3D Printed Prosthetic Research

As a university researcher, it often takes a long time until I can actually share my work publicly. As a result this blog often only tells part of the story, for example I recently posted about 3D printing a prosthetic hand by e-NABLE. What I didn’t say is that this was part of research into adapting the design to perform different tasks. Recently undergraduate product design student Cory Dolman worked with me to prototype some new concepts, and his work has been picked up by UTS who created this great video about his process and the ideas we’ve been bringing to life. You can also read all the details on his blog which was maintained during the project with me here.

For anyone who is yet to realise the opportunities of 3D printing technology, hopefully this video goes some way to showing how quickly designers like Cory and myself are able to iterate designs, constantly testing our ideas and expediting the design process. We hope that as we refine these designs, we will be able to share them back into the e-NABLE community, and allow anyone with access to a 3D printer to not only benefit from the prosthetic, but also continue to iterate and improve it collaboratively. This is what excites me about 3D printing – it’s not just about the technology, but what it enables.

– Posted by James Novak

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Ninjaflex Part 3 – Flexion Extruder Upgrade

20180515_Flexion Wanhao

This is the third post in a series about 3D printing with Ninjaflex, which initially began using the stock standard extruder on a Wanhao Duplicator i3 (click here to start at the beginning), before a 3D printed modification was trialled (click here for post 2), and now here we are with a completely upgraded extruder specifically for printing with soft materials.

Pictured above you can see some fancy red anodised components and exposed gears – this is the Flexion HT Extruder, a relatively expensive upgrade (US$179) which is about half the cost of the entire printer itself. It replaces the entire core of a standard single extruder; all that remains from the original is the stepper motor and cooling fans. So why upgrade?

Well as the previous posts discovered, the highly flexible nature of Ninjaflex (shore hardness of 85A) meant that it was difficult for the standard extruder to force down through the hotend and out the nozzle. Imagine taking a length of soft liquorice and trying to push it through a hole that is smaller than the liquorice diameter! As a result, after a few minutes of printing, it was common for the filament to begin looping out the back of the extruder. The Flexion extruder has much tighter tolerances around the filament the entire length it travels, so there is nowhere for the filament to go except down. Also, it has adjustable pressure using the round dial you can see with the knurled detail in the photo above – this means you can apply more force on the soft filament to maintain a strong grip against the stepper motor gear. By rotating the dial, you can quickly scale the pressure back when you change to a rigid filament like PLA, with 4 levels of variation possible and a grub screw to really dial in each setting. The design is completely open, (when it was assembled I initially thought something was missing!), which means you can see the filament and gears, which is great for maintenance and adjustment. And while I haven’t tried yet, according to the Flexion website the nozzle can handle higher temperatures than a standard extruder, up to 290°C, which is great for plastics like nylon and polycarbonate.

The photo at the top right is one of the first 3D prints done to test the abilities of the extruder, taking approximately 4 hours. It looks good from a distance, although there are some small gaps where we started with too much retraction and not enough flow – at this point we are still experimenting with settings to get the best results, currently trying 107% flow, 40mm/s print speed and 1mm retraction. If you are using a Flexion for Ninjaflex and have some reliable settings, I’d love you to post a comment and share them!

– Posted by James Novak

3D Printed Assemblies

20180420_3D Print Moving Assembly

One of the most interesting features of 3D printing is that it’s possible to print multiple parts in their assembled state, reducing the need to bring together a whole range of different pieces and assemble them using screws, snaps, glue etc. While this is normally easier using the Selective Laser Sintering (SLS) process, with a bit of experience and some clever design skills, it’s possible to 3D print moving assemblies on a basic desktop FDM machine.

Pictured above are 2 objects I’ve been wanting to 3D print for a long time as great examples of what can be done with an FDM machine. The first is called an Air Spinner and is free to download from Thingiverse. Due to the tolerances and angles between each part, no support material is needed, and you can literally start spinning each of the pieces straight off the printer, functioning like a gyroscope. A nice quick print, and a great demo piece. Below is a video I found of someone printing and spinning one so you can get the full effect.

The second print pictured to the right is a Planetary Gear Keychain, also free to download from Thingiverse. This one is much more of a test of your printer’s settings, the first time I printed it all of the pieces were completely fused together and impossible to free. Even this print required a knife to separate pieces that formed part of the first layer, with the squished plastic bonding them together as my nozzle was slightly too close to the print plate. This one is remixed from another design on Thingiverse which I recommend you check out for all the instructions to help get the best result, and read how other people achieved successful prints. Here’s a short video to see the planetary gears in action

If you’re looking for some fun prints to share with people, these 2 are very much recommended and relatively quick, although I’m still a very big fan of the Kobayashi fidget cube from one of my previous posts whichis another great assembled object. If you’ve got a favourite 3D printable assembly, leave me a comment/link below and I might add it to my list of things to make!

– Posted by James Novak

Ninjaflex Extruder Mod – Fail

20180409_Ninjaflex Mod

This is a short little update following on from my last post attempting to 3D print with Ninjaflex filament (soft TPU):

After limited success using the stock extruder on a Wanhao Duplicator i3, I found a 3D printable Extruder Drive Block on Thingiverse to supposedly help stop the filament from finding its way out out the back rather than being forced down into the nozzle. Well, as you can see from the photos, it looks like it fits quite well, although I did have to slice and file a few areas to fit properly – most notably around the shaft of the stepper motor which was far too tight and stopped it from turning, and the wheel that pushes the filament against the stepper gear which was blocked from putting any force against the filament so did not drive it down into the nozzle. Admittedly, the file on Thingiverse was designed for the Duplicator 4, so it was a bit of a long shot to work with the i3.

So back to the drawing board I’m afraid for Ninjaflex printing – perhaps time to upgrade to a Flexion extruder, or look at some other TPU materials that might be slightly stiffer and more suitable for this basic extruder. Flexible PLA looks interesting. If you’ve had any successes 3D printing with Ninjaflex on a printer like the Duplicator i3, leave me a comment 🙂

– Posted by James Novak

3D Printed Ninjaflex – First Test

20180406_Ninjaflex Wanhao

I’m sure if you’ve been 3D printing for even a short time, you’ve heard of Ninjaflex – a brand of flexible filament for your FDM printer that has rubber-like properties, rather than the usual rigid plastic parts that are more common with ABS or PLA filaments. While I’ve known about them for many years, I’ve never risked clogging my printer after hearing some bad experiences with these softer materials. Until this week!

I’m currently working with fashion postdoctoral researcher Mark Liu, who purchased a Wanhao Duplicator i3 v2.1 for some of our research – not coincidentally, it’s identical to my home Cocoon Create 3D printer. We decided to give the Ninjaflex a go to see if it would print, and if so, what sort of quality we could get since the printer and replacement parts are cheap if we really screwed up! Photographed above is one of our first successful prints, although the truth is we had quite a few failed attempts getting to this point as we experimented with settings and carefully watched each print. The primary settings we are using for these first tests (based off the recommended settings for Ninjaflex which are available in the Printing Guidelines) are:

  • Extruder Temperature: 230°C
  • Build Plate Temperature: 40°C
  • Print Speed: 15mm/s
  • Layer height: 0.2mm
  • Retraction: 5mm (I think this is too much and we will try 0mm or 1mm)

These may not be perfect yet, and I’m keen for anyone’s feedback on what’s led to more successful prints with these soft filaments. The main thing we’ve noticed is that the soft filament is challenging for the extruder to push down into the nozzle and force out the tip – it is quite common for the nozzle to clog and filament to keep feeding through until it comes out the back of the extruder. Luckily nothing has jammed up yet, you can pull the filament back up out of the extruder and try again. With a bit of a search online, it seems that some 3D printable parts may solve this problem, in particular this modified Extruder Drive Block available on Thingiverse which closes the opening where the filament likes to escape, and will hopefully better force it down through the nozzle. The video below from Wanhao USA helps highlight the problem, and how this 3D printed part can fix it.

It’s early days with this filament, and I know the stock extruder of the Duplicator i3 is really not optimised for this type of material. But it can be done, and I’m sure with some tweaking can be made more reliable. Stay tuned as I am currently printing the new block to install on the Duplicator in the coming days, and will report back with results.

– Posted by James Novak

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

3D Printed Kobayashi Fidget Cube

20180115_Fidget Cube 3D

One of the great opportunities presented by 3D printing is to print multiple parts as a single object, and have them move afterwards as a complete assembly. There are many great examples, and this Kobayashi Fidget Cube has been on my “to-print list” for some time now. The file is freely available on Thingiverse, and it is pretty awesome!

The photos above give some idea of how it works; a series of cubes that are linked, allowing them to rotate around through a series of positions as you fold and open sections of the object. However the video below (not my own) shows exactly how it works, and is basically a form of fidget device that is currently a popular trend.

As well as being a fun object, it is a great test of your printer’s accuracy and settings, and I must admit my Cocoon Create only had average results. The cube works, but some of the movements are much stiffer than the video. This is probably to do with my settings, I was a little impatient in printing so did not optimise as much as necessary things like layer thickness (used 0.2mm and should’ve tried 0.1mm) and printing speed (50mm/s instead of perhaps 30mm/s or less). I also had to use a knife to slice some of the bottom layers where the cubes had fused together on the print plate. Not a bad first effort, but I might try printing again soon to get a really smooth operating fidget cube.

– 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

Return of the Beer Bottle Lock

20170823 Beer Lock Blank

It’s been quite a few years since I first posted this design on my blog – check out where it all began here. One of the great things about sharing designs like this on file sharing websites like Thingiverse or Pinshape is that you get to see when someone enjoys your design and shares their own photos of the print, or even better, remixes it to add their own unique twist to the idea. Someone even made a video on Youtube which featured this lock 🙂

Occasionally I get requests, either on these websites, through social media, or on this blog, for me to make alterations to a design, or share the native design files for someone to more easily modify. 9 times out of 10 I’m more than happy to help. A few days ago I was contacted through Twitter to make a simple variation to my Beer Bottle Lock, removing the text on top that says “hands off my beer” to provide a blank surface for someone to more easily add their own custom text.

Given that the file is parametric in Solidworks, the alteration only took a few seconds. However rather than email the files direct, it seemed like a good opportunity to share a remix of my own design on Thingiverse, and hopefully benefit even more people. So you can now download this design for free by clicking here, just like the original.

This got me thinking about remixes, and the fact that many of my favourite 3D printing sites like Pinshape and Cults don’t really allow for remixes to be clearly linked to the original source file. I can either upload a print of a design (just photos, not a new STL file), or upload a completely new design. If I want to let people know this new design is a remix, I have to manually write this in the project description, and supply a URL to the original file as you can see on my upload of this new blank version beer bottle lock on Pinshape. On Thingiverse, you can specifically say your design is a remix of another with the click of a button, and a link is created so others can easily go to the original, and see all remixes to find the one most appropriate for them. This is a better system that ties in with the whole Creative Commons (CC) licencing used by all of these websites.

I hope some of these other file sharing websites will take up the challenge to make file attribution and remixing more transparent, it shouldn’t be left up to the user to understand the licensing options and manually enter this information. A common standard across a website, as done by Thingiverse, would really help encourage more sharing, and appropriate attribution to designers.

– Posted by James Novak