Hello, I thought I’d introduce myself, I’m Jonny and have always had a bit of an interest in casting. My friend and I had a coal fired furnace in High school we melted cans down with, this was about the limit of my experience casting. I recently lost foam cast an engine as my first real project and I think the results were pretty good all things considered. I watched Kelly’s videos which gave me more than enough information for the relatively simple pattern. Now I have another project on the go which will also involve lost foam casting and am hoping to pick the brains of some of the experts here. The project is a V4 350cc 2 stroke motorcycle engine. I’m hoping to get some advice in regards to gating and other considerations. If anyone is interested in helping I will share the Step files for some feedback. I might be keen on outsourcing the casting but I have no idea what something like this will cost. So I may pour it myself. The equipment I have is an electric kiln 400x400x600 deep and some home made thick steel crucibles. The kiln gets up to 1250c. It’s at my work and I can use it whenever. here are some pictures of my first casting project which I have successfully raced without any failures.
Welcome to the forum Jonny. Those parts look nice, it must be satisfying to have raced with them. What CAD and CAM are you using to make your STEP files and patterns and machining passes?
Welocme Lifan! I think most would consider that to be more than just a simple pattern. -Very well done on both the pattern and casting. Congratulations. Now it never stops I dont think STEP will be necessary and just some images should suffice, but when available, I'd be happy to comment. There will be some challenge in the crankcase design for a V4 2-stroke. I'll look forward to a future post from you on that. Is there a non-V4 donor engine from which parts will be used? The crankshaft and crankcase seals would seem to be the challenge. If you are an infrequent caster, I'd just use what you have access to, but kilns can have some longer heat times depending upon power level due to there thermal mass. But, you can just turn them on ahead of time and add your crucible and charge later. Just make sure you have a high integrity crucible because if it fails, in addition to personal safety, you could find yourself in a difficult situation with the kiln owner. Also any minor splashes on the heating element will cause them to rapidly fail so use great care when adding metal and handling the melt. Also, the odor from lost foam casting won't win you any friends unless you manage the pour and mold sand well. When you are planning the melt for you next project, you'd better plan for 25-50% more melt capacity than the weight of the casting itself. Generous gating increases success, and there is much more control when pouring from a crucible that is not brim-full. It's also worth giving some consideration to the total weight of the crucible and melt, as to how you will lift and pour. Being able to accurately position a heavy mass for 30 seconds at hip level is diffrerent than merely lifting it.......especially when it's molten metal! I really like my resistive electric furnace, but when you get into bigger melts, it's relatively easy and inexpensive to build a larger propane fired furnace.....if you have the space/place for it. Based on your result, I'd say you're a quick study and doesn't look like you're in need of much help to me. What did you use for aluminum casting stock? When you're making real engineered parts, mechanical properties matter for both strength and machinability......which I'm sure you are well aware. Best, Kelly
Ambitious indeed! I am looking forward to following this project. With respect to posting .STEP files: I do not think you can post them directly on this (or most forums). But someone recently showed me how to post them on GoogleDrive and then post the link on a forum. I would like to be able to look at the files as I could load them into my CAD software (Onshape) and slice and dice them for a much better view of what is going on than can be seen by a few screenshots. So, if you don't mind the bother... Denis
Welcome Jonny. Impressive results casting aluminium. I usually simulate cast iron casting technology and calculate gating systems, but would love to try to do this for aluminium. Have seen guys taking numerous trials to cast aluminium simple thin parts. This one looks complicated.
hopefully it comes out right on the first attempt, trial and error is all I’ve got in my situation though. I’ll upload a google drive link when I get on my PC.
Just be advised, he is using the lost foam method for these castings. They are not conventional open cavity sand castings. Unless your software is capable lost foam modeling/simulation (is it?), there will be very little correlation as metal velocities and fill times are a much stronger function of the rate foam can be evaporated and purged rather than gravity induced head and feed system cross section. Best, Kelly
I can do lost foam casting process simulation. However, I have not done it even close as much as simulations in greensand. In short I can create shell model (custom material and thickness) around the foam core and further in simulation it considers the foam core restricting the flow and. It can be seen in simulation how the foam or wax melts and disintegrates. Example like in this video.
Sorry, but I dont think so. That looks more like how an open cavity mold would fill with that feed system, for example maybe a lost wax shell mold that has been fired and already had the wax removed prior to the pour, but that's not even close to how a lost foam mold of that part and feed system would fill. For lost foam, that part would fill in a much more orderly fashion from top down, not chaotically raining molten metal through the foam pattern and filling from bottom up as shown. In lost foam the pattern becomes insulated from the molten metal front by a liquid and vapor boundary layer of the decomposed polystyrene. The liquid and (primarily) vapor vents through the refractory coating and mold media allowing the metal front to advance at velocities typically much slower than in an open cavity mold of similar geometry. I know this to be true not only from having seen many sims from industry and acedemia, but also through my own experience observing pours behind glass, and observing short pour fails which indicate top fed parts fill from top down. Also, if the metal just rained through the foam pattern to the bottom of the mold as shown in the video, it would be laiden with fold defects and the unbound sand mold would likely have suffered localized mold collapse in many places. As an aside, I would never feed an open cavity mold from the top like that exactly because of what the simulation shows.....the chaotic manner of fill......but in lost foam it simply doesn't occur. Best, Kelly
The factors I mention are a major complication for simulating lost foam. It would be one for discussion in another thread, but we do appreciate your posts on simulations......they can be very helpful and enlightening. Best, Kelly
