Some success (finally) with lost resin investment casting

[Mcgyver]

I finally 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 curing 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 never really appealed, so I had an idea for a cast hand wheel with spokes.






Two years of heartbreaking attempts (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.  The burn out (I think) expands it slightly damaging the mold, so I switch to "Plasticast" which is supposed to tougher.  Still endless problems, and with so many variables (and a lack of experience) its challenging to sort it all out.













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.  This is using 873 silicon bronze (no zinc!)





No major surface flaws




after a bit of pickling




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


As an 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!
















[

[tghs]

  looking very good

[Keith1500]

Nice resolution. For $290 printer I would be happy with that. What’s the printer that you are using?

[Mcgyver]

Thanks Gents,

Keith its an Anycubic Photon mono 4k.  Fairly high resolution (about equivalent to 700 dpi) but a small work envelope.  The 4k is the product of matrix length and width, so a 4k with small work envelope gives the highest resolution, vs a 4k with a bigger work envelope.  The printer is $232 US now. (my 290 was CDN)}

[Kim]

That is really slick!  You really stuck with it to get your lost-resin casting method to work.  Well done! 

And the elbow flange fittings look really great!  Those would do any model proud

Kim

[cnr6400]

  Great looking parts! Congrats for sticking with the development.

[PJPickard]

Great work, I've done this so far without success, the printing part is OK but I have failed at the casting. There is a LOT to getting this to work!

[wagnmkr]

The time spent experimenting seems to be worth it. Good quality there. 

[Admiral_dk]

Great to see and hear that all your effords finally are paying off 

Per

[BillTodd]

That's really impressive   

[Jasonb]

Looking good.

It would be interesting to see how they clean up with a light bead blasting which as well as cleaning may remove some of the still slightl visible print layering, but they ar elooking good. If the handwheel had it's spokes painted and was spun up against some emery to brighten up the rim I doubt the layers would show.

You show the green prints and then when they are in the flask they are off white, have you coated them with something?

[Mike R]

Please share your "recipe" that worked for you.  I'm probably a few years behind in terms of casting but I'd like to get there one day, and even if my variables may be different, having your process details would give a great place to start from.

[derekwarner]

That 90 degree - extra short radius bolted flange set for 1/4" OD tube is excellent  .....

As you say, some of the casting trees are tight. Do you think the flanged 3 x way T for 1/4" OD tube, which lost the top outlet flange during the cast was due to an air pocket?, so would small capillary air riser assist? 

We must remember you are replicating some complex forms, in the same manner that the full-sized counterparts were box & core cast in Iron and later Steels in the late 1890's [of course with the single flange at each end]

Well done
Derek

[Mcgyver]

Thanks again for the kind comments.

Jason, I'm going to work on the handwheel.  I've various polishers/tumblers and media but never really figured out the optimal process.  Whatever I seem to try it sits for 6 hours and doesn't look much different at the end!

Doing anything with the pipe fittings, bead blast or tumble, I'd be concerned about losing detail, e.g. the threads.  If painted i think the lines would close to disappear.  They are more prominent when the part is by itself and enlarged, much less visible when 2 feet away on the bench (and you squint a bit).

I've toyed with real bolted connections, but you're down to 0-80 threads on the 1/4" onces.  Trying a 3/16 version now which are evey smaller.  Not sure they would be strong enough, and that is a lot of very small fasteners to make.

On the colours, different resins.  The one that worked (the pic with all the items on the build plate) starts off a very dark green.  Its cured in alcohol, no UV light, and after drying appears white.

What worked is X-One castable resin, 873 bronze, 510C flask temp that was taken to 740C (about 24 hour cycle, first to 150, then 350 then 740 with very slow ramps), metal pour temp 1030, R&R plasticast investment (i think its a bit of BS that its any different from their regular ultravest, just reporting what I used here), 39:100 ration, water at 21 degrees, 3 min of mixing, 2 of vacuuming, pour investment, 1.5 min more of vacuuming then a two hour sit before the furnace cycle, then vacuum cast.  There, hopefully that saves you two years! 

Each pour, between print, tree build, investment setting and burn out is about three days, obviously not full time but there is lots to attend to so you can't if there is lots on over the weekend.  Five attempts can be a few months work so the failures grind you down.  Bit of a rabbit hole ...... was at a party last night I realize looking around the room just how little anyone there would care about a bronze handwheel, like not at all, yet its been like Everest to me for two years!  I think I need to get out more 

Got another pour happening today....will post about it.

[Dick Morris]

Nice work. Your flanged elbow came out particularly well.

I feel your pain on how much time one can invest into a single casting session, especially when all you have to show at the end is a bit more knowledge of what didn't work.

I've been doing lost resin casting for 2-3 years. I've had some successes and some failures. In the most recent failure, several of the flasks had significant cracks to the point where they weren't usable, i.e., on some investment fell out after burn out and they seemed too soft. I'm still pondering on what I did wrong. Maybe I got the water to investment mix wrong or heated the flask too quickly (3"x9" and 4"x5" flasks). In at least one case I don't think I allowed enough space around the "wax." The recent castings have all been silicon bronze, but I have also had decent results with generic bronze from bearings. Even some castings with 10/90% aluminum and copper weren't too bad.

I'm casting parts for a 1/8 scale steam locomotive. you and I are going along a somewhat parallel path. Among the things I've cast are handwheels of about the same size, but mine didn't have a crank handle, and pipe fittings - except my fittings were 180 return bends for 1/4" tubing with a cored hole.

I've used an Elegoo Mars, Mars Pro, and Saturn printer. All have given suitable parts once I had the settings dialed in. I've tried four or five brands of resin. None have performed better than Siraya Tech Cast purple, and the price and availability of Cast is good. I vacuum my investment and vacuum cast the parts. I use SRS classic investment because there is a supplier who will send it via USPS flat rate boxes. Some of the suppliers only use UPS, which to Alaska is unaffordable. I'm comfortable my equipment and supplies are up to the task as I made had some nice castings with them. The challenge now is to get more consistency. 

[Mcgyver]

Hi Dick,

Thanks for the encouragement.  Been sick for a few days and was travelling before hand so slow getting back to you.

I really really want to make Siraya Cast work but just have had endless problems.  You really caught my attention claiming it was you best for consistency.  Mine all centre around surface finish issues (using new Plasticast, R&R's supposedly tougher material for resin, but also had the same issue with ultravest) which I believe is damaged caused during burnout (expansion of the material?).  Burnout is a long slow PID controlled cycle R&R recommends.  Siraya the most reasonably priced; but I can't get it to work!

I've kept very detailed notes and will post them here in the next day or so.  Would be great if you could look them over and give any pointers.

I also found their curing instruction frustrating.  Initially VOG gave hot acold water process he says Siraya told him to use, but that was NOT what their web site.  Several fails with both approaches (all done under glycerine).   

The last time I tried I used VOG's new advice on Siraya, it to was a fail.  I also tried various curing times, from an hour to seven.  Still get fails.    Prints were always good, just fails on the casting surface finish.

cheers
Mike

[Dick Morris]

Just to clarify, a couple of other resins I have used worked as well as Siraya, but cost significantly more or became unavailable when the supplier stopped shipping to Alaska. Neither worked any better and one required a higher burn out temperature. Siraya is not only cheaper, but with Amazon shipping is free. In fact, when I bought a couple of bottles in September I caught a sale at $67.50 for a 1 KG bottle. (I try and have enough on hand to get me through the winter before it gets cold. I don't imagine leaving it to freeze in the mailbox would do it any good.)

I'd like to do a side by side comparison between curing in glycerin and in the air. I've had a couple of pieces that I had to cure in air because they were to big for the amount of glycerin I had and I'm not sure I could see a difference, but it wasn't an apples to apples comparison. Also, I'm not making jewelry, I'm making locomotive parts. Surface finish is still important, but probably not as important as for jewelry.

Attached are photos of some of the best results I've had that I know were with Siraya Tech, so I know what is possible. Now the challenge is to consistently get this quality.