slittlewing
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Post by slittlewing on Jan 7, 2020 5:41:47 GMT -5
Very awesome work, thanks for sharing the information! So just to clarify, you made a 3D printed part from PLA, plastercast, melted out the 3D print and then pour in the liquid aluminium - What temperature can plaster take? Is it normal plaster? And what furnace did you use to melt the aluminium?
Many thanks
Scott
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monty
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Post by monty on Jan 7, 2020 9:51:20 GMT -5
Very awesome work, thanks for sharing the information! So just to clarify, you made a 3D printed part from PLA, plastercast, melted out the 3D print and then pour in the liquid aluminium - What temperature can plaster take? Is it normal plaster? And what furnace did you use to melt the aluminium? Many thanks Scott Scott,
You basically have it correct. I use regular plaster of paris, but I add about 2/3 to 1/1 silica sand/POP to the mix. I also mix it on the watery side compared to the usual mix. This makes the mold more porous and lighter when the water evaporates.
This is basically a classic investment mix. You can add things like diatomacious earth and other things to improve hot strength, and there are actual plasters made for doing this kind of work. They aren't that expensive, but the closest place I can buy any is in Vermont...the shipping is horribly expensive for a 50 lb bag. Because of this I've been trying to develop my technique with good old, readily available hardware store stuff. The main thing to doing this is the mold MUST be dry. The drying happens in two stages, one at 230F and the other at 500F. Doing this the mold is good for low temp metals like aluminum-less than 1400F. If you need to do bronze or something higher temp, then the mold must be fired at high temp. This really requires all the high temp additives and careful mixing to get right. I would just use commercial investment mix for that. Fortunately for me; the less expensive stuff can be used for aluminum.
To melt the aluminum I use a gas fired foundry furnace. I have a 20# crucible, and this pour was at the limit for the equipment I have. 20# of molten aluminum at the end of a stick will concentrate the mind!! My set up is pretty basic:
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slittlewing
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Post by slittlewing on Jan 7, 2020 16:21:50 GMT -5
Excellent, thats great info thanks! Have always wanted to try casting, your success is motivating! Have you tried with sand for non hollow parts?
If you go any bigger you might need a tilting furnace!!
Cheers
Scott
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monty
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Post by monty on Jan 7, 2020 16:37:32 GMT -5
Excellent, thats great info thanks! Have always wanted to try casting, your success is motivating! Have you tried with sand for non hollow parts? If you go any bigger you might need a tilting furnace!! Cheers Scott Scott,
Give it a try! all you need is a good propane burner and some fire bricks to do small amounts. You can use a stainless or small jewelry making crucible. Start small! Sand is actually easier to do than the plaster stuff. you don't need a burn out oven or any of that. I'd start there. Budget casting supply is pretty good for supplies. Don't skimp on the PPE though. You need good boots, a leather apron, leather gloves, long sleeves (cotton or leather) and face shield. Make sure everything is DRY!!
Check out myfordboy's youtube channel, lot's of good stuff on there.
I have access to a 30# crucible at work. It takes two people, one on each side to do a pour. Much beyond that, and I'd take it to a foundry and piggyback on somebody's big pour.
You might also see if there is an art club that does lost wax casting nearby, or a vocational school with a small foundry (sadly less and less of these because of perceived liability)
Monty
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monty
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Post by monty on Jan 8, 2020 20:30:47 GMT -5
Shave and a haircut:
Heat treat for 24 hrs:
Rough machine:
Bead blast, next step finish machining:
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monty
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Post by monty on Jan 10, 2020 21:57:53 GMT -5
Lots of chasing my tail....almost a whole days worth:
Making sure everything is squared away:
Finally got tired of chasing things and drove a stake in the ground.....no going back now:
Monty
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monty
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Post by monty on Jan 11, 2020 23:04:06 GMT -5
Long day today...
Progress....
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Post by racket on Jan 11, 2020 23:37:08 GMT -5
Very nice :-)
Enjoyable watching someone who knows what they're doing .
Cheers John
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Post by turboron on Jan 12, 2020 5:05:57 GMT -5
All, the amount of knowledge and "hands on" know how of the group is amazing. I went to school when we had mechanical labs, machine shops and foundries IN THE SCHOOL. That's all gone now. Many so called engineers of today never had a ratchet in their hands.
Thanks, Ron
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monty
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Post by monty on Jan 12, 2020 10:06:40 GMT -5
All, the amount of knowledge and "hands on" know how of the group is amazing. I went to school when we had mechanical labs, machine shops and foundries IN THE SCHOOL. That's all gone now. Many so called engineers of today never had a ratchet in their hands. Thanks, Ron Ron,
I'm amazed at what can be done now with the tools available. That casting (at least as well as I can measure it) is within about 0.4 mm of volumetric accuracy maybe a little less!! CRAZY! That's after printing, casting and shrinkage. I used 1.3% for my shrinkage allowance. Although it "could" be made using old school pattern making techniques....YIKES! I wouldn't be doing this if I had to do that. CAD, 3D printing, and CNC are simply amazing tech for us little guys.
I designed the midframe casting so it can be made with the RPM process if I need more than one. But the cost of the tooling and the time to develop it caused me to try the lost PLA method for the prototype. Now I can put the first engine together and make any changes/revisions without going to the trouble of all that pattern work.
I hear you on the lack of fabrication ability in most engineers. It is a serious and growing problem. I was lucky. I had 2 years of mechanical drafting on the board in high school. I had shop class from 7-12 grade. During that time I took machine shop I&II and welding courses. I've kept at it, learning as I go. Most of the industrial arts classes are gone now, so it's not really the students fault. The sad thing is, all this ability to make things is going to waste, because nobody has the basic knowledge to employ it. Although youtube is good for finding info....some of the examples of casting I see on there are just cringe worthy, and dangerous.
You can't work on cars without a computer science degree anymore, and everything else is a throwaway and buy new situation. Very few people have any experience wrenching on anything. Although the technology is great, if you choose to only use it for instant gratification type things (video games etc)....ah well.
I don't know what the solution for the bigger problem is, but I sure am enjoying what all this new tech allows me to do.
All of my hobbies are populated mostly with gray hairs...It's good to see younger guys like Anders on here.
Monty
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Post by turboron on Jan 12, 2020 11:56:03 GMT -5
Monty, the sad thing is that the young guys don't know about the tons of fun we are having as we built things with our hands and brains.
Thanks, Ron
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monty
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Post by monty on Jan 12, 2020 23:33:52 GMT -5
Very nice :-) Enjoyable watching someone who knows what they're doing . Cheers John John,
STOP! you're are going to jinks me!! Just look at this:
SNAFU...not quite FUBAR....but a comedy of errors. An associative sketch in my cad model (I know better) lost associativity. While I was center drilling I thought....why did I space these holes so strangely??? Why is this 17 deg 45 min and XXX seconds and this next one is 17 deg 23 min and xxx seconds....was I on drugs!? What is wrong with this silly engineer??? Everything should be 19 degrees!! So the engineer looked at things and fixed them. Then the machinist forgot what side of the circle he was on....At least both of them know they are prone to mistakes and constantly cross check....and there is this thing called JB weld....
Fortunately it looked weird, so the machinist didn't drill all the way through! Don't tell the engineer...
Onward and upward...or something.
This barely worked, lots of WD40 and no more than .25 in at a time. Then withdraw the bit, blow it clean with compressed air, more WD40 another .25 in.....:
More to follow...internet is being strange.
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monty
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Currently being spanked by mother nature.......
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Post by monty on Jan 12, 2020 23:55:21 GMT -5
How do you make a 30 degree chamfer?? Silly engineer assumed CNC equipment!! You use a 95 degree countersink tool tilted 12.5 degrees...
Then drill the oil jet holes at 30 degrees: Possibly the worst butt puckering moment of the whole thing was tapping for the 6-32 grub screws.....
The big take away:
Monty
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Post by racket on Jan 13, 2020 0:00:15 GMT -5
Hi Monty
LOL................its nice to know I'm not the only one that makes machining mistakes :-)
Then other times the most complex and critical bit goes so easy you get worried because it did .
Still looking good ;-)
Cheers John
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Colin Heath
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Post by Colin Heath on Jan 16, 2020 1:17:35 GMT -5
Very nice :-) Enjoyable watching someone who knows what they're doing . Cheers John John,
STOP! you're are going to jinks me!! Just look at this:
SNAFU...not quite FUBAR....but a comedy of errors. An associative sketch in my cad model (I know better) lost associativity. While I was center drilling I thought....why did I space these holes so strangely??? Why is this 17 deg 45 min and XXX seconds and this next one is 17 deg 23 min and xxx seconds....was I on drugs!? What is wrong with this silly engineer??? Everything should be 19 degrees!! So the engineer looked at things and fixed them. Then the machinist forgot what side of the circle he was on....At least both of them know they are prone to mistakes and constantly cross check....and there is this thing called JB weld....
Fortunately it looked weird, so the machinist didn't drill all the way through! Don't tell the engineer...
Onward and upward...or something.
This barely worked, lots of WD40 and no more than .25 in at a time. Then withdraw the bit, blow it clean with compressed air, more WD40 another .25 in.....:
More to follow...internet is being strange.
Beautiful work in here! I have done it the other way to and questioned myself on offsets because they look strange and sure enough after correcting I realise there was a reason. Great to see the casting technology being used. I have a 3D printer and gas forge I could use. I did build an induction furnace years ago but sold it along with an electric furnace which worked great for aluminium. I will enjoy following
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