My MPCNC made in China

[forcerouge (Roger)]

Hey guys, Breaking news!

You’re about to see the first MPCNC part made of cast aluminum!

So, As it turned out, I tried yesterday and had a great success with my first cast attempt ever. Sure, the part is not perfect, but I’m pretty surprised how well it turned out. Let’s see some pics first:

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The second pic is kinda bad, the part looks quite a bit better IRL.

Anyway, here is the process:

First, I had to create the mold. My plan was to go for the lost PLA technique, because this technique would allow me to do a lot of great things, using the 3D printer to make metal parts.

So, basically, the first step is to 3D print a part (I used a Z motor mount I had in spare already). Then, add some channels for the metal to go in, and some other channels to let the gases escape. I just used some regular blue foam for that.

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The next step is to pour plaster all over it, then wait for it to cure. I waited about a week, just to make absolutely sure that all the moisture was gone, but it is probably not necessary. I guess one day or even a couple hours would work fine too, but I didn’t want to take any chances for my first attempt.

Then, you have to remove the plastic and foam from the mold. For this, I’ve put the mold in my furnace, and gradually moved up the temperature, from 50 degree C to 400 degree C. I’ve let it in the furnace at that temperature for about 24 hours, but I guess 4 or 5 hours would have done the trick.

My mold came out of the over absolutely flawlessly, not a single crack, which is actually quite a great achievement in itself:

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Next step: heat up the aluminum to about 730 degree C, remove the dross, add a bit of salt to lower the surface tension, then pour into the mould:

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I was supposed to wait for about half an hour for it to cool down, but I was just too impatient, so I waited 10 minutes and threw it in a bucket of water

After cracking the mold open, here is what came out of this:

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Even the tiny screw holes came out perfect, I didn’t even had to drill them for the screws to fit perfectly into place!

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Same thing about the tube holes and the motor fixing places, everything fits perfectly!

I still have to remove the channels, give it a bit of sanding and cleaning, and sure it is far from perfect (a lot of tiny holes, also a spot under the motor wasn’t filled properly), but in some places the quality is just astonishing. You can even see the 3D printing artifacts, which were extremely tiny since this part was printed on my very well calibrated delta printer. For example, the tube holes came out absolutely incredible.

So I’m super happy with that, I end up with a functional part at first try, it really isn’t that complicated and it was pretty cheap to build. That’s a very nice DIY thing I recommend you all to try!

I think I’ll try to build a full aluminum gantry for the MPCNC soon, just need a bit of time to improve a bit my technique.

Cheers!

[vicious1 (Ryan)]

NO WAY!!! More, those screw holes worked!!!

[forcerouge (Roger)]

@vicious1

NO WAY!!! More, those screw holes worked!!!

Yeah, the screw holes worked just fine and even the tiny little gap between the two parts of the clamps, which is about 0.5mm wide, for which I had no hope at all that it would ever work. So basically, I just had to put the screw in there, tighten it and it was holding the tube super tight. I just don’t know how this could even work at all, I guess I was lucky enough to get my hands on some really good plaster.

It felt so good to see the part coming out from the mould so well, metal casting is great!

I now have to find why the surface quality isn’t perfect everywhere. I’m not sure yet what is the reason, maybe my 3D printed part wasn’t totally watertight and some plaster infiltrated inside it. I’ll put a light coat of wax on the plastic next time to see if it helps.

[vicious1 (Ryan)]

I can’t wait to see more!

[jeffeb3]

Whoa! You said you were gonna do it, but this is much better than I expected. Nice work.

[jamesd256 (James Donnelly)]

Awesome work. Been dreaming of lost PLA casting and plasma cutting for a while now, but you actually go an do this stuff. Pretty cool.

[forcerouge (Roger)]

A bit of sanding, a bit of brass wheel buffing and it looks awesome.

Too bad some parts of the casting didn’t went perfectly smooth and too bad the center zone wasn’t filled, otherwise it would look just great!

Hopefully next castings will be better, but I’m still very satisfied with this one, those are just cosmetic details that don’t impact the use.

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[vicious1 (Ryan)]

That is so crazy and you are just getting started with the casting stuff. Seems like a good mix of awesome and terrifying.

[mcanabal (Marcos)]

Incredible, this man is advanced.
Simply a wonder …
It was very interesting to read the whole development process from 00.
My congratulations for the quality and creativity.

[derechtelanger]

I love your casted aluminium part and am now thinking about something similar. For that i also have to build an electric furnace similar to yours and i have a few questions about it:

I have a realy hard time figuring out where to buy those bricks you used, mainly because i dont know how they are called in german. What kind of density, isolation and maximum temperature do they have? They look like Ytong, but those arent temperature resistant enough…

How do you secure the heating wire in there and make sure it doesnt touch other things (e.g. shorting when in contact with the crucible)? Also its propably important that it cant be turned on when the lid is open, do you have a way to ensure that?

What kind of temperature control did you use?

[jamesd256 (James Donnelly)]

I have no doubt the electric route is better, but what caught my imagination about making a foundry was this guy:

This way still appeals to me for some reason.

 

[derechtelanger]

Yeah, i know that video but those extreme efficency losses from the open design kinda hurt me. Thats why i plan to go with an electric, closed design.

That leads to another question at the OP: Did you close the furnace while burning out the PLA? Or does it need lots of fresh air/oxygen?

[forcerouge (Roger)]

@derechtelanger

I have a realy hard time figuring out where to buy those bricks you used, mainly because i dont know how they are called in german.

I can’t really help you for the german translation, but those bricks are called “alumina silicate bricks” in english. Should’nt be very hard to find, it’s fairly common stuff.

@derechtelanger

What kind of density, isolation and maximum temperature do they have?

No clue about the density or insulation, but they are very lightweight. They are supposed to withstand about 1300 degree Celsius. But 800 is enough if you plan on doing aluminum.

The wire I use is a nichrome wire, about 1mm thick, supposed to withstand about 1350 Degree C.

For the temperature control, I just use a cheap PID controller, nothing really special. Any PID controller should work. Mine was given for a temperature range going from 0-400 degree C, but it turns out to be a software limit, you can change it in the settings. You just need to find a thermistor capable to withstand those high temperatures, and then set up your PID controller to work with it (I can help you to set it whenever you’ll reach this step, it’s not very complex but it is a bit tricky).

So basically, you’ll just need:

-A PID controller

-A thermistor

-A Solid State Relay capable of handling the current. For example, if your furnace is 2200W, you’ll need at least a 10Amps SSR. But I recommend you to double this figure and go for a 20Amps SSR, it will heat less and last much longer.

-A switch, to be able to manually disconnect the SSR

@derechtelanger

How do you secure the heating wire in there and make sure it doesnt touch other things (e.g. shorting when in contact with the crucible)?

The wires fit into the groves, they stay in there just with the wire tension. The wire tends to want to keep it shape straight, so it naturally pushes in the outward direction. So it just stays there by itself. The shorter your wire is, the more power you get. If your wire is too long, you’ll have too much resistance and it will take hours to get to the target temperature. If the wire is too short, it will draw too much power and you risk melting either the nichrome wire or (worse) ruining your home electrics if your circuit breaker is not working properly. My furnace is drawing 1500 Watts currently, which really isn’t that much, but it takes a bit too long to reach 750 degree (30-40 minutes) so I’ll probably shorten the wire a bit to get to 2000-2500W.

@derechtelanger

Also its propably important that it cant be turned on when the lid is open, do you have a way to ensure that? What kind of temperature control did you use?

I thought about that but it didn’t worth the hassle. I just turn it off whenever I want to move the crucible or the mold and pay extra care not to touch the wire. But maybe I’ll add a switch at some point, it’s pretty easy to do.

@derechtelanger

OP: Did you close the furnace while burning out the PLA? Or does it need lots of fresh air/oxygen?

Yes, the furnace was closed, otherwise it would have been unable to reach that kind of temperature (about 500 degree C). My furnace is not air tight, there are a few tiny holes so the gases can escape easily. I can see the fumes coming out during the burning process (it smells pretty bad).

[forcerouge (Roger)]

I’ve made another casting part yesterday, still using the lost PLA casting process:

Super hot crucible, I’ve almost burned my hand through the casting gloves just by standing 30 cm away from it

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Here is how it came out from the mold:

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After a bit of sanding:

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Then fine sanding with 600 grit paper and a bit of polishing, nothing super fancy but I think the result looks pretty great already:

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It is a bracket for a LED lamp, I made that for one of my coworkers.

The result is not perfect, a few tiny holes all over the surface, the little cross shape in the center is a bit too rounded and should have been a bit sharper, and the side grooves didn’t came out as the original drawing, but in the end it works and most of the defects are not visible and did not affect the function.

So, I call that a win too!

I still need to experiment more to get better results, I will try a different feeding technique next time. Also I may have to try using some kind of vacuum system, to get all the tiny details, but I have no idea how to build such a system yet so I’ll need to make some research.

[lionkev55 (Kevin Lopez)]

Waiting on all aluminum mpcnc with stainless rails…ooooh the rigidity

[jeffeb3]

This oven seems pretty well documented. I don’t know if you saw this before you built yours, but it sounds similar:

[jeffeb3]

Also, nice part. I love the idea that you can just make all those support pieces and just cut them off and melt them back into your next part.

[forcerouge (Roger)]

@jeffeb3

This oven seems pretty well documented. I don’t know if you saw this before you built yours, but it sounds similar:

Yeah, I think I’ve seen pretty much every resource related to furnaces on Youtube. I like to do as much research as possible before starting any project, especially when it involves potentially lethal stuff

This particular furnace was pretty well constructed, I think that was my main inspiration for the PID enclosure. I’ve just tried to make it smaller and easily removable, so I can use it for different projects if I ever need to.

[barry99705 (Barry)]

Just don’t try using your aluminum chips from the router. Too much aluminum oxide to be worth using.

[forcerouge (Roger)]

I’m making some stock of aluminum ingots for further castings. I’ve melted 6 Hard disk drives aluminum casings and got about 1.2Kg of nice aluminum. Does anyone has any idea what kind of aluminum this would be?

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