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27th October 2012, 07:13 AM #16Senior Member
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The post date is already saturday and here in the office it's still friday.
As you know by now, the OZ-people are always ahead of us!
Stefan is my casting mentor.
To my big fortune, he came to my very first casting party. We were all clueless. All we had was a furnace, sand, a few patterns and a lot of ignorance.
At that Saturday, he showed us all the basics.
He was a mould and pattern maker by trade, so I couldn't find someone better.
So I'm very thankful to him. I don't know where I would be today with his support.
Nick
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27th October 2012 07:13 AM # ADSGoogle Adsense Advertisement
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27th October 2012, 03:27 PM #17
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28th October 2012, 01:50 PM #18
Hi Nick,
For casting small parts with fine features, I'm thinking of a simplified die casting process. Basically the idea is as follows. It's the opposite of vacuum
1. The die is made of multiple parts 2-3-4 whatever it takes.. So you can get the finished part out
2. The plunger and reservoir is be made to screw into to the pattern, so as to be re-usable
The die and the reservoir are assembled as one part, the plunger is used to pressurize the molten aluminium into the pattern ( a bit like a linotype machine I guess )
Load up the reservoir with a preformed aluminium slug in the pattern in the electric furnace, that way I can get precise temperature control of the die and reservoir.
I don't have to worry about the aluminium solidifying in the pattern, since it's the same temperature as the reservoir.
When the aluminium reaches pouring temperature, remove the assembly from the furnace and operate the plunger until the aluminium reaches the riser, and then block off the riser and put a load on the plunger to maintain pressure while it cools.
Since the molten aluminium inside the pattern is under pressure ( not too much ) it should flow into all the corners and fine features of the die.
If that's not making sense, perhaps I could should draw a diagram.
Regards
Ray
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28th October 2012, 07:11 PM #19Senior Member
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remove the assembly from the furnace and operate the plunger
The best I could get was 4 strokes of the plunger, then it seized. BTDT.
Here is a video. It is not public, because it failed and I gave up that path.
Hot Chamber
I don't even have a video of my cold chamber die casting machine. That one also failed. But better, with more efford.
Nick
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29th October 2012, 05:38 PM #20
Hi Nick,
Thanks for that video, I am thinking of a similar process, but with some differences to your approach,
first, steel dies, and it's a one shot process, not multiple parts, second the reservoir screws into the die, and third difference, I'm thinking to heat the whole assembly in the oven..
The parts I'm wanting to make are similar to commercial diecast boxes for a small custom electronics project, except for the small number I want to do, the commercial tooling cost would be way to expensive..
Regards
Ray
PS.. I should have known you would have already tried it..
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29th October 2012, 06:39 PM #21Senior Member
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- Germany, Outback of Munich
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- 213
I have some buts ...
The plunger WILL seize. You will have to bore it out. A hammer is not enough. I bored out four, then I got bored.
How will you remove the dross when you assembled the whole thing and then melt the aluminium?
Steel dies are not that hot. Something like 200 °C or so.
To some extent, my cold chamber die casting worked better. The problem was, that the amount I wanted to cast was too small. As soon as I filled the chamber, the aluminium solidified (almost) and it didn't get through the bore into the die anymore (except once).
That plunger worked much better (and I found a trick to make it seal), but I used weights to push down the plunger. More than 10 kg weren't enough. I think that requires hydraulics or a long lever. I have a book about die casting. If you want, I can look for the pressures involved.
Hot chamber with ali is very uncommon. The reason is, that the ali fuses with steel. I tried CI and SS, none worked for too long. Maybe chrome plating helps?
I'm really happy that I gave up that pressure die casting route. And I'm very confident that the vacuum assisted casting will work with steel dies too.
Nick
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29th October 2012, 10:13 PM #22
been watching this , and have been left with out words ,
FRIGGIN WOW
i had to say something , as a newbie to casting , thank you for posting
cheers ken
at 999 posts where do i post my 1000 , wood turning ,. instrument making , CNC , or here ?how come a 10mm peg dont fit in a 10mm hole
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30th October 2012, 03:09 PM #23
Hi SawDustSniffer,
I remember when I cast some bronze parts, and was feeling pretty proud of the efforts, when a friend pointed out that the Greeks and Romans were doing this stuff 2000 years ago...
And as Nick said earlier, this stuff isn't new, people have been doing this stuff for a long time..
We are drifting off the vacuum casting topic, so I won't hijack this thread any further with die casting, I'll start a new thread for that.
Regards
Ray
PS.. I think I'm almost catching up with the Bronze Age, 3200BC to 500BC, still haven't got to the iron age
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