Hello from Southern California. I discovered this forum through Kelly Coffield's YouTube videos on lost foam casting. My casting experience is from High School Metal Shop, last century... A couple of us from the Lotus Europa forum would like to reproduce a few Hermes intake manifolds used on a some of the Renault powered Europa's. Please see attached photo. The issue with the Hermes intake is that there are multiple parting lines and I have absolutely no idea how to create a pattern to be used in a standard drag an cope setup. I started out creating a digital meshed model that I could 3D print using a low temperature plastic. This turned out to be a time consuming effort and mesh models are almost impossible to manipulate, particularly at my budget level. I still have to figure out how modify the mesh model to make the runner cores. Before I spend anymore time on this project, I would like get some recommendations on which casting process to consider? A lost foam casting technique would solve all my parting line problems? All thoughts and opinions are appreciated. Regards, Scott Edrington Escondido CA
Hey Scott, welcome to THF. How many is a few? It would also eliminate the need to make cores and core prints on the pattern. You already have the cad model. If you knew someone with a CNC router, making the foam patterns in two halves would be straight forward. It would be an easy part to cast from there. You could try lost PLA. You could print it in pieces and glue it together, then invest it and cast it. All the same benefits of lost foam but printable pattern. Downside, it's sort of large part and would take a larger investment mold and burn out oven. Best, Kelly
Parting line looks pretty simple unless I'm missing something... You need to think a bit in reverse on things like this... the core prints can be used for some of the draft issues... so back up a bit and design the cores.. If your only going to make one or two lost foam is great and you don't need alot of foundry stuff like petrobond or sodium silicate for the cores. But having a pattern you can ram up anytime you want is nice also, especially if you plan on making a few...
Thanks for the videos and appreciate it. I’m probably over complicating things, but if I wanted to make a pattern that duplicated the original design down to parting lines, how would make it? My limited pattern design reference is a single plane with half the part above and have below the parting line. With this manifold, I see both horizontal, positive and negative sloped parting lines going in different directions. I’m not sure how to make a pattern that replicates this.
If you have the original piece you should be able to see the parting lines on it to see how it was molded. Typically you can see a definite parting line but sometimes it might have been ground or sanded smooth. The V in the manifold ( you have it labeled as 2) looks to me like it was reworked after casting. Keep that in mind. Also the cores might not share the same parting lines as the pattern. You scanned an original correct?? Do you do any cad modeling?? You see, you need to model this part yourself as scanning it will only be able to generate the finished part as it is. A casting is not a finished part in most cases. It needs fefining/ machining. So to keep this short, dummy down things to their basics. If you care to share the cad model I can look at it for you and get you pointed in the right direction.
You are absolutely correct that the cores do not share the same parting line as the pattern and the part has had a lot of post processing performed on it. The mounting flanges on the cylinder head side have about 1/2 inch worth cutting and grinding marks indicating it could have had an appropriate draft angle on the flange where as now I'm not sure how you could pull it out of a mold without damaging the mold. I'm also wondering if the manifold was cast in 3 different pieces and welded together? There is some porosity in the V area of the manifold; also, the finish work is lacking. I can send you an STL file of the outer shell that I scanned. I have not found a good way to covert the STL to a proper DXF file so I'm having to create the CAD file by taking measures off the original.
If you want to just copy an original you would need to create a core box to make cores with mounting stubs on each end. Then you use Bondo or wood putty (wood putty cleans off easily later) to make matching stubs on the original part to allow a place in the sand to set the core so it will straddle the mold. Rectangular stubs are good to keep a core in alignment. As far as matching the parting lines, that's easy. You lay the pattern on a board so the parting line is nearly horizontal as you can get it. Then you put a drag over it and ram sand using your fingers to get some sand under the overhangs. You finish ramming and flip to add the cope. You use a spoon or other tool to carve out a bowl around the pattern and slowly work your way down to the parting line. It is really very easy to get a nice dish shaped cavity down to the original parting line so draft is established. Now you ram the cope, split the flask and remove the pattern, add the core and feed system and reassemble and pour. Look up a video on casting a boat prop and you'll see how cutting to the parting line is done. If you were making a lot of them you could make a follow board. That just replicates the finished drag sand contour so you can ram quicker but for only ten or less you may as well spend your time making a nice core box and cores and just cut to the parting line by hand. I do it regularly on this pattern. Ready to ram the drag Drag rammed and flipped Notice the sand was not packed tightly under the pattern. Start cutting Mostly cut Cut to parting line Ready to ram the cope Not a car part but you get the idea.
How attached are you to the Hermes text being cast on the intake?? It looks like they split the runners at the V in order to get the proper draft angle on the font. That would entail a multi piece mold likely in a resin or ss bound mold that was glued up. For this to be the case though this area would show a different draft angle from the other side. See picture... The other possibility is the text itself is cored in. If it was then you should see the area around the text having been reworked. Hard to say though..
Could just be a visual anomaly from the scan also..?? Im not a big fan of working with 3d scans. Was going to print it and look at it, but the scan is just a shell, and after making it solid in meshmixer I'm still running into errors with having a flat surface on the print bed. I'll play with it more later. But your better off cad modeling this yourself rather than fighting with the scan...
Flattened the bottom so I can print it. It's oh so close to being able to split it in a straight line.. Still thinking..... Can you post a couple full sized images from a couple of angles so I can get a better visual of possible parting lines?
Old iron farmer - Thank you so much for your write up and it is very helpful! I never thought of using the original part as a mold but it makes sense. DavidF - Yes on Grumblebuns - The scan I sent you is not as good as the original mesh due having to make the file smaller in order to email. I have not tried using meshmixer yet. - I will send you some photos of the parting lines tonight. - Concerning a CAD model, I agree and have been working on one but it is not ready for prime time.
Had to go to work, but I think it's just split straight, atleast judging by this one photo, but with a couple cores on the sides to give it the right draft. Like this..
