Mold Natches

3D design and 3D printing are enabling a rethinking of mold natches. The precision of the process is such that now natches are not even needed in some multi-piece molds. When they are there is now so much flexibility regarding how they can be incorporated into working molds.

-Provisioning holes in the 3D-printed parts permits inserting 3D printed fittings for propagating natches, embeds and retainers into whatever is being cast.
-Provisioning cutouts permits rooting of platforms onto which
This method of printing in a hole also enables the use of commercial natches. By adjusting the size of my own the same block mold can be used to deploy either my own or the commercial natches.

Related Information

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.

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 the case molds are all that is needed to adapt to these.
-3D printing case and block molds means we have to pour plaster and rubber into shells with planar mating surfaces downward, they must sit flat on the table. Clips with a very thin flange solve this, they hold the embeds inside in place.
-Casting an embed into a mold is more flexible since we can glue (or friction fit) a natch or a spacer inside.
-Since there are no natches protruding on the flat mating surfaces these can be sanded for better flatness and optimal 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).

Version 4 Ball Pitcher 3D printed block mold

3D-printing v4 of Medalta ball pitcher mold

This project continues to demonstrate that multiple redesign, test cycles are a fact of life when making a new shape. 3D printing makes this so much easier. Here are the changes from v3:
-This time I am not going to back fill with plaster. I have heftier side rails that should hold things firmly in place.
-The rim is now cast in into final shape.
-The includes a distinct footring, this will enable easier cleanup of glaze on the foot and a cleaner edge line.
-The handle is thicker and looks a little further from the body (to enable getting my fingers in there).
-I am using natches this time, the two 9mm holes will mount embeds (the retainer and embed are shown beside the holes) - they will position flush in the case mold (I will propagate the embeds into the working mold also).
-I am casting it upside down, positioning the spout between the lower handle join and the foot ring. We will drain for ten seconds then plug the hole using a plaster insert made to fit snug. Remaining slip inside will refill the hole and even build the wall a little thicker there (increasing wall strength by the lower handle join).

Ball pitcher v.4 case molds cast

3D printed PLA mold to plaster case mold

We are just using pottery plaster for now. Notice the embeds for the natches. This time I did not backfill the 3D prints, that is better - because they are flexible they were much easier to remove from the set plaster. The side rails help keep them firmly in place and scotch tape on the backs was sufficient to keep them lined up at the join. These prints have a wall thickness of only 0.8mm. I did not need to use a parting agent nor did I do any smoothing on the 3D prints (although some cleanup on the plaster case mold will be done). Next step: A working mold, version 4.

By Tony Hansen
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