Flexible Resin Mold

Just curious if anybody has tried using the flexible resin to print molds for casting hard urethane? Would be nice to skip making a silicone mold from a printed part and directly print the mold on the Form1. Any experiences would be welcome but i’m specifically thinking of molding hard urethane.

I haven’t used flexible for a mold yet but I did use standard black resin to make a 3 piece mold for an automotive bushing. Worked pretty well.

Very interesting, What type of material did you use for the bushing? How many pulls from the mold before you noticed mold damage?

We made 6 or 7 polyurethane parts from the mold without any damage. I just used standard mold release and poured. The material shrinks just enough to allow the center shaft to release easily.

As long as the part doesn’t have any overhangs that would lock the material into the mold it should last a long time.

I’ve made molds using the standard grey type 2 resin. I use them to “over-mold” electrical cables where the cable comes through a panel. It’s similar to the over-mold you’ll see on a phone charger where the cable exits the plastic case. I’m over-molding cables that are about 6mm in diameter though. I’ve used my latest mold in excess of 40 times now with polyurethane and the mold shows no obvious signs of wear. The mold is in two parts and the top half has two holes…one for injecting the PU and one at the same height in a different location to allow air to exit. The two halves of the mold go together with M5 screws as I’ve actually tapped holes in the grey resin. I’ve tried a few mold release agents and the best I can find is wax base. I didn’t have so much luck with a PTFE based release agent.

I do have flexible resin here so I guess I should try making a mold tool out of that sometime.

Very interesting Matt. The main reason for asking about the flexible resin was concern for the hard urethane releasing from the mold, sounds like your experience is the urethane releases okay. The part i’m making is an electronic enclosure (basically a 5 sided box) and has 3 degrees of draft on the sides perpendicular to the mold parting line. I’d be interested in hearing more about the mold release you use.

The PU I’m using in the mold has a hardness shore rating of 85. The wax based mold release I have is made by Rocol and it’s calles RS-7. It comes in an orange spray can. I bought it from RS Components but I’ve checked and see they no longer sell it. Not sure whether it’s a discontinued product or whether RS have just stopped stocking it. I’ve probably had this can about 12 months.

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