Injection Hole/channel Question

[ipt]

So can anyone shed some insight to me on why all the aluminum molds that are for sale have the injecting hole coming out of the side of the mold (where the 2 molds meet)? instead of just having the hole come through the top of the mold on one 1/2. this would make it so the molds sat flat when you injected them and not on their side easily tipped over.

my 2 ideas could be to create a longer channel for a better sprue. the other would be so the micro venting holes are aligned vertical instead of horizontal.

thanks!

[mark poulson]

I'm no CNC machinist, just a carpenter, but my guess is that it's easier to program in the sprue hole on one half, and then just reverse the instructions for the other half.

Also, having the fill sprue in both halves allows mold maker to connect multiple cavities and inject them all at once.

And having the fill sprue in the edge allows you to clamp a bunch of molds together to pour quantities of the same colored baits.

Lastly, I think it is far easier to strip a plastic bait out of a mold with the sprue in both halves, so it comes out with the bait, instead of have to be pulled through a separate hole that might damage the bait itself.

I only have one aluminum mold (thank you Bob L) but I have lots of two part POP molds in wooden boxes, and they are all edge filled, both the hand pour and the injection. For me, it was a lot easier to make the POP molds and then cut in the fill sprue through the edges afterward.

[Jig Man]

It also makes it easy to do laminates when you are filling from the side.

[johnny438]

I don't hand pour anything I use injection molding machines and of the molds I have had built they inject through the back of the stationary side of the mold on the machine and inject into a runner that runs the legth of the mold and has a small gate opening to each cavity. But these molds also shoot a lot of lures at one time. To do two color baits there are two injection holes one injects in the runner going to the front of the baits and the other coil injects into a runner feeding the tail. There is a pneumatic bar that runs through each cavity that closes the tail from the rest of the lure. One color injects against one side of the bar and the other color injects on the other side seconds after the injection is done the bar moves up and lets the two colors meet and adhere to each other. I know you didn't ask for all this info. but just thought I would share it..

[gcl58]

i have about 8 to 10 molds that i purchased from here and other sites with the same problem, i drilled the bottom plate out to the injection port.

 

drilled and tapped the side port and place a piece of 1/8" alumn plate on the side port with two screws, had no problems injecting from the bottom

[SlowFISH]

Wouldn't you lock the bait in place if the runner/sprue isn't on the parting line?  Granted I assume you can cut the sprue at the bait very quickly and easily and then just pull the bait from the mold and then the runner/sprue from the backside of the mold... but my guess is that process isn't typical of most "molded products" and is probably why you dont see it often.

 

Also agree with Mark.... you'd have to flip and machine from the back whihc takes time, programing and effort..... machineing everything from one side is much easier as well.

 

       J.

[ipt]

i had the injection hole on the top, it was workign just fine, what i did was just  grab the top sprue and pull it straight out, that was snapping it between there and the bait.

 

it seems to work fine, but i did realize that they take up way more real estate when you lay them down flat. when you have multiple molds to pout it works way better on its side.

 

my other observation is the air gaps (if you have any) will be on the flat part of the baits. if you have them on the side, the imperfetions will work their way on the side and be less noticable.

 

conclusion: it works either ways, but in terms of mass production and minimizing flaws, i have converted my molds to side injection.

 

thanks for all the input