Designing 3D Printable Shoe Last Joints in 3DShoemaker for Rhino

In previous 3DShoemaker tutorials, I’ve explained how to 3D print and assemble a couple different kinds of shoe last joints using the models available on 3DShoemaker.com. This was handy for shoemakers that don’t necessarily want to get into computer aided design of shoe lasts but do happen to have access to a 3D printer. But for shoemakers already doing the design work, it makes sense to also design the joint. This can now be done in all editions of the 3DShoemaker plugin for Rhino 3D. In this tutorial, I’ll show you how.

Designing a Shoe Last Alpha Hinge for 3D Printing

Below is figure showing the various elements of the 3D printable alpha hinge. There is of course the front and back parts of the shoe last which are sliced at the Main and Alpha cut planes. Then there is the Spring which firmly keeps the joint in the open or closed position. Though the spring can be designed in the plugin, a manually improved version can be found here. The final printed parts are the discs. These too have been improved in the latest version of the plugin, and now have shafts extending into the back part of the shoe last to reduce joint laxity. As far as hardware, common screws can be used or quarter inch dowels, the latter of which can be ordered from various hardware suppliers, or can be purchased directly from 3DShoemaker.com. Standard thimbles are also provided.

3D Printing a Shoe Last with a Working Alpha Hinge Diag

Shoe Last Alpha Joint (v-hinge) hardware

To design a shoe last alpha hinge that can be 3D printed, press the Make button on the 3DShoemaker side panel in Rhino. A form will come up with a variety of options. Some of the more important settings are as follows.

3D Print Shoe Last Alpha Hinge Settings 3

Spring Stretch: This is the amount of stretch the plastic elliptical spring is subject to when the hinge is in the closed position. Increasing this number will shorten the distance between the pivot holes on the elliptical spring, forcing it to be in a more stretched position. A more stretched position means a tighter alpha hinge.

Pivot and Spring Pin Hole Diameters: These setting determine the diameters of the holes passing through the elliptical spring and the corresponding holes through the shoe last walls. The default settings are for using #8 wood screws (standard size for deck screws). The advantage of wood screws is that they are readily available. The disadvantage is that the tightness of the hinge is limited. For a tighter alpha hinge using the same settings, a 1/4″ dowel pin (now available here on 3DShoemaker.com) can be used (the latest update provides a toggle to choose this).

Pipe Thimble: Thimbles are important if you plan to hold the shoe last on a lasting pin as otherwise the plastic can crack. Either a standard half inch copper pipe can work or a standard thimble can be accommodated via the toggle. Standard thimbles can be purchased here on 3DShoemaker.com.

Percent Length Along Dorsal Profile for Cut Position: Depending on the size and type of shoe last, you may want to move the alpha cut position forwards or backwards. A positive number for this setting moves the cut position forward along the dorsal profile and vice versa.

Disc Wiggle Room: This is the gap between the discs and the cavity walls in which they sit. The same gap is applied to the elliptical spring and its cavity walls. Higher precision 3D printers can get by with less wiggle room.

Lateral Offset From Hinge Center to Last Center: Depending on the relative shape and position of the top and bottom of the last, it maybe necessary to laterally offset the hinge center using this setting.

When you are satisfied with the settings, press the ‘Go’ button and the hinge will be designed. By default, an option to orient the parts for 3D printing is turned on, the results of which are shown below. The most recent version of this function also provides options to just create the thimble or just create the joint.

Shoe Last with Alpha Hinge oriented for 3D Printing

Designing a Shoe Last Rail Joint for 3D Printing

An alternative joint to the Alpha Hinge is the Rail Joint. The front and back parts are connected by a rail. A screw is rotate to slide the back part up along the rail. This effectively shortens the shoe last length, allowing it to be easily removed from the footwear. It makes de-lasting extremely easy. One thing to keep in mind though is that closed footwear like a boot without lacing etc. will not have room for the back part of the shoe last to move into. For those types of footwear, it’s best to stick with the Alpha joint.

3D Printed Shoe Last Rail Joint

The rail joint design selections are on a separate tab on the Shoe Last tab of the Make form. It’s rare any of the settings need to be changed, so I won’t go into detail on them here. The one useful option I will mention is the Non Articulating option. This creates what I call a fixed rail joint, where the rail is simply used to permanently fix the back and front parts together. It just makes it easier to 3D print a shoe last without support material and without requiring much 3D printer build volume.

3D-Printing-a-Shoe-Last-with-a-Working-rail joint