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Home made molds
7 replies to this topic
Posted 03 March 2005 - 09:02 AM
Hi what is the best way to make a split lure mold like the ones where you pour the foam in? Is there one material that works better then another? It looks a little complicated I mean the ones that I?ve seen on this site. I see that some molds have aligning pins and some don?t is it easy to put them in? I?m looking to make my first one but don?t know where to start. Thanks
Posted 03 March 2005 - 10:41 AM
Making a 2 part mold is very easy. I've made them for lead, I imagine they'd work the same for foam. You can use plaster of paris or floor leveling compound, but I prefer Bondo automotive body filler cause its quicker.
Basically you start with your model, which has been oiled to facilitate removal from mold. Try not to create any undercut situations which will make removal more difficult, and I generally incorporate the sprue hole into my model. Now find a suitably sized container, like a plastic lure box, oil it and fill it half way with Bondo. put your oiled up model exactly half way down into the bondo and let cure. Takes 5 or 10 minutes.
While its curing you can poke a few holes in the bondo wth the backside of a drill bit which has been oiled (this will facilitate lining up the 2 halves later).
Once the bondo is hard to the touch, lightly oil the whole thing and fill the rest with Bondo. By the way, I use wd40 spray as the lubricant in each case. In 5 or 10 minutes the whole thing will be dried and quite hot.
Carefully seperate the halves and rmove the model, oil again and let cool. you will probobly need a utility knife to take it apart, be careful, and don't wait to long as it will be nearlly impossible to seperate tomorrow.
Now you have a 2 part mold ready for making molds. You can use electrical tape or a clamp to hold the mold closed when pouring, I like a vise grip, but don't over tighten, it may break. When pouing hot lead I get about a dozen pours before the heat damages the mold. I would expect you'll do better with foam, although I've never tried it.
Posted 03 March 2005 - 10:44 AM
Incidentally, you asked for the best way to make a mold. I believe this is the fastest, and easiest way. But for the highest quality reproductions, you would need to have a machined mold of aluminum or brass, thats very time consuming and expensive.
Posted 06 March 2005 - 09:59 PM
Thanks for the info Rocfish. Does the bondo flow good or is it thick where it has to be pressed into the pattern I never used the stuff be for? What would be the best foam to use and where would I get it at?
Posted 07 March 2005 - 01:04 AM
It all depends on how many you want to make.If it's a dozen I suppose bondo is ok but if you want production runs bordering on a small business then Silicone J is the one.There's acouple of disadvantages though.It's bloody expensive and you need a vacuum chamber.Iv'e used a two shot mold for nearly 3years now and Plaster of Paris out 2 lures every 20 minutes.You just separate the mold give it a twist and out they Plaster of Paris.You don't need any mold release, however I spray the inside of the mold with white auto lacquer so they come out undercoated ready to paint.
Good luck Barramundi
Posted 07 March 2005 - 08:49 AM
Do You have a vent on that silicone one? I believe it doesn't work with ordinary air ?
Posted 07 March 2005 - 09:23 PM
I was thinking of reinforcing the Bondo with a steel plate with holes in it to stiffen it up when I clamp it together to maybe get a little more life out of it. I was wondering if I should use a syringe to inject the foam into the mold but I am not sure if I should use 1 or 2 or more spur holes. I shouldn?t get a head of myself I don?t even know what kind of foam to use yet I?m still doing the research. What I am trying to make is a minnow type bait about 5 inches long
Posted 07 March 2005 - 10:41 PM
I wouldn't bother with reinforcement myself. You don't have to clamp these things down very hard from my experience. As long as you have vents it isn't going to build up much pressure. I typically use one spur hole and may make very fine (very) fine vent holes in one or two areas in the bondo. I wouldn't recommend injecting the foam either. It really is very simple process. A lot of times it is a good idea to paint areas that have detail that might capture air with the stick you use to mix the foam. and then fill one half of the mold set together and clamp. I keep everything simple and the baits seem to turn out just fine. With a set of bondo molds you can churn out some baits rather quickly once you get a system going. As far as durability I am not so sure how many you will get out of a bondo but then again it doesn't take too long to make a series of the same mold when you start. I am sure others will be of more help, my experience with foamies is to a lesser degree than many on the site.