Stuttering Motors

A few days ago, i finished my new delta printer, a kossel mini. I get all the things i Need for my own and all printed Parts are printed by my self.
The kossel works quite well, but there also some problems: if i move the axis manualy with pronterface or via display, they Movie quite smooth, but if i Print Sommerhoff, the Motors See stuttering.

The vref of the Stepper driver Is about 0,85 and the carriage da Move also very smooth.

Have anyone an idea?

Printer Settings: Delta with Carbon rods with Traxxas rodends, igus tk-04 gliders, Nema 17 1,7a 1,8deg, Arduino mega with Ramps 1.4 and Marlin Software, drv8825 polulu Stepper driver.

It sounds like you are printing from an attached PC and the PC isn't supplying data fast enough. Print from SD card instead.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

It's my experience with marlin on a delta that you can't print fast with an 8bit arduino. Even worse when you have a graphic display.

Try to reduce overall print speed ( and print from SD-Card like dc42 suggested ) to 40mm/s.
When the stuttering is gone, raise the speed slowly to find the sweet spot. ( circles will be most problematic )

-Olaf, who bought a Duet 0.6 after 4 weeks of 8-bit frustration

i printed with SD Card.

this is my second Kossel. the first, from t3p3 with arduino and Marlin works very smooth, and there aren't any Problems like this. the only differents between both printers are the Motors (the "old" have a higher Torque), the heated bed and the stepper driver ("old" 1/16 vs "new" 1/32)

also the firmware and the igus gliders are the same.

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nimrod
i printed with SD Card.

this is my second Kossel. the first, from t3p3 with arduino and Marlin works very smooth, and there aren't any Problems like this. the only differents between both printers are the Motors (the "old" have a higher Torque), the heated bed and the stepper driver ("old" 1/16 vs "new" 1/32)

also the firmware and the igus gliders are the same.

The 1/32 drivers take a huge chunk of the performance, double that of the 1/16.

When I had that combo, my printer maxed out at about 80mm/s in the XY-plane, but faster with pure Z travel moves.
I didn't have an LCD though.

Edited 1 time(s). Last edit at 11/10/2015 04:28AM by Koenig.

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Koenig

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nimrod
i printed with SD Card.

this is my second Kossel. the first, from t3p3 with arduino and Marlin works very smooth, and there aren't any Problems like this. the only differents between both printers are the Motors (the "old" have a higher Torque), the heated bed and the stepper driver ("old" 1/16 vs "new" 1/32)

also the firmware and the igus gliders are the same.

The 1/32 drivers take a huge chunk of the performance, double that of the 1/16.

When I had that combo, my printer maxed out at about 80mm/s in the XY-plane, but faster with pure Z travel moves.
I didn't have an LCD though.

I copy that.
Plus the drv8825 has problems with microstepping at slow speed. I got much smoother moves when I did the "decay hack", but the max. speed was the same.
-Olaf

it sounds like it is better to replace the "better" drv8825 by the "old" 1/16er stepper.

first i will decrease the acceleration from 3000 to 1500 and try. if this doesn't work, i will replace the stepper with the others.

I had acceleration set to 5000mm/s^2 in Marlin and I only have 0.4A steppers...
-Olaf

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nimrod
it sounds like it is better to replace the "better" drv8825 by the "old" 1/16er stepper.

Or use 32-bit electronics, which can drive a delta without the performance being marginal as it is with 8-bit Arduino/RAMPS, and can provide other benefits e.g. built in web interface, software-controlled stepper motor currents, and fast auto calibration. T3P3's Mini Kossel kit now uses Duet electronics instead of Arduino/RAMPS.

I have also seen it claimed that when using 8-bit electronics to drive a delta, then Repetier is better at doing it then Marlin. I can't verify this because I gave up using 8-bit electronics last year. Or you could try changing the microstepping jumpers on your RAMPS board to use 1/16 microstepping on the drivers.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I used both Marlin and Repetier. Repetier has a chance to be quicker since it uses integer arithmetic for deltas which are not too big (i.e. a 16 bit integer overflow cannot happen). I did not have really speed problems with Marlin. I switched to Repetier because it does keep constant speed of the hotend instead of carriages. This leads to more even extrusion especially at higher speeds.

8-bit controller is barely enough up to print at about 150 mm/s speeds if you keep segments per second low (in the range 80 - 100). The problem is that the default config files set segments per second to 200 (at least they did in past) and that is too much. 100 is plenty enough from the precision point of view.

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hercek
Repetier has a chance to be quicker since it uses integer arithmetic for deltas which are not too big (i.e. a 16 bit integer overflow cannot happen).

I'm not convinced that is true. For example, with 200steps/mm (i.e. 0.9deg motors or 1/32 microstepping, and 16-tooth pulleys), overflow would occur when the carriages are 328mm above the bed, if Repetier uses a 16-bit unsigned integer to represent the carriage height above the bed. So no good on a 1m high delta like mine. But OK on a Mini Kossel with 1.8deg motors and 1/16 microstepping.

However, I thought that even 8-bit firmwares used 32-bit integers to represent axis or carriage positions in microsteps. Is that not the case?

Edited 1 time(s). Last edit at 11/10/2015 11:35AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Uff, I'm lazy to go to check the actual code but IIRC it really uses 16 integers if you can fit in them. Of course, when computing squares they compute them into 32 bit number and return back to 16 bit after the square root is done. There was some (preprocessor, typedef or whatever) magic which switched types to ... well I think floats (other option would be 32 bit int) when one would not fit into 16 bit integers for defining printer dimensions in steps.

TL/DR, I'm not convinced about it too! But there was some magic to select the proper type for the given printer size. And Repetier definitely works in steps instead of millimeters like marlin. It was a mistake to chine in when I'm not sure

Anyway, it is a good idea to use Repetier instead of Marlin because of the constant head speed movement. If they did not fix this in Marlin in the meantime too. I'm talking about versions from 2 years ago.

after i changed the stepper (now it works with the 1/16) and decrease the acceleration, the Problems are still there. it seems they are not only at the points where the motors change direction. but i dont know the reason... now i also changed the belts, the rods, but it isn't better than before. i can't imagine that this problem comes out of the 8bit arduino.

nimrod,
EDIT: took out what I said as you had replied...

How many steps per mm do you have now with 16 microsteps?

Edited 1 time(s). Last edit at 11/10/2015 02:09PM by Paul Wanamaker.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

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Paul Wanamaker
nimrod,
EDIT: took out what I said as you had replied...

How many steps per mm do you have now with 16 microsteps?

What did you mean?


I have 80 steps per mm with the 1/16er and 160 with the 1/32er. All Jumpers are enabled.

Do you have a graphical LCD attached to the printer with the problem? It's well known that Marlin can't drive a delta and a graphical LCD on 8-bit controllers.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I have the Full graphics display Controller. My other kossel has a normal Lcd Display. Is it possible that this Is the Problem?

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nimrod
I have the Full graphics display Controller. My other kossel has a normal Lcd Display. Is it possible that this Is the Problem?

That is precisely the problem. Personally, I would never run a delta printer with 8-bit electronics. But there are others on this forum who say that you can run a delta + GLCD from Arduino/RAMPS if you use Repetier firmware instead of Marlin. Or you could disable the GLCD support in Marlin but keep the SD card support.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

So i try and disable the Full graphic and Order a new normal 2 Line lcd Display. Hopefull this will solve the Problem. Are there some other Ideas?

Buy a duet and never look back!

I'm going to buy one, but for this project "Build a kossel without any Sets or kits" i prefered a simple Electronic. For the next Time, or the next Upgrade, a Duet Board Is in the top of my List.

Edited 1 time(s). Last edit at 11/11/2015 01:42AM by nimrod.

I remember a discussion at marlins github where someone stated "the 2004 display takes 90% of the loop time" because Marlin refreshes the whole display each loop. It must be even worse with the graphic LCD...
He suggested to split the refresh routine to "one line per loop", but I don't know, if that happened already.
-Olaf

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nimrod
I'm going to buy one, but for this project "Build a kossel without any Sets or kits" i prefered a simple Electronic. For the next Time, or the next Upgrade, a Duet Board Is in the top of my List.

Just remember, if you want on-board display for Duet, it's going to be Panel Due. Neither GLCD nor the 20x4 text LCD are supported.

after all, the stutter-effect decreases after i changed the display. now there are only some little effects at the points the Motors turns direction (but noch everytime) could i solve this problem by increasing the current of the Stepper driver? or are there ather possibilitys?

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grat

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nimrod
I'm going to buy one, but for this project "Build a kossel without any Sets or kits" i prefered a simple Electronic. For the next Time, or the next Upgrade, a Duet Board Is in the top of my List.

Just remember, if you want on-board display for Duet, it's going to be Panel Due. Neither GLCD nor the 20x4 text LCD are supported.

Not entirely true. I use a WLAN router to connect the Duet with my laptop/ tablet/ cellphone.
Duets web interface is as practical and feature packed as the PanelDue.
That way, I buy a versatile device which is also useable to slice, netfabb, and even CAD parts.

The panelDue only has one purpose and the price is higher than a cheap tablet.
-Olaf