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Dave Rennie

Home Made Injector

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Thank you very much!

 

If I vented up, would I be better having each vent going up the sides into one wider canal, or individual vents reaching the top of the mold?

 

Regarding the vent on the paddle tail, I understand about fluid following the path of least resistance, but would air pockets be trapped in the bottom part of the paddle, hence the vent being better placed at the bottom of the tail? Or am I wrong in thinking that?

 

Thanks

Dave

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I like how youve made use of every inch of space.. And making many different baits in one mold, why not?.. Less time spent making multiple molds.. Great idea

First problem i see is trying to shoot one cavity through another... The plastic will flow through the small passages, but as it thins out it will cool, blocking the passage off and leaving the one behind it void

I was looking at your picture sideways.. I see the set up now

Couple more problems though...

The mold is vertical, but the cavities sit horizontal.. Air bubbles could still be trapped this way

All the vents lead strait out, you may get the bottom cavities filled but then all your plastic will run out the vents instead of up the mold

My suggestion (and what i thought i saw when i first looked at the picture), inject each cavity separately.. That would take all the guess work out of it

Vacu-vent is an option too, with a little creative design!

Edited by JRammit
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attachicon.gif20150915_091004_zpshjs6x9fj.JPGattachicon.gif20150915_091024_zpsw3mccop9.JPG my injector

Roger, that's using your noggin and thinking outside the box! Is that a jerky shooter? My only problem with it is how do you preheat it? I have to preheat my injector or it will clog terribly. Maybe you load it differently. Share with us how you use it and any problems you had to overcome.

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J, Top down single cavity inject has been one of the worst layouts for me. Side inject works ok for many designs if there are vents at the high points on the high side. Bottom inject with cavities vertical has been the most consistent layout for me, but it wastes metal and plastic for small cavity count molds.

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Roger, that's using your noggin and thinking outside the box! Is that a jerky shooter? My only problem with it is how do you preheat it? I have to preheat my injector or it will clog terribly. Maybe you load it differently. Share with us how you use it and any problems you had to overcome.

I sometimes heat it up in the winter, just using a lamp, the exit hole is pretty good size , so it rarely clogs. I load by pouring the plastic in the barrel, never had any problems

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Bob, thats odd.. Seems the most simple solution, but you are the expert so i wouldnt question it

I havnt tried the side inject.. Dave R, it might be worth a go, but i still think the vents would cause you trouble

So which floats on the other... air vs plastic. Where does it go when you force plastic into a mold. Plan for it. Doesn't always work the way you think, but for the most part air floats on plastic.

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photo.jpg

 

This was my plan for my first 2 part mold, but now this vacuum idea has got me thinking that it could be incorporated.

 

Made of RTV, this will be filled with super soft plastisol for UL and dropshot lures, and to make super soft tails for bigger shads.

 

The pink lines are air vents.

 

Will this idea work?

 

Thanks

Dave

Here are my thoughts. Unless you vent the top of each bait there will be no vents when the plastic hits the the ones on the end. You need vents on the top of each bait. The nose to tail baits will not fill because by the time you get the plastic through the second gate it will not be hot enough to continue flowing. I have mostly top fill swim bait molds and have no problem filling them unless there's no vents at the top.
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Thanks for all the replies.

 

Bottom pour makes sense to me considering trapped air will escape easier up than down or sideways.

 

So how about this idea. Again, the pink lines are the vents.

Is it a good or bad idea having the vents form into a wider channel like illustrated?

 

Thanks

Dave

 

 

photo.jpg
 
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Thanks Dave,

 

So it's no problem that the individual vents run into a wider vent channel and up to the top?

 

If I was to have the paddle tails and V tails faced down rather than on their side, would a single vent in the middle of the tail be sufficient to vent all air, or will air still be trapped in the bottom of the tail?

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Thanks Dave, 

 

I was considering using 0.8mm spinner wire for the narrow vents, I'll position the lure masters so that these vents are as short as possible.

 

Now, to throw another element of trickiness into the mix...

I've just bought the gear to cast my own jig heads from pewter.

My plan is to make jig heads in the shape of the lure head using high temp RTV molds. (pic A)

 

So, If I wanted to pour the plastisol molds with my jig heads already inserted, would I be best positioning the head or tail next to the sprue. (pic B or C)?

 

 

photo.jpg
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This is why bottom pouring is the best idea.

Dave

I made a bottom shoot mold once.. Where i fill the tube, insert the plunger, flip and push..... Thought all the air would push up out of the mold, didnt work... Looking back, it could have been the air trapped between the plunger

Dave R.. I like the new drawing too, as long as the vents in the bottom tail cavity are long and thin enough, the rest should fill..... This is quite the project for your first 2 piece mold!

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This is why bottom pouring is the best idea.

Dave

 

Just be aware that the biggest danger of injecting a top or side inject mold from the bottom is if you slip you will shoot molten plastic all over the hand holding the mold.  I've got a wood worker's vise bolted to my pouring bench for testing any problem molds so my hands are not in the path of destruction.  I stand as far back as I can work safely so if something goes wrong it won't run down my pants legs either.  After the mold is full I just stand there and hold it for a good minute to make sure the mold sprue won't drip on me either.  I would note that this is something I only do when testing a mold that doesn't fill right to see if syringing it will fix the problem.  If it fixes the problem I recut it as a bottom inject mold like this.  

 

http://www.tackleunderground.com/community/gallery/image/8535-flipping-grub/

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I am not an injection expert, either, but I would offer a suggestion.

Having all those cavities in one mold looks very complicated.  Solving the venting is fun, but you might wind up with a mold that won't shoot.

Why not make three separate molds instead, so you know they'll shoot?

I see your point Mark, but if something is a challenge, it's more fun.

For me, I enjoy making lures and tackle as much if not more than the fishing itself.

It's good brain exercise.

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