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TPU with the Anycubic Vyper - M0YNG.uk

Created 2023-07-16

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3d Printing

The Anycubic Vyper is a pretty good 3d printer, in my experience of only ever using two 3d printers. It has a bowden tube, which means the extruder (that pushes the filament into the hot end) is a good 30+ cm away from the hot end so, can it print using TPU, a flexible and soft plastic?

YES!

Vyper mid TPU print, with pink filament dropping slightly as it heads into the extruder [IMG]

Go slow

This seems to be key, print slow, very slow. I'm finding 20mm/s works well (20 being the top speed, the outside is going at just 10mm/s)

I'm using Overture TPU which says it's suitable for "direct extrusion" - oops! The "shore hardness" is apparently 95A which is very flexible, maybe you can go faster with a more firm filament.

I'm mostly using the Cura preset "Generic TPU 95A" with 0.2mm layer height, 2 walls, 4 bottom and top layers, zig-zag pattern, 228 hot end, heated bed off, part cooling fan at 100%, retraction enabled, and a skirt.

I also find the experimental / hidden settings of "Infill travel optimisation" and a "combing mode" of "Not on Outer Surface" help avoid stringing from nozzle oozing as it travels between areas - because these both reduce or hide that travel.

With these setting the tyres for this tractor model[1] have basically no stringing in the middle and only the odd hair on the outside.

1: https://www.printables.com/model/81929-tractor

A stack of four pink tractor tyres [IMG]

The cali dragon[2] doesn't do quite as well, but to be fair it is designed to highlight issues like this! I find a gentle heat from a lighter or hot air gun can tidy up the strings pretty well.

2: https://www.printables.com/model/209121-cali-dragon

A small pink dragon with some blobby bits of filament on the horns and some blackened bits where the flame got too close [IMG]

Size can also help, I find larger models print much cleaner, possibly because the layers have time to cool. For example this owl model[3] prints perfectly until the top of the head where holes usually appear.

3: https://www.printables.com/model/349816-owl-fixed

The number one tip for quality 3d printing seems to be "keep the filament dry" and this is even more the case with TPU. It is stupidly hygroscopic and will start spitting and causing issues really quickly when exposed to the air. An initial dry in the filament dryer helped a lot and acted really quickly, I've been keeping mine in the filament dryer box since with some silica gel packets (and no heat) and it seems to be keeping dry enough.

Clogs

Clogs seem to be different with TPU, and much more common. With a hard filament if the hot end gets clogged the force get's passed to the extruder which will slip on the filament, making clicking sounds and breaking off bits of the filament where the teeth have bit in then slipped. I've only had one with PLA so far, and that was due to running a bunch of prints at a temperature that was too cool for the filament.

TPU doesn't transfer the force and there will be no audible warning of a clog. The things to look for are under extrusion (obviously, but harder to spot) and corkscrewing of the filament in the bowden tube near the extruder. Because the extruder will keep pushing and the filament has nowhere to go it will start twisting around and bunching up inside the tube, looking like a corkscrew. This seems a good reason to use a clear bowden tube to me!

Failed owl print due to a clog, the deposited filament becomes less and less dense with increasing voids especially visible in the infill [IMG]

Luckily I've found clogs to be easy to clear, prodding the nozzle with the thing poking thing the printer came with will spray molten plastic onto your hand and free up the backlogged filament to ooze out into a blob on the build plate.

Squishy Models

The tractor tyres are a little bit squashy, and a clog let me feel them only partly printed, and I liked the feel!

The owl prints great at 10% grid infill and is super squishy!

It seems to always end up with holes in the top though, and these can be good as it lets air in and out when you squash - giving a very satisfying feel. But I like to rub a 300 degree soldering iron over the holes (maybe with some spare oozed filament) to "weld" them shut which gives more resistance to a squeeze and a more robust feel. Although finding and welding all the holes seems impossible 🤷

A pink owl with welded patched on the head, although they aren't obvious unless you're looking for them [IMG]

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