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Help with chain calibration

Troubleshooting
#1

I’ve had a number of accuracy issues lately, so I am going back to zero to double check everything. I spent about an hour with a level and a laser level shimming one side of my frame to make it as perfectly level as possible. I spent about 2 hours in the calibration procedure and am I am not making any progress…

I am stuck on steps 1/2 of chain calibration. I can position my chain links (I use a zip tie and pull it tight until they just touch one another) in the dead center of the top beam, +/- some very small amount. I am not sure how to get it exactly center, as I don’t have a way of verifying that the motor sprockets are in an identical position - my eyes are not that calibrated. I am certainly within a 1/32" of an inch though. Just to double check, I counted the number of links on the chain from the same position of both sprockets and its the same #.

When I then move Y- to give the chains slack, over ~36" of the board, they seem to drift to the left approx ~1.5chain links worth.

Thinking this was a centering error, I went back and repeated the previous step. I did this multiple times, always with the same result. I finally counted the links and the RH side had 1.5 more chain links than the LH side.

What would cause both motors not to move an equal amount during this part of calibration?

M2 kit, latest firmware, latest version of Makerverse.

#2

I am a bit ignorant when it comes to the Maker Made calibration process, they have the chains meet in the middle?

#3

I show the process when I went through it in this youtube video. Hopefully that might help you some.

#4

Thanks @Orob
I had watched your video previously. Its pretty helpful, but you are showing basically what I have repeated 50 times at this point, except for a minor difference in the way you ‘pin’ the chains together*. Its possible there is a small amount of error in this step, but it is centered and should still unwind each motor equally.

  • On a related note, I would like to know what math happens behind the scenes at this step, as the cotter pin orientation can impact this, or pinning them together like you did can. I zip tied mine together, which is very consistent for identifying center, but the distance is likely a 0.030" or so closer than if I used the cotter pin? I’d love to just measure the distance between the last hole on each chain at this step with a pair of calipers and put that in.
#5

I don’t know the answer to your question. I think it might be interesting to know, but if you got a piece of string that was 1651 mm long and drew an arc on the waste board from each motor, you would be able to pinpoint the center line and the draw a vertical line to the true center. Which should be 2feet from both top and bottom of the spoil board. Drive the sled there, click reset chains. As long as your y motor offset and motor spacing measurements are taken in the correct plane, you should be close enough to proceed. I prefer the webcontrol holey calibration over the makerverse version of the chain centering deal, but I got them both to work reasonably well.

I pinned the chain that way because it clips that way in the ring. Actually one link up from there.

#6

That string/arc idea is a great one. The number would be different depending on your motor offset & motor distance, but relatively easily calculated. So you are saying, just skip the chain centering step, if I can nail the true center of the board? I’m certainly willing to give that a try. The string arc seems like it would be less error prone, but the offset from the face of the board to the motors (Z-height basically) could introduce some issues.

My concern is that when traveling vertically to let the chains slack, it appears one motor moves more than the other - I don’t see how calibration would fix that, but I am not 100% sure.

#7

I have the same issue at this part of calibration. My right motor moves a different amount than my left motor while moving only in the y axis.

step 1 - centering the chain ends while getting 12oclock on each sprocket
step 2 - letting out the chains for attaching the sled(only moving in y axis)
step 3(not working) - resetting the sprockets to 12oclock with only y axis movement. I get one motor at 12oclock and the other is at 10oclock or so. Setting both sprockets to 12oclock would now require x axis movement as well which I assume is not correct, besides not being available during this step of calibration in makerverse…

conclusion: left and right motors are letting out different amounts while moving the sled in only y axis.

note: the only thing I can think of that might cause this is that a previous calibration I did found that moving “vertically” requires a slight offset in the two motor movements. I had assumed doing a full re-calibration would not hold onto old calibration settings in this way.

Has anyone figured out how to fix this?

#8

I tried to open the video but it is listed as private and unavailable.

#9

try again.

#10

got it now. thanks

1 Like
#11

@Orob Sorry to drudge this back up, but I’m having a similar issue. I originally was using the Webcontrol software, but it suddenly wouldn’t let me press the action button anymore so I decided to try out the MakerVerse software. I had a few issues here and there but I finally got it calibrated…until the motors just stopped moving more than about .5 mm at a time and then stopped altogether.

I’ve tried:

  • Recalibrating from scratch
  • “jogging” the motors by switching to webcontrol (which sort of works) and then back to MakerVerse
  • a different motor/encoder shield
  • power cycling the entire setup (arduino, shield, computer)

I’m not sure what else to do…it’s frustrating that it was all calibrated and I was just moving the sled around from the MakerVerse software and then everything stopped. :expressionless:

#12

in webcontrol when the menu buttons stop, it means the page was loaded, but the server stopped. Check your serial connection or look at the text window for error messages from the server. If you are having issues with both webcontrol and makerverse, then verify your controller is still working. When you went to makerverse, did you reflash and recalibrate and also wipe the eeprom? ($RST=*).

#13

Does the server require an internet connection? Where I’m working on this, I’m waiting for a wireless AP to be installed.

I checked the serial connection through Arduino after flashing (before running MakerVerse, because it required 51.28) and it looked normal.

I didn’t wipe the eeprom, but to be honest I’m not sure how to do that without the Webcontrol software option. I did run a basic sketch to get it back to normal and then reloaded the 51.28.

#14

Can you see the terminal window when it stalls out? Are there any error messages in the window you can share?

#15

I didn’t see any error messages in the terminal window, just the most recent command I gave it. The last time I had an issue, I had told it to “Home” and it showed the x,y,z = 0 readout. I won’t be able to get any screenshots until tomorrow when I’m hooked back up to it at work; I’ll send some then!

If I wipe the eeprom, do I have to reflash the firmware to 51.28, or is more of a hard reset?

#16

the firmware is the instruction code on the arduino. The eeprom is the configuration memory. if you reset the eeprom, you basically wipe all settings on it back to default. No firmware flash is needed with a reset.

#17

no, webcontrol does not require an internet connection.

if you try to reload the webcontrol page, does it comeup?

David Lang

#18

Okay, that’s great to hear. For some reason, it’s been difficult to get the firmware to upload so I’ve had to try it from my Mac and then again from the PC…usually one works (same download).

I’m about to try resetting the eeprom and then see what happens. Here we go…

#19

Okay, I didn’t think it did but when I hear “server” I immediately think of internet haha.

No, it won’t reload. I have to shut the webpage down, shut down the webcontrol terminal and then reload it from scratch; even then it’s a crapshoot if I am able to make buttons work. It does connect to the Arduino and everything though and has my Gcode loaded up still.

#20

in that case there is something going wrong with webcontrol, and you need to
find the logs for it to find why it’s crashing.

you can try starting it manually from a terminal session so that any messages of
it crashing show up in the terminal

David Lang

1 Like