Bobby Saffel Posted April 16, 2012 Report Share Posted April 16, 2012 I am having some problems with dents in the nose of my injection flukes. The mold is del's 5 inch injection fluke mold. When I first start they will be good then after about 3 or 4 shoots then they start denting in the nose. I have varied the temp from 350 down to 310 and it still does it. I have also varied the about of salt, 2 tbps per cup of plastic for mf medium plastic and 1 tbps per cup of plastic for mf soft sinking plastic. I'm not sure whats going on. I have a 4.2 BT Bomb and double the salt mixtures and I have never had one dent. Don't know exactly whats going on. Any help would be great. Quote Link to comment Share on other sites More sharing options...
Cormorant Lures Posted April 16, 2012 Report Share Posted April 16, 2012 Definately sounds like the dents are coming from "suckback" due to not enough plastic in the sprue... As your mold gets hotter, you will notice that your sprues will become almost completely hollow at times... As your plastic starts to cool inside the cavity of the mold, it pulls in plastic from the sprue to fill in the remainder of the cavity... If you are not "topping off" your sprue, the cooling of your bait will start to suck in air and not plastic... I believe this is the process that is causing the dent(s) in the nose of your flukes... Quote Link to comment Share on other sites More sharing options...
mark poulson Posted April 16, 2012 Report Share Posted April 16, 2012 I get them when I inject too fast. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 16, 2012 Author Report Share Posted April 16, 2012 I have noticed a small hole hole at times in the sprue at times. That might be the problem, I will try that. Like I said, I get the best flukes out of the first 3 or 4 shoots before the dents start showing. Could I fill the mold up and keep pressure with what's left in the injector for about 30 seconds or so? Would that help "suckback" from happening? Quote Link to comment Share on other sites More sharing options...
gone2long Posted April 16, 2012 Report Share Posted April 16, 2012 As a rule I always do a 5 second count before pulling the injector then I purge some plastic from the injector into the sprue to top off. Seams that when the mold is still cool that the faster set time due to the cooler mold prevents dents but as the mold heats up it seams to draw more from the sprue. Quote Link to comment Share on other sites More sharing options...
Cormorant Lures Posted April 16, 2012 Report Share Posted April 16, 2012 As a rule I always do a 5 second count before pulling the injector then I purge some plastic from the injector into the sprue to top off. Seams that when the mold is still cool that the faster set time due to the cooler mold prevents dents but as the mold heats up it seams to draw more from the sprue. x2 Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 16, 2012 Author Report Share Posted April 16, 2012 ok. I will try topping off the sprue. That is something I don't do. I just fill it up and hold pressure for about 20 seconds and then take the injector off and clean it out while i'm waiting for the mold to cool, then take the flukes out. Quote Link to comment Share on other sites More sharing options...
J lure Posted April 17, 2012 Report Share Posted April 17, 2012 It will also help is your mold is preheated, throw it in the oven for a few minutes but not too long until you get a few pours in. Also it will help once you get a few good lures in pay attention and mark the spot on your injector rod that way it will come out the same each time. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 Ok guys, I really need some help. I have tried everything suggested today and nothing seemed to work. I just got off the phone with del and he gave me some suggestions. He said stir my plastic very carefully and watch for bubbles. Maybe I'm not sure exactly what he calls bubbles, but I didn't see any after stirring. Before I would stir, I would see small clusters of bubbles, but after stirring they are gone. He also said to not apply any pressure after the mold is full. When it's full then stop. i tried that, but no luck. I did top it off after pulling the injector off. He didn't say do or don't about that. He also said not to heat injector or mold. I didn't do that, but I had been injecting baits before I talked to him so when I tried all of his suggestions the mold and injector was hot. I have a few pictures of one of the worse dents I have gotten. This is driving me crazy. Please help me. Quote Link to comment Share on other sites More sharing options...
SHK Posted April 19, 2012 Report Share Posted April 19, 2012 the problem you are having comes from the bait cooling and shrinking. in our application (Hand injecting) we need enough plastic to stay hot so the bait can draw from the runner. that small "nipple" off the runner that the bait connects to is more than likely solidifying before the bait, which then leaves the bait with nothing to draw from and thus denting. i am going through this issue right now with a similar bait that i had custom cut. what i am trying is opening up that "nipple" area to hold more plastic and hopefully keep it hot long enough for the bait to cool. i think the only thing you can do in this situation is to try a stiffer plastic. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 Ok, I will try stiffing up my bait. Could I make the nipple larger? I don't want to ruin the mold, but if there is a pretty good change it will help with my problem, I will be willing to try it. Right now about 70% of my flukes have dents in the nose. I'm ready to turn it into scrap metal...just joking, but frustrating opening the mold and not knowing what your going to get. Quote Link to comment Share on other sites More sharing options...
smallmouthaholic Posted April 19, 2012 Report Share Posted April 19, 2012 Ok, I will try stiffing up my bait. Could I make the nipple larger? I don't want to ruin the mold, but if there is a pretty good change it will help with my problem, I will be willing to try it. Right now about 70% of my flukes have dents in the nose. I'm ready to turn it into scrap metal...just joking, but frustrating opening the mold and not knowing what your going to get. Inject slower w/ cooler plastisol and hold the injector in place w/slight pressure for 10 seconds. Are you monitoring your plastisol temps. w/an Infared thermometer? BTW- is this a CNC mold your working with ? Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 Yes I'm using an infrared temp gun and a cbc mold. I will try both suggestions when I get home. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 Cnc I mean. I've been working 7-12s for the past two weeks. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 (edited) Would anyone suggest using some hardener? I am having more problems with mf soft sinking plastic. My flukes with sinking soft are a little bit softer than zoom flukes. Maybe that's the problem. Edited April 19, 2012 by n5ozb Quote Link to comment Share on other sites More sharing options...
smallmouthaholic Posted April 19, 2012 Report Share Posted April 19, 2012 Yes I'm using an infrared temp gun and a cbc mold. What temperatures have you been injecting at? Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 From 350 to 310 Quote Link to comment Share on other sites More sharing options...
smallmouthaholic Posted April 19, 2012 Report Share Posted April 19, 2012 (edited) From 350 to 310 Is it safe to assume you're using an injection mold that is vented properly? Slow and easy pressure on the injector( to allow the air to escape) @ 310-325 w/ a med-hard plastisol should help. Spray the inside of your injector w/ PAM cooking spray to permit the plunger to slide easily w/ less pressure.Upon completion,hold pressure on the injector for 10 seconds then top of the spue entrances w/ hot,liquid plastisol( as suggected before) Edited April 19, 2012 by smallmouthaholic Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 I would assume the mold is vented properly. It is one of del-mart's injection molds. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted April 19, 2012 Report Share Posted April 19, 2012 It is my understanding that the colors we use with plastisol act as a softener, too. Could adding more color actually make the plastisol softer, and more prone to shrinkage denting? i guess you could test the idea by pouring a batch of clear flukes. You can always reuse them in another pour, and that might help you see if the coloring is the culprit. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 19, 2012 Author Report Share Posted April 19, 2012 I ordered some hardener today. I did not have any. I will try the clear fluke idea. I will also try adding more salt too. I want the fall a little faster. Maybe I will kill two birds with one stone. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 20, 2012 Author Report Share Posted April 20, 2012 Ok so I put more salt in my baits so they would stiffen up and get the fall a little faster. That didn't help much but I did notice after I stirred I let it sit for about 30 seconds and a lot of bubbles popped. Could this be the problem? Quote Link to comment Share on other sites More sharing options...
SHK Posted April 20, 2012 Report Share Posted April 20, 2012 in short, no the problem you are having comes from the bait cooling and shrinking and not having any plastic to draw from as it shrinks. i think the only thing you can do in this situation is to try a stiffer plastic. Quote Link to comment Share on other sites More sharing options...
Bobby Saffel Posted April 20, 2012 Author Report Share Posted April 20, 2012 Ok then. My hardener is coming via snail mail and will be here tomorrow. I am using 1 cup of mf soft sinking plastic, 4 teaspoons of floured salt. How much hardener would you recommend Quote Link to comment Share on other sites More sharing options...
smallmouthaholic Posted April 21, 2012 Report Share Posted April 21, 2012 Ok then. My hardener is coming via snail mail and will be here tomorrow. I am using 1 cup of mf soft sinking plastic, 4 teaspoons of floured salt. How much hardener would you recommend Try 1 teaspoon of hardener to 1 cup of plastison. Hardener must be added and stirred into cold plastisol before heating Quote Link to comment Share on other sites More sharing options...
