Jeshua Lacock Presents Lost Shell Sand Casting for PLA 3D Printed Models

Jeshua Lacock is back with a new metal casting technique for 3D models printed in PLA. After receiving feedback that his Lost PLA Casting Technique just 'looked like too much work,' he decided to try another route, and came up with something entirely new called the Lost Shell Sand Casting technique. Also working with PLA, this technique is easier, faster, and more affordable, and the results offer up finely detailed metal parts. The technique also works with ferrous metals. Read more at 3DPrint.com: https://3dprint.com/140523/lost-shell-sand-casting/
https://3dprint.com/wp-content/uploa...ntitled-81.png

way cool. dude !

But why is it a different method ?
Looks pretty standard to me.

Quote:

---

Originally Posted by curious aardvark

way cool. dude !

But why is it a different method ?
Looks pretty standard to me.

---

Thank you!

What is different is that with traditional sand casting the pattern is removed from the sand before the metal is poured. Since it has to be removable without damaging the fragile sand mold, it greatly limits the type of geometry possible (undercuts, cores, etc. become a design limitation).

With this technique, the pattern is left in the sand (allowing practically any geometry to be cast) and burnt out directly by the molten metal.

Hopefully I have answered your question, let me know if you have any other questions.

okay. Yes now you mention it.
In the lost wax/pla process you heat the mould to melt the wax out before adding the metal.

So why are the tubes (can't remember what you called them) for the metal in and gasses out so large ?

And would this process also work with lead ? or does that not get hot enough to vapourise the pla ?

These guys don't seem to have very high standards for their castings. If one of mine came out that poorly, I wouldn't be celebrating; I'd melt it down and try again. Burning the PLA inside the sand mold evidently disrupted the surface significantly, so any crisp detail was lost. I just hope nobody watches this video and hurts themselves badly trying to do it themselves.

Andrew Werby
Juxtamorph.com

Quote:

---

Originally Posted by curious aardvark

okay. Yes now you mention it.
In the lost wax/pla process you heat the mould to melt the wax out before adding the metal.

---

That is correct as well.

Quote:

---

Originally Posted by curious aardvark

So why are the tubes (can't remember what you called them) for the metal in and gasses out so large ?

---

The the pour tube is called a "Sprue". It is both tapered and oversized to help build up as much hydrostatic pressure as possible (also makes it easier to pour into). It also acts as a "Riser" that stays molten long enough to feed the metal as it shrinks as it cools which is called the "Suck".

Quote:

---

Originally Posted by curious aardvark

And would this process also work with lead ? or does that not get hot enough to vapourise the pla ?

---

Let's see; it looks like lead doesn't boil until 3,180F. So you could get it plenty hot enough to work for the process. How much hotter it needs to be over the melting point of 621F would take some experimenting. I imagine if you got it up to around 1000-1200F that seems like is should be adequate.

Quote:

---

Originally Posted by awerby

These guys don't seem to have very high standards for their castings. If one of mine came out that poorly, I wouldn't be celebrating; I'd melt it down and try again. Burning the PLA inside the sand mold evidently disrupted the surface significantly, so any crisp detail was lost. I just hope nobody watches this video and hurts themselves badly trying to do it themselves.

---

For staters they are sand castings - which will never quite have the same detail as investment castings. You are incorrect about any crisp detail being lost - many of the original print lines are evident and you can't expect to do any better than that from a 3D print.

Next, these casts are straight out of the sand - no touch up work at all was done to them. It only takes very minor work to sand things into shape.

Finally, where they came out a little rough it was only because the sand wasn't adequately packed tight enough - but a little learning is to be expected with a whole new technique. These are literally the first casts as we learned the new process. We didn't think of it at the time, but all we needed to do is flip the sand mold over and repack the sand from the other end.

And we take safety very seriously! I pour in a full fire proof proximity suit (with full head protection), we pour in a dry sand box, the molten metal is never lifted above waist level, the building is adequately ventilated, we use proper tools, etc. and so on.

Have to admit for an uncleaned model it looked pretty good to me.

Quote:

---

Originally Posted by 3DTOPO

For staters they are sand castings - which will never quite have the same detail as investment castings. You are incorrect about any crisp detail being lost - many of the original print lines are evident and you can't expect to do any better than that from a 3D print.

[If you were setting out to demonstrate the utility of this process for creating small detailed castings like the one you attempted, you have not succeeded. This process might be okay for rough castings, but since there's no way to introduce a core, it's not going to work too well for most of them either. Solid lumps cast poorly, and some of the problems in that one might be due to shrinkage porosity. If you try it again, use a chill and see if it works any better.]

Next, these casts are straight out of the sand - no touch up work at all was done to them. It only takes very minor work to sand things into shape.

[As someone who's done my share of that "minor work", I'd say melt it down and start over.]

Finally, where they came out a little rough it was only because the sand wasn't adequately packed tight enough - but a little learning is to be expected with a whole new technique. These are literally the first casts as we learned the new process. We didn't think of it at the time, but all we needed to do is flip the sand mold over and repack the sand from the other end.

[I think the process, such as it is, would be improved a lot if you used a refractory coating on the part before packing it in the sand. People who do the similar lost-foam process with aluminum use dry-wall compound, but there are lots of better ones that might stand up to hotter metals.]

And we take safety very seriously! I pour in a full fire proof proximity suit (with full head protection), we pour in a dry sand box, the molten metal is never lifted above waist level, the building is adequately ventilated, we use proper tools, etc. and so on.

---

[Yes, I noticed that. (Nice induction furnace, by the way! Is that home-made?). But I worry about the people who watch You-tube videos and go out to try this at home, in t-shirts and tennis shoes, with the kids all crowding around. You could shake off that "bottle rocket" explosion you got on your first attempt, but it might be a life-changing event for them (and not in a good way).]

Quote:

---

Originally Posted by awerby

[Yes, I noticed that. (Nice induction furnace, by the way! Is that home-made?). But I worry about the people who watch You-tube videos and go out to try this at home, in t-shirts and tennis shoes, with the kids all crowding around. You could shake off that "bottle rocket" explosion you got on your first attempt, but it might be a life-changing event for them (and not in a good way).]

---

It is an informational video of what we do here. We go out of our way to discourage others from trying it at home.

How many of these people that you have in mind, just happen to have an induction furnace laying around that is able to melt a pot full of copper at a flip of a switch?

I could only hope that if someone owns *any* type of professional industrial equipment, that they know how to use it properly and safely before attempting to even turn it on.

Note that I spend 5-minutes going over basic metal safety in this video:
Lost PLA 3D Print to Metal Casting; Complete

Quote:

---

Originally Posted by 3DTOPO

It is an informational video of what we do here. We go out of our way to discourage others from trying it at home.

How many of these people that you have in mind, just happen to have an induction furnace laying around that is able to melt a pot full of copper at a flip of a switch?

I could only hope that if someone owns *any* type of professional industrial equipment, that they know how to use it properly and safely before attempting to even turn it on.

Note that I spend 5-minutes going over basic metal safety in this video:
Lost PLA 3D Print to Metal Casting; Complete

---

While you can go hotter with an induction furnace, even people who have put together a home-made melting furnace (like the one in your other video) can do themselves a lot of damage, although I wouldn't exactly describe it as professional industrial equipment. I did watch that video, and I appreciated the safety information you provided in it, which is more than one typically sees on You-tube. You should tell people who watch the other one to watch that one before attempting to duplicate your feats of metal-casting. If you'd used the plaster-sand investment instead of straight sand, that little figurine would have come out better. But like I said, a refractory coating could help a lot.

Andrew Werby
Juxtamorph.com

Quote:

---

Originally Posted by 3DTOPO

It is an informational video of what we do here. We go out of our way to discourage others from trying it at home.

How many of these people that you have in mind, just happen to have an induction furnace laying around that is able to melt a pot full of copper at a flip of a switch?

I could only hope that if someone owns *any* type of professional industrial equipment, that they know how to use it properly and safely before attempting to even turn it on.

Note that I spend 5-minutes going over basic metal safety in this video:
Lost PLA 3D Print to Metal Casting; Complete

---

To be fair, you can build an induction furnace with not much more work than this casting process takes.

Quote:

---

Originally Posted by awerby

While you can go hotter with an induction furnace, even people who have put together a home-made melting furnace (like the one in your other video) can do themselves a lot of damage, although I wouldn't exactly describe it as professional industrial equipment. I did watch that video, and I appreciated the safety information you provided in it, which is more than one typically sees on You-tube. You should tell people who watch the other one to watch that one before attempting to duplicate your feats of metal-casting. If you'd used the plaster-sand investment instead of straight sand, that little figurine would have come out better. But like I said, a refractory coating could help a lot.

---

My point is there is a lot more to it than someone just seeing a video like this and duplicating my efforts. They are going to have set out to make a whole foundry. It can't just be copied on a whim.

Of course I can get finer detail with investment casting. The point of this method is it provides "good-enough" results for many many things and is much simpler, faster and less expensive.

Quote:

---

Originally Posted by Ama-fessional Molder

To be fair, you can build an induction furnace with not much more work than this casting process takes.

---

A 15KW or more powerful one? I would like to see that!

I've only see toy sized ones "easily" made. The amount of hardware alone needed to build a 15KW induction furnace is anything but trivial.

Quote:

---

Originally Posted by awerby

You should tell people who watch the other one to watch that one before attempting to duplicate your feats of metal-casting.

---

Actually - I won't tell anyone to duplicate my efforts - that isn't the purpose of the video. The description for the video reads in part: "WARNING: This is for informational purposes only. Fire, molten metal, high power and high temperatures are potentially extremely dangerous."

I'm not saying, "Yeah you can do just like me even if you don't know what you are doing or have any of the right tools" - quite the opposite.

Quote:

---

Originally Posted by 3DTOPO

Actually - I won't tell anyone to duplicate my efforts - that isn't the purpose of the video. The description for the video reads in part: "WARNING: This is for informational purposes only. Fire, molten metal, high power and high temperatures are potentially extremely dangerous."

I'm not saying, "Yeah you can do just like me even if you don't know what you are doing or have any of the right tools" - quite the opposite.

---

Nobody pays any attention to those warnings; it's like all those toys that come with tags saying "this is not a toy - not for use by anyone under the age of 18" that the toy company lawyers attach in an attempt to avoid the strict laws governing children's toys, or the ubiquitous warnings on every building in California telling people that something in there might do them harm: http://www.latimes.com/health/la-he-...v02-story.html . I thought the safety info in your original video was actually quite good - telling people not to do this on concrete, advising them to make sure anything they stick in the pot was pre-heated - this is important stuff.

But I've heard from lots of people on various forums who saw a few YouTube videos about casting metal in the backyard and were totally clueless about the dangers involved - there's a lot of enthusiasm for melting scrap metal in tin cans and flower pots and pouring it in molds made from who knows what. All I'm saying is that you should append the "lost shell" video to the other one, which has the safety info, rather than distributing it separately. There are a lot of characters out there jostling for their Darwin awards...

How's that deep-Z CNC router working for you? Have you worked out the 4th and 5th axes yet?

Andrew Werby
Juxtamorph.com

Quote:

---

Originally Posted by 3DTOPO

A 15KW or more powerful one? I would like to see that!

I've only see toy sized ones "easily" made. The amount of hardware alone needed to build a 15KW induction furnace is anything but trivial.

---

15kw really isn't that hard. The hard part is powering it. You need around 80 amps, assuming a normal inefficiency (likely that the efficiency would be much higher than 80%, haven't done the math) of 230v single phase power. A single sub panel in a well equipped home can handle that and the lights in the shop without significant issue.

Then, you need at least 1 awg power cable to handle the current draw, which isn't an issue since you should have the sub panel within a couple yards of the device. I would just be safe and buy 0 gauge, because it is more commonly available and not really any more expensive. So that gives you a pretty good safety factor on the power supply.

After that, you need a variable frequency drive of some manner. This can be purchased outright if you have the coin, or built if you have the knowledge. The mechanics of which I am not entirely clear on, though I do understand how to do it at a much lower current/voltage. I think it involves suitable capacitance. I could research further if I intended to build one, but if I recall my electrical courses correctly you would ideally do so in parallel.

From there, you have your work coil. You would use some solid copper and plenty of applied muscle to wind it.

Stick a nice crucible in the middle, and there you go. If you want to get really fancy, you can liquid cool the work coil.

It isn't really a matter of it being difficult, the problem is one of scale. 15kw is hard to obtain for a home user, but certainly possible.

I suspect I could build one with reasonable safety devices, liquid cooled coil, appropriate power (including professional installation of the sub panel) and have it running for maybe 3k USD.


BUUUTTT that's all theory. I have had enough practice on projects of that scope to know that there are always unseen obstacles that slow things down. That's the part where many home users cut corners, do something dangerous, and kill themselves.

Quote:

---

Originally Posted by Ama-fessional Molder

It isn't really a matter of it being difficult, the problem is one of scale. 15kw is hard to obtain for a home user, but certainly possible.

---

Actually swashing around 700 amps in the primary coil and many thousands of amps in the secondary (work) coil at 30-85 thousand times a second at 230 V input without blowing up is quite technologically demanding.

There is a reason modern induction generators weren't invented until the late 60s early 70s.

Just 15KW needs a fairly massive DC transformer, a massive water-cooled capacitor bank (totally deadly if mis-touched), a massive toroid, water cooled work coil, big fat water cooled insulated-gate bipolar transistor (IGBT) and a well designed control card.

Unless you can show me a web page with schematics and proof of working induction generator over 5kW, I think I have made my point. The biggest I am aware of is ~5KW and was designed by my friend Tim Williams - who went on to design induction generators for Radyne.

Besides purchasing all the hardware, it will take weeks (if not months) of someones time to build the circuit boards, order and assemble all the parts and just hope that it all works. The project is easily on the same level as a thesis project.

Quote:

---

Originally Posted by Ama-fessional Molder

I suspect I could build one with reasonable safety devices, liquid cooled coil, appropriate power (including professional installation of the sub panel) and have it running for maybe 3k USD.

---

Or - you can buy one brand new for around $1k. Sealed in an enclosure and working with instructions.

Quote:

---

Originally Posted by awerby

Nobody pays any attention to those warnings; it's like all those toys that come with tags saying "this is not a toy - not for use by anyone under the age of 18" that the toy company lawyers attach in an attempt to avoid the strict laws governing children's toys, or the ubiquitous warnings on every building in California telling people that something in there might do them harm: http://www.latimes.com/health/la-he-pro-con2-2009nov02-story.html . I thought the safety info in your original video was actually quite good - telling people not to do this on concrete, advising them to make sure anything they stick in the pot was pre-heated - this is important stuff. But

---

Quote:

---

Originally Posted by awerby

I've heard from lots of people on various forums who saw a few YouTube videos about casting metal in the backyard and were totally clueless about the dangers involved - there's a lot of enthusiasm for melting scrap metal in tin cans and flower pots and pouring it in molds made from who knows what. All I'm saying is that you should append the "lost shell" video to the other one, which has the safety info, rather than distributing it separately. There are a lot of characters out there jostling for their Darwin awards...

---

Well if people are going to ignore the warnings there, people are going to ignore them elsewhere too I suppose.


The point I have been trying to make, is, I wasn’t like look just stick something dangerous in a microwave (or something everyone has at home). Like: “gee-whiz folks - look how easy it is to be stupid! - you can be just as dumb as me if you want to” - and there are no end of those sort of videos that actually exist on Youtube.


The whole process takes special gear, and with that usually comes special know-how and respect - in my experience at least.


That said, the video does absolutely already link to the older video.

I am also considering making a basic foundry set up and safety video as well.

Quote:

---

Originally Posted by awerby

How's that deep-Z CNC router working for you? Have you worked out the 4th and 5th axes yet?

---

It has about 2.5 feet of useable Z and the machine works really well. I have a 4th axis going now. Haven’t really had the need for 5-axis but when I have the time I look forward to building one.


I am also finishing up a 4-axis metal lathe/mill combo conversion as well.

Quote:

---

Originally Posted by 3DTOPO

I am also considering making a basic foundry set up and safety video as well.

[That would be great; it's sorely needed on YouTube. Append it to any foundry-related videos you put out; it could save lives.]





It has about 2.5 feet of useable Z and the machine works really well. I have a 4th axis going now. Haven’t really had the need for 5-axis but when I have the time I look forward to building one.


I am also finishing up a 4-axis metal lathe/mill combo conversion as well.

---

What sorts of things are you making with that router? What materials does it cut?

Quote:

---

Originally Posted by 3DTOPO

Or - you can buy one brand new for around $1k. Sealed in an enclosure and working with instructions.

---

I have no idea where they are getting that 15kw rating from a device which runs on 110v single phase. That's simply not possible with any safe currents. You would need 140-150 amps to do so at that voltage.

http://www.mtixtl.com/15KWDualStatio...Q-SP-15AB.aspx


This one pulls 34a from the wall at 240v. That's 8kw, and they are calling it a 15kw unit also. Certainly a LOT more power than those 110v amazon units for around $1k are utilizing. Those ones don't even list an input current rating.

They would have to be using some massive capacitance to charge/discharge 15kw through that coil long enough to actually melt something, but these units claim they can run at 100% constantly... which means they aren't charging anything.

I was referring to building a *proper* 15kw furnace instead of one that is just "kind of" 15kw. The math just doesn't add up. If you have some insight as to how those things are magically taking at most 3500 watts of 110vac (you can run up to 30a on 110v if the wiring and outlets support it) and turning it into 15,000w (at any voltage) please fill me in. I am honestly curious.

Quote:

---

Originally Posted by awerby

What sorts of things are you making with that router? What materials does it cut?

---

I mostly use it for carving out EPS foam and wood for patterns for metal casting.

It will also machine aluminum if I am not in too much of a hurry.

Let me know if you need anything big carved! ;)

Quote:

---

Originally Posted by Ama-fessional Molder

I have no idea where they are getting that 15kw rating from a device which runs on 110v single phase. That's simply not possible with any safe currents. You would need 140-150 amps to do so at that voltage.

http://www.mtixtl.com/15KWDualStatio...Q-SP-15AB.aspx


This one pulls 34a from the wall at 240v. That's 8kw, and they are calling it a 15kw unit also. Certainly a LOT more power than those 110v amazon units for around $1k are utilizing. Those ones don't even list an input current rating.

They would have to be using some massive capacitance to charge/discharge 15kw through that coil long enough to actually melt something, but these units claim they can run at 100% constantly... which means they aren't charging anything.

I was referring to building a *proper* 15kw furnace instead of one that is just "kind of" 15kw. The math just doesn't add up. If you have some insight as to how those things are magically taking at most 3500 watts of 110vac (you can run up to 30a on 110v if the wiring and outlets support it) and turning it into 15,000w (at any voltage) please fill me in. I am honestly curious.

---

I believe they call it 15KW because that is how much power is in the work coil at resonance.

That said, mine will even pull 45 amps running at 240V - that is over 10KW.

I have no idea about the 110vac one you are talking about.

I am actually going to buy a 65KW unit. Well its 65KW on 3-phase and 48KW on 2-phase. I currently only have 2-phase here. That one will require a 125-amp breaker on 240v. For the money, it just can't be beat trying to build one IMHO.

Quote:

---

Originally Posted by 3DTOPO

I mostly use it for carving out EPS foam and wood for patterns for metal casting.

It will also machine aluminum if I am not in too much of a hurry.

Let me know if you need anything big carved! ;)

---

Thanks, but I've already built a router a lot like yours, from automation actuators. I can cut wood with it, but I don't think it's rigid enough for aluminum. I use mills for that.

Have you got a link to that 65KW induction melter? If I did want to make an aluminum piece that big, it would make sense to carve it in foam and cast it, rather than attack a huge piece of billet.

Quote:

---

Originally Posted by 3DTOPO

I believe they call it 15KW because that is how much power is in the work coil at resonance.

That said, mine will even pull 45 amps running at 240V - that is over 10KW.

I have no idea about the 110vac one you are talking about.

I am actually going to buy a 65KW unit. Well its 65KW on 3-phase and 48KW on 2-phase. I currently only have 2-phase here. That one will require a 125-amp breaker on 240v. For the money, it just can't be beat trying to build one IMHO.

---

Now that's some serious hardware.

Quote:

---

Originally Posted by awerby

Thanks, but I've already built a router a lot like yours, from automation actuators. I can cut wood with it, but I don't think it's rigid enough for aluminum. I use mills for that.
.

---

Quite true. Casting large items still involves its own work as well though - more hands on than running a robot unless you are the big foundries that do use plenty of automation.

Quote:

---

Originally Posted by awerby

Have you got a link to that 65KW induction melter? If I did want to make an aluminum piece that big, it would make sense to carve it in foam and cast it, rather than attack a huge piece of billet.

---

Below is a link to the company I have been dealing with through Alibaba.

I don't own a machine from them yet, so I don't have any experience with their hardware, but they have been very professional and helpful with all my questions. Their 65kw model is WZP-65 (they have other models the number is KW). The 25kw and up need 3-phase as standard.

https://yongdagp.en.alibaba.com/prod...836.186.ngNXj2

Quote:

---

Originally Posted by 3DTOPO

Quite true. Casting large items still involves its own work as well though - more hands on than running a robot unless you are the big foundries that do use plenty of automation.

[Yes, there's definitely a bit of work involved, at least until you've got the robots trained to do it.]



Below is a link to the company I have been dealing with through Alibaba.

I don't own a machine from them yet, so I don't have any experience with their hardware, but they have been very professional and helpful with all my questions. Their 65kw model is WZP-65 (they have other models the number is KW). The 25kw and up need 3-phase as standard.

https://yongdagp.en.alibaba.com/prod...836.186.ngNXj2

---

[Thanks for that, and please let us know how it works out for you. The information on that site is rather strange, though. Since aluminum has a Specific Gravity of 2.8 and steel has a SG of 7.8 I don't see how a furnace that holds 10 kg of steel at max can also hold 10 kg of aluminum. Maybe that "hotrolled cannabis cobalt" is having an effect...]

Andrew Werby
Juxtamorph.com

Quote:

---

Originally Posted by awerby

[Thanks for that, and please let us know how it works out for you. The information on that site is rather strange, though. Since aluminum has a Specific Gravity of 2.8 and steel has a SG of 7.8 I don't see how a furnace that holds 10 kg of steel at max can also hold 10 kg of aluminum. Maybe that "hotrolled cannabis cobalt" is having an effect...]

---

Induction generators will have different rated capacities based on the metal intended to be melted.

They sell the generator - its up to you to make the work coil and size the crucible, etc. - other than the one crucible and work coil it comes with which of course is a fixed size.

Quote:

---

Originally Posted by 3DTOPO

Induction generators will have different rated capacities based on the metal intended to be melted.

They sell the generator - its up to you to make the work coil and size the crucible, etc. - other than the one crucible and work coil it comes with which of course is a fixed size.

---

So it's not about the size, but the energy required to melt that amount of metal? It seems odd, then, that the same rig that will melt 30 kg of copper will only melt 10 kg of aluminum, which is a lot easier to melt. Or am I missing something?

Quote:

---

Originally Posted by awerby

So it's not about the size, but the energy required to melt that amount of metal?

---

Correct.

Quote:

---

Originally Posted by awerby

It seems odd, then, that the same rig that will melt 30 kg of copper will only melt 10 kg of aluminum, which is a lot easier to melt. Or am I missing something?

---

It is because while steel melts at much higher temperatures; aluminum conducts electricity much better than steel. When you heat metal with induction, you can essentially think of the work piece as being shorted out to your main. So the additional resistivity of steel allows more heat for the same amount of energy. Ferrous materials have an additional advantage too, in that they are heated by magnet eddy forces up to the currie temperature.

So while it seems counterintuitive, induction generators actually heat ferrous materials easier.

That said, one can use a conducive crucible (eg high purity graphite) and that is heated directly by the EM field and can be used to heat things that are both non-conductive and non-ferrous (eg you could melt glass). But in an ideal induction furnace, you want the metal to adsorb the energy directly; not the crucible.

The more I learned about induction; the more surprises it has reveled!

;)