Jack Cockle, CREATE Education Ambassador and Sustainable Product Design student at Falmouth University set out to look at the potential to develop 3D printed casts.
Orthopaedic cast immobilisation is one of the most common ways of treating broken and fractured bones, involving the use of materials to encase and restrict the movement of broken bones, allowing them to heal.
As technology has become more accessible, 3D printed casts have grown in popularity. They are much lighter, more comfortable and generally easier to produce than traditional casts. However, despite the evolution in cast production qualities, all casts share a fundamental flaw – they are single-use products. Since the job of a cast is to set body parts in a fixed position, they have to be tailor-made to the unique form/anatomy of the individual patients.
3D printed casts are also complex in their structure, these factors eliminate the possibility of reusing casts, even if hygiene issues were non-existent. Therefore, there is an opportunity to explore alternative strategies to make immobilisations casts more sustainable.
Jack set out to design a sustainable orthopaedic cast through the exploration of various sustainable design strategies with the aim of reducing the inevitable waste generated by their complex and tailored form and maintenance of hygiene standards.
The cast will be designed for the convenience of both patient and doctor using existing designs and techniques to produce and use.
How has Jack been using the Ultimaker S5?
The high-quality print and large build volume of the Ultimaker S5 have been the most useful features for my projects. Firstly, using University equipment, I 3D scanned my arm which allowed me to model casts within Autodesk Fusion 360, using the 3D file to create the perfect fit.
I then printed the replica of my arm to model around with materials such as Mod ROC.
This was made easier by the scale of the printer, otherwise, I would have had to split up the model into more pieces, which I would then have had to glue together. I have also used the Ultimaker to experiment with and develop a series of cast models in order to progress the project and design ideas.
As part of one of my final year projects whilst studying BA (Hons) Sustainable Product Design, I began by making a normal plaster cast, trialling traditional methods of the cast making to justify future design choices.
I then made a basic 3D printed cast. This was done by scanning my hand/arm using the university’s 3D scanner and software. I then exported the scan as an STL file into Autodesk Fusion 360, which was then converted to a b-rep file, allowing me to model a form around the hand/arm.
Next, I 3D printed the cast in Filamentive rPETG, Ravi Toor founder of Filamentive is my project partner for my other project, and provided me with a small number of materials for this project too.
Filamentive addresses the environmental concerns of 3D printing, where possible using recycled materials (from both post and pre-consumer stages). The rPETG is made from 67% recycled plastics.
After evaluating multiple design ideas and exploring how to make casts more sustainable, I decided to investigate whether 3D printing could allow the fabrication of casts that adapted to the form of the user. Rather than existing as a rigid form that is customised to meet individual patients needs.
To explore the scope of making casts more sustainable, I evaluated multiple design ideas through an iterative process. The aim was to investigate the possibility of fabricating 3D printed casts that adapt to the form of the user, rather than existing as a rigid form tailored to individual patients, thus making them more suitable for reuse.
This idea came to me as my colleagues tried on the 3D printed cast, which almost, but didn’t perfectly fit them due to the slightly different shapes of our limbs.
Owing to Auxetic materials and structures exhibiting certain abnormal mechanical responses, thanks to the possession of negative Poisson’s ratio response. Meaning they get thicker when stretched lengthwise and thinner when compressed. I began experimenting with auxetic forms in different materials such as TPU (printed on the Ultimaker) and Flexible Resin (printed on a university Formlabs machine).
In Rhino3D, I generated a series of cylindrical auxetic lattice forms, choosing the ones that required no support material (as this would be difficult to remove from such a complex structure). I printed them in both TPU and flexible resin to test how well each structure and material compressed under pressure.
Before Christmas, the concept was a flexible resin auxetic sleeve that fits over the arm of the patient, which is compressed by the rigid PETg shell, immobilising the limb.
In theory, the reusable cast would reduce waste, cut lead times (as a stock of casts could be kept) and the longer-term cost of casts per patient (since the costs of one cast could be distributed across several patients).
During my final semester, I have been developing the mesh further, to become elastic resin bands that are finer, have more layers, and are preinstalled into the cast shell before being applied to the arm.
Above is an exploded view CAD render, demonstrating the concept as it currently exists.
I have also used my Ultimaker loan to progress one of my other projects- TriSense, in order to enable easier print, assembly and disassembly, along with an overall more polished design.
I recently exhibited the TriSense with CREATE Education at the Birmingham TechAbility Conference in November.
In The Classroom
Why not use this project as inspiration for your own classroom project where students can design and 3D print their own models. Alternatively, you could focus on developing ideas for children with physical impairments by participating in the PrintLab Assistive Devices project.