foehnsturm

Well, something closes here on the top ... and the next shot is through some kind of window. .. and some seconds later it looks like a (front?) door is closed. Closed chamber?

Oh, interesting to hear :wink: I'm curious how it behaves with the stock UM hotend. I really didn't go for speed so far. But there is ridiculously low stepper torque required so the limiting factor will be the hobbed wheel or the gears. Even two extruders should be possible within a 45 mm cube. You could reduce the required width to some 60% with shorter Delrin parts. Or turn it 90° so that the worm gear is positioned horizontally.

@IRobertI Funny, I was meditating on exactly the same thing some nights ago. I think the answer might be boring in multiple ways. 3D printing will become useful for average Joe if there would be a large repository of boring, non-creative, non-fancy but truly useful everyday things. Things like gr5 described. Knobs, hooks, brackets, gaskets, fittings, lids, hinges ... Tried-and tested parts with fool-proof printing instructions. Even if they are dead simple, average Joe would never consider designing them by himself but he would print them instead of spending hours visiting a building center or something like that. Currently, if you are in the need of those things Thingiverse and - I'm sorry - Youmagine are a depressing experience.

@jhertzberg If I remember correctly settings were almost normal: 0.1 mm layer height, 1.2 wall thickness, 30 mm/s printing speed, retraction speed 30 mm/s, temp 215°C (for FlexiFil)

That part is not my idea. It's http://mutley3d.com/ work. Without the high gear ratio the flexible shaft would not handle the necessary torque.

Hi Bas, Thanks for the compliments. My experience with the hobbed wheel is limited so far. But yes, I'd say it is slightly more prone to clogging. I had no issues until now but I already noticed one or two grooves filled with some PLA residues. I still a little uncertain about the correct contact pressure. The grip is very good although the marks in the filament are less visible than those produced by the UM bolt.

Actually less cumbersome than some UM2 feeders IMHO. I'd love to try it on an UM2 but I don't own one. And I think it's kind of a question of philosophy. Right now there is the direct extruder approach and the bowden department but not so much outside the box I think.

Well, better, way better now

Definitely one of the ugliest robots I ever printed ... but without doubt the most flexible so far. Now looking for some serious applications.

The flexible filament just arrived. This is a test print with Formfutura's FlexiFil (a thermoplastic Co-Polyester with a shore hardness 45D). It feeds and prints without any issues, however I had bad inter-layer bonding so far. Therefore I increased layer height to 0.15 mm and wall thickness to 1.6 mm.

The parts (rev3, still under development) are now available at https://www.youmagine.com/designs/modular-printhead-ultimaker-flex3drive-merlin.

@chopmeister Exactly what I've learned. ActualIy I greased them (it's white grease and not that much, so it's not clearly visible on the picture). Before that I sometimes noticed some creaking sound and even some white wear of friction. But I should add that this was also due to a bad adjustment. Although this is the stringy 2013 ColorFabb PLA, retraction settings could still be optimized. I found out that with my Merlin hotend I sometimes get uneven extrusion close the the point where the print starts after a retraction when retraction speed set to 60 mm/s and more. This could be related to some properties of the flexible shaft but I would also assume that pressure build-up and release within the melt-zone just isn't possible with both: infinite speed and control. But to be honest I have no feeling about the acceleration and jerk settings on the e axis. What are your experiences?

No issues with 150 mm/s @ 0.15 mm.

Right now I'm printing with the same speed settings I used for the bowden (outer shell, inner shell, infill: 40, 60, 90 mm/s at 0.15 layer height) which are very safe settings for the Merlin hotend with most filaments. I'm more focusing on retraction performance and evenness of extrusion. Due to the high gear ratio the stepper could push even more than the already somewhat overpowered UM original feeder. The limiting factor should be filament slipping.

Now running rev3. I ordered some flexible filament. In the meantime I'm feeding all the old filament I couldn't use with the bowden tube anymore (too brittle, too short BTW: never order a sample pack with a bowden feeder ... as the samples are quite short you have to throw away some 20%).

Rev2 is printing rev3. This will be a "naked" version with improved fine tuning possibilities. I had a little too much play in one of my parts which resulted in inconsistent extrusion every now and then (can be seen in the top part). Don't worry about the ripples in the lower part, the hotend mount was loose ...

Some pictures.

@jhertzberg If mounted correctly (it looks like the supplied shaft "likes" a 270° turn) the resistance for head moves is much like the bowden. And I'm still using the Merlin hotend. Right now the gearbox is incorporated into the hotend-specific part of the printhead because I want to be able to switch back to the bowden drive without disassembling the crossbar and the sliding blocks. However, if I stay with the flex drive the gearbox should be incorporated in the part which holds the linear bearings. I'll post some pictures tomorrow, then I'm away for 10 days. Files will follow thereafter.

I'll do that. However I might be a good idea to ask Mutley3d if he is willing to sell a kit with just the mechanical parts: shaft, gear wheels, bearings etc. for a significantly lower price. I don't know how to easily source these parts elsewhere.

I think the high gear ratio is truly the key. First I thought about adding a bigger wheel to the motor-shaft coupler to make it easier to turn by hand. But as I noticed even fast extruding is accomplished by turning the coupler easily just between two fingers. Retraction speed is just stunning. The whole retraction process feels "digital": on/off instead of time-consuming pulling and pushing of filament within the bowden tube. The next iteration will be a spring loaded extruder arm with quick release functionality.

I had to try it out as the bowden tube for sure has some drawbacks: very limited choice of certain (flexible) filaments, high retraction distances, a considerable time lag during retractions, less than perfect extrusion control due to the springy character of the filament within the bowden tube ... But I wanted to retain the lightweight print head. As far as I know the idea is anything but new to the reprap community. However the (rather expensive) Flex3Drive comes as a plug and play unit for certain printers. The key for a highly precise and reliable operation might be the high 1:40 gear ratio it uses so the shaft has to handle only very limited torque. I made a plug and play component for my modular print head. What's nice about it is that the 1:40 gear ratio together with the 12 mm knurled wheel give approx. a fourfold increase in steps per e compared to the UM original. So I just changed from 1/16 microstepping to 1/4 and steps per e already were 98.5% on target. The worm gear can be adjusted for zero backlash. Torsional deflection of the shaft looks to be less than a 1/8 turn which corresponds to approx. 0.1 mm filament feed. This is the very first print:

Hi Lennart, (on an UM original) I used the PauseAtHeigth Plugin at 40% and 60% height, swapped the filament, purged the nozzle and resumed printing. If you don't purge you'll get a smooth transition between the two filaments, I used this for the Inception spinner but you don't want that for the ring. Markus

Unfortunately just a prolonged business trip. Leider nur vom 7. bis zum 11. August.

I wish you a nice time in Berlin. Can't come, will be in Israel the exact same weekend ...

Rectangular pillars and increased angle. Print time 45 min (speed set to 60%). With 100% (Cura settings shell, infill: 40-80 mm/s) I got a mess above 15 mm. @Dim3sioneer, I'm using a standard fixed coupling.