Urethane Resins

I was casting some parts yesterday .. Smooth-On’s .. Smooth-Cast® 310. While doing this various things came to mind.

  • The instruction sheet suggested using pressure during the curing of the casting. Done. I have a Harbor Freight Paint Pot modified to act as a pressure pot. I have added a pressure relief valve which keeps the maximum pressure around 40 psi. The suggested pressure per the instruction sheet though is 60 psi. A quick look yesterday on the internet suggest that there is a direct correlation between safe pressure for  such a pressure pot and the cost of said pot. In order to have a safe operating pressure of 60 psi it seems to me that the maximum pressure should be in the order of 80-100 psi. That apparently translates into $.
  • Smooth-Cast 310 has a 20 minute pot life and a 4 hrs cure time. That means I need (per the instructions) to keep the casting under 60 psi for 4 hrs.
  • I had purchased the resin without thinking it through. I believe that an alternate resin would make more sense. Just looking at the Smooth-Cast options makes sense:
  • Smooth-Cast 300 has a Pot Life of 3 mins and a cure time of 10 mins
  • Smooth-Cast 3000 has a Pot Life of 30 secs and a cure time of 5 mins
  • Smooth-Cast 305 has a pot life of 7 mins and a cure time of 30 mins
  • I can toss Smooth-Cast 3000 out immediately .. for me .. a Pot Life of 30 secs is insane.
  • Smooth-Cast 300 for me is .. call it .. iffy. A Pot Life of 3 mins is ‘dooable’ but I feel you would be pushing it.
  • Smooth-Cast 305 seems much better. A 7 min Pot Life should allow mixing, pouring etc. in that time period. You would have to ensure that everything was set out and ready. With the Smooth-Cast 310 you have 20 mins to find the various ‘etc’ that had been forgotten .. a weight to go on top of an open mold .  non-stick aluminum foil to go between the mod and the weight, something to ‘squeegee’ the top of the mold to remove excess resin .. with the 7 min Pot Life of Smooth-Cast 305 you would have to make sure that was ready .. for example the aluminum foil needs to be pre-cut and ready. Still .. dooable .. with prior planning. The 30 min cure time would mean it is quick enough to cast multiple parts in a day also. There are more things to that than simply a quicker cure time such as time for the mold release to dry and so on but still much quicker than a 4 hr turn-around.

Leave a Reply

avatar
  Subscribe  
Notify of