handle a max of around 1000 degrees F as long

as insulation is present between the heated probe tips and

upper carriage. This insulation is generally 1" thick,

but the identity of the material is kept proprietary by

many manufacturers. The insulation must be MACHINABLE and

able to withstand approx. 100psi. Does Macor sound like a

probable alternative? Does anyone know of a cheap material

that should be able to perform well in these conditions.

I've attached a photo of a similar fixture for reference.

The insulation is the layer sandwiched between the two

aluminum plates.

Thanks!

http://files.engineering.com/getfile.aspx?folder=12589af1-a640-4a64-8575-18

 

[unclesyd]

Ma cor will work. To get something reasonable in cost you are going to have to limit your upper temperature.

Here is Superfiretemp that we use by the truck load for insulation on polymer process at 600°F. Readily available in 1" thick material.

http://www.monoco.com/Super_Firetemp.asp

Here is a material that I've used from Cotronics.

http://www.cotronics.com/vo/cotr/cm_machinable.htm

Another material you may want to checkout is MICA

 

[Ceramicguy]

The insulation in the photo looks like glass bonded mica. It is produced by several vendors throughout the world and is sold by many resellers. The vendor I am most familiar with is Crystex Composites (the old Mykroy Micalex). They have three grades, 400, 500 and 1100 that correspond to maximum use temperatures in degrees F. All are readily machinable using standard machine shop practices. They are significantly less costly than MACOR.

Crystex is located in Clifton, NJ. The telephone # is 973-779-8866. Resellers include Aremco Products, Cotronics, and McMaster Carr to name a few.

This is a fairly massive insulator. There may be a tendency for thermal stress failure over time. If this is a problem, you could substitute Grade A Lava. It will perform as an electrical and thermal insulator and have the stiffness necessary for your staking operation. It is also known as pyrophyllite. It is a naturally occuring aluminum silicate mined in large quantities worldwide. Any of the resellers listed above also supply this material.

If it were my project, I would start with the glass bonded mica. It is readily available, produced domestically, a good thermal and electrical insulator and the easier of the two materials to machine.

Bruce

http://www.accuratus.com