Oh That’s Handy – 3D Printed Prosthetic

20180114_e-Nable Prosthetic Hand

If you’ve been paying any attention to 3D printing over recent years, no doubt you’ve seen at least a few 3D printed prosthetics. From the Iron Man prosthetic arm to the prosthetics being 3D printed for our animal friends, 3D printing is ushering in a new generation of low-cost, customisable prosthetics. Perhaps you’ve even seen my build of the fully robotic InMoov hand which has been documented on this blog.

At the extremely affordable end of the spectrum for humans, Enabling the Future (also called e-NABLE) is one of the most well-known names, developing a range of  open source prosthetics since 2013, which can be freely downloaded, printed, assembled and sent off to those in need. As part of my research I have wanted to build one of the e-NABLE hands for a while now to understand more about them, particularly in comparison to the more complex InMoov robot arm. As pictured above, I’ve finally got around to printing the Phoenix v2 hand, which is wrist actuated to open/close the fingers.

When you look at all the details, it really is a clever design which is optimised for 3D printing on a desktop FDM machine, with almost no support material or waste, and tolerances that fit really well together. Anyone with a 3D printer could assemble one of these, most of the non-3D printed parts can be sourced at a local hardware store or found in your shed (screws and fishing line). The instructions are very clear, and there are loads of videos to help demonstrate the assembly process and how some of the technical aspects of the hand work. Because I printed in ABS rather than PLA plastic, the only small hurdle I had was in the thermoforming process of the gauntlet (the bent white piece that mounts to the users arm), which required me using a strip heater in the university workshop. If you find yourself in a similar situation, you can check out the details which were posted in one of my previous posts. However, I recommend using PLA if you have the choice to make this part easier, only requiring some boiling water as demonstrated in this video. In itself, this is a really cool technique that I will use in the future to create stronger parts; you can always learn a lot from 3D printing other people’s designs.

Overall the e-NABLE community really has done a great job in refining this design over the years, and I’m already working on some of my own iterations which will hopefully be fed back into the e-NABLE community in the future. If you’re looking for a project to build and learn from, or potentially getting involved in the community and building hands for people in need, Enabling the Future is definitely worth researching.

– Posted by James Novak

Thermoforming 3D Prints

20171113_Thermoform 3D Print

Sorry for the blogging silence, this is the longest break I’ve had since starting a number of years ago. Long story short I’ve made a big move recently for work and am only just starting to get back into printing and making new projects. If you follow my social media, you’ve probably noticed some new things starting!

One of the projects I’ve wanted to play with since previously building the InMoov robot arm is the Enabling the Future prosthetics (aka. e-NABLE). This week I 3D printed and built most of the Phoenix v2 hand, which of course is open source and free to download. A really inspiring company, and a vastly more simple design compared to the electronic InMoov! Some of the pieces, which I printed on an UP Mini 2 in ABS plastic, can be seen above. I’ll post full details once I get it up and running, just waiting on some elastics for the fingers. The gauntlet piece, which attaches to the users forearm, is printed in a flat position and then bent into a C shape afterwards. This is a really clever idea for providing the strongest functional part with optimal layer orientation. But how do you bend a 3D print?

Well the instructions from e-NABLE require dipping the piece in boiling water for a few seconds to make it pliable – if you 3D print in PLA, which has a lower melting temperature than ABS. Check out the video here. However ABS is not really going to be affected by boiling water, and just to make sure I did try this technique with my first print. It did get a bit of a bend, but mostly a snap!

For print #2 I instead found myself a strip heater in the workshop, which is perfect for heating a nice clean line and normally used to bend acrylic sheets. A few seconds on each side of the print and it bent perfectly without de-lamination or splitting, and was easy to re-heat to make small adjustments to fit with the hand print. This is a technique I’d never thought of using, but has really given me a lot of ideas for creating 3D prints which are post-processed like this into a stronger shape than if they were 3D printed in their final more complex form. I think some of the simple enclosures I’ve made in the past could be much stronger if considered more like a sheet-metal part, although then this begs the question why not just laser cut the design? Well in the case of this e-NABLE prosthetic, there are some 3D details for snapping in other pieces, which could not be done using a 2D process like laser cutting. This would be important to consider if using this process with 3D printing, but it’s certainly an interesting technique worth further experimentation.

If you’ve done something like this yourself, or have ideas for thermoforming a 3D print, leave me a comment.

– Posted by James Novak

When Layer Orientation Matters

20160819_Meshmixer Plane Cut

Often when you are 3D printing the main thing you think about is how much support material your print will have, and you orient your print to minimise this – reducing material waste, print time and any manual post-processing to clean up the print. However sometimes the best print orientation for these reasons is not the best for mechanical strength, and I’ve just discovered this with one of the parts for the InMoov robotic arm I’m currently building (see the first collection of 3D prints in my previous post).

The “RobServoBedV6” part is where the 5 servo’s connect that control the individual finger movements, using screws to fix them in place. However some of the stands are splitting as I screw into them as shown in the photo above due to the layer orientation. Yes I could use super glue to fix them, but the split will just happen  somewhere else. So I’m going to completely cut the stands away from the part, and re-print just these stands in a different orientation to improve their strength. This is where the free program Meshmixer comes in very handy, and I’ve previously published a few examples of how to use it for my friends at Pinshape – just click here to find out more.

In the top right image you can see the first step of using Meshmixer to edit the STL file. I have used the Plane Cut tool to slice away the bottom plate, and then repeat the process to remove the other 2 segments which seem to be strong enough for the screws at the moment. This leaves me with the 2 stands that I’m having issues with. These can now be exported as STL’s ready to 3D print (orientation is not important here, this will be set in my 3D print software).

Cura from Meshmixer

I’m printing these parts as we speak on my Cocoon Create 3D printer, and have used Cura to prepare the parts and get the G-code. As you can see to the left, I have oriented the parts so that the layers are perpendicular to the original orientation, meaning that when I screw into them, the force from the screw will not pull the layers apart. Super glue will hold these replacements onto the original part really well as they are printed in ABS.

If you are designing your own parts from scratch in CAD and intend to screw directly into them, keep this issue in mind. However if you’re downloading a STL where modification isn’t as easy, knowing this simple trick in Meshmixer can really help you repair and improve a part rather than trying to re-print it from scratch and potentially use a lot of support material in a different orientation.

– Posted by James Novak

Cocoon Create with PET Filament

20160219_3D Print PET

I think I need to start off with a bit of a colour code:

My collection of 3D prints off the new Cocoon Create 3D printer is growing, and the quality is excellent! On the top left you can see the parts I’ve printed so far (SUP Paddle Clip, Motorcycle Key Guard, Motorcycle Rear Pegs Plug). Top right shows a comparison between the Up! Plus 2 and Cocoon Create for the same part, with not noticeable differences at all – a really great result considering the Cocoon Create printer is nearly a quarter of the price!

20160219_PET 3D Prints

PET+ is meant to be as strong as ABS, but more flexible which is particularly great for the Motorcycle Key Guard shown just above which must flex and snap around the top of some handlebars. The PET+ material prints at the same temperature as ABS, and results in a slightly more glossy finish. I also noticed there was no smell during printing, which of course is very noticeable when printing with ABS plastic – I wonder if this results in better air quality? There is of course a growing interest in the VOC’s associated with melting plastics for 3D printing. The quality of this part is actually better than my previous prints from the Up! Plus 2, and printed with almost no support material as shown in the image just above, whereas the orange print on the Up! Plus 2 was full of support and a nightmare to clean up with pliers. And did I mention the the Cocoon Create is only a quarter of the price? So far a real win.

If you want to read a bit more about this printer, which is based on the RepRap Prusa i3, just check out my First Impressions article, or head to the Cocoon Create website.

– Posted by James Novak