Some of my investment casting efforts

[Dick Morris]

In the overhaul of Alaska Railroad Consolidation #557, we came up short of universal joints to extend valve stems from the turret to the cab. I obtained drawings for the prototype Nathan part and drew it using Freecad. Siraya Tech "Cast" castable resin was used to print them on an Elegoo Mars Pro printer. They were then cast in silicon bronze. Accuracy was quite good and only minor clean up, mostly running a reamer through the pivot holes. finished them off. They have now been installed on the locomotive.

Wanting to test the capabilities of the process and to see if I could create some for my 1/8 scale model of 557, I then printed a slightly modified file of the U-joints at 1/4, 1/5, and 1/6 scale using the scale feature in the printer slicing software. Clamping bolts for the full-sized item were 5/16". For the models they were #1, #0, and #00. Pivots were unthreaded brass rod of the same number size as the clamping bolts. Holes were cast in place and only required clean up with a reamer.

For the first group of small U-joints I had some trouble attaching them to a tree for casting. I started with a small peg to attach them to a wax sprue. The castable resin that I use doesn't adhere very well to wax and the little parts were hard to work with and kept falling off. I then came up with a system using printed trees and added a pad to the castable resin "waxes." Using traditional wax to reliably attach the parts to the tree was still a problem. I then used super glue and it has worked great. Attached are photos of a tree and parts I'll be casting soon. The little castings were so successful that I sold a number of them as kits with all the proceeds going to the Engine 557 restoration.

1. U-joints and valve handles. I didn't cast the two bronze plates, they were done by Youtube's VogMan when we were both learning the process, but they show the level of detail that can be obtained. I did draw and print the resin Superheater patent plate which I haven't yet cast.
2. The newly cast and machined U-joint I made being installed on the locomotive.
3. Full-sized U-joint "waxes" still on the printer's build plate.
4. A close up of a couple of small U-joints.
5. A tree of small U-joints being prepared for casting.
6. An example of the printed tree and one of a couple of "waxes" with pads printed on them to make it easier to superglue them to the tree.
7. A full-sized injector overflow valve handle. One of the two originals on the locomotive was missing.
8. 1/6 scale injector feed water and overflow handle with mounting stand.

 

[A7er]

Excellent work! I have quite a bit more work to do to my garage/workshop, then I can order the materials to try my hand at lost wax casting. Very inspirational, thanks for posting.

[Mcgyver]

great post!

I've been working on lost resin casting for a year and have achieved some ok results but keep getting surface flaws.  I've tried several resins including Siraya Tech to no avail.  I'm using new investment, good equipment etc but keep getting flaws that suggest the burn out is breaking up part of the surface.  Its been very frustrating.

I would really love to hear the details of your process: print settings, curing, investment, investing timing/process, burn out cycle, casting etc.   I've literally been trying for a year going back and forth with a Bluecast trying identify the problem in my process

Thanks....and nice to see some great lost resin results.

PS - you printed the tree as well?  Clever....how are you attaching the prints to the tree?  I've been using sticky wax (rosin and beeswax).  Its ok but not great.

[Dick Morris]

"how are you attaching the prints to the tree?"

I've have good luck using superglue and, where it makes sense, including a gluing pad as part of my part. The wax doesn't stick to the Siraya Tech Cast resin very well. I've used about four types of resin previously, some didn't work very well, some were more expensive, and some became unavailable for shipment to Alaska. I haven't tried the newer Siraya Tech formula. It it ain't broke . . .

The printed trees are also more rigid than wax.

[Dick Morris]

Here are a couple of variations on using printed sprues. These are for the full-sized U-joints.

The U-joint part has a hole in the bottom, 1/4" diameter by 1/4" deep (made with milling cutter to get a good edge). The elbow goes into it and the other end goes into the hex piece. The hex piece slides onto a piece of 3/8" wax which is held in the sprue base. I cast six parts in the flask.

To speed things up, I went to a tree that had the central sprue and elbows printed as one piece but still used the U-joint pieces with a hole in the bottom. It has been a while since I did these, but I think everything was held together by a light press fit.

[jcge]

Some fine work there Dick - I'm amazed by the level of detail in such small scale parts.
I'd echo Mcgyver's question for more detail about your equipment and process because you results look fantastic.
Thanks for posting this.
John

[Dick Morris]

I have several flasks that are ready to invest and cast, probably within the next couple of weeks. I'll take some notes and share more then.

VogMan on Youtube is an excellent resource, especially his videos from about three years ago when he was getting started with investment casting. I was a few months behind him on the learning curve and learned a lot from him.

I've been using the SRS Classic investment. It's worked fine for me. There is a place in Hollywood, CA that sells it on Ebay with postage paid. I originally started with about 25 pounds of Kerr Satin Cast investment that was about 35 years old. Surprisingly, it didn't give me any problems. It was discontinued about five years ago but at one time it was a go-to investment for many people. I went to SRS because most places charge an outrageous price to send investment to Alaska.

I use the burn out schedule on the SRS web site for the Siraya Tech Cast. One of the castable resins I used previously required a higher temperature for burn out.

The last time I tried to cast some things was a disaster. The PID apparently didn't limit the upper temperature. I suspect it went as high as the burnout oven could put put out. The investment in most of the flasks was cracked, the bottom of some of the SS flasks got so hot they appear to have gotten very soft or melted where I had them supported on small pieces of angle iron, and it appear the angle iron may have slightly melted. A couple of the flasks looked usable, but the surface of the castings was really rough. The next time I use the oven I'm going to have to monitor the burnout process closely. I'll post more on this later. 

[jcge]

Thanks for the info on the investment materials
Will take a look at VogMan and look forward to seeing your future endeavours in casting.
Cheers
John

[steamer]

That's amazing work!  Nicely done....

Dave

[bent]

Following along too.  Very cool results! 

[A7er]

Artisan foundry supplies here in the UK sell the SRS investment, I have it on my order list. £24.00 for 5kg. I also have moulding wax, oil bound sand and a few other things ready to order. I can buy the silicone mould rubber locally in Cornwall from a fibreglass materials supplier. Artisan also sell ZL12 aluminium.

[Brendon M]

This is fantastic, thank you for sharing