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Core Shot - Laminate - Swirl

I just finished machining my first injection mold the other day, and have various supplies ordered to experiment with.

Based on reading various threads I think I already made one mistake with my prototype. I don't think I have enough reservoir built in to account for shrinkage during cooling. Not that big of a deal to fix though I think. The first one was a prototype to figure out how to machine the mold. I figured I would run into some issues with this first one.

Upon reading the various manufacturers websites it seems you are supposed to get a decent laminate bait by just taking to two injectors with nozzles to match or a mating manifold and injecting the liquid plastic side by side into the mold. 1. Does that give a decent uniform Laminate? 2. How would you make a laminate that is other than 50/50? Just use two different diameter injectors? 3. Why doesn't it swirl when you do that? Particularly in a detailed mold?

Core Shot. Another site I read says you can get a core shot affect by just filling the mold with your main color and then shooting in a different color. How does that work? If that doesn't work, how about using a basting syringe, inserting it into the mold and then withrdrawing it as you inject plastic in the core of the bait?

If the laminate method listed above does not swirl, how do you get swirl pattern baits?

 Bob
Apr 23
2010
Two injectors makes laminates. Usually injecting into the sprue, one on each side of the parting line. Almost impossible to use two different nozzle sizes and get non-50/50, because the injection stroke would be different, unless you also had different diameter injection pumps. Projections that come into the flow of the plastic more than about 40% of the diameter will cause mottling more than swirling. Swirl is done with a 'corkscrew' type vane in the sprue or at the nozzle. RichZ
Apr 23
Thanks Rich. I was looking at some of the dual injector manifolds. I could make one easily enough. Maybe make it in two pieces just like a mold so it can be unbolted and cleaned out easily. I ordered a cheap injector so I can see what kind of O-ring they use. I imagine its probably teflon. Then I'll just turn my own injectors in various sizes to play with on the lathe. Hmmm... might be a good excuse to get a rotary chuck for the mill. LOL. Bob
Apr 23
Well, if all goes well I should be doing some pouring today or Sunday. I'll start with the basics of course. (and since I only have one injector so far) I do have some aluminum tube and rod to make some more, but that takes time. Now I am experimenting (on paper) with making an injector to drop into a caulking gun for easier one handed operation. Bob
Apr 30
   
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