Duet3D Logo

    Duet3D

    • Register
    • Login
    • Search
    • Categories
    • Tags
    • Documentation
    • Order

    Pressure Advance killing extruder motor

    Tuning and tweaking
    10
    25
    1821
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • gnydick
      gnydick last edited by

      I'm using a 40:1 gearing on my extruder. So the motor is setup at 400mA, 8x micro-stepping, and jerk 600. When I turn on PA, and I try to print at 80mm/sec, my extruder motor just grinds and doesn't move. As soon as I turn off PA, everything works normally.

      M201
      Accelerations: X: 2000.0, Y: 2000.0, Z: 300.0, E: 120.0:120.0

      M203
      Maximum feedrates: X: 48000.0, Y: 48000.0, Z: 1200.0, E: 1800.0:1800.0

      M566
      Maximum jerk rates: X: 750.0, Y: 750.0, Z: 150.0, E: 600.0:600.0

      M572 D0:1 S0.1

      M906
      Motor current (mA) - X:1800, Y:1800, Z:1400, E:400:400, idle factor 60%

      M350
      Microstepping - X:64, Y:64, Z:16(on), E:8:8

      [0_1553910034110_LOW_RES_-_CRUSHED.zip](Uploading 100%) 0_1553910076310_LOW_RES_-_CRUSHED.zip.gcode

      1 Reply Last reply Reply Quote 0
      • NitroFreak
        NitroFreak last edited by

        I don´t know if this is related but 750 jerk seems kinda high. I have it set at 15

        gnydick 1 Reply Last reply Reply Quote 0
        • gnydick
          gnydick @NitroFreak last edited by

          @nitrofreak makes sense. When I reduce the jerk, the print goes sooooooo sloooooow. drawing a single, short line, it goes, woooooooOOOooOOOooOOOOOOOooooOOoooOOoooOOoooooooo. My print times would easily, literally be 50-100x longer.

          1 Reply Last reply Reply Quote 0
          • bot
            bot last edited by

            750 is mm/min, so that isn't too high for XY. 600 might be too high for your extruder, though. It's jumping straight to 10 mm/s. Lower that to 120, 180, or thereabouts.

            *not actually a robot

            gnydick 1 Reply Last reply Reply Quote 0
            • gnydick
              gnydick @bot last edited by

              @bot the weird thing is, without PA, it works fine. With PA, it just squeals and whines.

              1 Reply Last reply Reply Quote 0
              • gnydick
                gnydick last edited by

                I have a good, large printer. I want to be able to print fast. The prints are perfect slow and without PA. But at any kind of speed, the ghosting at the corners is terrible. PA usually takes care of it. But with this new extruder, I can't find the right combination of settings to allow PA to work AND not slow down the print tremendously.

                deckingman 1 Reply Last reply Reply Quote 0
                • deckingman
                  deckingman @gnydick last edited by

                  @gnydick What are your steps per mm with that 40:1 gearing at the 8x micro stepping you are using? Also, what value do you have PA set to?

                  Ian
                  https://somei3deas.wordpress.com/
                  https://www.youtube.com/@deckingman

                  1 Reply Last reply Reply Quote 0
                  • Veti
                    Veti last edited by

                    whats your value for pressure advance?

                    with a ratio of 40:1 your extruder prob cant move fast enough for a E jerk of 600 try going down on that.

                    1 Reply Last reply Reply Quote 1
                    • Edgars Batna
                      Edgars Batna last edited by Edgars Batna

                      If you use too low microstepping the motors can also start skipping steps, but, yeah, 40:1... I'd say 10:1 is the practical limit or you need to switch to 48V or higher.

                      1 Reply Last reply Reply Quote 0
                      • garis
                        garis last edited by

                        I have a zesty nimble. They have 30:1 gearing. I have done extensive testing with PETG, and jerk seems best in the range 50 - 70 ( or around M205 0.8 to 1.2)

                        Acceleration of 350 to 420.

                        Works fine with M350 E16

                        I am using a 0.6 nozzle. 0.4 may require a lower jerk and acceleration than a 0.6.

                        Pressure Advance around 0.02 +/- Retraction 0.7

                        Edgars Batna gnydick 2 Replies Last reply Reply Quote 0
                        • Edgars Batna
                          Edgars Batna @garis last edited by Edgars Batna

                          @garis The firmware jerk actually increases when you enable PA in the current implementation. It is computed as

                          pa_jerk = jerk / pa_time

                          so, in your case the firmware attempts to wiggle the motor 50 times faster than you've set it. At 8 microsteps (assuming TMC 2660) without interpolation you get loads of resonance fast. Plus at 40:1 it's a stretch to get it spinning as fast as 30mm/s with all the wiggling going on.

                          Have you checked if the EMF is too high on https://reprapfirmware.org/ ?

                          1 Reply Last reply Reply Quote 0
                          • Alexander Mundy
                            Alexander Mundy last edited by Alexander Mundy

                            I have Nimbles which use 30:1 and solved the jerk problem by using these 3.6 low inertia disc magnet steppers:

                            https://www.portescap.com/products/disc-magnet-motors/p430-disc-magnet-high-speed-step-motor

                            They are extremely expensive new but I lucked into a sweet deal on used ones which didn't break the bank.

                            Here is an 80mm/s retraction test that shows how fast that stepper can change direction:

                            https://youtu.be/sBAlXLfjx78

                            1 Reply Last reply Reply Quote 0
                            • garis
                              garis last edited by

                              Perhaps I haven't used a sufficiently high magnifying glass to understand what defects I should be observing or tolerating. My printing experience is limited and just now I am reprinting a few parts to upgrade the originals I printed for my Hypercube now that it is working.

                              As I understand it during the jerk phase the driver is asking the stepper to accelerate as fast as possible limited by the the motor current, up to the jerk setting leading to resonance in the more controlled velocity ramp during the acceleration phase. For the XY motors this is of concern but for the extruder I could imagine some/much of this resonance would be absorbed by the plastic, and perhaps some under extrusion if steps were missed. For a stepper with 2,600 steps that is likely to be of minor concern???

                              I am using a pancake stepper with lower inertia and it seems to work fine. (My original stepper was a recycled cheap one that did not move - it just growled at me - clearly the EMF was way too high on that one.)

                              The general print quality with PA of 0.02 was better than no PA. Using retraction speeds of 30 mm/s seems to be the sweet spot. The other variable is the print jerk with
                              the extruder being the slave but with the extruder able to limit the print speed - I am using XY jerk of 1,200 but higher values up to 2,000 + also seem to mechanically work ok, although print quality may be another matter.

                              I also don't know how far to go down this burrow given it seems to work ok and others don't seem have a problem - another limiting factor is the rotational flexibility of the nimble cable with the high performance magnetic motors just mentioned - curious about them.

                              Edgars Batna 1 Reply Last reply Reply Quote 0
                              • Alexander Mundy
                                Alexander Mundy last edited by

                                I don't have any data on the rotational flex of the Nimble cable. What I do know is that with the recommended Nema 14 and or the recommended Nema 17 pancake I could only increase extruder jerk to 60 and coupled with pressure advance made for really slow prints. With the disc steppers I can go to "normal" jerk and acceleration settings. Out of town so I can't see what they are right now.

                                1 Reply Last reply Reply Quote 0
                                • gnydick
                                  gnydick @garis last edited by

                                  This post is deleted!
                                  1 Reply Last reply Reply Quote 0
                                  • ayudtee
                                    ayudtee last edited by

                                    I can't explain the mystery as to why PA is causing this problem, very strange that everything works when it is turned off. PA is such a good feature, its worth trying to get it to work. I am recommending that you consider increasing your extruder motor current. 400mA seems low to me, as I am running 800mA on my Ormerod 2 and 700mA on my Delta.

                                    deckingman 1 Reply Last reply Reply Quote 0
                                    • deckingman
                                      deckingman @ayudtee last edited by

                                      @ayudtee The motor current is what the stepper motor can tolerate and a good rule of thumb is to 85% of the rated maximum. So increasing the current to 800mA would not be a good idea if the Op's motors are rated at (say) 500 mA.

                                      Ian
                                      https://somei3deas.wordpress.com/
                                      https://www.youtube.com/@deckingman

                                      gnydick 1 Reply Last reply Reply Quote 0
                                      • gnydick
                                        gnydick @deckingman last edited by

                                        @deckingman they're definitely rated for more. I think the logic is, at 40:1 gearing, anything much more than 400-500mA doesn't work well. I've tried it, it's not happy.

                                        deckingman 1 Reply Last reply Reply Quote 0
                                        • deckingman
                                          deckingman @gnydick last edited by

                                          @gnydick said in Pressure Advance killing extruder motor:

                                          @deckingman they're definitely rated for more. I think the logic is, at 40:1 gearing, anything much more than 400-500mA doesn't work well. I've tried it, it's not happy.

                                          Fair enough - there is nothing in this thread to state what the rated current of your motors are so I had to revet to using a crystal ball.

                                          Referring back to my earlier post of 30th March @ 05:51, I might have some ideas but you haven't answered the questions I asked.

                                          Ian
                                          https://somei3deas.wordpress.com/
                                          https://www.youtube.com/@deckingman

                                          1 Reply Last reply Reply Quote 0
                                          • Alexander Mundy
                                            Alexander Mundy last edited by Alexander Mundy

                                            It was explained to me this way. At such high steps per time frame required with high gear ratio the current doesn't have much time to decay and so higher current exasperates the situation. With 3.6 degree steppers I run normal current levels but couldn't with 1.8 degree steppers.

                                            1 Reply Last reply Reply Quote 0
                                            • dc42
                                              dc42 administrators last edited by

                                              With such a high gearing ratio, you don't need much torque but you do need low inertia and high speed. So I suggest choosing a motor with low inductance, modest torque, and a high ratio of holding torque to rotor inertia. Run it close to its rated current (e.g. 85%).

                                              Duet WiFi hardware designer and firmware engineer
                                              Please do not ask me for Duet support via PM or email, use the forum
                                              http://www.escher3d.com, https://miscsolutions.wordpress.com

                                              gnydick garis 2 Replies Last reply Reply Quote 0
                                              • Edgars Batna
                                                Edgars Batna @garis last edited by

                                                @garis said in Pressure Advance killing extruder motor:

                                                Perhaps I haven't used a sufficiently high magnifying glass to understand what defects I should be observing or tolerating. My printing experience is limited and just now I am reprinting a few parts to upgrade the originals I printed for my Hypercube now that it is working.

                                                You need to use a magnifying crystal ball, preferably with Christmas decorations within the ball.

                                                For the XY motors this is of concern but for the extruder I could imagine some/much of this resonance would be absorbed by the plastic, and perhaps some under extrusion if steps were missed. For a stepper with 2,600 steps that is likely to be of minor concern???

                                                At 40:1 there's basically no resistance whatsoever on the motor end to absorb anything, so there is just the rotor.

                                                1 Reply Last reply Reply Quote 0
                                                • gnydick
                                                  gnydick @dc42 last edited by gnydick

                                                  @dc42 thanks. Can you give an example of what qualifies as those suggestions? low inductance, modest, torque, high ratio of holding torque to rotor inertia?

                                                  1 Reply Last reply Reply Quote 0
                                                  • garis
                                                    garis @dc42 last edited by

                                                    @dc42 My pancake has more than enough torque @ 30:1. What is the reason to use high current?

                                                    dc42 1 Reply Last reply Reply Quote 0
                                                    • dc42
                                                      dc42 administrators @garis last edited by

                                                      @garis said in Pressure Advance killing extruder motor:

                                                      @dc42 My pancake has more than enough torque @ 30:1. What is the reason to use high current?

                                                      The reason to use a motor current close to the rated maximum is to provide enough torque to overcome the inertia of the rotor, because high gearing means you need high acceleration.

                                                      Duet WiFi hardware designer and firmware engineer
                                                      Please do not ask me for Duet support via PM or email, use the forum
                                                      http://www.escher3d.com, https://miscsolutions.wordpress.com

                                                      1 Reply Last reply Reply Quote 0
                                                      • First post
                                                        Last post
                                                      Unless otherwise noted, all forum content is licensed under CC-BY-SA