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P.S. the above is for Jean-Luc (Just search the Forum for his great start on this selfmade kit)
Mark: Great article!!!!!
I have a few questions (as I have tried some resin stuff myself)
1. My LEGO™ bricks do not fit that closely together (!?) .... the RTV leaking througth the joints like there were big holes ... do you seal the bricks?
2. I find your "sprue approach" interesting but also a little complicated. For Wheels and other simple stuff I only have seen one piece moulds. You do not have a seam line, you save expensive resin and the resin does not have to follow complex curves (with a good chance for air bubbles). Why did you choose this method?
BTW the resin I use is of a consistency like Revell /Faller glue maybe even a tad thicker (but cures in a few minutes) What do you use .. is it like water?
Thank you and
best wishes
Steffen
Steffen-
My apologies for not addressing your questions sooner. As a relatively new forum user, I had no idea there was a discussion group attached to an article. This site never ceases to amaze !
1. The Lego blocks fit fairly snugly, but there will indeed be areas that will leak slightly. That is why I wrap the outside of the Lego form with low-tack masking tape, and again at the bottom edges so nothing leaks out the bottom end.
2. The "sprue" method was utilized for two reasons: first, because there's less clean-up time on the wheel (less excess resin to remove from the wheel), and second, it is far easier to remove a cast part from a two-piece mold than from a one-piece mold, and as such, your mold will not tear from stress, like a one-pice mold can do. Another benefit is that you can cast several pieces at once if they're on a sprue, this is much more difficult with a one-piece mold. Try it, it's really not that complicated. You just have to be sure your parts are aligned on center with your pour spout and breather tubes, so your mold halves don't encompass any one attribute of the sprue.
The resin I use is available from MicroMark (www.micromark.com), it is their CR-600 High Performance Casting Resin. It has the pour consistency of water when fresh, and then to a light maple syrup about 4 - 5 minutes later.
Best regards-
Mark