Make Mold Natches in OnShape

These are even better than before

Until now, I have done these in Fusion 360. But in OnShape they are just as good. If you are a hobby maker like me, then OnShape is free. I have updated the design, there are now only three parameters:
-ID: Inside diameter
-OD: Outside diameter
-Slack: Addition or subtraction for a good fit.

Print all four of these at the same time. Repeat cycles of adjusting the slack parameter and printing again until they fit into and over each other well. Print them in multiples of seven: Two natches, two embeds, two clips and one spacer (these are the proportions in which you will be consuming them).

An advantage of OnShape is that it enables sharing; the link is below. You can open and edit this drawing in your browser. Two 3D print it select all four, right click on one of them, export to 3MF format, open that file in your slicer software, position (and replicate/orient items), then print or export to a G-Code file.

Related Pictures

DIY Mold Natches in Fusion 360

Natches, spacers, clips and embeds

Available on the Downloads page

This picture has its own page with more detail, click here to see it.

Plastic natches are cast into plaster molds to provide a durable and good-fitting interlock between pieces. The traditional self-interlocking 3/8" or 9.5 mm (nipple diameter) one has not proven suitable for mold making based on 3D printing. Our solution is a four-part system. To use it, your 3D printed mold shells only need matched 13.5mm holes.
-13.5mm holes in 3D printed case molds are all that is needed to adapt to these.
-3D printing case and block molds necessitates pouring plaster and rubber into shells with planar mating surfaces downward (they must sit flat on the table). The thin flanges on the clips cause minimal issues.
-Casting an embed into a mold enables gluing (or friction fitting) a natch or a spacer inside.
-The use of embeds permits flat mating surfaces - these can be sanded (for better flatness and fit). They also allow replacing natches if they get broken (assuming friction fit).
-A set of four interlocks (4 embeds, 4 clips, 2 spacers, 2 natches) weighs 8.7g.
Our drawing 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 fits (however, a looser fit can be better, adjust to a 4.8mm nipple radius instead of 4.9). 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).
Some dimension changes may be needed to fine-tune for printing in your circumstances.

Videos

Links

URLs	https://cad.onshape.com/documents/3f2b2366ca28ad176c9acaec/w/6d6aa6deebb92615ab8a0c06/e/4087f6d9b21d0e2784d922c6 3/8" mold natch, embed, spacer and clip in OnShape. Sign up for an OnShape account and you can open this file, take a copy, edit it and 3D print these.

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