PLA urethane mold

[lovethepirk]

I am doing a mold in PLA.

I just had a thought that the urethane pour may cause a chemical reaction above the temperature that PLA likes.  Anyone have thoughts/experience with this.

Also the chemicals could eat away at the PLA, but I am not sure.

[Jimc]

well i dont think you ll have a problem with the chemicals since there are no real solvents in casting urethane and the poly and iso in it arent harsh in a way that they will attack other plastics. the isocyanates do carry high degree of health hazards though.  as for the temp, that depends. the faster the urethane is the higher the temp. a fast urethane can certainly get hot. you would not want this anyway with a mold that has some thickness to it. if the casting gets too hot it will crack. always get nice slow resins. they are easier to work with and give alot more working time. only other thing to worry about is bonding to the mold. be sure you use plenty of mold release.  

[Robo]

Casting a hard substance in a hard mold could be trouble, be sure to use plenty of release agent on that.

[Nick Cecchi]

I recently did some Urethane rubber into ABS casting with the mold coming direct from the printer. It went fine - the exothermic reaction really didn't get that hot. 

That part looks fairly thing, so I think you will be good.

If it is urethane plastic, you may want to look into printing a soft material or printing a positive then taking a mold off of it.

Nick

[lovethepirk]

Nick,

I am doing urethane plastic shore 85A.

I have a positive print and it is nice.

What is a quick and dirty way to get a mold done for urethane plastic?  Material, where to purchase?  I'd like to produce some parts for testing by Friday....

[Robo]

smooth-on.com is a great source for urethane, resin, silicone, etc for casting and molding. I've used their stuff quite a bit and it's always yielded great results.

[MBuser]

www.bjbenterprises.com is another.

[Nick Cecchi]

I was going to suggest Smooth-on also. Their products can be found at Reynolds Advanced Material Locations.

I really like the Mold Max (http://www.reynoldsam.com/Silicone-Rubber-an/c2_1113_1135/index.html) or Mold Star (http://www.reynoldsam.com/Mold-Star%3D-15,-1/c1306/index.html) depending on the part shape and complexity.

You want to cast urethane into silicone to prevent the part bonding to the mold. 

I was able to print the mold jackets for my parts also.

Take a look at that image. The Purple thing in the foreground is a 3 -part mold curing. the printed plastic around it is the mold jacket which I printed out. The purple things in the right upper middleground are parts for the same mold - a removable plug for casting a void inside the part.

The parts on the left in the orange molds are duplicates of the part that is between the two purple molds on the left. I glued it to a flat sheet of metal with a printed mold fence around it in order to cast the molds.

You can also see a second 3-part mold with removable mold jacket in the upper left.

[lovethepirk]

Cool! Thanks