Tuesday, September 20, 2016

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!


Fabiola Saldivar said...

Thanks for your post, I just took mine apart when it started blinking red/green non stop after pressing the extrusion button to power it on. I found two pieces of filament stuck under the gear. It worked for a bit more but now it's back to the non stop blinking, love the design of the pen but way too flimsy for its price :/

Steven said...

Hey Fabiola,

I think many found the same happening to their pen. The disappointing aspect is that Lix apparently came up with a more reliable feed mechanism, but were asking for more money from backers (who were also being asked to return the faulty pen at their cost, likely so that parts could be recovered to reduce production costs).

At this point I decided to stop wasting time and money with Lix so I'm not sure how the new design is working out for people.

For the longest time I gave Lix the benefit of doubt and they shipped (eventually) a flawed product with no support for the loyal customers that allowed them to create and ship the product in the first place.