Tips/Techniques An adventure in lost resin casting.

[Mcgyver]

I finaly had some success with lost resin investment casting. This is like lost wax investment casting, however the pattern instead of being was is a special castable 3D printing resin.

Been at it for 2 years, each attempt takes so much time and there as so many variables; what resin, what printer exposure settings, what curring process, what metal, what burnout, what investment, what mixture etc etc. Very tedious and lots of blind alleys. But on the weekend, success!

The main subject is the reversing handwheel for a Stuart Triple Expansion Marine Engine. The one on the drawings did not do the engine justice imo.

Two years of heartbreaking attemps (each one takes Friday - Sunday and is a lot of effort). I'd get close, but too many surface flaws. I can do a perfect lost wax casting, but the resin behaves differently.

That is a lot of attempts!!



I tried a new resin on the weekend, X-one resin which is not cured with UV light.

'
Keep your fingers crossed

Well, finally! They didn't all turn out great but one did and the results are better than anything so far. Most of the rest suffered from ( I realized after) a poor tree layout. It is being vacuum cast, but there are limits to how much it will run up hill.

 

[Mcgyver]

No major surface flaws

after a bit of pickling

This is enlarged quite a bit, its hardly over an inch in diameter so I think I can live with few flaws there are.


As experiment I also took some model flange fittings I'd been working on and made assemblies out of them using fake nuts and bolts. The idea is if you silver soldered a piece of tube to it, it would look like a bolted flange connection. This one is for 1/4" tubing.

Check out how the fake threads even came through - It gives a good idea of the resolution and detail you can get with the resin printers. Those fake bolts are .060" diameter. There is a new league if super fine printers that can print to two microns.....but they are >$200,000 so my $290 one will have to do for now!

 

[DavidR8]

That is just amazing work. Well done.
I so want to try casting!

 

[Dan Dubeau]

Quite a long journey, but the results are simply amazing. I love those flanges. Can't wait to see a model build utilizing them.

 

[Arbutus]

Very nice! Thats a lot of patience I'm seeing there.

What was the resin product that worked for you? Does it behave differently than standard resins when printing?

I have been playing with wax filaments for lost wax casting, supported by plaster of paris, but with limited success because the filament breaks every few minutes during the print and the resulting print distorts easily. It also creeps, weeps and sags while sitting on the shelf so any attempt at precision is futile. The filament approach works for blocky, chunky objects, but I doubt these detailed parts you are making would look as nice. This lost resin approach looks promising.

 

[Mcgyver]

Thanks guys!

Arbutus, the resin that worked is X-One by bluecast, however ALL the resins I've tried were specifically castable, i.e. intended to be burned out.

For lost filament casting I would highly recommend polycast. It is simply brilliant, great bed adhesion, great prints and a complete burnout. I'd tried some awful stuff before, just get a roll of Polycast. You do however need to keep the humidity way down. I run a dehumidifier in the room at its lowest setting for a day or two and that works well enough.

You don't get the detail, but its a lot easier and lots of parts don't need detail....polycast print vacuum investment cast in AL

 

[jcdammeyer]

A few questions.
This video outlines the X-One resin process.

Did you do everything in the video? Like Cure with Ethanol? Burn out at 750C?
What type of printer do you have?

 

[Mcgyver]

Haven't seen the video, but largely followed the written guide. The burnout cycle went to 740. Their literature says its all burned out at 680 or 690. Depending on who you listen to, the investment can breakdown at around 800C, so you don't want to go more than that (and with this resin isn't needed). I used the crappy tire fireplace fuel for curing which is ethanol and isopropyl alcohol. I want to try methanol and see if it works, that fire place fuel is too expensive.

Printer is a <$300, an Anycubic photon mono 4k. Its 4k but with a small work envelope so its both cheap and gives greater resolution than a 4k with a larger envelope.

 

[jcdammeyer]

Haven't seen the video, but largely followed the written guide. The burnout cycle went to 740. Their literature says its all burned out at 680 or 690. Depending on who you listen to, the investment can breakdown at around 800C, so you don't want to go more than that (and with this resin isn't needed). I used the crappy tire fireplace fuel for curing which is ethanol and isopropyl alcohol. I want to try methanol and see if it works, that fire place fuel is too expensive.

Printer is a <$300, an Anycubic photon mono 4k. Its 4k but with a small work envelope so its both cheap and gives greater resolution than a 4k with a larger envelope.

Did you also use vacuum to remove the air from the investment? Was it just simple plaster of paris or something exotic. I have a kiln and the ability to degas. I've thought about burning out PLA but so far nothing has come up in the project #42 category that needs this but it's very interesting.

 

[Mcgyver]

Yes, investment was degassed. the whole thing is very scripted. 20 degree water, 39:100 water to investment mix. Its not even regular investment but R&R Plasticast. Supposedly tougher than Ultravest (but I didn't notice a difference....they all gave crappy results until the X-one). Burn out is in a programmable oven (have to for correct ramp and soak times at various temps) and casting is done with a vacuum caster. I use one of the little not too expensive electric melters Amazon and other sell. The flask was at 520C for the pour, the metal (973 bronze) was a 1030 or 1040 (cant remember)

If you are going to burn out PLA, consider the polycast instead. Its more money but burns out perfectly.

 

[PeterT]

You are making great headway! I can't help but thinking a skinny circular wheel with spokes would be present challenges over & above all the other variables, so kudu's.
Maybe I missed it but what was the alloy being cast? Have you tried aluminum at all or you're just focusing on your immediate to-do list?
Roughly how thick are the spokes/parts at their thinnest section?

If you ever want to try a something 'finned' just for interest, I'd happily CAD you up a coupon part, but maybe you are CAD proficient already.

 

[Mcgyver]

Thanks for the encouragement! The small end of the spokes are .052, the outer ring is .113 thick. I tried a few silicon bronzes, the latest is 973 which has no zinc so is nice to work with. I have done a few investment casts with AL, didn't get great results but that was earlier in the adventure. I believe results would be a better now. The bracket above was AL (but filament). Here's an AL investment casting based on a resin based pattern.

Probably no more casting for a bit, have to finish my watchmakers sized quick change tool post thing, get this handwheel hub machined and get back to the triple

 

[Mcgyver]

update......

to bore and face the wheel's hub I had to finish my miniature QCTP, based on a Tripan but much smaller. The body is about an inch long and thats a 3/16 tool bit. Specifically designed for 8 and 10mm watchmakers lathes.

got a little carried away with inserts.....made two tool posts so each will have lots

Depth stop are via this little bronze castings. 3/32 rod was used to pin them to the body and then control the depth via a rod with a set screw

little turret lathe to cut the pins off

 

[DavidR8]

Wow, that's fantastic!

 

[Mcgyver]

on to the lathe

bored and reamed - 1/8 bore

Drilled and tapped for a 1 72 set screw

and installed! Its the reversing handwheel for my Stuart Turner Triple Expansion engine. Probably have two years in the handwheel, but it was a lot of learning and development.

 

[140mower]

on to the lathe



View attachment 41286


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bored and reamed - 1/8 bore


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Drilled and tapped for a 1 72 set screw

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and installed! Its the reversing handwheel for my Stuart Turner Triple Expansion engine. Probably have two years in the handwheel, but it was a lot of learning and development.

View attachment 41290


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Don't know that I have ever had a shortage of words...... But here I am.... Stunning execution sir!

 

[Susquatch]

Probably have two years in the handwheel, but it was a lot of learning and development.

Beautiful Mike. Incredible work too. Very impressed.

 

[Dan Dubeau]

Pretty incredible results. I can only imagine how rewarding that must be to finally have a process down that you can rely on. That sure opens up a lot of possibilites. Well done Mike. Thanks for sharing all your trials and tribulations as well. At some point in the future I would also like to explore lost resin casting and you've saved me a lot of money thus far with what NOT to use as far as expensive resin.

 

[thestelster]

Wow!! Simply wow!

And I love those faceplate hold-downs.

 

[Tom O]

A triple expansion wow that’s quite the undertaking.