Serious Help Needed

[Psychotically Obsessed]

Been @ it a while, made molds of all kinds of materials incl, M-polymer, Resin, RTV and even POP. All good and well, but and here's the thing that drives me NUTS. I keep getting either a huge indent or a air pocket trapped (no indentation) in my swimbaits (right underneath the sprue).

So how do I get rid of this, must still take pics of my molds, perhaps the problem lies there. Any other advice would be highly appreciated

[SnakeHead]

Can you add a picture of the mold?

[Husky]

Been @ it a while, made molds of all kinds of materials incl, M-polymer, Resin, RTV and even POP. All good and well, but and here's the thing that drives me NUTS. I keep getting either a huge indent or a air pocket trapped (no indentation) in my swimbaits (right underneath the sprue).

So how do I get rid of this, must still take pics of my molds, perhaps the problem lies there. Any other advice would be highly appreciated

I remedied that problem by making the sprue larger so that the plastic flows in quicker and that the spew reservoir holds enough hot reserve plastic to supply the casting with ample plastic to offset the shrinkage caused by cooling. Here's a view of what I did.

http://www.tackleunderground.com/community/topic/19705-two-part-pop-molds-for-swim-baits/page__p__147363__fromsearch__1#entry147363

Edited June 27, 2010 by Husky

[powerworm]

your sprue area does not have sufficient volume to allow the plastic to fully expand and fill that void thus the dents i imagine

[Psychotically Obsessed]

Can you add a picture of the mold?

Will try and do that tomorrow but will have to paint the flat surface of the mold black so as to get a better picture of the sprue and the vents.

[VANNDALIZER]

You could cut a small vent from the troubled area to the outside of the mold.

[Psychotically Obsessed]

I remedied that problem by making the sprue larger so that the plastic flows in quicker and that the spew reservoir holds enough hot reserve plastic to supply the casting with ample plastic to offset the shrinkage caused by cooling. Here's a view of what I did.

http://www.tackleund...http://www.tackleunderground.com/community/topic/19705-two-part-pop-molds-for-swim-baits/page__p__147363__fromsearch__1#entry147363

I thought as much but also had an idea of heating the mold prioir, but this only seemed to cause more trapped air pockets as opposed to having more solid but dented lures. will also give this a try in the morning

[Psychotically Obsessed]

You could cut a small vent from the troubled area to the outside of the mold.

there's roughly ten vents all over some even right next to the sprue but these get clogged up as I inject the plastic which is good as no air gets trapped, the problem is the cooling down phase, if the sprue is clogged and seeming cooled down before the plastic inside is cooled it tends to (if the mold is polished) pull away from the side of the mold and then forms a dent in the lure, if the mold is rough and not shiny it causes the same volume but an air bubble in the lure without any indetation on the outer of the lure.

[Delw]

Try purging your injector before you shoot the mold, you can be actually shooting air into the molds( your were saying you had 10 vents)

to purger your injector suck up the plastic and hold the injector at a 60º angle, (spin it if you can) then slowly push the handle up till you get only plastic coming out, Kinda like what the doc does before he sticks than needle in ya.

The other problem can be you have air bubbles in your plastic if you do than thats going to cause you problems as well

Delw