printing hard plastic in a flexistuder

Hi folks!
I’ve got a Taz 5 with a flexy-dually v2 head, and a use-case for dual color ABS prints.

Previous experience with the default tool head shows the Taz can use 1.75mm filament and get good results, so long as Cura is told the filament size and the print is less than ~8 hours (after that it tends to clog for some reason).

My understanding is that one shouldn’t use hard filament in a flexy-struder because friction of the filament against the extended PTFE feeding tube will damage the tube, and replacing it is difficult.

Does this mean that it’s safe to print hard plastic through the flexy-struder, so long as it’s 1.75mm filament? After all, the smaller filament diameter should mean there’s no appreciable friction against the PTFE tube…

Thanks and best regards,

  • Ken

the fillament typically enters the top of the extruder at an angle. it’s going to contact the sidewall generally. It will probably last longer, but it may still wear.

sure… but flexible 2.85mm filament makes full contact with the tube. Even though it’s flexible it’s still going to cause some friction, so clearly the tube isn’t completely intolerant to contact, right? seems to me the friction for 1.75mm hard would still be less than for 2.85mm soft…

The fillament acts as a rope saw. basically the small area it is still in contact, you are going to get a notch worn into the side. A 1.75mm wide notch instead of a 2.85mm. The tube stuff isn’t expensive and it’s not particularily hard to install if you have the right drills for it and a drillpress, so I wouldn’t worry about it too much personally, but if you don’t know the tube installation process it can be a pain. The V1 and V2 assembly are pretty much the same, so this guide will show the process https://ohai.lulzbot.com/project/flexystruder_assembly/ basically the V2 omits the side tension screw and has a hexagon nozzle that fits into a lower socket.

Actually, it looks like it doesn’t work anyway. Something about the structure of the flexi-struder makes it unable to extrude the smaller diameter filament… The extrusion gears turn, but no filament feeds. Darn. Not looking forward to spending $500 on a dual non-flexy extruder…

Anyone happen to know what the practical effect is once the PTFE tube becomes damaged by hard plastic? Is it just that you can no longer print flexible filament, or does it render the extruder completely useless?

you could just print out the parts to make nonflexy head and remove the flexy one and reassemble

Excess friction leads to some print quality issues, that you may or may not be willing to live with.

No, there is way too much space between the bolt and the PTFE tube wall to be able to grip the smaller diameter filament. As for using hard vs flexible plastic, it really depends on the type and amount you damage the tube. You can rip tube pieces off and get them plugging the nozzle or causing the filament to be ground/wrapped around the bolt.