Producing parts with lost wax

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Producing parts with lost wax

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CHR15	CHR15 posted 8 Years Ago HOT Topic Details
Group: Forum Members Posts: 1, Visits: 27	I'm working on an engine and need to make some new intake runners, i could make some tooling and have them cast, or machine them from solid, however, i'd like to have a go and see if i can do them from carbon. i've worked with fibreglass before, and used carbon in bought in sheet form, but never tried laying up my own carbon things. my idea is to machine a block which bolts to the cylinder head, machine a block which bolts to the throttle body and clamp them into a split mold tool. then block one end and fill the mold with investment casting wax. once the mold is split, i can lay the carbon around the machined end parts and the cast wax. once the carbon is finished i can warm the part to remove the wax, hopefully leaving a carbon tube, joining the two parts and with a decent surface finish on the inside. i was thinking of using expandable carbon sleaving, with carbon tape at each end to neaten things up a bit. hopefully theres some pictures below to explain things a bit. is this a reasonable idea or am i barking up the wrong tree? the mold tool (mating half hidden) with two end pieces fitted the mold tool with two end pieces and filled with wax (pink) the part, ready to apply carbon
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Hanaldo	Hanaldo posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Nice drawings, wish I had that level of CAD ability. In my opinion, you're sort of making life a bit harder than it needs to be. I can understand what your thinking is, and it will work, but I think there is a better way considering you are already machining a mould. Do you have the facilities to use OOA pre-preg? If so, then I would suggest machining your split mould tool as you have drawn it there, and machine your end pieces as you have drawn them but with a slight change to the measurement where they fit inside the split tool (probably 0.8-1mm smaller, though you will want to calculate this based on your specific layup). Then layup your tool with pre-preg carbon, and insert your end pieces on top of the carbon. Lay some additional reinforcement over the top of the end pieces to lock them in place, then bag it all up as one piece and cure. Alternatively, layup the split tool initially and bolt the 2 halves together to cure as one piece. Then upon removal, you can use a structural adhesive to bond your end pieces inside. This is a bit more forgiving with your measurements, but a bit extra work and not quite as neat. Doing it this way would give you a perfect cosmetic outer finish, and pre-preg still leaves a fairly smooth surface on the inside for air flow. In my opinion you will find this a bit more consistent and much less tedious than the lost wax method. If however you do still want to go for the lost wax method, then what you have suggested will work. Use some heat shrink tape around the outside to get some consolidation into the layers of carbon, and it will give you a nice strong part. If you need a cosmetic finish on the outside then you will need to do a bit of clean up work to get it finished off. Edited 8 Years Ago by Hanaldo
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Warren (Staff)	Warren (Staff) posted 8 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 8K	The lost wax method will work fine, albeit it is a lot of work to create the tools. You may find it easier to use your CAD model to have a foam block CNC'd to shape then wrap the carbon around as you suggested (once the foam surface has been prepared for moulding). You could use a foam such as polystyrene/styrofoam and then dissolve it afterwards with a strong solvent or use a typical PU/PVC foam and just dig it out afterwards which should be easy if the intake runners are not too long. Alternatively the out of autoclave method would work fine with decent tooling. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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