Curious about moldmaking

[NeoMiller]

I am a novice in machining so please dont laugh at my questions.

I want to make a simple mold out of mild steel for a hollow plastic cylinder used as a spacer for mounting PCBs. Size 3/8inch dia, length 1.5inch hole 5/32inch. The injection molding will be done with a hand molding machine. The surface quality of the product is not an issue and nor is the production speed. The mold will only be used to make a few hundred pieces in all.

The only machine at disposal is a Taig CNC micromill. I dont have any lathe mahine which might seem necessary for this but I think the job might be done using only the mill.

Questions:
Can I use aluminum or brass to make this mold.
Which software should I use to design the mold.
Are ther any simple reference design files for moulds avaialable on the internet or can anyone share one.
Are there any videos avaialable that show machining being done on a mill.

thanks for any help. rgds. NeoMiller

[HomeCNC]

I'm going to be making me a home built injection molding machine to do small plastic parts. Make your mold out of aluminum. It will be much easier to machine and will be fine for 100 or so shots.

Don't know about you last three question.

[ullbergm]

Originally posted by HomeCNC
I'm going to be making me a home built injection molding machine to do small plastic parts.

that sounds interesting, do you have any plans already or any websites with examples of home made machines?

[ToyMaker]

NeoMiller:
For the a short course on home mold making, check out "Of Runners, Gates and Cold well plugs:" at

http://www.seattlerobotics.org/encod..._art/molds.htm

robotic regards,

Tom
= = = = =
When religion was strong and science weak, men mistook magic for medicine; now, when science is strong and religion weak, men mistake medicine for magic.
- - Thomas Szasz, American psychiatrist

[NeoMiller]

Great article for beginners like me. Thanks ToyMaker.

ullbergm, I have seen a couple of home built molding machines. Dont have any pictures of them though. In fact, they had appeared so simple and the molds that they used for small jobs were so straight forward (without any alighnment or ejector pins), that this is what initially got me intersted to enter this field. I am basically in small scale manufacturing of customized electronics and often require project specific plastic hardware for fittings and stuff.

[HuFlungDung]

While I applaud your initiative to get into molding thermoplastics, for this particular app, would it not be easier to get some plastic rod and drill the hole through it? I suspect that you might have a fair bit of a tussle to pull the mold core out of the part?

[ullbergm]

Originally posted by NeoMiller
Great article for beginners like me. Thanks ToyMaker.

ullbergm, I have seen a couple of home built molding machines. Dont have any pictures of them though. In fact, they had appeared so simple and the molds that they used for small jobs were so straight forward (without any alighnment or ejector pins), that this is what initially got me intersted to enter this field. I am basically in small scale manufacturing of customized electronics and often require project specific plastic hardware for fittings and stuff.

please let me know if you find some links to pictures/drawings of some examples.

thanks,
magnus

[NeoMiller]

HuFlungDung, how about if I make the plastic rod in a bit of a taper. The mold will have the cavity in plate A and the pin for center hole in plate B. The hole pin can also be made into a little lesser taper. So when I open the mold, the piece is sticking on the plate B with the center hole pin. That should be easy to remove. Wouldn't it.

[HuFlungDung]

Oh certainly, Neomiller, those are ways to do it. But, I would select the easiest method of production, and save your mold making for parts that are not as readily produced from barstock.

[cadcam]

I would say the aluminum die would work well. i have done this with complexe mold shapes and able to get 500 plus part from glass filled plastics..

So I say have at it.

[hardmill]

Originally posted by HuFlungDung
While I applaud your initiative to get into molding thermoplastics, for this particular app, would it not be easier to get some plastic rod and drill the hole through it? I suspect that you might have a fair bit of a tussle to pull the mold core out of the part?

Gonna have to agree with hu on this one.
Seems pretty straight forward.

PEACE

[HomeCNC]

Ullbergm,

Yes I have a book called 'Secrets of building a plastic injection molding machine'. By Vincent R Gingery

http://www.lindsaybks.com/dgjp/

It shows you how to build the machine, make a simple mold, and gives you instruction on the injection process.