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Selection of the material for the jig of special purpose

Selection of the material for the jig of special purpose

(OP)
Hi All,

I would like to ask you for some advice regarding to material selection for designed jig.
The size of the jig will be approx. 20mm(H)x180mm(L)x120mm(W).
The jig will have some groovings etched on its top surface. The heating coil (max 1000W, 230/240V) will be inserted into those groovings every ~1minute and powered for approx. 10sec.
I need to select the material for that jig which would fulfil the following requirements:
- nonconductive (electricity),
- low-abrasiveness,
- capable of withstanding temperatures up to ~1050C,
- machinable material (to mill the grooves on one of its surfaces and bring to it some curvature shape).

I think that good choice could be some type of the ceramic (composite?) material.

I would be very appreciated for your opinion and help.

Thank you.

Greetings,

Hubert

RE: Selection of the material for the jig of special purpose

Hi Hubert,

You could try hexagonal boron nitride. It has most of the attributes you have identified in your notes. It is a soft, easily machined material. It is very inert to most metals even at elevated temperatures. It has good thermal conductivity and low expansion coefficient which are both desireable for resistance to thermal shock and stress. The application temperature of 1050 C is above the recommended use temperature in air of 900 C but if it is your heater reaching 1050 rather than the ceramic, it may work fine. The second caveat to boron nitride is its microstructure is fine grained without the features typical of refractories that deflect and arrest the cracks that inevitably develop especially in cyclical heating applications. There are a number of composite ceramics of which boron nitride is a constituent that may offer better performance. There are a number of suppliers world wide. If you tell me your location, I can get you in touch with one of them or a quick internet search for boron nitride will yield multiple sources.

Bruce

Bruce
www.accuratus.com

RE: Selection of the material for the jig of special purpose

Forget Macor for this application. It will crack on first use. Its fine microstructure, high expansion coefficient, and low thermal conductivity will do it in.

Bruce
www.accuratus.com

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