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danluc

Belt and pulley pitch

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I was wondering if anyone know how much does the printer head move linearly X&Y per revolution of the motor. Also know as the pitch. I am not talking about the specks of the motor since adding a pulley with different number of teeth and diameter can change the pitch of the system. Also I was wondering the same thing about the Z axis which is coupled directly to the shaft but I don't know the pitch of the shaft either. Any help will be greatly appreciated.

The reason for all this is simple. I'm trying to get rid of the belt system the UM uses.

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I was wondering if anyone know how much does the printer head move linearly X&Y per revolution of the motor. Also know as the pitch. I am not talking about the specks of the motor since adding a pulley with different number of teeth and diameter can change the pitch of the system. Also I was wondering the same thing about the Z axis which is coupled directly to the shaft but I don't know the pitch of the shaft either. Any help will be greatly appreciated.

The reason for all this is simple. I'm trying to get rid of the belt system the UM uses.

If you look at the firmware settings, or the hello message the UM is giving you everytime you turn it on, you'll see the XY steps/mm of 78.74steps per mm

#define DEFAULT_AXIS_STEPS_PER_UNIT {78.7402,78.7402,533.333333333,866}

it should be mathematically very easy to calculate how many mm a revolution of 3600 (1/16) steps has.

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Based on my calculations, 78.74 steps per mm is equivalent to 12.7 micron steps. Is this with or without microstepping?

In addition, the largest source of error is probably the backlash (which I wouldn't be surprised if it was anywhere between 15 and 50 um.

I want to switch out the pulley system too and use ballscrews with minimal-backlash nuts. I'm okay with near-perfect positioning at the cost of speed.

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Based on my calculations, 78.74 steps per mm is equivalent to 12.7 micron steps. Is this with or without microstepping?

this is counting the 1/16th micro steps.

 

In addition, the largest source of error is probably the backlash (which I wouldn't be surprised if it was anywhere between 15 and 50 um. I want to switch out the pulley system too and use ballscrews with minimal-backlash nuts. I'm okay with near-perfect positioning at the cost of speed.

are you sure you did your error calculations properly? as a non-engineer, I would say the variations in the filament diameter will cause a mach greater XY dimensional error than the positioning system we currently have?

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I don't want to be rude, but the specs for the motors are well known and documented. And yes calculating how manny steps per rotation isn't hard either.

Since I can't seem to find the specks on the pulleys use (found the ones on the belts) and the pecks on the Z axis screw and brass nut, how can I find out the pitch of the system? That depends on the outside diameter of the pulley, number of teeth etc etc etc.

Can someone help? This is so i can use Cura and the current Ultimaker electronics when i change the belts system.

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I don't want to be rude wither, but I believe the words MXL are printed very large on the belts, and Mr Google would tell you that they are belts with a 0.080in (2.032mm) pitch, and I believe the pulleys have 22 teeth, but that is also something very easy to count and verify.

The z rod is a acme lead screw, standardized to 3mm pitch (easy to deduct from the 533.333 steps/mm in the firmware settings).

none of that is of any importance since you plan to replace your belts and lead screw, and can calculate your own new values from the specs of the materials you are buying.

The most important fact in this slightly whiny post, is that YOU can enter new values for the XYZ and E steps/mm in marlin, either temporary or permanently, since neither marlin nor cura are UM specific.

I am also slightly scratching my head how and where you got the idea to change all the transport mechanisms without a grasp that those values are plainly visible every time you start up your machine, or how other reprap machines deal with this.

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So as I mentioned before I do have the specks on the belts. I also found a variety of OD sized pulleys for the same exact belts except the ones used in the ultimaker for some odd reason.

And from what I was told Cura is not open source (told this by UM staff) and there isn't any real way to change those particular settings. Since I'm trying to keep the same software settings and such I'd have to modify the hardware. So yes Joergen it doesn't look like I would be able to change the XYZ values in the UM Cura version so to speak.

But if you do find this post a bit to whiny for your taste please ignore it especially coming from such a new user of 3d printers such as myself.

I will pay closer attention when I start Cura next time and see the values you speak of. Don't scratch your head too much on the how and where, its simple. I'm not a fan of the belt system at least on my UM. And having so many rewraps out there I wanted to stick with the UM software config, since for me at least its easier to modify hardware then software.

Again, thanks for your input. Cheers.

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So as I mentioned before I do have the specks on the belts. I also found a variety of OD sized pulleys for the same exact belts except the ones used in the ultimaker for some odd reason.

And from what I was told Cura is not open source (told this by UM staff) and there isn't any real way to change those particular settings. Since I'm trying to keep the same software settings and such I'd have to modify the hardware. So yes Joergen it doesn't look like I would be able to change the XYZ values in the UM Cura version so to speak.

But if you do find this post a bit to whiny for your taste please ignore it especially coming from such a new user of 3d printers such as myself.

I will pay closer attention when I start Cura next time and see the values you speak of. Don't scratch your head too much on the how and where, its simple. I'm not a fan of the belt system at least on my UM. And having so many rewraps out there I wanted to stick with the UM software config, since for me at least its easier to modify hardware then software.

Again, thanks for your input. Cheers.

Please, you need to separate your facts: cura is a gcode slicer, using skeinforge as the slicing engine. (see http://daid.github.com/Cura/)

The Ultimaker printer is using a firmware called marlin, developed by erik v. zalm and others (see https://github.com/ErikZalm/Marlin, which is basically arduino code, which gets compiled and uploaded to the arduino in your printer. You can change ANY aspect in the firmware to your liking, compile it, and upload it to your printer, you can even change all the steps/mm setting on the fly via the ulticontroller. You can also change the steps/mm via a simple gcode command in your .gcode, or via the printrun or repg or cura command line: M92 Xxx.xx Yxx.xx... Daid included a function for users to make the upload and customization process easier, which is why you seem to have trouble recognizing that those are actually 2 different things. In order to keep things easy, the default firmware is using the default values that are good for all UM users. he even made a great tool to create your own custom versions of marlin: http://daid.eu/~daid/marlin_build/ where you can even customize your elusive XY steps.

In regards to the specs for the pulleys, I don't know whats so difficult to simply count the teeth of the pulley.

If you would like to read more about how to do simple math, feel free to read through a lengthy thread that should explain everything perfectly: https://groups.google.com/d/msg/ultimaker/kZBniGOXA88/eVtiYzBhKPwJ

short summary:

 

MXL belts have a 0.080in tooth distance (measured and as per specs), or 2.032mm

using 20 tooth pulleys, one rotation is 40.64mm, so it takes 78.7402 steps per mm (3200/40.64)

(3200 micro steps because the steppers are 200 full steps per rev, but they are driven as 1/16th micro steps: 200*16=3200)

I hope this helps you on your quest: the marlin firmware can support basically any stepper driven method, as long as you are able to calculate the proper steps/mm

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Let me add one tiny thing on that. Cura and the firmware it installs hides about 250 values from you. You now want to hack around with your printer, that's fine. But you have to investigate time and learn how things work in your printer. As if you knew a bit about GCode you should have known that these details like "steps per mm" are not in Cura but in the firmware of the machine.

UM support does NOT know these details, they don't need to know. I wouldn't even want them to know. They deal with issues on standard kits, if you go hacking around you are on your own or with the community. If they said Cura is not open source, then somewhere there must have been a mis-communication, because all the source is on github. And there is a AGPL license with Cura.

Software wise our whole printer is open. We're working on making our standing on open source clear soon.

The Ultimaker is a basicly a wooden reprap,

http://reprap.org/

so you can find lots of information from there.

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Joergen,

Much appreciate the much needed software pointers. I'll have to learn tons more on the software side before I make the switch to the new printer. It does look like I won't be able to keep the software side of things unchanged. Oh well more work then.

Daid,

I know I'm on my own and still like certain feature of the UM which I will keep.

Thanks all.

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Perhaps I'm missing the boat here. Why wouldn't you be able to keep the software the same? GCODE works in it gives a the firmware a command, ie heat up, cooldown, move here, print here, etc. There are a bunch of these M-codes that are followed by coordinates or temperatures or other values. They do not set parameters like steps per mm. Those come from the firmware's interpretation of the GCODE, ie Marlin. In Cura, you can change the size of your build platform in preferences, so that covers any change you could have there. Then I'm assuming you are planning on running Marlin firmware? If so, then all you need to do is plug in the corresponding steps per mm in the builder on Daid's github. Correct me if I'm wrong here Daid, but Cura's print function doesn't care if you are a custom RepRap or an Ultimaker. If it's running Marlin firware, it should work. If you are running a UltiController or similar setup, again, it should work. The basic thing is GCode doesn't care about your steps per mm...

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