Dec 30, 2014 | By Simon

With a comprehensive skillset in all things automotive, aerospace and nuclear fusion engineering, Steve Wood, a mechanical engineer at Gyrobot, recently put some of the more complicated projects on hold in order to 3D print a custom insole for a shoe. With extensive experience in CAD/CAM design and even having access to his own 3D printing facility, Steve was the perfect 'fit' for the job.

In a four-part series, Steve breaks down the process of creating 3D printed insoles based on different infill methods for providing the best fit using additive manufacturing techniques. The series, which was inspired by Steve's exploration into the problem of foot ulceration, focuses heavily on insole structure and creating variable densities in 3D prints.

"What I aim to show within the next few articles is how anyone without any qualifications, experience or knowledge in the podiatry field (that's me) can produce comfortable insoles using a completely free open source tool chain," says Steve.

"There have been many 3D printed insoles before, certainly the more expensive multi-material printers have been showing off their exploits for a while now, however with this new democratised power of the maker movement, I would like to show and share some new found skills."

Starting with a recommendation of producing your prints with FilaFlex on a Lewihe Sneaker printer, Steve jumps right in with an overview of the series. If you don't have a scan or other existing workable data for your own foot, you can follow along with a 3D model that he uploaded to Thingiverse:

"When I printed my first insole I noticed it was extremely tough, rugged, and elastic, these were all great properties for long term durability. However I noticed that the insole was relatively watertight and so I thought this would be an issue for perspiration and therefore personal hygiene."

To counteract potential hygiene issues, Steve used Slic3r, a G-Code generator for 3D printers, to remove the top and bottom layers. What is left is now a breathable and lighter insole that not only takes less time to print, but also uses less filament:

Next up was time to test different types of infill patterns through trial and error. As Steve further explains,
"A triangular or honeycomb infill pattern such as the two photos above will have a stronger side wall structure in flexible filament than the square infill pattern below which has a tendency to "lozenge":

"The advantage of a square infill pattern is that it allows the side wall to conform to the inside profile of an off the shelf shoe more readily without the insole buckling." :

Using the CraftWare slicer, Steve was able to further explore the possibilities of infill options by rotating each layer by a specified increment. The result is similar to the other infill methods but gives users the option to provide more or less support depending on where they might need it.:

Once a proper infill pattern was established, Steve loaded up multiple colors of FilaFlex filament:

"For those that want to know, I used the Recreus Extruder fitted to my Witbox with a PTFE feed tube modification. This is probably going to be another post to show it in full when I get time.":

Using multiple strands of colored FilaFlex filament, Steve then printed his insole:

"It is now where we start to see a major advantage of 3D printing over existing insole technology. The traditional method to make a custom formed insole is to CNC machine the insole out of a solid block of a suitable chosen hardness of material. Post machining modifications can be implemented by added inserts in different materials etc. Any operation that requires multiple steps is adding to the complexity, inventory of different material stocks, skills and of course cost."

Using some test prints as a springboard for testing material density, Steve continues onto explore varying ways of approaching the infill by squeezing each test to get a feel for the levels of absorption:

Steve uses a custom insole model to demonstrate how soft and dense areas can be applied based on personal preferences:

Using Slic3r again, he then sets up the program's 'modifier meshes' feature to demonstrate how to create the variable densities:

If everything went as planned, you should be able to export G-Code for 3D printing. Steve has supplied his finished variable density insole on Thingiverse.

While the above is extensive in its exploration of infills and variable densities for 3D printing (for insoles or other objects), the series is surprisingly still not finished. The fourth and final part of the series will focus on Form Fitting and maximizing the perfect fit for the insole using various CAD packages. Steve encourages users to follow along with the provided models on his Thingiverse page.

Keep an eye out for the fourth part and read the series in-full over at Gyrobot.

Posted in 3D Printing Applications


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