Hand pour into Injection

[kipbass]

I wanted to make my 5" stick bait into an injection mold. I have already drilled out the pour spouts to 5/8 size to allow for the injector. That went fine.
The mold only has one vent per cavity at the tail. When I inject, I feel back pressure and think the mold is filled, I even top off the sprue. Some of the baits end of hollow or missing for the top half only. If I need to cut in some more vents, where should I start?

[Jason]

Can you post a picture of the mold and one of the vents?  It would also help to see a bait next to a ruler.

Jason

[ghostbaits]

What you need is a piece to put over your mold that allows you to inject all four cavities from one sprue.

If you head over to TU, you can see an example as it will alleviate your issues. I believe those guys did not even drill out thier sprues.

Basically, it is a cap that you can put on top of your mold with a single port on the top of for your injector. I suspect that with that, you will have enough air escape and enough reserve plastic so that you do not get any more half baits.

If you think you need vents, look over some of the injection stick molds on line and mimic some of their vent cuts.

Jim

[andrewlamberson]

I did the same thing to one of my curl tail grub hand pour molds and I found that I had to keep the temp of my plastic high (300+) for it to mold consistently. I thought it was because the mold was cold... I used to pour the center two baits first...then the outer two...or the plastic set too fast and blocked off the mold (when I hand poured).

I also have to inject very slowly!

[firetiger]

I tried the cap thing that Jim mentioned.  It worked great.  No drilling involved.

[kipbass]

Can you post a picture of the mold and one of the vents?  It would also help to see a bait next to a ruler.

Jason

Jason, Are you able to tell anything with these pics? Or do I need to take a few more?

[kipbass]

What you need is a piece to put over your mold that allows you to inject all four cavities from one sprue.

If you head over to TU, you can see an example as it will alleviate your issues. I believe those guys did not even drill out their sprues.

Basically, it is a cap that you can put on top of your mold with a single port on the top of for your injector. I suspect that with that, you will have enough air escape and enough reserve plastic so that you do not get any more half baits.

If you think you need vents, look over some of the injection stick molds on line and mimic some of their vent cuts.

Jim

Looking at one now on another site, my mold ends at the tail to abruptly. The other mold has more aluminum and the air vent starts thin then gets bigger..and the other is vented coming off the sprue, but that's not an issue since each cavity is a single sprue. maybe a then vent connecting all the egg sacks?

[Jason]

I would be really careful connecting baits with vents.  Depending on the bait and other venting it can push air from one bait into the next.  You may be able to do this with this one since you will be filling them one at a time - it would push to the empty cavity.  Just something to consider.

I would put a vent from top to bottom between the baits.  Then connect the middle ones to it and the outer ones to the outside of the mold.  Start with one at the top, and add more down the bait as needed.

Let us know how it works out.

Jason

[Frank]

Wish there was an easy way of explaining what is going on but here it goes from my experiance. When injecting baits from the top like you are causes it to fill like you are hand pouring but when you get half way it causes a bubble at the top. Everyone wants the injector to seal to the mating part, but I have better luck with sloppy fits. Jacobs injector with a tapered tip works best for the job you are trying to achieve, it has enough air leaking to prevent the bubble on the top. If you must vent, it needs to be as close to the top as possible and from both sides of the cavity of the mold. This is because you will close one off when you inject the neighboring cavity. I was the one who posted the one piece cap that went over all the sprues to convert hand pours to injection. Frank
 

[kipbass]

Well cutting my own vents into the mold didn't work, the baits still don't inject. Oh well. It's still useable as a hand pour, so that's what I'll do.