grundlman Posted December 17, 2015 Report Share Posted December 17, 2015 Has anyone ever tried to use high temp Lab Metal to make molds? I have a custom design I tried to use high temp silicone but the mold only lasted about 30 pours. This looks to have the consistency of jb weld or similar Thanks Jason http://www.eastwood.com/lab-metal-24-oz.html?fee=7&fep=870&SRCCODE=GA220010&adpos=1o1&creative=83580266340&device=c&matchtype=&network=g&gclid=CjwKEAiA18mzBRCo1e_-y_KLpXISJACEsANG42fW25uLhsUZSlmqjmaVmN1tuvMBmtF8TaXZd41GMhoCNA3w_wcB Quote Link to comment Share on other sites More sharing options...
JRammit Posted December 17, 2015 Report Share Posted December 17, 2015 (edited) I can't imagine using JB Weld as a mold material... Its too thick and nearly impossible to smooth out since it sticks to anything that touches it I looked at a few of the reviews on your link, there were complaints about this product curing too fast.. I think it would be a nightmare to work with, trying to "beat the clock" Which silicone are you using?... Some are stronger and less flexible, some are more flexible and not as strong Edited December 17, 2015 by JRammit Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 17, 2015 Report Share Posted December 17, 2015 It is a one part, therefore the only reaction is with the atmosphere. I suspect that if you tried to make a mold with the required volume, it would skin over and the rest would not harden. You could apply a skin of the lab metal and then back that up with a 2-part filler. Dave Quote Link to comment Share on other sites More sharing options...
grundlman Posted December 17, 2015 Author Report Share Posted December 17, 2015 Thanks guys That is a good point Dave I used the high heat silicone that is red colored and the area where the screw lock 'throat' was between the coil and the head on my shakey head wore out quickly Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 17, 2015 Report Share Posted December 17, 2015 It is hard to imagine how the mold can wear out so fast. I assume it is a 2-part mold. DAve Quote Link to comment Share on other sites More sharing options...
andy1976 Posted December 19, 2015 Report Share Posted December 19, 2015 I've done several hundred pores with bondo Molds Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 19, 2015 Report Share Posted December 19, 2015 The only way a silicone mold is going to wear out, is if you mold the part in one piece and pull the cast out through the pour hole. If this is the case, then if you make a regular two part mold with the silicone, your problems will go away. DAve Quote Link to comment Share on other sites More sharing options...
grundlman Posted December 20, 2015 Author Report Share Posted December 20, 2015 There is a very small area of mold material between the head of the bait and the screw lock holder......that small part pretty much wore out very quick Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 21, 2015 Report Share Posted December 21, 2015 Grundlman - so is your silicone mold one piece or two? DAve Quote Link to comment Share on other sites More sharing options...
grundlman Posted December 21, 2015 Author Report Share Posted December 21, 2015 It was a 2 piece mold. It was my first try at making a mold so I may have screwed something up as well....... Quote Link to comment Share on other sites More sharing options...
grundlman Posted December 21, 2015 Author Report Share Posted December 21, 2015 How exactly do you guys make your molds out of bondo? Will it hold up to the heat of the lead? Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 22, 2015 Report Share Posted December 22, 2015 (edited) I cannot get the Bondo brand here in Indonesia, but we do have a similar product, a polyester resin crammed with fillers. What I find is that the material softens after 2 or 3 pours. It is not a game stopper, but the softer mold will wear out quicker. A good mold design, with zero undercuts, were the cast comes out of the mold very easily, is going to last a long time. If you have to fight to remove your cast, then that means wear. If the split line is not exactly central on the master, this means that one half is going to be slightly undercut. Fighting to get that half out of the mold, slightly widens the rim and after only a few pours, the split line will become a visible step on the cast. As a designer in the automotive industry, I sometimes have to design injection moldings like bumper panels and internal trim panels. The minimum allowable draft is 3 degrees. We NEVER have vertical surfaces. Even stiffening webs and flanges are tapered a minimum of 3 degrees. The industry would never design a ball head jig as a sphere because there is no draft angle. We would chop a slice out of the middle of the sphere, such that the draft is 3 degrees. The life of an automotive injection tool must be minimum 500,000 but they are made from steel. That 3 degrees is a minimum, were possible we give more. Next time you make a mold, think carefully about the positioning of the split line. DAve Edited December 22, 2015 by Vodkaman Quote Link to comment Share on other sites More sharing options...
