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Looking for ways to smooth out the movement of my stepper motors.

Posted by Draytology 
Looking for ways to smooth out the movement of my stepper motors.
January 14, 2017 06:15PM
I have been tuning my set up for a few weeks now and have most of it dialed in. But, I still don't have my steppers operating like I want them to. They work fine but I want to decrease the harsh changes of direction, especially for short length infill. I have gradually turned down the accelaration and jerk all the way to 750/2.5. In cura I have decresed my speeds to 30mm and 15 for infill and it is still jarring. Today I upraded my mounts and and couplers so it can handle it but I would really like it to get this sorted out. I want to make it cushion the changes in direction so i can turn the speed back up. Also, during starts of moves or transition of lines the motors will make a harsh shuddering vibration and then go back to moving smooth. That is by far the most annoying problem of all.

Any suggestions would be greatly appreciated.

I am going to try to post a copy of my configuration.h
Re: Looking for ways to smooth out the movement of my stepper motors.
January 14, 2017 06:24PM
What sort of architecture is the printer? What kind of motors are you using? How much current? What kind of controller board? Power supply voltage?

Edited 1 time(s). Last edit at 01/14/2017 06:26PM by the_digital_dentist.

Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Looking for ways to smooth out the movement of my stepper motors.
January 14, 2017 07:36PM
Nema 17 motor's. 2 of the small ones, 1 of the larger 84oz.in on my x axis. Mega and Ramps at 1/32. I got my DRV8825's turned to 0.7v. My setup draws about 2.5a average (no heated bed). It's a DIY build pretty solidly built usuing a mixture of steel,aluminum, and pine for the structure. I'm using lead screws and it's basically 100% custom other than the components needed to run it. Maybe I need to turn up the current? I spent a lot of time tuning it when I built it there is not much friction and the motors definitely should not be working hard at all. I'm thinking because I am using lead screws and it's built pretty solid it increases the resonance but I am still trying to reduce the noise and especially shuddering. I have messed around with firmware but can't get it running nearly as smooth as I would like.
Re: Looking for ways to smooth out the movement of my stepper motors.
January 14, 2017 07:53PM
My main concern is the reason behind why the motors will sputter very hard during starts and stops. As far as the harsh changes in drection I have turned down the acceleration and jerk to 750 and 2.5 and its still pretty rough. Also turned my print speed down to 30mm and 20 on the infill. But that is more of an annoyance than concern because my printer can handle it no problem.
I am supplying 12v to my Ramps. BTW

Edited 1 time(s). Last edit at 01/14/2017 08:24PM by Draytology.
Attachments:
open | download - My configuration.TXT (35.8 KB)
Re: Looking for ways to smooth out the movement of my stepper motors.
January 15, 2017 12:44AM
The fact you are using lead screws ( on all axis?) is new to me. What kind of lead screw is it? It must be some special , otherwise you can't expect to print faster than 20mm/s or the like.
My lead screw z-axis on the Prusa only goes 3mm/s until it starts rattling.
Re: Looking for ways to smooth out the movement of my stepper motors.
January 15, 2017 01:21AM
There are fast lead screws available. Whether it makes sense to use them over belts is a different story.
Re: Looking for ways to smooth out the movement of my stepper motors.
January 15, 2017 04:36AM
What sort of guide rails/bearings are you using? Try posting some pictures/video.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Looking for ways to smooth out the movement of my stepper motors.
January 15, 2017 10:09AM
That's interesting, I thought lead screws were the norm. I didn't start reading through the forum until after built it. Originally I was planning for a CNC then decided to go with a 3d printer. I also didnt want to deal with the hassle of slipping and stretching belts. I'm sure with some quality belts that would not be much of an issue but that was my line of thinking at the time. I wanted a solid machine. Like I mentioned my build is 80% DIY, I only use purpose built parts where I had to. This was because of budget constraints and also just for enjoyment TBH. It is not perfect and I am sure it is not up to the standard of some of the more experienced, but I am quite proud of it, and I don't think it's too bad for someone who up until recently has 0 experience in 3D printing. I have been upgrading it non stop since I got it up and running. Yesterday I strengthened the motor mounts, leveled the x axis, and upgraded one motor. Ever since I upgraded a motor I have noticed a little slip at higher speed. I wasn't sure if it was my coupler or if I need to turn the current up on my driver. I keep the drivers set at about .750v for X and Y but I since turned up the larger stepper (84 oz/in Nema 17) to 1.0. It seems to have helped, but I also marked the positioned of the coupler and motor shaft to check if another slip happens. Right now I working on upgrading my coupler's because the nylon one I am using flex when tighten the set screw causing an imbalance and slight wobble. Suprisingly it hasn't hurt print quality too bad. But, I am not happy with it. I am using cheap hardware store lead screws and I felt like they were better because they gave me a higher resolution but after some thinking yesterday I will probably switch to some with a lower pitch so my motors can spin slower and I will be able to print at higher speeds. I am about to take some pictures and maybe a short video of it running so I can get some specific advice. Like I said I'm new so don't trash my baby too hard.grinning smiley
Re: Looking for ways to smooth out the movement of my stepper motors.
January 15, 2017 10:23AM
BTW I have been messing with the configuration and I turned my acceleration and jerk up some more to 1250 and 12.5 but I think I need to dial it back to +-1000 and 10 because I have some shifted lines on the y axis which never happens.
Re: Looking for ways to smooth out the movement of my stepper motors.
January 16, 2017 12:29PM
Regarding the slip at higher speed, what steps/mm do you have configured for that motor, and what speed are you trying to achieve? As your printer has leadscrews, it probably has a higher steps/mm than usual. High steps/mm can lead to 2 issues at high speeds:

1. Loss of torque at high speed due to insufficient supply voltage. Remedy is to use a higher supply voltage, typically 24V instead of 12V. See [duet3d.com] for guidance on what voltage you need. Not all 3D printer electronics boards are 24V-compatible.

2. Electronics not able to generate the step pulses fast enough. Remedy is to use faster electronics and/or more efficient firmware. Multiply the steps/mm by the speed you want in mm/sec to get the step pulse rate, then look at [reprap.org] to see what your electronics/firmware combination can manage.

Edited 2 time(s). Last edit at 01/16/2017 12:31PM by dc42.

Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Full disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
Re: Looking for ways to smooth out the movement of my stepper motors.
January 17, 2017 08:30PM
I did not think to try increasing the voltage. Except for on my drivers which is set to .800v and .900v on X and Y. Right now I am at 12 volts and the max I can go to with my PSU is 19.5. My Ramps board should be able to handle it so I think I will definitely give that a shot. I'm slowly getting it dialed in, I have been tuning speeds settings for about 3 days alone. I have been doing some reading and I have been looking into the problem you mentioned. I need to get my rpm's down so I can get some torque and speed back. I am trying to tune my setup for at least a comfortable 40mm/sec. Right now, after a few days of tuning, I can squeeze out maybe 20mm/sec. I didn't realize the limitations of leadscrews when I built the printer, especially the cheap ones I choose. I was able to find a little cheat to help, I turned my jerk setting waaay down between 1-5 to give me a nice cushion when changing direction and I am slowly trying to dial my acceleration in as high as possible and it is working but I am having a little trouble with resonance. I tried to give 1/16 microstepping a shot (currently 1/32) but for some reason during testing my motors spun extremely fast and would stall whether connected or dissconnected to leadscrew.
The second part you mentioned is actually one of my biggest limiting factors right now and is the reason I attempted to try 1/16. I normally set my speed in Cura to 40mm/sec and I will just print at a fraction of that and dial it up depending on performance. But, it seems like anything past 60% and it starts getting real choppy and freezes. Looking at something relatively cheap in the 32 bit range.

Right now I am at 4030.23 steps/mm on X and Y and 2048(1/8) on Z.
Which seems to be way to much for an Arduino Mega.
Thanks for the links I am going to check them out.
Re: Looking for ways to smooth out the movement of my stepper motors.
January 18, 2017 09:46AM
Quote
Draytology
I did not think to try increasing the voltage. Except for on my drivers which is set to .800v and .900v on X and Y. Right now I am at 12 volts and the max I can go to with my PSU is 19.5. My Ramps board should be able to handle it so I think I will definitely give that a shot.

Most RAMPS boards have 16V electrolytic capacitors, so check yours first. Also, you are likely to overheat the 5V regulator on the Arduino if you increase the voltage above 12V with an LCD power from it too, or above about 15V with no LCD.

Quote
Draytology
Looking at something relatively cheap in the 32 bit range.

I'm biased (see my signature), but I advise against using cheap electronics.

Edited 1 time(s). Last edit at 01/18/2017 09:47AM by dc42.

Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Full disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
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