For a large long term builder of blocks your injection idea might be cost effective, I can't say. But I suspect for a small maker the cost of the molds would be prohibative. It would just take to many sold blocks to cover your outlay.
As to the plastics to use and the advantages of polycarb. I see these +'s to polycarb.
1) stiffer
2) stronger
3) clarity
4)short term cost effectiveness
If Cathar is interested in long term building of blocks now, your injection molding may well work & be cost effective. But if he intends to build a few hundred as before for direct retail, then sell the rights to the design for future royaltys and other considerations then no I don't see molds as cost effective.
The greater stiffness of polycarb will reduce the chance of water getting past the O-rings due to softer material being used. And a block top can't be to strong. Polycarb is known to be the best currantly used plexi for block tops. These other materials will raise concerns as to dependability with buyers. Even in the face of extensive testing proof showing other materials such as nylon to be dependable. And there is the issue of the cost of such testing.
Last clarity of the material used will matter to the general market. There are large numbers of people to whom looks count for a good deal in the purchases they make. A clear plexi top would, I think, aid CAthar in sales. A solid colored plastic top of nylon could be taken as "cheap" &/or unattractive in the retail market, regardless of the real truth regarding dependability.
The more I think on the issue of top materials to use the more problems I see in implementing the use of alturnative top materials. As I said at the start of this post, molded tops could prove a good way to go for a large long term maker of blocks. But I don't see it for small makers or short term.
Reading this over I see I'm really more concerned with how well a alturnative top material would sell for Cathar. Although all the reasons given would be raised, regardless of true impact on performance.
BE
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