mark poulson Posted January 28, 2012 Report Share Posted January 28, 2012 I'm a hobby pourer, and I make my own injection molds out of POP, sealed with D2T. I use a Cajun injector, that I wrapped in plumbing pipe insulation (thank you Frank). I am getting incomplete pours on a mold that poured great when I made it. It's inconsistent. Sometimes four of the six will pour fine, sometimes all six will be messed up. It's a beaver-style mold, and the claws always pour fine. It's the bodies the sometimes wind up with voids and air bubbles. I typically pour around 325 degrees, so I can reheat without scorching, and I think that may be too cool, but the plastic is still hot enough to inject the one aluminum mold I have (thank you Bob) after I've done the POP mold. I'm wondering if I need to add vents next to the bodies, too. I was hoping you guys might be able to help. It doesn't seem to matter what brand of plastic I use. Quote Link to comment Share on other sites More sharing options...
SHK Posted January 28, 2012 Report Share Posted January 28, 2012 it could be a few different things, i would like to see a pic of the mold. if you dont want to show the cavity that is fine, i just want to see the sprue area and runner. Quote Link to comment Share on other sites More sharing options...
Jig Man Posted January 28, 2012 Report Share Posted January 28, 2012 When I get incomplete injections in my mulitcavity molds it is normall due to injecting too fast. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted January 28, 2012 Author Report Share Posted January 28, 2012 (edited) I can't post pictures. I do have trouble injecting slowly with my injector, because the nozzle gets clogged. I left 3/8" of the original needle on it when I cut it down for plastics. I will shorten it, and see if it lets me inject more slowly. Am I injecting hot enough? Edited January 28, 2012 by mark poulson Quote Link to comment Share on other sites More sharing options...
Jig Man Posted January 28, 2012 Report Share Posted January 28, 2012 I like my plastic hot so I usually do 350° at least. I add stabilizer for reheats. Quote Link to comment Share on other sites More sharing options...
SHK Posted January 28, 2012 Report Share Posted January 28, 2012 im usually around 300, unless i am shooting very small baits. Quote Link to comment Share on other sites More sharing options...
t-billy Posted January 28, 2012 Report Share Posted January 28, 2012 Try getting your plastic a little hotter first. I can inject most of my molds at310-320 but the plastic has to be at least 340 to get full tails in my ribbontail worm molds. If that doesn't solve it try injecting slower if you can. If that doesnt do it you may need to vent your mold. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted January 29, 2012 Author Report Share Posted January 29, 2012 (edited) Well, I spent the afternoon getting my stuff ready to fish tomorrow, so I didn't try pouring anything. I ran out of gas around 4:30, and decided it was time for a cup of coffee. I'm beat! But I did cut in some vents, midway up on the bodies, and deepen the sprue holes. If I have time tomorrow afternoon I'll give it a go. I don't have a problem with the tails filling. They and the side paddles fill fine, and the lower part of the main body, too. It's midway up on the body that the voids begin appearing. I'll report back as soon as I have results to report. Thanks for the help. Edited January 29, 2012 by mark poulson Quote Link to comment Share on other sites More sharing options...
SHK Posted January 29, 2012 Report Share Posted January 29, 2012 thats the reason i wanted to see the sprue, im guessing (without knowing what i want to know) its running out of material while cooling. try injecting slower if you can and keep it topped up. Quote Link to comment Share on other sites More sharing options...
carolinamike Posted January 29, 2012 Report Share Posted January 29, 2012 Mark I think a couple of people have already hit the problem on the head. I think a slow steady even pressure is going to be your biggest problem solver. The thing about doing injection by hand is like when you start getting close to the end you kind of speed up, I guess it just happens by nature. Kind of like if you're drinking a drink when you feel like there's just a little bit left in the glass, you kind of automatically drink it down quick. Just the fact that you're having an air bubble tells me that somewhere or another you're encapsulating the air, so it's either got to be not enough venting to let the air out or the plastic moving faster than the air can get out. Quote Link to comment Share on other sites More sharing options...
powerworm Posted January 29, 2012 Report Share Posted January 29, 2012 if its on the sides of the body and an aluminum mold i took all of my beaver molds i used to have to a local machine shop and he took a 1/2" flat tool in his machine and cut .001 around the edges of the bodies and this allowed the bodies to completely fill. Quote Link to comment Share on other sites More sharing options...
SHK Posted January 29, 2012 Report Share Posted January 29, 2012 I'm a hobby pourer, and I make my own injection molds out of POP, sealed with D2T. I use a Cajun injector, that I wrapped in plumbing pipe insulation (thank you Frank). I am getting incomplete pours on a mold that poured great when I made it. It's inconsistent. Sometimes four of the six will pour fine, sometimes all six will be messed up. It's a beaver-style mold, and the claws always pour fine. It's the bodies the sometimes wind up with voids and air bubbles. I typically pour around 325 degrees, so I can reheat without scorching, and I think that may be too cool, but the plastic is still hot enough to inject the one aluminum mold I have (thank you Bob) after I've done the POP mold. I'm wondering if I need to add vents next to the bodies, too. I was hoping you guys might be able to help. It doesn't seem to matter what brand of plastic I use. little reading helps. he is having troubles with POP molds. Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted January 30, 2012 Report Share Posted January 30, 2012 I also make my own injection molds (POP and Renshape). I've had had issues with voids and sink/shrink issues on a few baits I've made located on the widest parts of the bodies... while it slows things down from a production standpoint, I now hand pour a little plastic in the bodies, close the mold and shoot. Doing this eliminated all of the issues I was having and after figuring it out I started doing a different color for the hand pour and the baits look great, basically look like a laminate sandwich. Not sure if this technique would help you, but if the voids are most notable in the bodies, it may be worth a try. J. Quote Link to comment Share on other sites More sharing options...
