RepRap using wax for making bronze molds?

Hiya all,

I found the RepRap from Neal Stephenson's FaceBook post, and think this is terribly terribly cool. Were I not planning/prepping for living on a sailboat, I would have already ordered a kit from someone!

The interesting intersection of sailboats and RepRaps, though, is that sometimes you want a custom piece of hardware made for a sailboat, and bronze is a great material for this... but getting custom bronze work done can be difficult. One of the ways that bronze items are typically made, though, is via the lost-wax process. ( [en.wikipedia.org] ) Basically, you make a model, cover it in latex to make a female mold, coat the inside of the mold with wax to make a solid "copy" of the original, then coat the wax copy with ceramic slurry. You then fire the ceramic copy in a kiln, which hardens it while simultaneously melting out the wax (hence the name of the process). Finally, you pour in bronze, let it cool, and break the ceramic bits away to reveal your bronze item.

What I'm wondering is if you couldn't speed up this process by using a RepRap type machine to extrude the wax model, which can then be coated with ceramic and cast by someone who knows bronze?

What would be even cooler would be if this machine had interchangeable "print" heads, one that would work with wax, the other which would be a standard RepRap head. You could then prototype the part in plastic, test it for fit and suitability for purpose, then make your wax one for casting.

I'm not the type of guy that can design this myself, but I can definitely see the use for one. What sayeth the crowd?

(PS: You can buy granulated wax readily from various sources... [www.candlewic.com] 35 pounds of white wax: $61)

Quote
jason
What would be even cooler would be if this machine had interchangeable "print" heads, one that would work with wax, the other which would be a standard RepRap head. You could then prototype the part in plastic, test it for fit and suitability for purpose, then make your wax one for casting.

I don't see why this wouldn't work.

And remember, the RepRap machines only use 12v so you should be able to run it on your sailboat! You could use a bicycle frame and a generator to keep the battery charged (or a hand crank generator but that is more work). I guess it depends on how big your sailboat is... If it's big enough for the RepRap then the bicycle generator should also fit.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

[blog.reprap.org]

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[www.hydraraptor.blogspot.com]

Bob, I didn't see that the machine is a 12V machine. Very interesting. Honestly, though, I think it would take up too much room on a boat. Sailboat interiors don't typically have much room, especially if you tend to like smaller boats (like I do). On the other hand, most boats have very well established 12V power systems, including solar panels and water/wind mills to generate power. Were someone to make a smaller one, it could probably fit just fine.

Nophead: Very cool. I was thinking that you could use normal wax rather than one of the plastics so you could send it off to a foundry where they really know the bronze side of things. I've talked to the owner of Bristol Bronze in the past... I'll drop him a line about this and see what he thinks. He might use sand costing rather than lost-wax. If so, could be easier to just make plastic parts and send them to him for casting.

This question of extruding wax for casting comes up over and over again in these forums. Until somebody tries it we won't know for sure, but it my thoughts are it will not work because wax is too runny when hot. It would certainly need a new extruder designing as you can't get a reel of wax.

Using PLA instead seems like the perfect solution. I don't see why you can't sent it to a foundry and Vik has shown it melts / burns away just as well as wax would.

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[www.hydraraptor.blogspot.com]

Ahhh. I did a quick search on "wax" before starting this topic to see if it had come up before, and got no hits. I must have been searching wrong.

I've fired an email off to a bronze part maker to see what he thinks. Will report back.

Jason,

It should be fine, after he fiddles with his setup a tiny bit. Bronze foundries cast thermoplastics all the time when artists bring in "found object" art and cast toothpaste caps into bronze.

Here is the RepRap wiki page on bronze casting.
[reprap.org]
(please log in and edit )

Let your foundry buddy know that he can make a bit of cash by making molds from a set of mendel parts and selling the parts in our forum.

Here is mini-mendel:
[reprap.org]

Also, VDX did some work on Sodium Silicate Concrete
[reprap.org]

This may be a good candidate material for non-critical sailboat findings. (Stuff where if the part fails due to corrosion or under stress, it doesn't kill you.)

Edited 1 time(s). Last edit at 04/23/2010 02:54PM by SebastienBailard.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I think the forum search does not work with three letter words. Google "site:forums.reprap.org wax"

Edited 1 time(s). Last edit at 04/23/2010 04:28PM by nophead.

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[www.hydraraptor.blogspot.com]

I think some of the waxes used by jewelers, machinists, and sculptors are a mixture of thermoplastics and "microcrystalline" wax. I think microcrystalline wax is paraffin wax with additives to reduce the grain size.

When you try to deform paraffin wax, it shatters into large crystal-like flakes. Microcrystalline wax doesn't.

Nophead is right about the flow properties; You'd need a heated syringe. And you don't want to say, to have a leak spray wax onto hot electronics.

Wax is the most dangerous thing you find in a bronze foundry, frankly. This was cool, however:
[reprap.org]

Stick with thermoplastics or powderprinted starch.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I've seen a jeweler who 3d prints wax for investment casting so I know it's possible.

What extruder, or what composition I do not.

I imagine any thermoplastic which can be vulcanized would be adequate.

The lost wax process (investment casting) could be used for reprap parts, but unfortunately it won't improve your productivity. It can effectively take a plastic part or wax part and convert it to a metal one, but as a general rule both the master part and the mould are destroyed in the process. So you only get one part from one part.

It is pointless trying to make a wax part on a reprap then investment casting it. If the final part is OK in plastic. Just printing it would be quicker as its one operation. Investment casting is only used if you need a metal finished part. Remember also that you will need risers and fill gates on your part which all takes a lot of time. Its a common joke in engineering that its called "investment" casting because you have to invest a lot of time and money.

Investment casting can also be carried out using a plastic master covered in ceramic. Reprap in plastic, and melt it out when firing your ceramic mould. Invert the mould so that most of the plastic master runs out as a liquid.

Remember also that the reprap is ideal for making either the PART or the MOULD. I see a better process methodology as follows:-

Reprap the MOULD in plastic (ie the negative of the part. You can reprap all the risers and fill gates. Make a two part mould so it can be split off the part.

Ceramic coat the mould and fire it.

Cast the part in Bronze or other metal. You then have a metal mould

Use this metal mould multiple times to cast plastic parts. This will improve your productivity. One part giving rise to many. By careful decisions as to what you cast the mould out of, you can cast metal parts in the mould. You can cast anything that has a lower melting point than the mould material.

@martinprice2004: You totally missed the point of his original post.



He needs bronze parts for his sailboat not plastic parts so creating a mold out of bronze to make plastic parts doesn't help him. He wanted to know if he could use RepRap to create plastic parts that can then be made into bronze.

To cut to the quick - the answer is YES!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

@Rob: Exactly. I was thinking that this would be a good way to make one-off (or very limited numbers, anyway) pieces for use on my as-yet-hypothetical sailboat. Still quite interesting to see other takes on it, though.

The gent I contacted is Roger Winiarski, owner of Bristol Bronze (http://www.bristolbronze.com/) He seemed very interested in the idea, saying the following:

"Dear Jason,

Thanks for the e-mail and for your interest in Bristol Bronze.

We do both sand casting and Investment Casting (lost wax) depending on the size and complexity of the fitting needed.

We could certainly give the method that you mention a try. If you have a piece in mind we could use it as an experiment to see how it would come out.

Roger W
Bristol Bronze
401-625-5224"

Now, I don't have a RepRap, or any particular parts in mind, but on the off chance that someone else on the board would like to give it a shot, I told him I'd post his info here.

Cheers, all!

Sorry guys I mis read the original post. My apologies. I promise I shall go and sit on the naughty step for the next hour.

Plastic masters are used for investment casting as is foam, wood and frozen mercury. Perhaps trying an abs or pla master would be the thing to try first.

Edited 1 time(s). Last edit at 04/24/2010 07:05PM by martinprice2004.

I belive thereis no difference in wax and any plastic in case of bronse casting.

... the main difference are the fumes - some plastics are extreme toxic and carcinogenic when burned away ... remember Seweso/Dioxin

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I think wax would work. It doesn't need a high temperature, so it would liquify at PLA or ABS temperatures, but isn't it pretty easy to change temperature? And of course you can't buy strings of wax, but it would be pretty easy to make a gravity-fed, heated wax hopper.

I'm experimenting with lost-wax casting with scrap aluminum and will definitely try this when I finish my reprap. It would be pretty neat.

edit: Oh, oh! I just got the best idea. You could try sand-casting as long as you don't have any overhangs, which is necessary for reprap anyway. Basically, you press the piece into a box of wet sand (I think you might need green sand, but I dunno for sure) and pour bronze/aluminum/tin/copper/whatever into the impression left by the piece. This seems like it would be perfect for things like gears that really should be in metal and not plastic if they're taking heavy wear. The best part, though, is that you can cast as many pieces a you want from one printed part!

Edited 4 time(s). Last edit at 04/30/2010 12:59PM by wayland.

I know its an old thread (hey I'm searching) But why not make the plastic negative mold and cast wax into that, to produce multiple wax molds for metal casting?

rhmorrison Wrote:
-------------------------------------------------------
> @martinprice2004: You totally missed the point of
> his original post.
>
>
>
> He needs bronze parts for his sailboat not plastic
> parts so creating a mold out of bronze to make
> plastic parts doesn't help him. He wanted to know
> if he could use RepRap to create plastic parts
> that can then be made into bronze.
>
> To cut to the quick - the answer is YES!

... you have to 'fill' somehow the horizontal voids between the layers or it's nearly impossible to remove the solidified wax from cavities with steep walls ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

same problem exists with any standard methods, no? (If there are center voids)
If he was just making cleats, or mounting bases, don't see much a problem.

Guys I think this could be possible, we just need a rod that has the right wax (I am a foundry man myself, and reprapper, was is all about the composition, which types you put on it and the room temperature of course crucial here, we would have to use heated chamber for machine and spool.

Anyway, the right composition could make a normal spool like the one we use ABS PLA, then we need to heat it up, probably much less, just enough to not melt it, but be able to move it around and place it on the bed, not heated of course if not the was piece dissapears in 5 seconds.

It is a great project i will pursue some day any interesents lets please keep contact.

J.

From Instructables:

Bronze casting your 3D print
How To Easy Sand Cast 3D Printed Objects

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How often I found where I should be going only by setting out for somewhere else. - R. Buckminster Fuller

[apapageek.com]

MMMMMMM that is very interesting, but it would me fantastic to print straight on wax.

How about using the "Parametric two-part mold generator for OpenSCAD" on Thingiverse to create a MOLD for your object (in ABS) and then fill with a wax.

Wax melting points:
mould wax = 60-62°C;
dipping wax = 65°C
BEE'S wax = 45°C
carnauba (a vegetable wax) = 78-85°C
paraffin (a mineral wax) = 47-65°C

ABS can withstand 100°C so this should be no problem.

Edited 1 time(s). Last edit at 01/11/2013 09:23AM by rhmorrison.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I've been toying with a crayon revolver idea for an extruder. The temperature does not need to be so high as to melt the wax. You just need to soften it enough to push it through the nozzle.

The revolver idea I will probably abandon in favor of a vertical feeder tube. Originally, I was going for a multi-color design. Walk before you run.

I'll throw my stuff up on the Wiki if anybody wants to play with crayons.

Hey Jcarber your drawing looks interesting can you explain more how it will work... thankssss

The basic idea is to use a long tube with an I.D. of 8.5mm (crayons are ~8.25mm). The tube holds your feedstock. In this case, it would be crayons.

Most of the extruder can be made of ABS because the glass transition of crayon wax is really low. The wax would be extruded similar to a paste, and would only require enough heating to soften it, not melt.

The image I posted shows a crossection which illustrates the use of an O-ring to seal off the "melt" pot of the nozzle. It is not intended to represent the finished design.

I had another design that used a revolver to hold multiple crayons of different colors, but it's mechanically a very challenging design, so I am putting it away for now, in favor of the tube.

So I stumbled onto reprap in the first place while looking up 3d printers that could print wax for lost wax casting. I'm a jeweler by trade, and while some of the suggestions in this have been insightful, they don't solve the general problems.

Wax is used instead of plastic in casting for jewelry in order to make it so that the inner surface of the mold is as smooth as possible, eliminating the need for finishing in areas that our tools, quite frankly, can't effectively polish. Plastic would leave a small amount of residue which would be unsuitable.

There are a few extruders that have come up in my searches work for different ceramic composites, etc., but none have succeeded in doing what ultimaker or stratasys are currently doing, which is making castable lost wax machines.

You can buy reels of wax that is flexible instead of brittle, that melt at different temperatures, and have different degrees of hardness (all still not being brittle). You can get it in round and half-round [www.riogrande.com] . They also sell their own "digitalwax rapid prototyping machine," but I don't have 10k to throw around.

I'm a total newbie to this, and I haven't built my first reprap yet, but wax is my driving goal so that I can make cast jewelry and increase the variety of designs that are available to me (right now I'm working with the traditional sheet and wire mostly). So, given that there are reels that are to be had, that they are very flexible (and flexibility and malleability increase with very little heat), what other considerations should I make in modifying an existing extruder?

Also, a difficulty that I imagine facing in the near future is that if there are any pores or seams in the wax, when the ceramic mould is poured over, it will seep into those and ruin the integrity of your casting. There are a few tricks you can use to seal up your surface, but when printing on a 3d printer, is there any way to ensure that the wax is definitely fused to the previously laid surface seamlessly?

As wax has some properties similar to sugar, you might want to have a look into sugar print heads:

[blog.reprap.org]
[blog.reprap.org]
[www.thingiverse.com]

Even a wax printhead exists:

[blog.reprap.org]
[reprap.org]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

P.S.: not to forget the Waxuum: [reprap.org]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY