basskillr Posted August 28, 2007 Report Share Posted August 28, 2007 I was wondering if anyone has tried venting the bottom of an aluminum mold and attaching a small vaccume pump to it to draw the plastic in? The reason I'm wondering is that I have a bait that that has to have a very thin section where the legs attach to the body, but it has large appendages below the attachment site. This makes it extremely difficult to pour normally without the thin section clogging up and leaving a void in the lower part of the legs. I know all about the dangers of pressure injecting, so I was thinking that putting a vaccume at the bottom and drawing the plastic through the mold. Will it work, or has anyone tried it? Quote Link to comment Share on other sites More sharing options...
GARVINBASSMAN Posted August 28, 2007 Report Share Posted August 28, 2007 funny you should ask this question im having the same question come up with a bait i want to have a mold made for. Quote Link to comment Share on other sites More sharing options...
SwampBaits Posted August 28, 2007 Report Share Posted August 28, 2007 I'm sure it would work if you had the right sized attachment. Might not be to safe though. I guess you don't know till someone tries it? Quote Link to comment Share on other sites More sharing options...
basskillr Posted August 28, 2007 Author Report Share Posted August 28, 2007 It would have to be safer than injecting, and I'm thinking that you should be able to get the same results as injecting. With a slight vaccume on it you should be able to pour like normal with a cup and get plastic all the way through the mold like injecting. The only drawback I can see would be maybe having to trim some small threads from the vents if you set them up to draw the plastic into the mold. Quote Link to comment Share on other sites More sharing options...
Delw Posted August 28, 2007 Report Share Posted August 28, 2007 The vacuum pump doesn't work as good as one would think, We made one about 4 years ago using a AC vacuum pump the mold was for those small berkley trout worms. One of the major problems is the mold cools the plastic way to fast. this might be fixed by using POP or RTV since they stay warm longer, Alum tends to cool off too fast. the other problems are once the plastic gets down the the bottom were the vacuum port is it cools due to the air rushing from the top to the port. The one Guy I made the mold for used it but it wasn't as good pouring the bait then shooting air through a syringe from the top forcing the plastic to the bottom. Any air movement in the mold will cool the bait causing the plastic to harden up. If you want to try it you can get Vacuum pumps from Harbor freight for around 19 bucks. then home depot will have hose's and fittings and so will harbor freight. Or you can goto a local pawn shop and get vacuum pumps pretty cheap. use 1/8 fittings with 1/16-1/8 hose ends. or you can use a set of a/c gauges with quick connects. Let us know if you get it to work successfully as it would open some doors on different baits. we played with it for a few months and it wasn't 75% successful so we scrapped the idea . Delw Delw Quote Link to comment Share on other sites More sharing options...
jmik26 Posted August 28, 2007 Report Share Posted August 28, 2007 Been there done that, save your time and money. Vaccum would suck down the plastic right away and clog the vent, then you got an air bubble. One thing you have to remember is with a vacuum your sucking down and once it gets to the bottom you loose the force of pulling. In our case the vacuum was a complete failure. We also tried to attach a pump to push the plastic in and it kinda worked but put alot of air bubbles in the bait. When we tried it as a two man operation, one pouring, and one pumping it seemed to be a little better but the plastic would go everywhere. PLEASE remember that if you try this, water and plastic do not mix. Sometimes moisture can be in these pumps especially when moving from cold to hot. Just a 10 minute truck ride in the cold to a warm shop almost was a mistake. Thank god I turned it on and put my finger on the tip to test pressure. Basskillr - I have designed a couple of baits that I thought were awesome but I could not get the bait to fill to save my life. I would talk with some mold designers and ask about the bait you describe. It can be done, but alot of care has to be taken in the main body design. Get as many tips on venting as you can, that will be the key.... Hope this helps....Jeff Quote Link to comment Share on other sites More sharing options...
basskillr Posted August 28, 2007 Author Report Share Posted August 28, 2007 Thanks guys. That's why I like this site. I can find out from others mistakes without having to make them on my own! Quote Link to comment Share on other sites More sharing options...
One Sock Posted August 31, 2007 Report Share Posted August 31, 2007 I have seen some baits poured with a metal turkey baster where the molds would not fill completely. It nseemed to work ok but was a little time consuming, I bet it would work better with del's recessed molds as you have more room at the top of the mold Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted August 31, 2007 Report Share Posted August 31, 2007 Ironic that this idea discussion has been going on in two independent threads at the same time. I thought it was a unique idea, turns out it has been tried many times. The conclusion is that it fails because the air movement cools the mould too quickly or keeps it from heating up, the plastic solidifies and blocks the narrow access to the extremities. Someone mentioned the use of a syringe to innitiate the vacuum. If this was operated after the pour was started, it would just pull a cc or two of plastic into the feet and not affect the pre-heat of the mould. This has probably got the best chance of working. The real solution is in the design process, avoiding the bottle necks. But we continue to push the boundaries. Quote Link to comment Share on other sites More sharing options...
