All Glossary

Pour Spout

Plaster molds intended for slip casting have a spare at the top to act as a reservoir. This enables overfilling the mold to accommodate the dropping slurry left. 3D-printed spouts make a spare unnecessary.

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Details

3D-printed pour spouts make it possible to create plaster molds that do not have a spare. The spare at the top of typical molds acts as a reservoir enabling overfilling the mold - this accommodates the dropping slurry level as the mold pulls water. Although a traditional mold maker might consider this concept of a spareless mold ridiculous, 3D printing makes it not only more convenient, it just works better.

• The spout has a flat bottom and can be quickly glued to the mold top using the slip.
• The reservoir is not dewatering or using any of the slip so less scrap is created and less slip consumed.
• The 3D-printed spout is easier to clean.
• The quality of the lip or upper edge of the cast piece can be better.
• Pour out is much cleaner.
• 3D-printed spouts enable lips that can flare outward. The spout can provide a high-quality guide for finishing the insides of container lips. Upper edges can be cut cleanly along the mold edge after spout removal (which can be done shortly after pour-out).
• The falling slip level visible on narrow taller spouts enables fine-grained control of knowing when to empty a mold.

Related Information

A 3D-printed pour spout on a mug cast-jigger mold

I prepare to attach these by simply touching them to the top of the slip (it is sticky and coats the underside evenly). Then it is just a matter of setting it in place and and it glues down in seconds. I make these a little larger diameter than the top of the opening in the plaster mold (e.g. 2mm), producing a small overhang on the cast piece (this one has 0.8mm thick walls and prints quickly). During the time in the mold, the clay slurry creates a thickness against the plaster walls that also extends upward above the top (inside the spout). Shortly after pour-out I put these into the cuphead on the jigger wheel and make a cut and lift the spout away. This leaves an over-hang and over-height that enable finishing the rim using the jigger template.

Slip cast calciner after pour out

Pouring was made possible using a 3D-printed PLA pour spout. This enables overfilling the mold. The overhang lip is still optional, it was not possible to dry them enough to remove them from the mold without cracks appearing under the overhand (although if the mold is laid down as soon as possible after pouring this could work). Later we modified the spout to be flush with the inner wall and taller. And we added a drain hole so that pour out was not necessary - the spout thus just acts as a reservoir. Shortly after pour out we were able to remove it and cut the wall flush with the top edge. This enabled the clay to pull away from the mold with equal resistance all the way around, resulting in amazingly straight-walled pieces. And very thin walls were also possible.

A 3D-printed spout enables a flared rim on cast ware

It was glued down using the casting slip itself (it stuck in seconds). About ten minutes after draining a fettling knife was run around the inside, then it detached easily. The overhung lip produced imparts structural strength that resists warping, for drying and firing, to the thin walled piece. This spout has advantages over the traditional "spare" built in to the upper part of a mold. It enables a one-piece mold. The lip can be more overhung. Draining is cleaner and easier. Molds are lighter. Extraction can be done sooner and it is easier. The spout does not absorb so there is less scrap. The degree of overhang is adjustable by simply printing new spouts.

An impossible spout is possible by 3D printing

This mold is for a Medalta Potteries ball pitcher having a closed top with a teardrop-shaped spout (lower right). 3D printing makes it possible to create a pour spout that inserts perfectly into the angled hole, thus the plaster mold itself does not need a spare. The size of the pour spout reservoir and the degree of insert can tuned so that when the level drops to the bottom it is ready to pour and the pour hole is perfectly formed.

Bottle calibration mold demos some casting process improvements

Three slip casting methods are examples of the flexibility potters have compared to manufacturers (especially for small molds like this).
1) 3D-printed locks are stuck on to hold the mold halves together. The casting slip itself adheres them. Dipping the flat surfaces and attaching them takes seconds. By using this method the mold halves can be aligned accurately.
2) The 3D-printed pouring spout is also attached using the slip (it also helps hold the mold halves together) and acts as a reservoir and pour-out indicator.
3) There are no notches or natches (the halves were poured into disposable 3D printed PLA masters - and mate perfectly and align easily).
These three factors simplify mold design, reduce mold size, improve the fit of parts and simplify pouring, demolding and cleanup.

Why 3D design and printing is a better way to make slip casting molds

I dread the process, the mess, all the supplies and tools involved in the traditional mold-making process for functional ceramics - it just feels old. I am not a mold-making expert either, but 3D design and printing are enabling a rethink of every aspect of the process. This is the future. And it is much more fun!
-I spend most time on design, pouring the plaster or rubber takes minutes.
-Many fewer tools are needed, the process is less messy.
-Sanding of flat mating faces is possible (for better seams than I've ever had). This is because natches are added later.
-I can make my own natches and coupling schemes.
-No spare is needed, the 3D-printed pour spouts work better.
-The range of shapes seems limitless. Especially because designs can be split up into pieces, each printed in optimal orientation (and then glued together precisely).
-I make molds through multiple design-print iterations. 3D makes do-overs or changes in design as easy as a reprint and plaster pour. So, I can make a mold just to test an idea!

By Tony Hansen Follow me on

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