v2 Digitalfire Mold Natches in OnShape

These are even better than before

Available as a Product on the Downloads page

Until now, I have done these in Fusion 360. But in OnShape and my new dimensioning method they are even better. If you are a hobby maker like me, then OnShape is free. This updated design only has three parameters: ID (inside diameter), OD (outside diameter), and 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 (the better quality your printer to smaller the "slack" dimension can be). 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. To 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.

Available as a Product on the Downloads page

Related Pictures

v1 DIY Four-Part Mold Natch System

Essential for 3D mold-making in ceramics

Available on the Downloads page

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

Plastic natches are used in traditional mold making for slip-cast ceramics (instead of registration keys). They are cast into plaster molds to provide durable and good-fitting interlocks between pieces. They are self-interlocking, a popular size is the 3/8" or 9.5 mm (nipple diameter) natch. However, these have not proven suitable for the mold making process described on this site. The Digitalfire four-part system accommodates 3D printing (usually using PLA filament) case molds for pouring plaster, block molds for pouring rubber case molds and even hybrid solutions. Here are some features of our system:
-13.5mm holes in 3D printed case molds are all that is needed to adapt to these.
-3D printing case and block molds necessitate pouring plaster and rubber into shells with planar mating surfaces downward that must sit flat on the work table (traditional natches don’t work in this setting).
-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.
-A set of four interlocks (4 embeds, 4 clips, 2 spacers, 2 natches) weighs 8.7g.
Consider starting with a 0.1mm allowance (e.g. 4.8mm nipple inside a 4.9mm space). Print all four to check for fit. Then do cycles of adjusting the allowances and printing again until they fit.

Standard 3/8 inch Self-Interlocking Mold Natch

We can 3D print these and improve them

Available on the Downloads page

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

Once you try these you will never go back to the use of registration keys in traditional mold making. Unfortunately, these natches are not easy to get in North America. Or even online. But you can 3D print them yourself (we use PLA filament, but TPM would be a good option). 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 things we noted (and changed):

-The base can be widened for sticking on the build plate better.
-Glue the build plate, on your 3D printer, to make sure these stick well.
-The inner edge is chamfered to ensure better insertion of the nipple.
-Print without infill for better strength.
-These are hollow, no print 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.

Once we moved to the use of CAD and 3D printing of block and case molds, these were abandoned in fovor of a four-part system.

Glue-sticking the 3D printer bed for better adhesion

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

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.

Videos

Links

URLs	https://cad.onshape.com/documents/3f2b2366ca28ad176c9acaec/w/6d6aa6deebb92615ab8a0c06/e/4087f6d9b21d0e2784d922c6 3/8" mold natch, embed, spacer and clip in OnShape. This works without sign-up or sign-in (in view mode). Create an account at OnShape to be able to edit this.

Got a Question?

Buy me a coffee and we can talk