Home Made Injector

[Dave Rennie]

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

[JRammit]

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 September 16, 2015 by JRammit

[Apdriver]

20150915_091004_zpshjs6x9fj.JPG20150915_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.

[JRammit]

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

[Travis]

Like the creativity but in my opinion you are going to have all sorts of issues with that mold.  I would seriously reconsider your plan of attack.  I would expect over 80% failure rate (incomplete fills, trapped air, etc...).  

[Roger Linnell]

That looks like a really clever setup.  Did you adapt an existing caulking gun, or does one come with the alum tube?

It's jerky gun I bought at Cabela's specifically to make into an injector. I did the same thing with cookie dough shooter, another caulk gun style, they are the bees knees

 

 

 

 

i

[Roger Linnell]

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

[Vodkaman]

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.

This is why bottom pouring is the best idea.

Dave

[Frank]

 

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.

[Dave Rennie]

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

 

 

 

[Vodkaman]

Much better. I would say it had a chance.

Dave

[Dave Rennie]

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?

[Vodkaman]

The vent network is a good method. The shorter the narrow vents are, the smaller the diameter can be.

Example - take a long thin straw and blow as hard as possible. Now cut a 1/2" length and blow. Which one was easier?

Dave

[Dave Rennie]

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)?

 

 

[JRammit]

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!

[Dave Rennie]

Thanks JR, I like to jump in head first... and usually make a cock up of things first time.

[Vodkaman]

I like B, but I am not talking from a great deal of experience here. There are guys reading this thread that should have a lot more to say.

DAve

[Dave Rennie]

I like B, but I am not talking from a great deal of experience here. There are guys reading this thread that should have a lot more to say.

DAve

I also fancied B as the winner. Thanks.

[mark poulson]

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?

[Dave Rennie]

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.

[Dave Rennie]

FYI.  Cavity vents only need to be a few thousandths deep.  I tend to go with .002 for blade vents and .003 for point vents.  Then I dump them all into a deeper easier flowing main vent.  

Thanks Bob, are you talking inches there?

What is a blade vent, and what is a point vent please?

[Dave Rennie]

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/

Thanks again.

If all goes to plan, the mold and copper pipe will be contained inside a plastic box held in place with bricks or something similar, and the dowel will push through an almost perfect sized hole in top of the box.

[Dave Rennie]

Blade vents is all around or a large portion of the cavity. Point vent just vents a single point. Yes inches.

Thanks Bob.

[Cub48]

I made a injector out of a shock for a lift gate on a Tahoe. If u know someone in the automotive field have them to save u some we change them often. The piston is aluminun with a oring the bore is smooth, it is design for pressure. i bought some aluminun rod that would fit tight for the tip i put a set screw in it to keep it from coming out. I have not thought about a tip made made of a wooden dowel but that would be a lot easier it has to be tight so it don't leak air. But the only thing would be if u heat your injector like i do the wood would burn. if u keep your injector warm after u shoot u can push out all your plastic and cycle if a couple times and blow the plug out so u don't have to clean it between shots. I used one of these for two years before i bought two from lurecraft. Only reason i changed was the ease of cleaning the injector as i am using dual injector for two colors now. PS, Only one of the shocks will work as the other has a place in the bore it still may work but i did not use it don't know why it has two different shocks but u can see the line in the outside of the shock. Cub48  

 

                                                           

[Dave Rennie]

Thanks Cub,

That's a good idea.

I'll be trying the wooden dowel idea like JR suggested first, as it looks simple. There's a Paul Adams video on YouTube using the same method, and he wraps the end of the dowel in aluminium foil to prevent burning.

I've got a nice design drawn up for the mold now that will hopefully fill all the cavities, I've already made about 10 masters from polymer clay, but have changed my mind on the jig heads that I was going to have in place the mold at time of pouring.

I need a bit of advise on this and will start a new thread soon.