Direct Drive, Bowden, or Remote Drive… oh my!
-
Thanks guys
What got me thinking about it was a comment I saw from Michael on sublime layers mentioning that he didn't feel that his remote systems were in the same class as the Titan Aero or the BondTech BMG. That surprised me enough to ask some questions and get others opinions. Your answers more or less confirmed what I already thought.
For reference I am currently using a Bushang 17HD40005-22B that I scavenged off my Tarantula, which while not ideal is much better than the Kysan 1124092 that I was using prior. With my current tuning I am getting about 30mm/s retractions (firmware set to 40/1800/120 @ 700mA) up to about 4mm before the motor stalls out; since I started using pressure advance most of the time I am getting away with 1 - 2mm of retraction. I plan on tuning it more and getting a more appropriate motor.
Which leads me to my follow up question(s) hopefully Dave or someone can clear this up for me, what makes a shorter stepper better at spinning quickly? They all seem to be low current / high inductance which is more or less the opposite of what you want every place else.
Also….
What is the difference between maximum instantaneous speed changes and accelerations both in scientific as well as practical (print speed) terms. I suppose this question isn't strictly related to extruders as honestly I would love to know for other axis as well.Here is my config for those that want to pick it apart.
[[language]] M350 E16 I0 ; Configure microstepping without interpolation M350 X16 Y16 Z16 I1 ; Configure microstepping with interpolation M92 X100 Y100 Z800 E4390.344 ; Set steps per mm M566 X900 Y900 Z12 E40 ; Set maximum instantaneous speed changes (mm/min) M203 X12000 Y12000 Z180 E1800 ; Set maximum speeds (mm/min) M201 X1500 Y1500 Z250 E120 ; Set accelerations (mm/s^2) M906 X600 Y600 Z600 E700 ; Set motor currents (mA) -
the OMC short ones are not particularly high inductance but the main advantage is that there is much less mass in the Rotor to access decel which is what improves the velocity response and I am currently running with 1mm retract on mine and don't use Pressure advance I let KissSlicers preload algorithms do the work. 4mm retracts on a RDD is far to much and the reason that too high a retract speed might not be advantageous is that it tends to break the filament rather than retract the melted portion which can lead to ooze.
Edit for typo's
-
I too use KissSlicer but my personal experience is that pressure advance has given me better results. Using the tuning wizards in KISS my "best" setting for preload was essentially 0; however I was able to tune pressure advance to produce very consistent extrusion. So I just run my PA tuning script on every filament at my average temp for that filament and then load my tuned PA command into the MATL GCODE tab in KISS. My machine prefix script sends this command, along with whatever acceleration settings I have set for the printer to RRF before it starts each print.
I agree 4mm is too much, was mostly posting that for reference, however you may have just explained why on my ooze tests I started seeing stringing again at about 3mm retraction LOL.
-
Isn't stringing more to do with too low travel speed coupled with too high hotend temp?
-
With the short retraction distances of RDD extruders, the peak retraction speed is likely be acceleration limited. So a high ratio of torque to rotor inertia is desirable.
-
Thanks! Can you provide what motor you are using, or the specs for it?
https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-17-bipolar-18deg-13ncm-184ozin-1a-35v-42x42x20mm-4-wires-17hs08-1004s.html - that's exactly the one I'm using. Smaller one is better because you don't need all that torque with the gearing on RDD, and the lighter rotor is easier to move.
-
The peak retraction speed is very much acceleration limited and I'm am quite dubious they achieve the speeds people think they do. Easy enough to test send M207 Fx and vary their retraction increasing gradually the speed. At some point the motor will cease to turn any faster. At this stage you have to nudge the acceleration up to get it to go faster an you may stall. This presumes firmware retract is in use.
David if running at speed 200% are retracts and unretracts performed faster also? If so you'll need to leave yourself some headroom when tuning the extruder, in case you want to go a bit faster when printing.
-
If running at 200% speed then retracts/unretracts specified in the GCode using G0/G1 commands will be speeded up, but not firmware retraction commands.
-
Hi Msquared,
I perhaps misread your question, (synapses misfiring??). taking it as being one about print speed, as opposed to retraction speed (thought it odd). Regarding email, send again (or use contact form on website) and I should receive it, there were some (unusual) site issues toward end of last year.
re motors: Whilst motor spec is important, with the wrong order of tuning steps, an "optimal motor" will perform far below a less optimal motor tuned correctly. I have had large (long can) NEMA17s performing just as well as small NEMA14s and most others that are in between. Avoid very high inductance motors though, and use only 1.8 degree step angle type. 24v system voltage can be beneficial. Of greater importance however is the tuning. This goes from choice of microstepping, motor current and jerk set to a minimum, then dialling in on accels (in fw) and speed (in slicer).
This is simplfied but preferring to keep short on here. Ping me a message and I can assist in greater depth.
J
-
If running at 200% speed then retracts/unretracts specified in the GCode using G0/G1 commands will be speeded up, but not firmware retraction commands.
Another sound reason to use firmware retraction.
-
Does anyone have a good script to convert KISS's software retraction into hardware retraction? If not I am going to write one in Node.JS and I will share it here.
Why doesn't KISS support hardware retraction!? It's really interesting to me what slicers will do and what they don't. To me firmware retraction seems like the kind of feature that could be implemented in about an hour for pretty much any slicer.
SMH.
-
Isn't stringing more to do with too low travel speed coupled with too high hotend temp?
Generally yes. I feel it is a combination of a few factors. travel speed, temperature, latent nozzle pressure, and retraction (one of the many ways we attempt to solve that last issue). As I am sure you already know most of the retraction / ooze tuning suggestions out there use 3 - 4 models placed at varying distances to create different travel speeds, etc. What I was noticing is that when using KISS to tune retraction distance (KISS has a tuning wizard that increases a variable every layer so that you can tune a parameter based on Z) there was a sweet spot where there was no oozing or stringing but as the retraction distance got higher the stringing / oozing came back. The filament breaking and not being retracted properly would account for this behavior which I otherwise found slightly puzzling.
-
Hi Msquared,
I perhaps misread your question, (synapses misfiring??). taking it as being one about print speed, as opposed to retraction speed (thought it odd). Regarding email, send again (or use contact form on website) and I should receive it, there were some (unusual) site issues toward end of last year.
re motors: Whilst motor spec is important, with the wrong order of tuning steps, an "optimal motor" will perform far below a less optimal motor tuned correctly. I have had large (long can) NEMA17s performing just as well as small NEMA14s and most others that are in between. Avoid very high inductance motors though, and use only 1.8 degree step angle type. 24v system voltage can be beneficial. Of greater importance however is the tuning. This goes from choice of microstepping, motor current and jerk set to a minimum, then dialling in on accels (in fw) and speed (in slicer).
This is simplfied but preferring to keep short on here. Ping me a message and I can assist in greater depth.
J
Thanks Jason, will do
-
Does anyone have a good script to convert KISS's software retraction into hardware retraction? If not I am going to write one in Node.JS and I will share it here.
Why doesn't KISS support hardware retraction!? It's really interesting to me what slicers will do and what they don't. To me firmware retraction seems like the kind of feature that could be implemented in about an hour for pretty much any slicer.
SMH.
I've not used KISS before, is it open source, can you put in an issue in github? I've found most 3d printer firmware teams very responsive to sensible ideas. Failing that other slicers are available many of which can do firmware retraction.
-
Does anyone have a good script to convert KISS's software retraction into hardware retraction? If not I am going to write one in Node.JS and I will share it here.
Why doesn't KISS support hardware retraction!? It's really interesting to me what slicers will do and what they don't. To me firmware retraction seems like the kind of feature that could be implemented in about an hour for pretty much any slicer.
SMH.
I've not used KISS before, is it open source, can you put in an issue in github? I've found most 3d printer firmware teams very responsive to sensible ideas. Failing that other slicers are available many of which can do firmware retraction.
http://www.kisslicer.com not open source and anything but simple. That being said I have pretty much switched away from Simplify3D and started using KISS exclusively. The way it manages profiles for styles, printers, and materials is the best i've seen. Even Simplify3D doesn't support firmware retraction….
