Creating molds from 3D Printing?

[python]

Thanks !

I wonder if this can also be done with uv-sensitive resin prints.

[navkram]

Ah, OK. There's a good writeup (with lots of pictures and video) of lost PLA casting here: http://3dtopo.com/lostPLA/

Edit: Comprehensive writeup of lost ABS casting here: http://jason-webb.info/2012/11/lost-...minum-casting/

Thank you for these links great information in both of them.

[navkram]

IF you need to do a lot of molding you may want to check out this roto-mold that looks like it will be on kickstarter soon. RotoMAAK

thank you Jzatopa, for this link.

Being new to this forum but not new to 3d printing and mold making I did not want to make it feel I was only spamming the forum, and hopefully can contribute to this forum.

I am the creator and builder of the RotoMAAK, we have done lots of testing and prototyping to get a solid machine, we are finishing up the final info for the kickstart campaign.

this was developed out of a need that I had, a customer came to me and wanted a scale model sample of a large rotational cast plastic part to justify the change to a $80,000 mold, I printed a scale model of the part close to 12 hr print time for the first one, they past this on to their customer for the engineering department to show the salesmen what the proposed changes were going to be. once in the hands of the sales department they got the green light to make the changes. meanwhile the sales department loved the model and request 10 more "salesman" samples to allow the sales to show their customers since the actual part was the size of truck bed and it has been easier for them to sell the product if the customer can hold the part.

to reproduce 10 samples on my printer would take min. 120 hours of print time not including failed prints etc. so I made a silicon mold of the printed part and developed the rotomaak to cast hollow parts, I could have cast the part solid but that was just a waste of resin, 5 lbs of resin compared to a couple ounces.

I took the first machine to the detroit makers faire to just have sitting the running because it looks cool spinning. I got tremendous response from other makers on what niche this machine could fill. so with the support of a few key companies I proceeded to make changes and now we are very close for release.

[Larry]

Has anybody ever experimented with creating molds via 3D Printing and then pouring liquids into the mold to create the object? Kind of the inverse of what we traditionally think of when 3DP'ing.

This is actually what the European Space observatory is doing with 3D printing. They make molds of parts for their telescopes with 3D printers and then pour aluminum into those molds.

[mechadense]

I tried printing flexible PLA as a mold for PU. I used silicon spray as release agent. => The mold got destroyed after only one use.
My grey soft PLA behaved like chewing gum :S very little shape memory.

For small quick and cheap stuff I now use ogoo (acetic silicone + corn starch). It sticks on PLA while wet and goes off easily when dry - just perfect.
I used wax based release agent to quickly make around a dozen PU copies from a single mold from a specific PLA part (PLA positive -> ogoo negative -> PU positive)
An other release agent might be better (less viscous)

[LambdaFF]

There is a quite simple technic that you can use. With electro plating you can create a metallic layer of zinc or copper or nickel on you part. If you make the deposition thick enough it can make a mold. You will need to put some conductive paint on your plastic part first as it is not conductive.
Conductive paint : ~14€/400mL.
Copper Sulfate : ~20€/1kg
Car battery, a pair of crocodile pincers.
And then you remove the plastic by heating. It's easier if it is wax, but perhaps it would work as well if you do it with a soluble material like the ones for support.
However, it only works if the end material is supple enough to be extracted. Otherwise you need to cut the design to make separate mold parts.
CATIA has excellent molding design tools.

On a different note, for the release agent. If your part is big enough, most composite manufacturers cover their big (read costly) molds with teflon adhesive or a teflon coating. I never saw it in Europe but in China you can find it in spray cans.