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.

Key phrases linking here: mold natches, natches, natch - Learn more

Details

3D design and 3D printing are enabling a rethink of almost every detail of how molds are made. The way in which natches are incorporated into working molds, what natches need to be and even if they need to be there at all, are all on the table. The precision of 3D-printing can really be leveraged to imagine and create new ways of interlocking multipiece molds.

At its simplest, incorporating natches in mold parts is simply incorporating holes in 3D printed shells to accommodate clips or retainers (and what they connect to, either a natch or an embed). Natches and spacers can then be inserted (and glued) into the embeds after the plaster has set.

More advanced options involved fitting natches to already created working mold parts. This is done by the incorporation of smooth recessed 3D printed platforms to which natch hardware can be positioned and epoxied.

While natches can be purchased, the other hardware needed to embed them necessitates 3D printing anyway. So you might as well print the natches also. Making them all yourself enables not only flexibility in shape and size but also assures that you will never be caught out of stock.

Related Information

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).

Our natches, spacers and 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.

Three-piece vertically printed mold with natches

These 3D prints slide into slotted side rails for each pouring of plaster. Since the plaster releases easily it is possible to use these multiple times. This method is suitable for prototyping in larger quantities than prints that integrate rails. These are printed on edge so print times are drastically reduced and surface smoothness is much better. This version has a bottom piece eliminating the seam across the base. It also enables putting embossed logos on the base. The holes enable mounting flush embeds - making it possible to sand the mating surfaces flat before gluing in the natches. The three-piece mold produced is shown on the bottom.

Slotted natches make this bottle mold possible

These enable pulling apart the top halves of our ceramic beer bottle molds while the leather hard bottle is still embedded into the base. Starting upper left and clock wise:
#1 The 3D design for making a rubber case mold.
#2 It has been 3D printed in three parts (which are then glued together).
#3 PMC-746 rubber was poured in and the 3D printed parts were peeled off.
#4 Natch parts have been 3D printed.
#5 The embeds have been rubber cemented onto the rubber mold (to hold them in place during casting).
#6 Plaster was poured in.
#7 The plaster working mold has been extracted from the rubber, the embeds firmly rooted in place.
#8 The slots have been epoxied in place (lined up and positioned accurately so the natches hit the end of the slots just as the halves contact).
Centre: The mold partly assembled.

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
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