Some time ago ( I think it was already 2 years ago) I bought an old ex-military breadvan for scrap money. I swapped its engine with an Mercedes OM603 diesel 6 inline engine. This is its new inletmanifold I'm trying to cast. I was already building the foam pattern when I discovered this forum (which opened up a magical box of know how) so I realize some features can be questionable.... The overall lenght is 620 mm, its height about 20 cm. The foam is all made with a small Chinese budget-router which is also part of the learning curve. The 3D drawings I create using Fusion360. All suggestions or questions are welcome! Thanks for watching! Koen
The pattern looks good. You will need to tie the individual ends together to keep them stable and in place when molding. It can be cut off afterward but you may want to attach it so you can machine the faces of the mounting flanges, otherwise you may need a complicated machining fixture. What do you have for a flask to mold it? You may need to make a box to cast it in the position of your last picture. It will need sprue height above that and it will be heavy so you'll need high energy vibrator. You must fill evenly and vibrate in stages as you fill so the sand doesn't distort the pattern. The gating will need to distribute the metal across the length of the pattern. It may increase melt needed by 25-40% of casting weight. You'll need a big pouring cup....perhaps 20-25% of casting volume to be safe. Best, Kelly
Thanks for the tips! Would it be ok to use a big disposable empty (beans) tin as a pooring cup (for now)? Or would that take to much heat out of the molten alumininium? Regards, Koen
Yes. I'd be inclined to keep the bottom in the can and cut a hole the size/shape of your sprue in the bottom closer to one of the walls. Circular cups tend to aspirate air due to coriolis affect. Offsetting the sprue hole tends to supress this. For the same reason, the sprue is probably better off being rectangular rather than round, and slightly tapered......all easy to do with foam. Keeping the bottom in the can prevents sand displacement from the pouring stream impingement. Fill the flask to the top of your sprue and place the cup on top of your sprue, and then fill the remainder of the flask with sand to/near the top of the cup. This prevents leakage at the base of the can/cup due to the head pressure in the cup height and further insulates the cup. Immediately after the pour while the metal is still molten, if you grab and slowly extract the can with a pair of pliers, the metal will just take the space once occupied by the can and you can save yourself the labor of having to peal it off to recover the residual aluminum left in the cup. With the metal being molten it still retains head pressure until it freezes, but by this time the fate of your pour and casting has already been determined. It will need to be a good sized can, but there's not much steel in a food can and as the cups get larger, the heat loss is comparatively less because of the larger volume of molten metal in the cup. Depends upon how particlular you are, but if the can has coatings, preheating it to obtain a black oxide layer will keep your melt cleaner and there's an outside chance it may even let you reuse it a time or two.....but probably not. Best, Kelly
Although the pattern isn't completely finished yet, I would like to ask your opinion about the gating at the top. The setup is only a rough sketch and only partially build. Overall thicknes is 1 inch, at the sides 1/3 inch. In the center I was wondering if it is necessary to devide the inlets so each 'ring' gets its feed separately or is one sollid blop enough ( regards the fact that sand will have a hard time getting between it). The top entry is 1x2 inch. I'm gonna source a rectangular tin can as a pooring cut. Am I correct when I use ratio 1 to 25 kg for foam-alu ? Regards Koen
Hello, Yes that was one of the questions. Meassuring its volume is also an option but dipping it into a bassin filled with water would dissolve my glue I think. Best Koen.
If I am doing the parts in Fusion360 by 3D print or machining, I will add in replicas of gating and assign all the solids the physical material 'aluminum 5083' and do a 'properties' on the complete design to get a weight. To weight the foam to figure the aluminum, you will need to know density of the foam like ,016-,024-,032 g/cm^3 (1-1.5-2 PCF) and make that a ratio to aluminum at 2,7 /cm^3 (168.6 PCF) so it is more than 1:25.
Never had much luck with weighing the foam (on triple beam scale) to estimate casting weight. I always just break the part into crude approoximations to derive volume and then multiply by the density of aluminum. Too late for me to give a detailed response Koen but if you can wait until tomorrow I can give a more detailed response. In short, I dont think you need the gating in the internal locations "rings". Also, any wide horizontal surface will likely be loose/unstable as far as sand packing. You would need to position the pattern such that the plenum surface is at an angle for better results. As opposed to the large central "runner, I'd probably have just have two somewhat smaller ones down the length of each side. As I mentioned previously, if you don't tie the loose ends of the inlet tubes together, it is unlikely they will be in the expected positions after they are molded and cast. Sorry, I realize this might be a bit vague, I'll try to post a picture tomorrow afternoon. Best, Kelly
Hello Kelly, Ah ...unstability in a plane was a thing i wasn't thinking of. .... it's still hard for me to think like liquid aluminium . Is it always better to cast from the outside of the part inwards ( on larger parts) ? Is it an angle of 45° you're suggesting or is 15° enough ( starting from horizontal)? The lower part, I didn't tackle yet because on the Merc engine there are brackets bolted on to the ties between the individual tubes . I was planning on using the original part as a reference but having changed the path of the inlet tubes some brackets need athernation too ...which isnt much of a diffiulty except maybe for the throttle cable bracket. My idea was attaching a couple of linkages at the bottom too ( two smaller ones, connecting all 6 tubes ) but that will be when everything else is ready and glues together... Thanks! Koen The next couple of days are working days for me so no time to play...
Hi Koen, you could also make a chart / spreadsheet with the simple volume of each piece from Fusion360, add together, and multiply by the density of the metal. This might be easier if you do not have a complete assembly in the computer.
Horizontal surfaces or blind cavities should be avoided if at all possible. It's very difficult to fill them without sophisticated vibratory apparatus and very good mold media. Not necessarily. Ideally, I like the part to fill uniformly from the top down, then solidify from the bottom up, but practically speaking, the shape and position of the part, the shape of the flask, and location to gate all affect the choice. It does not have to be 45 degrees, but best advice I can give is if sand will naturally fill all features, especially internal features and hollows by merely pouring in sand, then it will pack well with vibration. In general, it is best if sand can flow through features as opposed to just flowing into a feature. If it can merely flow into a feature it must do so from above, not below. When sand is vibrated, it becomes fluidized. If you think of the sand as being water, if there are places in the mold that would trap air if slowly filled with water, it will do the same with sand. The pieces tieing the lower tubes together would be just for casting, and maybe fixturing/machining, but would be removed after the last operation. Even if you get the tubes to cast without deflecting, I can't imagine being able to machine the sealing surfaces without very elaborate fixture. A feature that attached to the edges of all the flanges would stabilize the tubes for machining the faces and then could be removed afterward. What you have done as far as gating may work ok, but in general I try to minimize the number of metal fronts that must converge together as they can form "knit" lines and can create oxide flaws where they merge. I prefer to gate into surfaces that will be machined anyway, especially if they are more massive parts of the casting.......it minimizes clean up and improves cosmetics. For your present/proposed gating method, I would position in the mold as shown below. For me, since I use cylindrical barrels as flasks, I would gate and position as shown here. Another consideration is how you will support the pattern during and after coating. They get very heavy when covered in wet slurry and this can cause distortion of the pattern. I dip coat which can add to the challenge. I presume you will brush coat. You might consider doing it in stages allowing the pattern to dry in between. Lot's of factors for success when it comes to large lost foam castings. Best, Kelly
Wow ! Thanks A LOT Kelly & Tops for the awesome suggestions and idea's!! Helped me a lot!! I also have been reading some more posts on the forum (at work). My two flute milling bit arrived too. Cyclone is operational too. I also have decided i need a good (propper) pooring cup ... just need to source the ceramic fiber stuff in Europe. Kelly, I've followed your suggestion about the gating. Made a rough sketch of it today... About the mud: i was wondering if spraying it on with a spraygun could be an option ?? Otherwise i will go for the dipping option. I was thinking of mounting a wooden plank on the bottom of the 6 pipes....and another at the top ...the surface won't be covered in mud when I take the wooden support off after dipping but that surface will need milling anyway... I will install more supports in between the pipes to get the base more rigid while vibrating. The two bars at the bottom will help me also to clamp the piece on the mill. Maybe i will need to make a steel support in an angle to get it all clamped but i dont see any big problem in me constructing that. In the pictures the angle is the one I think I prefer....it will need the least amount of sand ..... The top of the gating has yet to be constructed ....
I think spraying is fine as long as you can easily cover all surfaces, but hard to see how you will manage the interior of the tubes. On a part like that, I have used "slush coating". Basically make a couple foam plugs for each end of the tube, pour in some thinned mud/caoting, and tilt it around, then let the excess run out and do the next tube. Sort of like I did here: This was fairly early in my learnings about how to provide for stable cores and I failed a few times before succeeding on this one. http://forums.thehomefoundry.org/in...r-upright-wheel-carrier.543/page-3#post-11324 I think you'd probably be better off just brush coating the exterior surfaces. Just remember you only need enough thickness to cover the foam and change the colored foam white. It's permeable coating not mold structure. A wood fixture to hold it all in place while it dries is a very good idea. After it dries, the part will be much stiffer. Honestly, I think I would just attach a piece of foam that attaches to the edge of each flange and runs the length of the part. If it attaches to the edge, it can still allow machining the face and maybe even serve as a fixturing surface. When the machining is completed, just cut off the unwanted excess material. If you can find the material, I think you'll be happy you did so. Besides a proper controlled fill, another big advantage of the cup is the "buffer volume" of molten metal it provides. This is very helpful in dealing with that classic "pause" and then rapid change to how quickly the casting takes metal during the pour. It gives you more time to respond and keep the cup full. If you allow the sprue to become uncovered and interupt/gap the pour, this will cause a failure. Here's an idea for you to make a conforming flask to minimize the amount of sand required and weight of the mold. http://forums.thehomefoundry.org/index.php?threads/automotive-intake-manifold-lid.366/ Your parts, like the valve cover and intake manifold, are pretty advanced and challenging parts for a hobbyist with any casting process, especially lost foam, but certainly able to be done successfully with the right approach. Best, Kelly
Good evening, Today I tested the "Belgian Franken-cup". I ran into some fire resistant products in a hard wear store nearby. Not knowing it was the proper stuff I just decided to go for it.... didn't break the bank neither so... The Franken-cup holds a combination of heat resistant fibre putty, some sealant and chicken wire. I made it quite a while ago so I was pretty shure it was dry. Recently I (re)saw Kelly's movie about reusable pooring cups....which made me decide to build a completely new one ...but thought I should just test this one and see what happens. First test is to see if it can stand some heat... if that goes well I'll do an actual poor with it. I placed the cup in my steel crusable so there was no direct contact with the flame. After fiddling quite a while because the diesel burner played up, I got my furnice up to about 900°-1000°C...left it at that temperature only for a couple of minutes, then left it cool down very slowly It does hold, allmost no cracks.... which is pretty impressive if you ask me. Next step is casting a piece with it.... Keep you posted! Koen
Hello, Just made a reusable pooring cup. It's square sprue is about 1.25 inch. I build it using some left over fibreboard, the black stuff should take 2732°F (a big number i know).... Gonna leave it to dry now and put it in some heat tomorrow. Still need to make the cradle. Keep you posted! Koen.
