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Unexpected Behavior and Results

edited January 2014 in WaterColorBot
My daughter and I were very excited to receive our Bot.  We put it together, My daughter (9) created a smiley using RoboPaint OSX.  But when we print, the Bot, we make sure its a the starting position, makes lot of stuttering sounds, cleans up many times and no matter what color we pick, it always only using black ink and our circle looks like a blob. Same true with the sample images,

When printing from Inkspace, same issue on only using black color, and when bot is trying to clean on the second water tray, it stutters a lot, losses it position and instead of picking the colors, its trying to dip into nothing.  

I will try to make a video tonight. I dont have a reference to to how tight or loosen the threads should be.  We are very excited about the product, but disappointed with the results.  

I will appreciate any help you can provide.  Thank you


  • Just completed my WaterColorBot last night and had the same behavior.  Tried RoboPaint and RoboPaintRT on three seperate Macs (different ages and OSs) with the same behavior.  Lots of stuttering, some jamming.   Just from observation, it looks like it 'thinks' it is moving farther onto the paper than it actually is.   But if I hit zero, it travels the 'full' distance back so it gets to the zero position and keeps trying to spin the motors.  Like Sha, I made sure it was in the starting position each time.  The only point I deviated from the instructions was that I didn't unmount and remount the motors - I just wrapped the wires in place.  I can provide a video if that would be helpful. 
    Final comment - the brush lifting works fine.

  • I just adjusted the current to the motors by slightly turning the potentiometer on the EBB and it is MUCH happier now.  That seems to have been the problem.
  • Hi Sha,
    I'm sorry to hear about the difficulties.  There are several different issues here, and we need to work through them one at a time.

    First off, I'd suggest putting away the paint, water, and paper until you can tell that the machine itself is operating correctly.  The robot is not yet configured correctly until the motion is clean, smooth, and without any "stuttering" type behavior of any sort. 

    There are two different behaviors that might be described as "stuttering": One, which we call "cogging" is where the motor tries to turn but cannot and jumps from one position to another. The other, which we call "stuttering" or "chattering" is where the motor is turning properly, but the carriage is undergoing stick and slip type vibration as it moves along the rod(s).  The latter can be annoying, but is not generally harmful (although it can cause the bushings to wear out prematurely), and is most likely caused by not having the two rods fully perpendicular.  However, what you are describing-- where the motor loses position -- is cogging, and is much more serious. 

    Now, onto fixing the problem.

    Unplug the bot (both USB and power), and turn the winches by hand— one at a time —to move the carriage to the home corner, and then to the opposite corner.  As you go, check the following:

    (A) Is the spectra cord properly routed around the three ball bearings, riding in the groove?
    (B) Are both rod ends fully square to the frame (up against their stops, without any gaps) at each end of travel?
    (C) Is the motion clean, smooth, easy, and without binding of any kind?

    If the answer to all three is a resounding "Yes, absolutely, positively!", then your robot is mechanically set up correctly, and you likely need to adjust the motor current. (Skip down this text until you get to the part that says "If you need to adjust the motor current.")

    Otherwise, we need to work on the mechanical part.

    Begin by turning the winches by hand to move the carriage to the center of the frame. Remove the rods from the carriage, by lifting up the rod end sliders and pulling the rods out, sort of like you did at the beginning of assembly step 28.  Leave the carriage attached to the robot by its cable guide, but set the carriage out of the way, for example on your table behind the frame. Re-install the rods.

    Next, move the winches by hand, returning the two rods all the way left and back, as though you were moving the carriage back to the home corner.  Starting with the Y axis (motor 2 and its cord), check that the string is routed correctly over the entire path,as described in steps 15-18 of the assembly instructions. In particular, follow along with the numbered arrows on the frame, and make doubly sure that the cord is still laced into the grooves of the two ball bearings at arrow positions 3 and 6 on the WaterColorBot frame. Next, check that the rod ends are absolutely, positively square to the frame (without any gap, as shown in step 20). (If they were not square, then that would certainly cause the cogging that you had.)

    Turn the Y winch by hand, all the way to the end of its travel and back.  The motion should be clean, smooth, easy, and without binding of any kind-- much like an Etch-A-Sketch. (Your daughter should be able to turn it!)  If you have enough tension, the cord should will still be laced into the grooves of the ball bearings.  If you have too much tension, the motion may have too much friction, and won't give that smooth motion that you need.  In practice, the amount of tension is pretty forgiving, up to those two limits.   Finally, after moving the rod to the end of its travel and back, check again that the rod ends are square to the frame.    

    Then, repeat these steps for the other axis, and finally re-install the carriage.

    If you need to adjust the motor current...
    First, be sure that you need to.  *DO NOT* adjust the motor current unless you're sure that (A), (B), and (C) above are true. Then see our troubleshooting guide about how to adjust the motor current:

    As for the other issues-- black paint and so forth -- please get rid of the cogging first, and then try to describe to me what the current behavior is, and I'll do my best to help from there.
  • Hi LongArc,
    I spent so long on that first reply that your first and second comments came before I had a chance to reply.  I'm glad that you've got it working!
  • Windell,

    I checked and re-confirmed that my ABC steps are YES.  I went on to step 4, adjusting current, I follow the procedure and it took two clicks to get the motors running smooth and no funky sounds.  BTW what is the use of the Sand Paper? :)

    I did not have chance to do an actual print test to see if color issue is still there or any prints are same as on the screen.  I will do that tonite.

    Thank you so much for such a detail and helpful response.  Best Customer Service!!!!
  • Hi Sha,
    Fantastic-- very glad to hear it!

    When you get a chance to try a test print, I'd suggest running your first one without a paintbrush inserted-- make sure that it looks like it's doing everything right before using up any more paint and paper, and please let us know how it goes.

    As it says in the getting started guide, the sandpaper isn't called for in the instructions, but is there in case you find any rough edges on the WaterColorBot and don't have any sandpaper hand. ;)
  • Hello,

    Thank you again for the quick response.  Sorry took a while to get back to it.  All is good now.  We are making prints and hope to share them.

    Thank you again for the help and such fun bot...

  • Windell -

    My WCB does fine with simple pictures but tends to fail if the painting is too complex.  It loses it location for a second and then all heck breaks lose - painting on the board between the water dishes, knocking over the water dishes - kind of funny actually.  I can actually hear it when it happens so if I stop it in time, no damage done.  But I was wondering is there anyway to re-calibrate it in the middle of playback?  I wouldn't think so but I though I would ask.  I bought a big pad of watercolor paper so I usually just reset and start from the beginning.

    Also - I was going to try to lower the current a bit more and see if that helps but I wanted to ask: What is the indication that the current it *too* low?  Is that a brown-out situation where I risk burning out the motor itself?  Too high = stuttering, too low = ?   Looking for indications of the Goldilocks point.

  • Can you tell if the problem is one of software or mechanics?  In other words, is it genuinely correlated to how complex the drawing is?  (And if so, which software are you using?)  Can you clarify exactly what is happening when it "loses location for a second?" You said that you can hear it, so that suggests that you're hearing cogging, or something similar is happening-- please elaborate, so that we can help correct the situation.

    If it is a software issue: There is a known problem in the previous release of RoboPaint (v 0.6.4) that would cause seemingly random lines to appear when the file was too complex.  (See here fore more info: ). If this looks like what you are seeing, and you are using RoboPaint, please make sure that you're using the latest version (0.7.0).

    If it is a mechanical issue: Once the WaterColorBot is properly tuned, it will not lose steps anywhere.  (And once it's tuned, it should *stay that way* for months on end.)  So, check the steps that we listed above, and make sure that the motor current is appropriate.  

    For what is "appropriate," please read the link above about adjusting the motor current-- we have a lot of hints and advice there.  If the current is too low, the motors will be weak, and you'll get cogging, resulting in a loss of position.  (It will not burn out the motor.)  If the current is too high, the motors will be hot, jerky, and noisy.  There's always a "goldilocks zone" in the middle.

    The method of re-calibrating in the middle of painting depends on which software you're using.  For example, in RoboPaint RT, pause the painting, click Motors:Off (to turn off the motors), manually move the carriage to the home position, click Motors:Zero (to declare that the carriage is in the home position), and resume.

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