Large Scale Central

"Lost Resin" for casting parts

Modeling
#1

So we started down this rabbit hole in my MIK thread. Before it goes too far off the rails I decided to ask this here and see if anyone has ideas.

I have a hard time getting reliable pours when I cast white metal into rubber molds. I have in the past, a long time ago in Jr High School, made a ring using the lost wax method of casting. I like this idea very much as it makes a lot more sense to use inertia to throw metal into the mold and displace the air. I am thinking this would give me much better results if I get the equipment.

As I started googling I came up with a couple ideas that I am wondering about. Lost wax casting takes a wax master and you pour some sort of stuff like plaster around it in a metal cylinder. Once that dries you put it in a kiln and burn out the wax leaving the negative in the mold. You put that mold, metal cylinder and all, into a centrifuge and you pour in your molten metal and let fly. The metal is forced by inertia into the negative space. You then break the stuff out of the metal cylinder and you are left with your metal casting.

So my original thought was to see if their was a resin for 3D printers that could be used to make the “wax” masters and then pour the plaster stuff around it, burn it out, and then cast it just like you would lost wax. While this would be fine, resin is a lot more expensive than wax. This got me thinking of the evolution a bit more.

Dave T uses a high temp silicon rubber for his casting. which means he can use a mold over and over to cast white metal parts. I am thinking that a hybrid process could be done. Make a silicon rubber mold that is made to fit inside the casting cylinder and then it would, I think, be able to be cast, removed from the cylinder, parts removed, and then it could be used again.

If this were reasonable, then you would only have to make the 3D printed master (or any other master such as an existing part) one time, make the mold with it, and you are done. Just like in any other casting you would have a reusable mold. It there any folly in my thinking?

Yet another idea if that wouldn’t work well, would be to print the parts in resin and cast them into a silicone mold. Then instead of casting the metal into it, a person could cast wax to make the masters for lost wax casting. You would making a mold to mold the wax pieces instead of the metal pieces. Then the process would be the exact same as lost wax casting. My thought here is that wax has a very low melting point, enough so that the molds could easily be kept above the melting point of the wax and then if necessary a vacuum could be applied to even further pull the air out of the mold and fill the negative space with wax.

#2

You can purchase printable wax and the photos look ok.
https://all3dp.com/2/wax-3d-printing-how-to-3d-print-wax/

#3

Ha that’s awesome. This will be a great way to turn all the parts I have designed for resin printing and make white metal parts of them. A dental centrifuge is under $200 bucks. I have the printer. So really this wouldn’t be a huge investment. I kinda am liking this idea. Just one more rabbit hole to go down.

#4

I’ve done some printed burnout resin to metal casts. Worked well.
What’s the melting point of white metal?

#5

Many, many moons ago I worked for a short while at a foundry that used “lost Wax” patterns.
The molds were made in green sand using the wax pattern.
The molten metal melts the wax immediately, exhausts the wax fumes from the escape vent and replaces the pattern. That is why it is called “lost wax” you lose the pattern. If the pour fails, (and it sometimes can) you don’t have another chance unless you have the artist make more patterns
We also used styrofoam as a lost pattern.
I do not know the melting point of Resin. You have to know that so you heat your metal hot enough.
But most of our pours were made with removable patters made of wood.
We only poured Aluminum, brass and bronze.

Pewter is best for modeling because of its low liquifying temperature.
As to small parts that would used on models, you are better off with a re-usable pattern and a centrifugal mold to force the pewter into the mold.

#6

Devon, Are you talcum dusting your mold between using? Are you heating your mold to about 400 Deg. before pouring in the metal? If there is consistent parts that do not fill, then you have an air bubble and you need to create a vent! Extra “Risers” to create a flow thru from one side to the other, will help fill the cavity, and pour from one side until the metal comes up the other side helps.

On “White Metal” Pewter of the 92-97% Tin type, there is a Melting point temp, and a Pouring point temp. Make sure that you pour at the higher temp, but don’t "Burn the metal by going way to hot…

#7

Skip a few steps here:

#8

Dave, I did dust them, you suggested that to me back when I was initially having the issue. That helped. I never did try heating the mold but that makes sense. I also never did buy the high temp rubber for my molds that you suggested. I gave up before getting that far.

I do believe more than anything it was my ability to make good molds more than any other factor. I just never got far enough to where Ii said I was having a “specific” problem and just gave up.I go into 3D printing shortly after and figured it was going to be my got from then on for the parts I need. But now I am wanting to revisit it all. Metal is still by far my favorite materiel for detail parts.

Being able to take my designs and do either lost wax or even use silicon molds and spin cast metal parts would be a happy marriage between the two. I am thinking it would be very doable to use the high temp rubber you use for molds and make a mold that would fit in the cylinder of the spin caster. Then spin the metal into it, take the mold apart and remove the part, rinse and repeat. If that doesn’t work then lost wax investment casting would be also doable.

#9

Its an expensive service. I looked into it. Just not worth it for one offs.

#10

So one rabbit hole I went down was the idea of making a negative mold of a part in Fusion and then printing it in a resin that would withstand the heat of pewter. No such luck. All the resins are much lower temp rated than the melting point of say 97% tin pewter. But I did learn a skill on how to make negative molds of positive things I have designed.

Mold 1
Mold 1454×540 52 KB

Mold 2
Mold 2565×520 66 KB

A simple wagon wheel I had made up and was easy to grab in fusion. I won’t bore you with the details but I was successful. The only thing I could see at this point using this for would be to make repeatable wax masters that could then be lost wax cast.

All in all I think the answer is that it would not be all that hard to either print or mold wax masters of the stuff I am 3D printing and then either investment cast or see if I can build a cylindrical reusable rubber mold that would allow me with either process to spin cast metal parts . . . safely and repeatedly.

#11

I do believe that that mold would fail at about 6-8 points… For a mold like that it would be WAY BETTER to lay it flat ( not vertical ) and fill it from the center, and than put 4-6 vents all around the rim…

I think that that mold would, as shown, wouldn’t even fill with wax for “Lost wax” casting.

Also it would fail in a spin caster…

#12

All good advice and well taken. That was just a quick question answered on how to work in CAD to accomplish the task. Not so much thought was put into whether or not it was an actual good design. But with that said I am glad I posted it so that you could “show” me the errors in my ways. I would argue that my mold making skills are far less than stellar and could very well be 100% of my past problems.

As a 3D printed mold, at this time it would be for wax casting for making the masters. There is no resin that will tolerate the heat of molten metal. But casting wax may still very well be the route I go and then do lost wax investment casting. That all remains to be seen. But no matter what way I go, I’d love more critique of the mold designs so I can learn from those with more experience like Dave.

#13

Just for curiosity sake. . .why would it fail in spin casting? I thought the very idea of spin casting was that the weight of the metal and inertia would shove it into all the areas of the mold and air really can’t get trapped because it is displaced by force? Now this is all theory as I really have no idea what I am talking about. But I thought that “was” the benefit of spin casting is that it is able to force its way in and displace air through the main opening.

#14

Devon,

want a spin casting machine? it is available in my garage for free in southern NH.

In all seriousness if the end result is metal parts look @ the new shape ways site. depending on size you could have done in lost wax, or the various sintered steel offerings. be wary of shrinkage with the sintered products, my past experience is archived here somewhere. i will use them again when i need brass parts for sure.

I have moved on long ago to 3d printing almost every thing, and have found a resign that will stand up to abuse in thin cross sections,(and not break) and with the new Form 4 machine the surface finish is like injection molding. Formlabs does offer a couple of resigns that are made for burnout, but are more expensive than the normal ones.

AL P.

#15

Is anyone else seeing that this might be the actual moment of Devoning commencement? :grin:

On the more serious side, I’ve often wondered if someone could crack the nut on 3D printed master to cast metal part. I say, go for it! But maybe not in the context of this build, since it may become a huge effort in itself?

Regardless, maybe you’ve seen vids such as these, which represent very different approaches.

https://www.youtube.com/shorts/pbbNipnsejQ

Cheers,
Cliff

#16

Cliff I wouldn’t even throw this in the true Devoning category. This is just a lot of theory and day dreaming and what ifing.

I would like to get proficient in casting but I am not heading down that road again anytime soon.

#17

hmmm, to me that sounds like a plausible description of “Devoning”

#18

No Devoning would be to actually have a specific project in mind and then overthink it to paralysis and put it aside and start another project.

This is just aimless wandering (wondering) at this point.

#19

well, you are the specialist. so i must believe you.