<VV> RE: Corvair Fan (Kent Sullivan): Material Selection

[JVHRoberts at aol.com]

PEEK is also ferociously expensive, and challenging to process. PPS and PPO  
are less expensive, and also have desireable properties for less. But molds 
are  VERY expensive, especially for small runs. Investment casting in aluminum 
is  perfect for such a small run of parts. Thin sections, low cost tooling, and 
VERY  precise dimensions from this technique. 
Engineering thermoplastics require a LOT of knowledge and expertise to make  
them work right. Fine, if you're molding millions of headlight bulb bases, 
valve  covers, etc.,, but probably too pricey for this. 
 
In a message dated 7/10/2005 8:49:33 AM Eastern Standard Time,  
franmary at adelphia.net writes:

Kent,  My company had a "special" project to replace Delrin, which  was 
being eaten by a mild acid.  We went through an extensive (read  as 
multi-million $ DoD spending) material selection, design, manufacture  
and test process.  We finally settled on PEEK  (polyether-ether-ketone) 
for the part.  PEEK is a very high  temperature material, extremely inert 
and very strong.  It comes in  many flavors, including fiberglass and 
carbon reinforcements.  Its  one drawback is that it is expensive as a 
raw material.  For building  a fan, a major cost will be in the mold 
design/manufacture process.   The material cost may be secondary if the 
quantities are fairly low.   PEEK raw material is made by Victrex in the 
UK (http://www.victrex.com),  but is widely availble around this  country.

Fran