I got this job from an acquaintance in the blacksmithing world, he was making a railing for a client and they asked him if he knew a casting guy to produce a piece for an apartment building they are remodeling. (he was making a railing for said building) Originally I was told that this was for a doorbell (hence the hole) but it later turned out to be a bezel plate thru which a door handle would pass. Here is the original that was provided to me: Note: Deep draws, no draft, undercuts, rough finish. Not usable for sand casting. Perhaps someone doing investment castings could use this but it is not my forte. So I set about making a new pattern that would be usable for sand casting. I scanned the part on a flatbed photo scanner and used Vectric Aspire to make vector traces of all the features, as that is what I am most proficient with. I then imported the vector drawing(s) into Fusion 360 and extruded all the parts to make a 3D model. The birds were the only pieces with curved surfaces so I left them flat to be hand-carved afterwards Now with the model generated I could add some draft and use an appropriately drafted cutter and make a pattern on my CNC router. Total machine time was around 5.5 hrs. I had to make two patterns, the first had some features that were too small to fill out that I did not notice on the computer so a second revised one was made. So from there an aluminum sample could be made: The client asked for a casting that could be nickel plated to match the other hardware being used. I know there are ways to plate Aluminum but a high copper bronze seemed to fit the bill, so Everdur silicon bronze was chosen as the material. I was a bit apprehensive on this as I had never cast bronze before but it seemed straightforward enough. ~$300 worth of Everdur Ingot A problem I ran into with the Bronze is that it excessively burned up my (already tired) Petrobond. The pour range for Everdur is 1800-2250F and I needed it on that upper end to get the fine details to fill. The smoke that filled my shop was excessive, as well. I needed another solution. I mixed up a fresh batch of 130 mesh traditional greensand. I had the stuff to make it on hand but had not needed it up til this point. The sand does not provide as fine a finish as the Petrobond but it was acceptable to the client and does not fill my shop with smoke. This pours HOT compared to the aluminum I am most accustomed with, but not as hot as the Iron I used to pour back in the day at the foundry I worked at. The order was for 10pcs. I could pour two at a time with my #6 crucible, and I only had two flasks in which these reasonably fit. If I had more pieces to make I would have made multiple patterns and used a larger flask. I made 6 pcs the first day, refilled my propane tanks and made the remainder the second day. I ended up casting some TIG filler rods as a few of the castings had cold shuts that needed minor repair. The order complete, with a counterbore machined to fit the handle (the handles were an afterthought I guess and it was discovered they would not fit the piece. I offered to machine the castings to fit. Redesign of the pattern would have set the project well back beyond the already tight deadline) My shop-neighbor kindly lent me use of his bead-blaster to even out the finish for a fine result: This project was completed start to finish in roughly 3 weeks with much waiting from the client. Many cups of coffee (and beers) were consumed and the times I saw 4AM or later on the shop clock would require two hands to count. Hope you enjoy the pictures, I've glossed over many steps but this tells the story well enough I think. I am relieved to be done with this one.
I am very impressed with the detail you got from green sand. That is pretty close to ceramic shell detail. I know you said you poured hot, but did you measure the temperature or the pour before pouring? What was the pour temp?
Very nice work.. I should have told you about the sil bronze rig rod air gas sells. It's a dead ringer for your everdur bronze. Sorry about that. When ya making the leap to shell?
Thanks. The muller is essential! It was an expensive piece of kit but it beats the pants off my DIY muller and has proved its worth in the shop. Next up will be a molding machine... missed out on a cheap one on eBay down your way. You didn't happen to pick it up did ya? Thank you! My immersion pyrometer only goes to 2000F. So I maxed it out and then judged by colour from there. The Petrobond casting had even finer detail. I will post pics of that. No worries, time would not permit ordering anything anyway. It was not essential to weld the bits I did but I wanted to give it a shot! Tricky to weld. Ended up using AC with a low + balance for a little cleaning action. I kind of want to try shell, but the $barrier$ to entry seems a bit prohibitive. Is there a thread here somewhere or video showing the whole setup with everything needed?
Those look very nice Rocketman. You noted that the features and finish on the original prompted you to scan/model them and produce the pattern. That's sort of curious because the lack of draft, deep draws, very thin sections suggest a lost wax process was originally employed but seems a better finish would have been likely if so. Either way, the subtle changes you incorporated for sand casting produced very pleasing and authentic looking reproductions, and certainly less work than shell, especially with a multicavity pattern. Was this your first time pouring Silicon Bronze and if so, any learnings or surprises in melt management? Does the customer intend to apply some patina or use as is? Best, Kelly
Start here http://forums.thehomefoundry.org/index.php?threads/ceramic-shell-supplier-r-r.676/ then click the link in my signature to take you to my youtube page. I only run ceramic shell. I've done a fair amount of teaching on how to use the stuff there. The 4part tutorial is dry as toast, but has the most teaching. The fox build is another good series to learn about shell.
