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Triple stepper Z Axis

Posted by o5i 
o5i
Triple stepper Z Axis
October 08, 2016 04:18AM
Hi i am buildn a ultimaker clone, but bigger...
Because of the bigger size i wanted to use 3 steppers on the z axis to avoid problems..
I thought if i use the 3 steppers it should be possible to auto calibrate the z axis using a proximity sensor..
I saw there is a options called auto leveling..
The controller i want to use is a ramps 1.4 whit triple stepper expander..
Someone did this or can give me some infos about how to implement it on the controller?
What proximity sensor to use? capacitive, inductive or ultrasonic - analog or digital?
Thanks
Re: Triple stepper Z Axis
October 13, 2016 06:06AM
The biggest problem with multiple steppers on the Z axis is keeping them in sync because when you first power up the machine, they will all jump to the nearest whole step. Some will jump forwards and some will jump backwards so after a number of power cycles, the problem will be exacerbated. For info, my bed weighs around 7Kg and is lifted using 3 screws but with a continuous belt and a single Nema 17 motor with 1:1 gearing.
Re: Triple stepper Z Axis
October 13, 2016 12:04PM
Quote
o5i
Hi i am buildn a ultimaker clone, but bigger...
Because of the bigger size i wanted to use 3 steppers on the z axis to avoid problems..
I thought if i use the 3 steppers it should be possible to auto calibrate the z axis using a proximity sensor..
I saw there is a options called auto leveling..

I have exactly this sort of auto levelling on my work list for RepRapFirmware. But it's 32-bit firmware so it doesn't run on RAMPS. If you are going to build a large, expensive printer, I suggest you use good electronics in it anyway instead of budget electronics such as RAMPS.

Quote
o5i
What proximity sensor to use? capacitive, inductive or ultrasonic - analog or digital?

That depends on your print bed surface. Take a look at the differential IR sensor that I sell, which works well with most bed surfaces, although some like PEI need to be prepared in a certain way. See [miscsolutions.wordpress.com].

Quote
deckingman
The biggest problem with multiple steppers on the Z axis is keeping them in sync because when you first power up the machine, they will all jump to the nearest whole step. Some will jump forwards and some will jump backwards so after a number of power cycles, the problem will be exacerbated. For info, my bed weighs around 7Kg and is lifted using 3 screws but with a continuous belt and a single Nema 17 motor with 1:1 gearing.

Actually they jump to the nearest multiple of 4 full steps that matches the phase currents. I'll be adding code to avoid this issue in RepRapFirmware for the Duet WiFi, by detecting power down and moving each motor to one of the correct positions ready for power up. I can do this because the Duet WiFi has two power monitor circuits on board. However, with the planned auto levelling, it won't matter if the motors jump a bit when you cycle power, if you run auto level every time you power on.

Edited 3 time(s). Last edit at 10/13/2016 12:09PM 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]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Triple stepper Z Axis
December 20, 2016 08:43PM
Couldn't the same calibration result be achieved by pushing the motors in question to a known axis limit and then, once that's triggered, push them a bit longer until they error out due to not being able to push farther?

I can't say if this was done on IBM PC floppy drives, but the Apple ][ series determined which was track 0 or 35 by deliberately going enough steps to guarantee it'd get to the limit: in other words, it'd go until it crashed, then it kept beating the read/write head against the limit. While it was crude and made a bit of noise, it worked.
Re: Triple stepper Z Axis
December 21, 2016 12:18AM
The problem with beating the motors against a stop is that you end up with a position uncertainty of 4 full steps, which is going to be too much.


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]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
o5i
Re: Triple stepper Z Axis
June 30, 2017 03:14AM
Hi, i figured out that there are some printers who do auto calibration at the start.. Do you have some idea wich firmware they run?
Re: Triple stepper Z Axis
June 30, 2017 02:57PM
Do you mean automatic delta calibration, automatic XY skew compensation, automatic bed levelling, or automatic bed compensation (often incorrectly called automatic bed levelling)? Or something else?


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]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
o5i
Re: Triple stepper Z Axis
June 30, 2017 03:58PM
i have a utimaker clone whit triple z axis and z probe.. what i want is adjust the bed to be flat automaticly by measuring the distance on 3 points of the bed (where the steppers are) its like a triangle... i saw that it is possible but what firmware is the best to use in this case?
Re: Triple stepper Z Axis
June 30, 2017 11:38PM
Ok, you mean true automatic bed levelling. I am not aware of any firmware that supports it properly yet, although RepRapFirmware lets you get close, see [www.duet3d.com]. It's on my list to support it natively in RRF and some of the preparatory code has already been implemented in the latest beta firmware.

Edited 1 time(s). Last edit at 06/30/2017 11:39PM 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]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Triple stepper Z Axis
July 11, 2017 09:16AM
I'd really like to have this feature also available in RepRapFirmware, that could be the day I'd actually buy a Duet Wifi and switch from my current solution.

If you can't wait, you can already use it in Repetier firmware (scroll down to "motorized correction"): [www.repetier.com]
You can see it in action here: [www.youtube.com]

Some guys in the German forums use it on RAMPS/Mega2560, but it will also work on some ArduinoDUE-based printer electronics.


Best regards / Viele Grüße
microfortnight

Printers: Sparkcube V1.1 XL / P3Steel Promenadenmischung / Skimmy's DICE (under construction) / Creality Ender-2
Re: Triple stepper Z Axis
July 12, 2017 02:10AM
This facility is now mostly implemented in RepRapFirmware 1.19beta9, for 2, 3 or 4 leadscrews. See [duet3d.com]. It will be completed before the 1.19 release.


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]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
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