The mold-making technique we have always needed

I have long wanted an easy way to make molds for slipcasting handles that mate perfectly to any shape mug (or pitcher, teapot, etc). These are the answer. These shells print quickly to only 11 grams of PLA filament. They peel away from the set plaster with a heat gun to give fine detail and perfect fit. These use 3D-printed pour spouts (printed separately) and enable cutting the joint surface cleanly and accurately before the handle is removed from the mold (a version of this is also available with spares). This is the product of a long development process. This drawing is available on the downloads page.

Worried about mixing or tuning your own casting slip recipe? We have lots of help on doing that.

Available on the Downloads page

Related Pictures

CAD drawing for 3D-printing plaster mold natches, spacers, clips and embeds

Plastic natches are cast into plaster molds to provide a durable and good-fitting interlock to ensure pieces line up perfectly. The traditional one familiar to most people is the 3/8" or 9.5 mm size (nipple diameter). Because of issues surrounding their use (not the least of which are price or even finding a supplier), we designed our own. Ours have several advantages:
-There is never an issue with supply, we make them.
-13.5mm holes in case molds are all that is needed to adapt to these.
-3D printing case and block molds necesititates pouring plaster and rubber into shells with planar mating surfaces downward (they must sit flat on the table). The thin flanges on these cause minimal issues.
-Casting an embed into a mold is more flexible since we can glue (or friction fit) a natch or a spacer inside. In addition, they permit flat mating surfaces to be sanded (for better flatness and fit).
Our drawing (right) shows the measurements we use. 3D printing is precise enough that the inside dimension of the embed is the same as the outside of the natch shoulder, yet the natch slides in perfectly. The same good fit happens with the clip and embed and the natch nipple and spacer (although it is necessary to chamfer the bottom corners and bevel the top corners of the spacer for better insert).
There is a good chance some dimension changes are needed to fine-tune for printing in your circumstances. Since these are printed in batches of many, failed print jobs will result if insufficient attention is given to this (and to whether to use a glued plate).

3D printed three-piece jigger case mold complete

It is now practical to make true-round, perfect-fitting, all-in-one case molds for jiggering using a consumer 3D printer and PLA filament. This is a one-off test mold to demonstrate the method. The process: Create the drawing in 3D CAD (e.g. Fusion 360), print the three sections, glue them, turn the assembly upside down, fill with plaster, let it set and peel out the inside two pieces using a heat gun.

Things to note:
-This is very light and prints quickly, the walls are only 0.8mm thick.
-The shoulder (C) is printed solid and the PLA printed surface from A to D is left in place permanently, this enables precise and durable fit into the cuphead. I print the outside shell upside down, so no printed support is needed.
-The down-pointing flange (A) embeds it into the plaster providing a durable edge against which to fit the pour spout (F). The glue joint connecting A & B breaks when B & E are removed.
-B and E are printed upside down, no support is needed for B, since the top is open, it thus prints quickly.
-The base E has a flange that enables gluing it precisely into B. Debossed logos are practical. It prints upside down for maximum quality (print support is generated but because it is short it prints quickly).

You can get this on the downloads page.

CAD steps for a 3DP block mold to make a rubber case mold

The objective was to make a rubber master case mold for the production of working plaster molds. 3DP is a great solution. This drawing was done in Fusion 360.
1: A make a sketch of a box, around the handle, on the XY plane. Offset that outward by 1.2mm (my printer prints 0.4mm wide, three passes give good strength).
2: Extrude to create box 1: The base backward by 1mm and the sides forward by 20mm.
3: Use five sides of the box as cutting planes to slice it out of the mug.

At this point I could print this in PLA filament, pour plaster into and then use a hair drier to peel it off. But let’s make rubber molds instead.

4: Move the box-with-handle away from the mug. Pull the four sides out by 5mm to thicken them.
5 & 6: Create box 2 around the outside of it, as a new body, 1.2mm wider and taller, 1mm more frontward and 1mm less backward.
7: Use box 1 as a cutter to remove material from box 2 and then pull the outer 1.2mm sides 5mm backward.
8: Shell out the back side to 1.2 wall thickness and make two 9.4mm holes (to accommodate natch clips).

To make side 2 mirror-image a new body using the front or back as the reflexion plane. The back side is then filled with PMC-746 rubber to make the block mold. Plaster is poured into that to make each working mold.

Coming soon: Throw the teapot and slip-cast the lid

How would you like to be able to create a parametric CAD model of a teapot lid? Then 3D print a case mold and pour a multi-piece plaster working mold? Imagine easily making multiple-size one-off molds to accommodate any teapot you throw!

This is perfect for M370 or Polar Ice (both have throwing and casting versions). Or, how would you like to be able to formulate a casting slip having the same appearance and degree of maturity as the throwing body you use? More information coming soon (based on the L4807 casting body).

Next, imagine casting the handles and spouts also. Information on how to draw and print them also coming soon.

Links

Media	Drawing a Mug Handle Mold in Fusion 360 Lilly will take you step-by-step through the process of drawing a shell mold that can be 3D printed and used to cast a plaster mold for slip casting perfect-fitting handles.
Glossary	Casting Slip Casting slips are among the easiest clay bodies to make yourself. The ability to make and tune your own will open many doors in your production process.
Projects	Mug Handle Casting

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