3D Printing a Mold for a Slipcasting Mold

Intro: 3D Printing a Mold for a Slipcasting Mold

I have always loved the 3D model of the 'Vaas met oor' (Cup with ear) by Joris Van Tubergen. A couple of years ago I did my first attempt to make ceramic cups of the model. I succeeded and love drinking my coffee from these cups.

Recently I wanted to make some more of them. Only thing: I did not like the handwork that was needed to create the mold.

Inspired by the option 'Mold' in the software for my Ultimaker 3D printer (Cura) I started to think about printing a mold for a mold.

This Instructable shows what I did to print a mold for a mold and how I was able to use it.

STEP 1: Create the 3D Model for the Mold

Create a mold in your favorite 3D modelling software.

I used Autodesk Fusion 360 to substract the 3D model from the cup from a cilinder. I cut that model in two and I added small spheres on one part and two small sperical holes on the other part so the 2 molds can be easily positioned correctly.

STEP 2: 3D Print the Molds

So here's the trick. Print the model hollow without a bottom or a top.

Preferably, if your slicing software provides the option to spiralize the outer contour, that would be the best.

DO NOT REMOVE YOUR MODEL AFTER PRINTING!!!

STEP 3: Poor the Plaster Into the Mold

With your model still on the printer platform, prepare your plaster. This Instructable by Eckert perfectly shows how to mix plaster like an Italian pro :)

After the plaster has cooled and solidified, you can remove the model from the platform.

STEP 4: Remove the Mold From Your Mold

Gently cut through your 3D printed mold. It does not matter when you cut too deep, it's just the outside from your mold.

Remove the 3D print and let your mold dry.

(In case you're having difficulties removing your 3D print: consider using a paint stripper. By heating up your 3D print it will become flexible and eventually easier to remove.)

STEP 5: Poor Your Ceramics or Stoneware

You are now a digital craftsman!

You are able to create a mold without too much manual work :)

You can now cast the cups in the preffered material.

New to slip casting? Check out this Instructable by Chanw612.

(The pictures show briefly how slipcasting works: poor stoneware or ceramics into your mold, wait for ±20 minutes, poor out the stoneware or ceramic and look!: *MAGIC!* There is a layer of stoneware in your mold :) Wait for another 20 minutes and gently open and remove your mold. Let the model dry before you continue.)

STEP 6: Sand Your Model, Bake, Glaze, Bake and Enjoy Your Coffee!

To finish: sand, bake, glaze and bake your model and enjoy your coffee!

Be aware: during the baking proces the model will shrink. The 3D files used for this Instructable will make lovely espresso cups :)

Comments

[stechi]

Nice idea! Probably set the 3D model to use the thinnest possible shell, so as not to lose too much detail?

[KamilM24]

Shell must be thick enough to prevent from expanding while liquid plaster goes in. I printed with 1.6 mm and was a little bit too weak. Hydrostatic pressure of the plaster expands top of the shell, and the mold is not assembled perfectly.

[Charlotte_J]

Not necessarily. Actually I used a 1mm nozzle and made a shell of only 1 line. But I did use a layer thickness of 0.15mm's for a smooth result.

[jogarcej]

The first picture of step 5 shows the outer part of the mold and some sort of shiny metal-like substance. What is it? Now, I suppose you also need another mold for the inner part of the cup, right?

[Charlotte_J]

Thanks for your answers @rduarte15 and @anjoschu. As soon as I cast some more cups I will take some more pictures to clarify this.

There is no inner mold. When I first casted this surprised me as well :) The technique of slip casting is magic!

[rduarte15]

That's clay slip. She's using the slip casting technique, which involves filling the mold with liquid clay and then pouring it out. That picture is before she's poured it out. The technique is for making hollow, thin-walled ceramic forms. It requires a plaster mold (which absorbs moisture from the clay slip), which is why she is making a "mold of a mold" and not just simply creating a plastic mold.

[PaulB646]

Nice catch, I saw that too. So Charlotte_J, what is that, some kind of metal cylinder that will define what the inner cup will be? Please explain.

[anjoschu]

The shiny substance is porcelain slip - the material that is being casted.

There is no inner mold. Slip casting works by the plaster absorbing moisture, effectively creating a dry-ish layer where the material is in contact with the mold. The thickness of this layer is controlled by the time elapsed before you pour out the rest of the porcelain slip.

It will all become clear when you read the Instructable that Charlotte linked to (in the penultimate paragraph "New to Slip Casting?").