Printing A Mold *UPDATE* I printed a mold


#1

Has Anyone tried to straight up print a mold? I make little figurines and I want to start making molds of them ButI don’t have the money for a vacuum chamber and pump (if you know where to get a cheap one that would be great too!).

I am not sure if I will be able to cast in plastic if the mold its self is made of plastic, maybe there are other hard materials I could cast in? If anyone has tried let me know! I plan on printing one in a couple of days and testing things out


#2

It’s funny you should ask that because I was thinking about trying to do the same thing after reading this article yesterday http://makezine.com/2014/03/21/resin-casting-going-from-cad-to-engineering-grade-plastic-parts/

I was also wondering if it would work. I’ll be curious to see your results.


#3

Yep, many people have printed molds. We recently put up a video of one of our customers who prints out molds to make complex diagnostic models. I know that many have also simply made a mold from the printed positive (@annsidenblad of Rawrz Toys does this frequently!).


#4

Awesome, thanks for the vid link Sam. I guess I’ll be giving this a try in the coming days. I already have the smooth-on starter kit so hopefully I can use the resin that comes with it for this process.


#5

Depends on the type of material you want to cast. Hard plastics can’t be cast in a hard mold easily, most will stick to the mold.

You don’t really need a degassing chamber to make a silicone mold since there are the 2 part putty silicones that are really easy to work with and will handle resins and even pewter.
The nice thing about the putty type of mold material is you can build half the mold, set the part into it and apply mica powder then add the rest of the mold material. When cured the mica powder creates a separation so the mold just pops apart. You could probably use talc as a separator though I never tried.

As far as degassing chambers I build one for under $50 using a mityvac hand pump used in the auto industry for bleeding brake lines and a sturdy plastic container and some plumbers putty as a seal for the container. I printed a hose connector off of the Form1 because I was too lazy to machine one.

So far the degassing chamber worked nice for some cold casting I did.


#6

thanks for the video, and I have never heard of putty silicone but I am definitely looking into it! I hope to print a mold this weekend, I will post my results :slight_smile:


#7

Looks like your parts are pretty small, you could fabricate a mold frame out of a piece of pvc pipe and make a cap to compress the contents.

Though you can simply squish the putty around the object to make a mold you will capture the finest details if you mold it under pressure.

Cut a piece of pipe long enough to cover your part + 1/2".
Mount the pipe down on a flat sheet, I used a chunk of plexiglass that was 1/4" thick but you can use something a little thinner.
Next make a cap. You can use a another piece of plexi but cut it so it fits close to the inside diameter of the pipe. Closer the better but it should still move freely.

Fill the mold frame half way with putty, put your part in half way, powder the exposed putty then fill the remainder with putty so it is slightly above the top of the frame.

Next slowly press the cap in and toss a couple of weights. You only need a few lbs. When you see extra putty ooze out that is good.

Let the putty cure then take it out of the mold.

Once your done you will need to cut:
A spru (where the resin is poured into)
A runner (where the resin flows)
A gate (small opening that goes into the mold cavity)
Some vents (small channels on the opposite side to let air escape as the resin is poured into the mold)

Looking at the types of models that you have they should be fairly easy to cast without any special equipment since they have pretty solid bodies.


#8

oh wow Ken, thank you so much! this is a lot of help. I am going shopping tomorrow and I will have to try this out~


#9

Contenti Company sells the putty version as well as Smooth-On, you can compare prices, both are reputable companies to deal with.

Romanoff International sells the Mica powder that works excellent as a mold separator for the halves.

Over the years I have done the majority of my purchasing from Romanoff, extremely helpful and just really nice people to deal with.


#10

For vacuum degassing of silicone on the cheap, Harbor Freight to the rescue:

(Depending on their coupons any given day, you can usually get that one for ~$80-100 or so.)

Vacuum chambers can be had on eBay for about the same money and have nice sheet of clear acrylic to see though.


#11

I have a high volume pump but the problem is regulating it for small containers. Without a regulator the most containers will just collapse then leak. I primarily use the big pump for a vacuum table to hold stock down.

There are food storage containers that have vacuum seals and pumps that should be enough for thin liquids
http://www.walmart.com/ip/Vacucraft-Versatile-Vacuum-5-Piece-Food-Container-Set/33710582.


#12

ooo nice find, thank you so much!


#13

this is great! you have been so ridiculously helpful :’) I ordered the silicone putty, hope it arives soon~


#14

If you don’t have the mica powder try talc to keep the mold sections separated. See if you can get the unscented so there isn’t any additives.

I was looking at your figurines and you may have to do the mold in multiple sections. Make a parting line through the ears parallel with the front legs and one cutting through the tail also parallel with the back legs and set the gate on the belly with it’s own split. This will allow you to make an air vent at the tips of the ears tip of tail and bottom of feet so the resin can flow.

Maybe others that do more figurines would have some suggestions.

Because of the short working time you may want to set up the putty amounts in groups so you don’t mix the entire amount needed for the entire mold at one shot. When I used it that is what I did and it gave me time to work.

There should be some tutorial videos to explain on Smooth-on or Contenti on usage…

Make sure each of the parts is mixed (no skim of oil). Contenti’s part b is white and usually is a little oily when sitting around and needs to be mixed thoroughly then measure out each of the parts and mixed them thoroughly, You will notice the putty getting warm in your hand as it activates.

Good news about these types of silicones is they are easy to cut the spru’s, gates etc.

Down the road you may want to model the spru, runner and gate into your model once you get a good feel of how it all works for your pieces.

If your casting in one of the urethanes definitely wear gloves, There are all kinds of colorants for them. I never tried any of the epoxy or polyesters, Little leery about the odors from polyester resins.

Keep us posted, love to see the finish pieces.


#15

OK! So here are my results. I think for me its a “success”, being this is the first time I have ever made a mold or cast anything :smiley: and I learned a lot! the figures arms, ears and tail didn’t really come out but thats really my fault in that its legs and tail were WAY too small, so If I want to do this again, I will design something that can be cast in rubber a bit better.

I printed in 50, the mold is a little over an inch big and the final figure (of what remains) captured the detail pretty well! you can see a bit of the print lines but only if you really look closely.


#16

That’s pretty amazing! I am wondering though if maybe those smaller areas like the feet, tail and ears need some sort of air hole at the tips of each to allow the liquid plastic to flow through correctly by allowing air to escape.


#17

Exactly you need air vents where the resin didn’t flow to.
Air vents generally head upwards towards the spru side (if you simply drilled holes the resin would flow out of them and empty the mold).

As far as bubbles you may need to put the mold in a vacuum chamber. Alternatively slow mixing of the resin should reduce many of the bubbles right off. Also tapping the mold will cause the bubbles to rise. Expensive degassing machines vibrate as well as suck the air out of the chamber.

Very impressive first try.


#18

ooo airvents, alright thats great to know! and slow mixing, that sounds great too, I am going to get one of those vacuum sealing food containers you showed me ken, and I really hope it works D: If anyone else Tries printing a mold, let me know, I would love to see.


#19

Congratulations Sasha… isn’t it the best feeling when you pull your first successful part.

I’ve been printing ABS molds for an RC project using a FDM printer (upgraded MakerBot) and casting in rigid urethane foam. I’ve done a whole series of videos on the process I’ve developed that you may find useful. My Form1+ is been repaired at the moment, but as soon as I get it back I’ve got some molds read to be printed.

I really like the idea of printing the molds in the clear resin. That way I wont be working blind when I’m casting as I will be able to see exactly where the material is going :smile:

Have you thought of trying the clear resin for your molds?

Any way here is a link to the playlist to the videos i did -


#20

What type of mold release do you use?
Though looks like your urethane foam parts are flexible enough to pop out of the mold, I think it would be extremely difficult to do the same with a figurine and the mold design would be more in line with an injection mold.

As far as getting bubbles out you may have to tap the mold then toss in a vacuum. I didn’t try the vacuum food containers but they look like they work a little better than my Mityvac hand pump. The box I built did work for a cold casting I did and brought the bubbles right to the surface with only a couple of psi.

I have been looking at plastic domes, used on campers that are sturdy and could make good bells for a vacuum chamber and maybe even use a connector for a shop vac to draw the air out.