All Glossary

Side Rails

Precise railing is a key to success in mold-making for ceramics. This page provides various examples of how we 3D-print these (rather than using traditional techniques). These rails, when properly made, impose perpendicularity, precise cornering or rounding and accurate dimensions.

Advantages we have observed:
-The potential precision enables notch-free molds.
-The ease of making them enables rails that are custom-fit to each mold being made.
-No tools or clamps or trips to a hardware store are needed. Rails can be stored with matching mold, enabling quick assembly and casting.
-Rigid rails enable printing lighter-duty block molds (because the rails impose perfect corners and perpendicularity).
-Rails can act both to contain plaster and to create a shape that needs to fit into a cup head.
-PLA print filament produces a surface that plaster releases from so not parting agent is needed.
-3D-printed rails can wrap under a mold, keeping them securely in place during pouring.

Related Information

3D drawing of a side rail for plaster containment

The parameters define most dimensions so I can easily specify the size and send a rail to the slicer for 3D-printing. At the slicer a rail can be duplicated and reflected to enable printing two pairs (the normal requirement). I print at a thickness of 1.2mm (three times the width of the nozzle), this produces a rigid rail that prints quickly. The vertical flange only needs to extend enough so clamps fit securely. The width of the bottom flange determines the rigidity of the corner and sides. A wider bottom flange also help assure the rail will stick better to the heated bed of the printer.

3D-Printed rail to cast working plaster jigger molds

The grey outer rail on the left was printed in two parts and glued together (at the shoulder). Its vertical split enables me to open it a little. The center model of the outside contour of the mug (on a two-step base) was made by casting the plaster inside another two-piece 3D-printed form I had made (we had to use a heat-gun and scissors to get the PLA printed form off of that plaster). I smoothed the surface on the wheel using a metal rib and trimming tool. Then I stretched a rubber band around the first step at the bottom (because the rail was a little lose-fitting). Now it fits perfectly and clamps tightly in place. To cast a jigger mold it is just a matter of soaping the plaster model and the inside of the rail and pouring in a mix of 1300 pottery plaster and 900 water.

Vertically printed 3D side rails

I made these specifically to fit this case mold. To be more rigid I printed a wall thickness of 1.2mm. The flange at the bottom fits under the mold and assures that no plaster will leak under and displace it upward (provided of course that the vertical flanges clamp together with a tight fit).

Version 2 ceramic beer bottle block mold

This time I printed the block mold, rather than the case mold, in six pieces on my consumer 3D printer.
Top: I printed the two halves upright (creating them in the slicer rather than Fusion 360). Because the print lines run concentric the quality is so much better than the previous version printed flat. The ribbing inside made the halves strong so they did not go out of shape when filled with plaster (to give them weight).
Second: The mold halves were simply laid against each other - they mated perfectly (and stayed in place because they are full of plaster). The four rails were then clamped in place.
Third: The PLA was soaped (using Murphy's Oil Soap) and rubber poured in (Smooth-On PMC-746). The next day it easily pulled out.
Fourth: The finished rubber case mold. The sides are pretty flabby so I make them rigid using the four rails (placed upside down).
Right: Using a plaster mold created from this rubber case mold I slip-casted a bottle using my L4768D recipe, glazed it with GA6-B and fired it at cone 6.

3D design, printing and use of a slip clay test bar mold

This is for making test bars of slip casting clays bodies for use in the SHAB test (to measure drying shrinkage, firing shrinkage and fired porosity). I designed it in Fusion 360 and 3D printed the light-duty rails and case mold. I poured plaster into that to make the two plaster working mold halves (top right). The funnels provide a reservoir so the bars be cast solid. This mold can produce a set of three bars in less than an hour.

3D-printing basic rails suitable for some pours

This type of rail eliminates issues with lifting from the bed when trying to 3D-print them upright. These can be cut to length with scissors at pouring time and clamped on the flange. This type of rail is only sturdy enough for shallow pours. And when a little movement during casting can be tolerated.

Printing my own version 1 block mold in two pieces

Of course, this is far too large to print in one piece on my printer so I sliced it in two and added tabs to clamp the halves together. Notice the size rails are part of the print. The 3D rendered version was, of course, smooth but there is quite a bit of stair-stepping on the 3D printed surface, I did not worry about smoothing it and it did not prevent casting two plaster molds. No mold soap was even needed, the plaster molds came out using compressed air. The long side rails did require some stabilization (they were flexing with the weight of the plaster).

By Tony Hansen Follow me on

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