What do you guys use to make a CNC cut mold. Something pretty good sized like an airplane cowling?
Do you always make a plug and then pull molds?
There are multiple options and it really depends on your expected mold finish and mold life.
For a full-size airplane cowl you could NC cut a female out of high density urethane foam, fill and primer it and pull a few parts right out of it. These type a molds only work for a few parts. If you need more longevity, you can cut out of stacks of MDF, saturate the surface with resin, and paint it with an 2K urethane. You can get more parts from this type. You can also lay on multiple coats of resin, remill, and layup right onto the resin surface.
If a higher part count mold is required you can mill a positive out of high density urethane, fill, paint, and pull a mold of it. If you don’t want spend the dough on high density urethane you can cut a little undersized in a stack of extruded polystyrene and layup a few layers of fiberglass/epoxy on the surface. Then sand, fill, paint, and pull a mold of the master.
Your last option is the one we’re exploring. I was just wondering how you would get a durable mold without doing the plug.
The only way to get a durable mold without a plug is to cut it from durable material. Durable materials take a beefy machine, are more expensive, and take longer to mill. In your case of the cowl you would need a beefy BIG machine and a large blank…$$$$$$$$$.
I have the beefy BIG machine. I need ideas for the large blank. Please don’t say aluminum. That is too cost prohibitive.
Steel…
Another option is to CNC in a sturdy material, MDF, tooling board, high density PU, or Master Works (look up the last one) and every time you need to make a product, vacuum a PVA film into the mould. This will be your mould surface.
Otherwise it might be cheaper in the end to do female mouldings. Fairing, sanding and painting a negative shape is a bitch. So much easier on positive shapes.
Undercut a cheap EPS foam, spray with Masterworks M2, mill to exact shape, sand and paint, and make a mould with a polyester based rapid tooling system.
herman, what is a polyester based rapid tooling system? Are you talking about something like Neomold from DSM?
Use ren board…best option and reasonable, we have used it to physically make the mould, pulled many parts from it, sands easy and is super dense. Good for about 40 parts out of the mould made of ren.
it is molded mould
In th plastic kayak industry they cast a rough ali mould or pieces then if need be weld the lot together into one mould and then CNC machine it saving on all the wasted ali had it been done from a block. But then they pull thousands on thousand of boats from the mould.
They also cast aluminum molds for rotomolding plastic kayaks. They make the sand casting plug from simple materials. Quite a few years ago I made CNC cut plug components for Riot Kayaks to give the slip system bottoms design/texture (Disco, Grind, etc.)