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Dearmitt1976

Mold Problems

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I recently purchased a ring swimbait mold and I'm having issues with the ring not completely filling, the always have little chunks out of the rings. I inject it with two other molds and have positioned it first, second and third and have had no issues with the other molds. Any suggestions on what could be causing this? My plastic is always poured at 350. Thanks in advanced for any help.

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You said pouring,then shooting. Which is it?? You also stated you used 225-230 degree plastisol.I'd check your temperature equipment. I can shoot 280-290 degree plastisol from a heated injector but not 225-230.

 

Put you mold in a vise and tilt the entrance of the mold upward. As suggested earlier,just let the weight of your hand push the injector downward-slowly and hold for 5 seconds.Top off your mold as the plastisol receeds

 

Are you using new plastisol or used plastisol?

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I inject the plastic and 325 not 225 just a typo.

I'm using new plastic as well

Injector tip- Pull the plunger all the way back( w/ the tip of the injector off.) Check the top of your injector(behind the plunger for pieces of cured plastisol & remove if necessary.) Spray the inside of the injector w/ PAM then depress the plunger all the way, expelling all the old plastic remnants and PAM. Wipe off the "O" ring or quad ring,which ever is in your injector.Now you have a smooth,operating injector.

 

Using an UN-heated injector CAN/MAY lead to the internal plastisol cooling off. If you try and compensate by over-heating in your microwave, that can/may lead to other problems.

 

Note to Frank- You're successful w/ you non heated deal and that's great. Not trying to start a heated/non-heated injector war again. I personally will not work w/ out a heated injector system.

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I let my injector tip sit in the hot plastic for 20+- seconds to preheat it, then draw and expel some plastic, before refilling the injector and shooting.

I do not shoot a lot of big molds at once, so I don't know if that will work for multiple molds, but I works for the six single cavity skirt molds I shoot at the same time, and for the five cavity wooly hawg craw injection mold I made.

Edited by mark poulson
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This is how I pre-heat my injector and molds while warming up my shop I have a forced hot air furnace with a 6" pipe coming through the wall into the shop. When I first fire up I put the molds-injector in this pipe for a couple of minutes it doesn't take long. I was shooting some tubes today and decided at the last minute to shoot a drop shot worm mold without heating it first. only filled 1 of the five tails of these baits, warmed up the mold reheated the plastic, and the second shot came out great  

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Looks like air entrapment to me. Ring type molds are a bugger because it is hard to vent out all of the air in the mold when you shoot them just because the nature of how the mold is cut. How do you orient the mold when you shoot it? It would be ideal if you shot the mold with the parting line (the seam on the bait where the two halves of the mold come together) is in the north/south position. This allows any air to rise to the top as you shoot the mold and be vented out. If the parting line is not in the north/south position but instead in a east/west position the air will rise to the top of the rings and become trapped with nowhere to go. Using some additional hand pressure when you shoot could help reduce the incomplete rings but not as much as proper venting.  

Edited by McLuvin175
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Looking at the pics - it seems like you're trapping air away from the vents.  I think there are many suggestions above to try - I'd also recommend one easy one..... shoot the mold on a slight angle instead of straight up and down (say 20 or 30 degree tilt).... I have a few molds that seem to fill better when clamped in my vice on a slight angle... theory being the plastic fills "down" in the mold first then pushes the air up/out as it fills..... on a mold held perfectly vertical there is no "up" for the air to seek as it fills and trap in the ribs areas. 

 

  Hope this makes sense.

 

     J.

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