Lix 3D pen teardown

Ok, so not really a teardown, more a why-the-heck-wont-it-feed? kind of taking apart.

As I said in the review, the Lix team have done a remarkable job of squeezing a 3D printer into the barrel of a pen.

Overall, the way the pen is constructed is pretty good. Plastic separators to hold the components in place are tethered together by slim steel rods running the length of the mechanism.

A tiny PCB connects to the buttons and motor by way of a thin ribbon cable, and it looks like power is sent over separate wires. Its neat and quite an engineering feat, but the main issue of feeding filament persists, making it an area of focus.

The filament is drawn through the pen by means of a worm drive. The worm gear itself has a sharp edge to dig into and therefore provide purchase on the incoming filament. The backside of the feed tube at this point has a tiny 'u' shaped piece of plastic which is designed to rest against the inside of the pen barrel and reduce the 'give' of the feed tube as it passes under the worm mechanism.

Unfortunately it doesn't seem to be enough to allow smooth transit of the filament through the pen.

Before the filament reaches the heated tip, it has to make a kind of 's' shape inside the feed tube, so that the molten material emerges from the tip which is on the central axis of the pen. I'm left wondering if friction from contorting this way, plus the pressure needed to extrude in the first place is backing things up.

The root of feeding problems on the Lix

Tolerances are very fine around the feed area. My attempt to place a shim behind the u-shaped piece of plastic failed - it was just too tight. I'm now thinking a coat or two of varnish or nail polish on this component might be enough to offer more purchase to the worm drive.

After I reassembled the pen I put a filament through coated in Vaseline in a effort to reduce the friction of the feed tube. At the time of writing, this didn't seem to make much difference to the feed performance of the pen, but I live in hope!

Update: After writing the above, I returned to the pen and got some consistent feeding action, to the point that introducing a new filament to the worm drive was proving to be enough to extrude the remainder of the old filament.

Result? I think so - at least for now the pen seems to be working as before. If yours is jamming try applying a little vaseline to a filament and helping it through the pen.

Update to the update: While I got through several filaments without too much bother, the pen is back to it's old ways and jamming way too easily. On the plus side, this afforded me the opportunity to take it to bits again and take better photos and at the same time try modifying the u-shaped piece in some way. Stay tuned!

The Lix 3D Pen

So, the Lix pen. For those that don’t know, this is the result of a much delayed Kickstarter campaign. Amidst much acrimony from backers, the small team behind the Lix pen finally delivered mine after backing the project 27 months earlier.

So I’m happy to report that after all that time they pretty much pulled off the original promise of producing the world’s smallest 3D pen.

The upmarket feel of the pen starts with the premium packaging. Pulling the lid off the stylish box reveals the pen nestling neatly in high density foam. Under the pen is the power adaptor and a UK 3-pin plug adaptor. There are tubes of spare black and colour filament which is accessed by pulling on a little ribbon tab. Very neat.

The original pitch for the pen was for a device that would run from a standard USB port. The team have gone half way to achieving this as the power adaptor is indeed USB, but a 2A supply, suggesting the Lix might not run from a standard 500mA USB socket. I haven’t been brave enough to try it on a laptop in case the current draw fries something, so I’m sticking to the supplied adaptor. It should be noted that Lix ships a neat branded adaptor instead of the generic type you might expect.

My Lix came in smooth black anodised aluminium and is slightly longer and slightly fatter than a regular ink pen. The machined knurled grip has two buttons – more on those later – and a matching black clip in steel at the top.

The tip seems to be stainless steel, topped with a black steel mesh heat guard. At the opposite end are two holes – one for the barrel-type power plug (the Lix pen USB philosophy doesn’t extend to micro-usb) and a hole in which to feed raw filament.

Connecting to the USB causes a strip of 4 red/green LEDs to blink each colour in turn – a kind of self test to show everything is powered and ready. Because the pen accepts ABS or PLA filament which each have different melting points, the initiation of the heat for each type of material is set by pressing one of the buttons in for a couple of seconds, lower button for ABS, upper for PLA. Otherwise, the pen stays in standby and cool. For ABS, the LEDs show red, and for PLA, green. The strip of four LEDs present the increasing temperature one LED at a time and only when all four are lit does the pen allow the feeding mechanism to start working.

The pen came to me pre-loaded with some filament and during the warm up time some of this was extruded from the tip. I’ve discovered this is normal and happens every time as a result of the natural expansion of the molten material, but is a little disconcerting the first time.

Of course the tip gets hot – very hot – but it’s easy to nip off excess plastic without burning your fingers.

Now comes the moment of truth – can I draw in the air, in 3D, with this pen? Short answer – yes! Long answer – like drawing on a sheet of paper, it kind of depends on your artistic talent of which I personally have very little…

The extruded plastic material takes a few seconds to cool to hard after emerging from the tip, so if it’s straight lines you want, you have to apply a little tension to the 3D line you are trying to create. This can be a little tricky in 3D space, to pull the line in the direction you want without introducing a bend along the way. As a result I found it best to keep straight lines to a couple of centimetres or less. Again it is down to individual artistic talent and confidence using the pen in 3D.

Starting a new line on existing material needs the application of a little technique, basically to melt the material before starting a new extrusion, then finishing the ‘thread’ on another bit of plastic, where the molten material coming out the tip readily melts – and crucially – sticks fast. Rather like a plastic-spinning spider in fact.

Over a few minutes use the pen gets quite warm. Longer and the pen gets quite toasty around the grip. Lix advise 15 minute sessions and they’re not wrong – the barrel of the pen gets hot to the touch meaning the interior is very hot perhaps where it shouldn’t be which perhaps is the cause of the pen’s main failing – the feed mechanism.

Considering all of the pen – the heating element, the electronics, the power, the feed motor – are crammed into a pen barrel, it’s remarkable the pen works at all. It’s only when you have a jam in the filament feed the frustration with the pen surfaces.

I’ve encountered jamming basically with each new filament, and only with considerable pressure applied to the filament sticking out the top (or with a fresh rod of filament) has got the pen going again. It’s frustrating and wasteful of filament but so far I’ve been able to recover the pen back to working every time, perhaps sacrificing 3cm of filament in the process.

When it’s working, it works well and allows me to sketch in thin air some splendidly spindly geometric nonsense which is exactly what it’s for.

After writing the above review, my Lix basically stopped feeding filament on it's own, prompting me to take it apart. Stay tuned for the teardown photos!