Best design for building a reliable direct extruder printer for flex filament?

After a longer time thinking I've decided the best approach for me is to buy a CR-10 3D printer and then 3D print parts for making a platform with a direct drive for flexible filament. I want 2 printers anyway.

What 3D printer design is the best? best extruder for flex? I've parts for half a 3D printer in 2020 extrusion, 8mm rods, gt2 timing belts, pulleys, 8mm rods, nema17 motors power supply endstops etc.

Only requirement is reliability I don't want to spent the same amount of care taking as use of 3D printing time. 3D printing will be a tool for me and not a hobby. some years ago I built one and later own a commercial printer - both I spent too much time calibrating and taking care off to the point it was not cool.

where to begin.... extruder!

The E3D Titan works well for flexible filament because there is a guide tube that runs from the drive gear down to the entrance of the hot-end, which prevents the filament from bending and jamming up the extruder.

Reliability...

You have plenty of experience with printers. What were the biggest causes of failure? What was the biggest time sink?

In my own experience, prints coming off the bed is the primary cause of print failure. Build a proper bed and that problem can be minimized. The other big time sink for me was configuring the printer back when I used crappy A/R controller in my first printer. I have since had to update multiple printers at the makerspace and ran into the same problem over and over- having to compile the firmware using flaky, obsolete Arduino IDE and USB drivers. What a disaster! Get a 32 bit controller that stores the configuration in a text file. You edit the file, reboot the board, and you're done. No screwing around.

I build printers that have decent beds and electronics and they end up being pretty reliable. I don't use or need autoleveling because the machines are built right. I can transport the printers in my car (only one will fit at a time), take them out and start printing without making any adjustments.

I don't use stuff like flexible, end supported guide rails or any of the other stuff that leads to frequent readjustment or print quality issues.

You can see how I build them by clicking the links, in my sig, below.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Designing a reliable extruder for flexible filament isn't difficult. They key element is to guide the filament as good as possible directly after the pressure is applied. Some extruders do this by using a continous PTFE tube with only a small opening for the transport, others are designed to have a pickup close to the transport. Both work and depending on how close to the transport they can come you get higher or lower extrusion speed. I am currently using a design without PTFE tube and i can reliably print super flexible TPU and Ninjaflex with up to 60mm/s, though print quality with flexible stuff can already suffer even if the extruder works fine. I don't think there is much use going for higher speeds, the reliability is a much more important factor and with my current setup i can print over night without any worries.
The hotend itself is not of much importance, but the lower the resitance it offers the easier it is. With my Merlin hotend setup that means i can reliably print at speed with a 0.3mm Nozzle. Anything smaller and i have to reduce speed a lot due to the increase in back pressure.
Edit: I fully agree with the digital dentist on building mechanically sound. It pays off many times over. Like he i don't use bed leveling and even though i transport my printers now and then they never require recalibration. Reliable printbeds are no betting game anymore as well, for me it is Ultem sheets that do the trick, but the optimal surface depends a bit on what will be your main filament.

Edited 1 time(s). Last edit at 08/15/2017 11:25AM by Srek.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

You asked for design suggestions for flex filament. The only printer design, that doesn't suffer much from a heavy direct drive extruder is the Cartesian printer were the moving bed is the limiting factor in terms of speed. ( Prusa 2020? )
Another option is to use a cable driven extruder, were the stepper weight sits on the frame not the gantry. ( Flex3drive or Zesty Nimble are the options I know )
Such an extruder would suit any printer design and in case you want to print different filament you have the option to raise print speed. ( Delta or CoreXY )

I've printed X60 filament successfully using the Zesty Nimble. This is the most flexible filament I've been able to find (photo below isn't mine).


[flexionextruder.com] (the flexion extruder is also an option if your happy to keep stepper on carriage)

The Nimble main unit weighs in at around 26grams (currently the worlds lighhtest extruder thats on the market), drive cables vary with length but usually only a percentage of the drive cable weight is on the carriage/effector.

We had one customer get his carriage from over 432g down to 160g [zesty.tech]

At least one of our customers is targeting sub 100g, we're fairly sure it's possible with the Nimble and the right hotend.

I'm a co-creator of the Nimble so feel free to ask me any questions you have.

Edited 3 time(s). Last edit at 08/22/2017 12:27AM by briangilbert.

Yes, There is also THE original Flex3Drive which has 33% more precision and driving torque than the nearest competitor, and 33% less driveshaft loading. Lifetime warranty on all driveline parts. We also have a substantial range of designs to suit different machines all based on the core driveline system.

Installation is straight forward without need for additional parts as everything comes in the box including carriage mount and fully integrated cooling solution for hotend and print cooling including 25mm fans, complete with print ducts and hotend shroud etc.

Crucially the filament path is also fully constrained from right under the drive gear and not broken or split by the tension arm. As we know, flexible filament needs only the slightest excuse to get bunged up.

Here at Flex3Drive we pioneered the remote drive (flex shaft) extruder so feel free to contact us with any questions

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Flex3Drive.com

I agree with the Digital Dentist, build surface and a strong frame are the most important aspects for trouble free printing.

Sure, a good extruder is needed, but all professional extruders will do flexibles. The X60 is the most flexible filament at the moment (afaik) and the Flexion is designed specifically for it. But as Brian mentioned, the Nimble handles it fine.

The bed, I would suggest to go for a mains powered heater, as it heats up so much faster. Bed surface can be anything as long as it handles your material well. A lot of the current print surfaces need or glue or other tricks to be able to release flexible prints. Check with the filament maker what they suggest to use.

As for the frame, yes, use a Cartesian unless you really need tall prints, then a Delta seems logical. Advantage of a Cartesian is the fact the you can make it all strong and sturdy, minimising adjustment time needed. Also, you then have more options when it comes to extruders.

Lastly, have a good look at filament diameter. 3mm flexible filament is usually easier to handle than 1.75. But, can you get that size in your preferred filament?
If you use a direct drive, or a remote direct drive, there is not so much difference between 3 and 1.75. It is just that 3 mm gives a stiffer filament and less issues with feeding it in.

By all means, go for a 32 bit controller. I am very impressed with the DuetWifi. Not only for the unit and the firmware but also for the support, great guys!

For the hot end, I personally would go for a V6 Lite. Why? Because it has PTFE into the hot end, all the way to the heat break. Makes the insides a little more slippery for the filament than the full metal one.

I have to say, I am looking forward to see what you pick and choose, so please keep us updated?

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Lykle
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Co-creator of the Zesty Nimble, worlds lightest Direct Drive extruder.
[zesty.tech]