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).

Available on the Downloads page

Related Pictures

DIY natches, spacers and embeds in a plaster handle mold

Natches, spacers, embeds in a plaster handle mold

This is our third-generation alternative to the use of traditional mold natches (like the red ones in the photo). Here is what you are seeing:

Right: A 3D-printed case mold for a mug handle. Clips (retainers) have been inserted from the bottom side. An embed has been pushed down over the one in the rear.

Center: The plaster mold created from it. The embed at the rear is ready for inserting a spacer (the nipple of the other half will it into that). A natch has also been inserted into the embed in the front. These fit tight enough in the hole that glue was not needed here.

Left: Spacers have been inserted into both embeds. A standard natch fits into the one in the rear and one of our natches fits into the one in the front.

Soon the CAD drawing for these (natches, spacers, embeds, clips) will be available on digitalfire.com.

The mold-making technique we have always needed

I wanted an easy way to make molds for slipcasting handles that mate perfectly to any shape mug (or pitcher, teapot, etc). I want to pair cast with thrown or jiggered elements and join them using just slip (even when the clay is stiff). We have developed a flexible CAD design that puts 3D printing of case molds within the reach of almost anyone. It requires so little tooling it can be done in a kitchen using spoon mixing and a paper cup! These PLA shells, for example, print quickly to only 11 grams and they peel away from the plaster with a heat gun to give fine detail and perfect fit. Multiple cycles of redesign and print are practical to achieve just the right shape and fit. Cast handles can be produced in quantity and stored in a damp box, removing one of the biggest hassles in the production of handled ware. The feel of the handle is the first thing customers notice, even a hobbyist can now turn a "wet noodle" handle into something designed and utilitarian. You can get this drawing on the downloads page. Worried about mixing or tuning your own casting slip recipe? We have lots of help on doing that.

Standard 3/8 inch mold natch

Once you try these you will never go back to making molds without them. Unfortunately, these are not easy to get in North America. Or even online. But you can 3D print them yourself. This design interlocks with standard 3/8" natches used in industry. There are more aspects to printing and using these than meets the eye, here are some aspects to know:

-The base can be widened for sticking on the build plate better. If you need to print large numbers it might be advisable to use a glued plate to make sure they stick well.
-The inner edge is chamfered to ensure better insertion of the nipple.
-Print without infill for better strength.
-These are hollow, no support is needed.
-The bottom can be widened to stick better to the build plate.
-The ribs can be moved.
-A 9.8 mm hole is needed in the mold.

Glue-sticking the 3D printer bed for better adhesion

Many objects are unprintable due to plate adhesion issues. Some objects print successfully when done alone, but doing many of simultaneously can fail when one releases mid-print. In these cases, objects can be guaranteed to stick using a hot bed PVP glue stick like this one from Amazon (even a paper glue stick can be used, it sticks pieces even better but does not apply as evenly).
-When applied to a heated bed using long strokes it goes on evenly and dries hard.
-It can be washed off and replaced after several prints.
-The glued surface sticks pieces very well, this enables reducing the area of contact and lightening objects (giving success even when the slicer issues a "low bed adhesion" print stability warning. For example, these spacers and clips would normally release from an unglued plate.
-Objects having a large contact surface may not be removable without damaging them or the plate. Or, pliers may be needed to pull objects off (flat-bottomed pieces giving the most difficulty).
-The ten clips (right) are quite delicate, having 0.8mm walls and 0.4mm thickness base flanges. When adhesion is too great these can be damaged when removed with pliers, when not enough they release during printing. We adjust for this by increasing flange diameter when adhesion is too low and reducing it when it is too high.

Links

Projects	Mold Natches Natches are an interlocking mechanism using in plaster molds for ceramics. They enable quick and accurate registry when assembling multiple pieces of a mold.
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.
Glossary	Mold Natches At digitalfire we are big fans of slip casting and want to help people and companies (even hobbyists) to integrate it into their production.

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