Going from CAD files to moulds

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Going from CAD files to moulds

Author	Message
bkayyar	bkayyar posted 9 Years Ago HOT Topic Details
Group: Forum Members Posts: 5, Visits: 22	Hey all, I am trying to make a mould for a certain carbon fiber part that has been designed using CAD software. Traditionally, polystyrene foam has been used -a negative mould is made in the foam using a CNC cutter, and the surface of the mould is then prepared using layers of epoxy and bondo. The top layer has always been a hand-sanded super-smooth layer of epoxy. Given the amount of labour involved, I am looking for alternative methods. Specifically, my idea was to use the CNC to cut the part itself out of the polystyrene foam such that I have a positive mould, which I would then coat with a thin layer of epoxy. I then intend to use the Uni-Mould system, treating the epoxy-covered foam as a regular part, to obtain a negative mould. Any suggestions or reasons this would not work? I am especially concerned about the layer of epoxy on the polystyrene foam reacting with the epoxy-based gelcoat and hindering its release.
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davro	davro posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 300, Visits: 2.2K	There are a few ways to leverage the power of CAD/CAM the method your suggesting creating the buck and then making a mould using a mould making system. or Milling the mould directly and skipping the part where you need a buck, mill directly into aluminium or even cheaper using wood and tooling gel coat I use the wood + tooling gel coat method for making moulds for parts I'm only going to use once or twice. ) Roughing operation. ) Ball end mill finishing operation -1mm ) Paint with tooling gelcoat. ) Ball end mill gelcoat finishing operation. David Stevens YouTube: Comment \| Rate \| Subscribe Instagram Composite Projects Body Package for Dax Rush RC Car Touring Body 1/10 Scale
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bkayyar	bkayyar posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 5, Visits: 22	Thanks for your suggestion, David. I had a few questions regarding the videos you embedded: 1. You applied the gelcoat before the finishing pass using the ball endmill. Why not do the finishing pass first, and then apply the gelcoat? 2. Between the finishing pass and the resin infusion, is there any surface prep you do with the gelcoat layer? Do you sand the gelcoat on the mould or apply another layer? I noticed that you achieved a smooth finish on the wing mirror surfaces, but I assume that this would not be possible if you lay the carbon immediately after the finishing pass.
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davro	davro posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 300, Visits: 2.2K	Hi, 1. You applied the gelcoat before the finishing pass using the ball endmill. Why not do the finishing pass first, and then apply the gelcoat? I done a pass first but with a -1mm offset to allow for the gelcoat thickness, then done the finishing pass on the gelcoat without any offset. The reason I done the finishing pass last is to mill flat any high spots in the gel coat as it was brushed on ... . Between the finishing pass and the resin infusion, is there any surface prep you do with the gelcoat layer? The finish pass was with a 3mm ball end mill with a 2mm step over, so the finish was not bad, just compounded the gelcoat a few times and polished the gelcoat finish and then applied semi release and release wax, On the product there are some tiny machining marks 0.1mm ish in the epoxy resin but they disappear in the clear coat. David Stevens YouTube: Comment \| Rate \| Subscribe Instagram Composite Projects Body Package for Dax Rush RC Car Touring Body 1/10 Scale
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*VVS*	*VVS* posted 9 Years Ago HOT Post Details
Group: Moderators Posts: 226, Visits: 334	Search epoxy tooling block. I know little about this but you can machine and work straight from it, could be expensive!
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bkayyar	bkayyar posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 5, Visits: 22	Great, thanks!
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bkayyar	bkayyar posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 5, Visits: 22	The epoxy tooling block seems to be similar to the polyurethane model boards being sold, but I will give it a shot. Thanks!
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scottracing	scottracing posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 460, Visits: 5.2K	what is the size of the component? and do you want to use the machined buck as a mould tool? If so what temperature and method of composites will you use? PU block is cheaper than Epoxy tooling board but only goes to around 80degrees, where epoxy tooling board goes to about 120-130 degrees as standard but you do get high temp versions. The Ep978 epoxy tooling block is the main stable for our short run tools at work, has a very nice finish when machined too. http://www.johnburn.co.uk/product.php?grpId=232 http://www.johnburn.co.uk/product.php?grpId=251 As above you can get away with an MDF tool and seal it, then take a mould of it and it costs a lot less too.
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bkayyar	bkayyar posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 5, Visits: 22	The part is about 80 inches long (7.5 feet) in length and about 20 inches wide. I wanted to make a smooth-surfaced buck at a reasonably low cost, which is why I was thinking of using foam coated with a layer of smoothed epoxy. I will probably have to make the buck in separate pieces and then join them together. The manufacturing method is a wet layup - epoxy is used to wet the carbon fiber before it is laid and vacuum bagged. My main concern with MDF is the final volume and weight of the finished mould. I would really like to reduce the space and effort needed to store it! Thanks for the recommendations and advice.
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