How hot?

[Pooch]

When you fellows are pouring plastic, how hot do you get the liquid then pour? I shoot for 350 degrees.

How much pressure do you apply to the plunger? If I go "light" on pressure filling the mold, I sometimes get small air bubbles in the finished worm.

For some reason today I'm getting a lot of "flash" between the cavities. I'm sure the fish don't care, but I do.

Pooch

[Canga~]

i dont usually measure temps after the initial heating to 350, but i would guess i usually pour between 320 and 330, i inject pretty slowly most of the time, but it depends on the mold, and the venting in the mold. some molds like to be injected faster than others, just gotta experiment with it to find the right speed and temp.

flash likely has to do with clamp pressure, if its too light the plastic can get between the sides, thats the only time i get flash.

[Bill Krejca]

Yeah, clamp pressure seems a likely cause, used to do that back when I did plastic. Could also be the liquid is too hot, so it flows into the crack more easily?

Bill

[Spoon]

I have 4 molds and they all behave differently regarding pouring temps, clamp pressure and even clamp location. Seems when I clamp 3 molds together the best results always seem to be the middle mold. I'm starting to think it could be my clamps, they seem to have a small clamping surface. Might try some steel bar stock when clamping to try to spread pressure more evenly across the face of the molds. That or I'll invest in better clamps.

[Kevin23]

When I poured, i always used an extra mold or just piece of alum stock on each end when clamping. It evens out the clamp pressure and acts as a heat sink (can use them to keep molds hot, or to cool them by switching out the ends often).

Flashing could be uneven clamping, plastic too hot, too much pressure, or a bad mold. I always shot with light pressure, dropping the plunger with the weight of my hand plus a little extra. Slow filling will help with air bubbles. Air voids could be the plastic being too hot, too much shrinkage in the plastic, or just bad mold again. Adding salt usually helps a lot with dents/voids. Can't help on temp, we didn't use fancy thermometers too much back then, was more on feel and consistency in the mixing pots.