New Printer on the horizion

Our family company was bought a few weeks back by another small business owner. Well he actually has a few small businesses. Our shop is the mold making and molding portion of his endeavor. One of his other businesses is a company that makes the plastic for 3d printers. So naturally he wants to get into 3d printing of prototype cavities and cores for injection molding. On Friday we are going to assemble a team of people who will be tasked with getting a printer, and figuring out how to effectively use it. I am department head for the cnc side of the shop and have about 10 years programming experience. I am sure I will have a ton of questions coming your way so please be patient. I am excited for this new opportunity. Is any body else on here doing this kind of thing?

PegroProX440 said:

Our family company was bought a few weeks back by another small business owner. Well he actually has a few small businesses. Our shop is the mold making and molding portion of his endeavor. One of his other businesses is a company that makes the plastic for 3d printers. So naturally he wants to get into 3d printing of prototype cavities and cores for injection molding. On Friday we are going to assemble a team of people who will be tasked with getting a printer, and figuring out how to effectively use it. I am department head for the cnc side of the shop and have about 10 years programming experience. I am sure I will have a ton of questions coming your way so please be patient. I am excited for this new opportunity. Is any body else on here doing this kind of thing?

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We did some testing on this with both an FDM machine (Uprint) and a UV curing machine (I believe the samples were made on an Objet machine). The FDM plastics don't work very well for this. They are designed to melt / get soft easily to work on the 3d printers so the melt flow tends to destroy the mold. Also the surface finish of FDM is not very nice so the parts come out looking ugly as well. Finally you have to print out the parts solid plastic which causes a lot of material to be used. UV cured resin type materials do work (plenty of examples online as well) as long as there are no thin wall parting lines and very good care is taken to cool things down between shots.

The other issue is that for a basic mold (no undercuts, no slides, simple core / cavity) you can have an aluminium insert done on your 3 axis CNC machine quicker and cheaper than what the 3d printers can offer. On some speciality cases I can see the 3d printed molds working well, for example if injecting something like a soft elastomer that can be pulled out of the tool you can make undercuts that a CNC machine could not make but overall I am not really sure how usefull this is. To me it seems like the same file you design to be printed can be machined on a CNC machine quicker and cheaper.

Please do report back if you go ahead and let us know what worked and what not.

^ strongly agree with this line of reasoning.

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Am inclined to think that direct-metal stainless steel of some futuristic 2400dpi incarnation will be the absolute killer device for making complex injection moulds, but in terms of the stuff that does plastics today, it might be possible to employ a UV thermosetting machine for doing tricky/freeform/flexible moulds with very complex mating surfaces, but the current crop of machinery is still an uphill struggle against porosity and resolution.

However, if you have a plastics expert and can custom-brew thermoplastic filaments, possibly of a carbon-fiber type, perhaps also running some sort of coolant through the mould, it might be possible to cook up something specific to moulding that could be run through a conventional machine, and that might be worth putting effort into as a saleable filament for the filament business as well as a service to provide from your shop. I'm not aware of an injection-moulding-specific 3D printable thermoplastic mould-making system.

Might be possible to print a "green" resin and then chemically process or bake the 3D printed mould to turn it into an ideal melt-proof moulding material, then final-machine and/or dress the surfaces.

We have had casting made using 3D printed patterns from Peridot Inc. Was quicker than getting a pattern for a 2 casting run (previous caster closed and destroyed pattern without telling customers). Only problem was they (Peridot) under estimated the shrinkage on a bore core and had to recast it. IIRC they might have been direct printing the cores. Finish looked like a regular sand casting until you did a skim cut parallel to the layers. Layer size was thicker than any plastic 3D print I have seen, which would also support direct printing of a sand slurry. Patterns were 1 piece so there was no reusing of the pattern for a second casting.

Not sure if OKfoundry is doing the same thing or if they print 3D models of the finished part, slurry coat them, and burn out the pattern with a furnace or molten metal.

So far the technology seems good for non-reusable patterns. From what I have been told most of the current 3D plastics are too soft for ramming a sand pattern against.

Rich C.