Plat 55 Injection Mold?

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Plat 55 Injection Mold?

Postby Booker » Sun May 19, 2019 9:14 am

Hello, one of my open pour molds the fins have about a 75% chance of filling with plastic. I took one on my injectors and when I got to the point when the fins were about to be filled I used the injector to apply pressure. This works 100% of the time but it gets a little messy. This leads me to the idea of creating a plat 55 mold just for injecting.

I make my molds by 3d printing my lures in 2 halves, laying one half on plexiglass and pouring silicone over it, once cured I glue the 2 halves of the lure together and pour the second half of the mold. I'm trying to figure out a way to incorporate the injector port and cooling cavity.

Heres my idea to go about this and I want to see if you guys think there is a better way:

Build the last 5inches of my hand injector in cad software. Keeping the sprue hole the exact size but making the shaft/cylinder 5mm wider. 3dprint in two halves and incorporate it in my normal mold making process mentioned above. After the mold is made, I would insert the injector into the cavity that is slightly bigger than the shaft, fill the mold and lastly fill the 5inch cavity to act as the cooling chamber.

Another thought was to maybe make the mold for the injector separate from the lure mold and somehow key it so it can sit on top of the lure mold.

Any thoughts?

(I've thought about Vac 50 but was told my fins have slightly too big of an undercut )

Unsure if I can share Youtube links here but the video titled "Trans 40 Translucent Mold Making Silicone" shows something similar to my goal. https://www.youtube.com/watch?time_cont ... q0A7-EVxSY
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Re: Plat 55 Injection Mold?

Postby dahlberg » Mon May 20, 2019 5:10 am

That sounds like a possible solution, although maybe a little more complicated than needed. I usually pull the nozzle off my injector and use it as the form which i incorporate into the mold. I'd also consider using a softer mold material like high strength 2 which will bulge slightly under pressure but return to shape when pressure is released. Obviously preheated mold also helps with fin detail.
Good luck with your project!
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Re: Plat 55 Injection Mold?

Postby Booker » Mon May 20, 2019 9:39 am

Thanks for the advice. What would the advantage be to go with a softer mold material?
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Re: Plat 55 Injection Mold?

Postby dahlberg » Mon May 20, 2019 3:24 pm

The undercuts are more likely to expand a little when you pressurize the mold with the injector so the plastic flows into the cracks and undercuts better. After the pressure is off, the mold relaxes and squeezes back to its original dimensions, usually with fins filled.
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Re: Plat 55 Injection Mold?

Postby Booker » Thu Jun 06, 2019 1:34 pm

I made my mold and it turned out great. I just shot the first one and found out I made two of the vent holes way to big and it leaked bad. Is there a way to repair silicone molds? Not just for the vents but for future reference.
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Re: Plat 55 Injection Mold?

Postby dahlberg » Fri Jun 07, 2019 12:05 pm

good question. The only thing that sticks to silicone is silicone, so if you use more silicone for a patch it will work. Plugging a hole or something that's easy to "contain" the silicone you're using for the patch is pretty simple. Other repairs can get a little more complicated.
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Re: Plat 55 Injection Mold?

Postby Booker » Mon Jun 17, 2019 1:24 pm

Ok great thank you! I was able to repair the mold!! Last question I promise lol... What tool is best for precisely cutting the silicone? I'm trying to cut new vent holes using exacto knife, is there something that will give me more consistency?

Almost needs something like the classic cheese cutter with the wire through it but super small.
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Re: Plat 55 Injection Mold?

Postby dahlberg » Tue Jun 18, 2019 5:21 am

No prob with the questions! I'm happy to help if i can. I use thin wall brass tubing from the hobby store to cut vent holes. I sharpen both the outside and inside of the tube with emery paper then just press it thru the silicone. I've got different diameters from half to quarter inch or so.
After youve made a decent smooth hole you can hack out a funnel shape with an exacto knife, being careful not to go too deep so you mar the interior of the mold.
BTW,That was an excellent question.
good luck!
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