Quote:
Originally posted by bigben2k
You know we're going to hold you to that 
Is the reduction of the complexity of the polycarb top make molding a viable option? Or is it too early to tell?
I like the straight walled polycarb tube approach, instead of brass barbs. I think you might get requests for a single barb or groove on it, but it's really not necessary.
If it's any help, that Weld-On #4 might come in handy there, if you want to try it, as a prototype. I'd send you some, if you weren't in Oz!
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No, I sincerely mean it. Hold me to it by all means.
If I'm going to bother with getting the middle plate molded, I'll just get the top plate molded as well in the same mold. The mold would have already been mostly "paid for" due to the middle plate.
Without going into exactly what each plate costs me to get them machined, we'd be looking at very significant savings on the cost to make the polycarb plates if they were molded, as opposed to machined. Enough to amortise the cost of the mold over maybe 200 blocks or so while still being able to reduce the final sale price substantially. Take off the cost of the barbs and tapping for the barbs as well, and it works out very nicely.
Getting the poly fittings "ribbed" like a barb when molding will basically double the cost of the mold, as it's a third dimension operation and requires attaching extra machinery to the mold.
I use straight copper pipe fittings on my radiators all the time, often without clamping while pushing 20PSI through the system and they don't leak. Not something that I recommend, but it shows how a straight pipe fitting can be just fine. Maybe taper the top of the fittings slightly going from 12mm to 13mm over say a 5mm length, so the hoses are easy to get on, but tighten up as you push them further down the fittings. This is basically what a barb rib does anyway and that can still be molded simply. Use 1.5mm thick walls for the fittings which gives a 10mm ID and enough strength, and a rounded base to the fittings where they meet the top of the plate for added rigidity at the stress point.
[Edit: Cross post with Since87] - Yes I'm aware of "drafting" for molds. For polycarb a 2 degree draft is sufficient.