Yesterday's investment casting

[Dick Morris]

After spending a couple of weeks repairing and upgrading some of my casting equipment I did some casting yesterday. Six flasks attempted, four successful.

One failure was because I didn't allow enough investment to cover the bottom of the flask and some of the investment fell out when I removed the flask from the burn out oven.

I attempted two cylinders for western rivers steamboat engines. One looks OK but has a lot of finning. This may be because I heated the 3" x 9" flask too quickly during burn out. The other has a hole in it, I don't know why. These are just over 6 inches long and weigh .9KG/2 pounds each.

Two flasks had a bunch of U-joint parts like those in a previous post. They were successful.

I'm particularly happy with some 1/8 scale patent plates that go onto the side of a locomotive smokebox. They are 1.9 inches long and the letters are only .050 inches high. I continue to be amazed at the amount of detail that this process produces. Both the "wax" and casting are shown.

[crueby]

How did you make the pattern for the patent plates? What was the material for the pattern, and what was it cast in?

[gbritnell]

Yes I'm curious also. How did you make the small lettering on the pattern?

[tghs]

I've looked at western engines for years,, what about just doing castings for the ends and joining them to a center tube section? in my plan stash is the Eade's designed civil war USS Osage,,,

[bent]

Dick,

Is the patent plate 3d printed in wax?  Or did you 3d print a mold for the wax?  Looks great in the finished form! 

[Dick Morris]

All of my investment casting has been done using "waxes" printed on a 3D printer. I'm on my fourth or fifth brand of resin. Some stopped shipping to Alaska, some didn't work very well, and some was too expensive. I have now gone through three or four bottle of Siraya Tech Cast (purple) and am quite happy with the way it prints and casts. I haven't tried the Siraya Tech blue but probably will next time I need resin.

These were cast in silicon bronze. 

I forgot to mention earlier that the plates are .065 inches thick.

The parts were created and the lettering done using Freecad and these parts were printed on an Elegoo Saturn. I've also use an Elegoo Mars and Elegoo Mars Pro and both printed equally well, although the Mars printed more slowly.

Long ago I wanted to do steamboat engines and was going to use tubing with cast or fabricated ends and center, but making sand castings for even those parts seemed formidable. That was over 20 years ago when I created this web page - http://www.alaska.net/~rmorris/steamboat1.htm

There is a guy on Youtube who has made small scale poppet valve steamboat engines (and the boat) that are pretty remarkable. Search for "Liberty Belle Steam Powered Model Sternwheeler ."

I've had most of the equipment for doing investment casting for over 30 years. (I got if from a friend who moved out of his house into a boat and sailed around the world.) I didn't use it until I came across Vogman on Youtube. He was just starting in lost PLA and I followed about four months behind him on the learning curve. When he shifted to castible resin printing I followed suit. His videos, low cost 3D printers, free 3D drafting software (Freecad), and the investment casting equipment I had on the shelf all came together for me 3-4 years ago and caused me to rethink my model building. The detail is exponentially better and I can do thing I couldn't do with sand casting. I find it easier to do than fabrication or using traditional patterns and sand casting, which I have done on and off for over 30 years.

[BillTodd]

How easy is it to melt out the resin?

[Dick Morris]

When things are going as they should, not hard. I use the same burn out oven and temperature schedule that is used for lost wax. Note that this is a specialized castable resin. Regular 3D printing resin doesn't out burn right and leaves lots of ash. PLA filament burns out well, but with a loss of detail compared to resin. 

[ddmckee54]

Sternwheeler huh???

Did you follow the build log of the W.T. Preston over on RC Groups?  If not, and you've got a couple of weekends to spare, here's the link.
https://www.rcgroups.com/forums/showthread.php?1497645-1-32-Scale-W-T-Preston-Sternwheeler-Build&highlight=w%20t%20preston

I said a couple of weekends because it's a long and impressive build, of both the boat and the power-plant.

Don

[Dick Morris]

I've looked at the W.T. Preston log, but I've got a prejudice for steamboat engines with lever operated poppet valves with all the motion flailing about where one can see it. I plan on using California/Cross cut off as is used in the Delta Queen. 

[bent]

Thanks again, Dick.  My son now owns an Elegoo (I think?  A UV resin printer anyways.  I'll have to talk him into doing some zinc castings somewhere down the road, either for his D+D models or for a flywheel or similar for me...

[Dick Morris]

Other than size, the different brands of resin printers should all have similar capabilities.

The largest learning curve for me has been learning 3D drafting to create the files to print from. Basic shapes are fairly easy, but complex parts can be a real challenge. The free software is extremely capable, I only wish I was competent in more of its capabilities.

I've used 3D prints to make patterns for sand casting, and this is probably what you want to would use for the zinc alloys. I've used castable resin and investment casting for bronze only. Commercially, investment casting is also used for stainless steel, titanium, gold, platinum, and other higher melting point metals. I've seen mention of using investment casting for aluminum - I think being successful would mostly be a matter of having the burned out flask at the proper (lower) pouring temperature. I've never seen anything on zinc alloys being investment cast. That may be because zinc is used to cut material and manufacturing costs when a large quantity of parts are needed. Investment casting is a slow and expensive way to create parts and the material cost is only a relatively small part of the overall cost.

I've sand cast ZA-27 zinc alloy and it casts and machines nicely.