Creation Of Injection Mould - Collapsed Baits

[CNC FREAK]

Hi everybody

 

i'm very happy i have found this interesting website ! great stuff

 

i hope somebody could give me some info about my problem.

I have a new cnc machine to make moulds 
For testing i have made an injection mould in composite material, its rock hard and easy cutting.

The surface is smooth and glossy like aluminum.
I use this becaus i have it for free...

But i have a problem.
My shad baits have a "inside bumb" (on one side) its like they are collapsed a little bit

i think a kind of cooling reaction in the mould.

So i tried several  things, i have enough air vents but i can't get it solved.
The mould contains 3 shad baits, the head of the bait is 3/4 " wide

the injection chanel is 1/4"

 

Do u need to heat up the moulds ? i have heated a little but without succes
maybe i should try with making this mould in aluminium but i think the problem would be the same.

 

any help would be great !

 

thanks,
Jonathan
 

[gone2long]

Sounds like the plastic is contracting you need quite a bit of reserve plastic for a 3 cavity mold to prevent it I would increase the diameter of your runner (channel) and make sure your topping of your sprue when the plastic is cooling. Also what size are your gates?

[School Master]

Gon2's dead on it sounds like. Increase the volume of plastic it can draw in after injection. Some people even extend the sprue to create more volume to draw from

[CNC FREAK]

thanks for the answers

Gon2,

in the start all the channels where 1/4"

the "head channel" and the connections to the baits are also 1/4"

BUT i have made the channels DOUBLE in size, problem stays !

the channels are now 1/2", the sprue is a little bit smaller - about 3/8"

the first bait is near the injection hole, this bait is better than the other ones, this one has no "collapsion" on the side.

i have made an extra room at the head of the bait, its quite large but i still have the problem

i'm getting crazy of it

if i need to make the channels MORE bigger than there is a lot of "channel plastic" in this mould !

i need to think very hard how to solve this,it needs to be fixed, thats for sure, i wont give up !!!!

lets do another test

Edited March 6, 2014 by CNC FREAK

[gone2long]

From the pic it sure looks like your gates are very small, the plastic is more than likely seizing up preventing the normal curing process which includes the still liquid plastic being drawn from your runner kinda like a reservoir.

[CNC FREAK]

Thanks Bob for the picture !i understand perfectly

HERE THE GOOD NEWS

i made the runner bigger and problem is solved !!! thanks 

bait nr 2 and 3 are perfect
bait nr 1, the nearest at the injection hole has a small collapse but i think i know how to fix it

i did not expected that i need that big runner when i started drawing this mould

has anyone expierence with "Corian" , "Hi Macs" composite material ?
i have made some awesome moulds, smooth surface and much higher cutting speeds than aluminum.

Its expensive but i get some waste material for free.
I spray some silicone oil in the mould and they come smooth and glossy out of the mould.
The advantage of this material is that u can SAND it easy and POLISH it
If i need a thick mould i glue blocks perfectly on each other without seeing this, after milling it looks like one solid block

 

I was wondering if this mould would work perfect to make laminates, 2 color baits.
With previous test (small runner) bait nr 1 was not perfectly shot in 2 colors, bait nr 2 en 3 perfect 2 colors in the middle.

any advice about 2 color injection would be GREAT. I

So i will make a new mould tomorrow and give it a try !

 

thanks guys
 

[texacan84]

Corain and hi-macs is the same composition, one is just cheaper than the other. I work with all solid surface material at work, corian, hi-macs, livingstone, surrell and a couple of cheaper brands. I use these materials to build counter tops with. From my experience over the last 13 years with it, it's not very heat compatible to much heat will melt the material. I couldn't tell you how many house calls I have made where the customer placed a hot pot or pan on it and scorched it. With heat it bends pretty easy. And yes it is pretty easy to shine up and looks good when it's done.... On a different note, do you plan on doing any aluminum molds in open pour, if so let me know and how much you would charge. I'm looking for someone to do a mold of a bait I designed. Thanks.

[CNC FREAK]

well, i have made several injection molds this week and it works perfect

but u need to use release agent like silicone oil before u inject the baits

not every time, i repeat it after 3 cycles

for me its perfect for making prototypes as long as i get waste material for free

I dont have any problems with melting. But i dont use these for mass production, therefore i will use aluminum.

 

however its not that easy to get it where i live, people who are using it for furniture, kitchens, save the small pieces because u can glue it to each other without any gaps.

Buying this stuff NEW is no option, way to expensive. So tomorrow i'm going to check if i can find some other kind of material to make prototypes. I'm thinking about POM, Polyoxymethylene

But i expect it would be more expensive than aluminum.

texacan84, it would not be possible to make your mold, i'm from Europe. Price for shipping would be to expensive.

Sorry mate,i'm sure there a lot of people in the US who can do that for u...

[texacan84]

Thanks for letting me know CNC FREAK... Yeah I guess it would be very expensive to ship it overseas, didn't know you were that far away, but thanks. Good luck with your new adventure.

[rcbv]

Hey texacan84, I'm setting up to cut aluminum molds which I have not done before and I might as well get my feet wet by making something someone can use. I'll cut your open pour mold for you as a freebie. If you want to give it a shot let me know.

[texacan84]

Hey rcbv. Thank you for the offer. I would like it very much to let you make a mold for me. You can pm me and we can set up the details. Thanks again.