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jes / 3d-metal-printing

Notes and information about 3d metal printing
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Attempt 6: puzzle part, brass, lost PLA casting #8

Open jes opened 4 years ago

jes commented 4 years ago

Same part from #7 but printed 2% oversize in all axes, and using a little "sprue" model to try to increase the hydraulic pressure inside the mould.

Haven't yet decided how I'll keep the part from falling over inside the flask.

jes commented 4 years ago

Here's the part stuck to the "sprue" stuck to the brass:

image

There's a pretty large excess of brass, to try and keep the pressure up.

jes commented 4 years ago

And here it is inside the flask as I was pouring the plaster in:

image

I used a chunk of solid plaster left over from last time to pad up the bottom of the flask, then placed the brass on top of that. I poured in a bit of plaster at the time and then gently wobbled the flask to make plaster get more liquidy and flow down into the gaps. I'm pretty sure the part will not fall over inside the plaster this time.

Need to remember to turn it upside down before putting it in the furnace!

jes commented 4 years ago

My aluminium has just arrived, but it is too late to put it inside the plaster, bah.

jes commented 4 years ago

Running this temperature profile for this attempt:

  1. Ramp 150 10m
  2. Hold 1h15m
  3. Ramp 400 3h20m
  4. Ramp 1050 4h00m
  5. Hold 1h00m
  6. Heater off

So, same as last time, but 4h hold at 1050 reduced to 1h. It will probably trip the breaker again, but if it does I'll just let it cool down and then see what's inside.

jes commented 4 years ago

From https://github.com/jes/3d-metal-printing/issues/7#issuecomment-535641871

I expect the next attempt to produce a usable part.

I should have known better than to say this :)

I got impatient and switched the furnace on this morning, only about 20 hours after pouring the plaster. In #3 the plaster didn't have very long to set, and it cracked and some material leaked into the furnace. Well the same thing happened this time, except there was a lot more material in the flask.

There is now a large amount of brass in the bottom of the furnace, stuck to the flask. I can move the flask up and down, but I can't get it out of the furnace because the brass spillage is too wide to fit through the opening. I'm probably going to have to take the furnace apart.

Another lesson learnt, though: we definitely need to allow more than 24 hours for the plaster to set.

I'm going to try to retrieve the flask from inside the furnace first thing tomorrow, then get another part inside ready to cast, and then try to cast on Tuesday, this time with Aluminium.

jes commented 4 years ago

It seems that you're supposed to be able to dry out the plaster in the furnace. Perhaps if we just increase the amount of time it spends at low temperatures, we could chuck the plaster in the furnace almost immediately after pouring it.

jes commented 4 years ago

Here's what I took out of the plaster. Much better than expected, and actually an improvement on #7 despite the cracked mould. You can see the spilt brass around the bottom of the flash in the background.

Unfortunately the mould shifted where it cracked, so it's not just a case of cleaning the flashing off and then having a usable part, although I might try and clean it up anyway just to see what it's like.

I definitely expect the next attempt to work!

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