Dent in 7 inch swimbaits

[Munro76]

Hi guys. Im having trouble with dents in the side of the head of my swimbaits. It is a basstackle 6004 swimbait mold. I have tried shooting at lower temp, holding injector pressure for up to 1 minute, topping up the sprue etc but it keeps happening to about 50% of the baits. Any help would be appreciated. Thanks.

[Walking Dead]

I have that mold and an extender fixed that problem. Even the extender requires a top off. That thing sucks down allot of plastic.

[McLuvin175]

If your sprue or gate keep freezing off and not allowing molten plastic to fill the cavity you might need an additional step. One other possible solution is to actually de-mold the bait as soon as you are able to handle it without tearing it up or deforming it. In the past I have had issues with denting on large baits. Through lots of trial and error pulling them out of the mold much earlier than i would have normally and placing into a water bath yielded good results. I think this is as a result of the way baits contract as they cool. While in the mold the baits tend to create a vacuum as it shrinks.  If the sprue of gate is frozen off then the shrinkage cannot be accommodated with more pressure or time injecting. The bait wanting to stick to the cavity walls resists until the vacuum is great enough to find the weak spot (the thickest part as it is usually still molten) and there goes the dent. As the bait cools in a water bath it does so evenly and doesn't have the cavity walls to contend with thus often eliminating the dent. The addition of some mold release may be needed if this step is necessary as it will aid in de-molding a bait that still has a molten center. Just a thought.

[Frank]

I have a bunch of those molds and as said before demold early and set in water. Hold it by the tail so the soft plastic will flow to the head and drop head first. Also keep your temps as low as possible like 300 hold pressure for about 30 seconds. This way marks for me but some still get dents once in awhile.  Make sure your water tub or bucket does not get to crowded as they will cool bent sometimes. 

[Munro76]

Thankyou all for the suggestions. My next step was a sprue extender any idea where i would find a couple? I will also give the water bath a go that sounds like a good option also. Thanks

[wallyc14]

You can make them or buy them

the easy way is a 5/8 copper plumbing coupling for 1/2 inch plumbing pipe which is 5/8 outside diameter a small piece of pipe and a coupling is all a small single cavity needs . You can make longer if needed I’ll post a picture soon as I can

[wallyc14]

[wallyc14]

These pics are using a little different type of plumbing fitting for copper . Same size though . You can make tons for them for cheap or free if your a plumber! :-)

[Frank]

With that mold the gate will freeze so no need to extend the Sprue.  It is a big chunk of Plastic and requires different techniques. That Sprue is long enough if the temp are low when shooting. 

[mark poulson]

Would enlarging the gate into the cavity help?

[Frank]

2 hours ago, mark poulson said:

Would enlarging the gate into the cavity help?

I could help but the design now gives you a nice round head. Enlarging it will make it more of a blunt nose. Plastic temp has more to do with it than anything else lower temp and hold pressure for a thirty count, demold  as soon as you can cool in water bath. This technique works on many larger baits. 

[Munro76]

Thanks for the help guys. I tried the sprue extension with copper pipe as wallc14 suggested but as Frank said it is freezing  at the gate. I tried injecting and then inserting a piece of thin wire in and out of the gate while keeping the plastic in the sprue soft with a butane torch. This worked well but is a bit of mucking around involved. I will try injecting at lower temp and demolding and placing in water. Thanks everyone.