Aluminum molds for Ultem???

[implmex]

Hi All:
I'm new to this forum; I'm glad to have found it.
I have a question: Has anyone on this forum built aluminum short run molds for Ultem?
I have 2 main concerns:
1) The mold needs pass cores with 2 degrees taper, shutting off against the aluminum. I'm afraid of the cores picking up on the shutoffs.
2) Ultem molds I know, are run HOT with oil temperature control. I'm worried about the effects of thermal expansion, especially if I try to mix hard steel cores and aluminum in this mold.
I need to get 10,000 parts.
Shot mass is about 30 grams, 2 degree drafts on most part details.
It's a shallow box...0.0625" wall.
Thanks in advance
Cheers

Marcus

[dpryor]

Marcus,

We have built (and run) some low volume molds for Ultem but we chose P-20 steel. Your 2° shut-off is tight for steel so I suppose aluminum would be even more subject to galling. We use electric instead of oil heat but the thermal expansion issues would be the same. Ultem requires very high injection pressure. I would be most concerned about the aluminum deflecting under pressure.

We have found that unless we are removing alot of steel (aluminum) from the mold blocks (i.e. deep cavity) then we are better off to just use steel. The only real savings you get from aluminum is machine time.

[implmex]

Hi Doug:
Thanks for your thoughts...much appreciated.
You've confirmed my worries nicely...I think I'll increase the shutoff angles to 3 degrees, and build in P-20 with S-7 pass cores.
Oil galleries can be sited just like water cooling I presume?
Will I need to spec Viton for Orings or can I get away with Buna-N?
Cheers

Marcus

[jetski]

Great advise going to steel Ultem is a creature. 10000 pieces would be a trick in aluminum. If it is glass or mineral filled I would go to H-13. Our shop makes most of our tools out of H-13 some P-20. I make them H-13 because the parting lines hold up so much longer for training process techs. I actually prefer H-13 and do not quote it any differently because of the faster moving machines with higher rpms. Tooling Engineer and Tool maker for almost 30 years.

[raynjer]

Good advice given so far about not using aluminum for Ultem parts.
I have had several prototype tools made of aluminum in the past (per customers request) and have been lucky to get 500 shots out of them at times. Especially if you have any actions like hand loaded inserts or anything. For only a 30 gram part, you're not talking a lot of money difference in savings using aluminum.
Use steel, consider some hardening even, increase the draft angle if you can, and you'll be in good shape to get your 10,000 parts needed

[PinnacleMachine]

Originally Posted by raynjer Good advice given so far about not using aluminum for Ultem parts. I have had several prototype tools made of aluminum in the past (per customers request) and have been lucky to get 500 shots out of them at times. Especially if you have any actions like hand loaded inserts or anything. For only a 30 gram part, you're not talking a lot of money difference in savings using aluminum. Use steel, consider some hardening even, increase the draft angle if you can, and you'll be in good shape to get your 10,000 parts needed

What are you talking about - 500parts. I build exclusively aluminum moulds and some of our older moulds have 500,000 shots out of them without any major problems and those were just 7075 cav plates. Give Copper and Brass in Port Kells a call and get some QC10 for the core/cav and go to 3deg shut offs. I'd be more concerned about the moulder not knowing how to deal with an aluminum mould correctly and since you are in the Lower mainland I know there are some aluminum haters around.

[raynjer]

Easy fella - the prototype tools I mentioned were designed to only get 500 parts initially - we sometimes got closer to 1500-2000 parts. These were never designed to get more than that. These were all complex parts with multiple hand loads for actions, poor draft angles on ribs. OEM's requesting these prototype tools, would not pay for better quality, so they didn't get it. That's all they needed. It was our experience though that poor molding could degrade the molds very quickly, by simply flashing parting lines. And we don't hate aluminum molds - they definitely have a place in moldmaking especially with some of the new grades available. Just not a good choice when running Ultem 1010.