Dobot doesn't move linearly


#1

Hello,

I bought a new dobot, calibrate and also firmware upgraded.

While I am trying to move linearly it doesn’t move linearly in X,Y,Z parameters, but in client it shows that it moves linearly. So what should I do ? Any help? Thanks…

Hear is the according video, I want only move in Z axis but it moves little in X axis. I have also this problem in X axis, I want only move in X but it moves little in Z axis.

https://youtu.be/A0ztRVCLmG0


#2

How’s the wrirings? Are they all correct? And seems your joint2 is near the limit position, so the arm is blocked due to the mechanical structure, try to put it a little far from the base, such as about 45 degrees, and see if it works.


#3

Hi,
Here is the video about the issue in X axis, as you can see I made a single move in linear mode in the X axis but it moves little in Z axis at the beginning of the steps. I have considered that it can be in limited position but I have tried it nearly in all area where dobot has ability, I couldn’t achieve. As you see, it moves little in Z axis but Z parameter doesn’t change.


#4

I think I know why it behaves like this, joint2 is still too close to limit position, increase it a little. That is to say make the X axis a little far from the base , the best range is about 150-300mm, if too close such as 100mm, than the movement will be affected by the mechanical structure. Also you can verify it like this, power off the arm and use your hand to move the joint3, when it comes to the base the Z axis will become higher, it’s the mechanical structure that caused this.


#5

Eric Hi,

Firstly thank you for your attention,

As I said before, “I have considered that it can be in limited position but I have tried it nearly in all area where dobot has ability”

I would like to make such moves in this video but for now I can’t. May be because I’m beginner in using Dobot.

Do you think, is there a problem in mechanical calibration or have you got any checklist that I can be sure Dobot is working properly?


#6

You can try it first, make your end a little far from the base. And how about check the sensor angles, are they proper? If you have an electronic protractor you can measure the angles yourself and input it in the** Initial config** tab, and test again. But remember not to reset the arm after you input the angles, if you do that it will get the angles from the sensor and overwrite them again. Or you can try to recalibrate the angle sensors according to the tutorial here:
http://www.dobot.cc/tutorial.html


#7

Hi again,

I think I observed a mechanical problem at Dobot, in axis-3 there is a gap, and if I fix the gap manually it moves linear.

So anybody can help me to fix the gap?


#8

Seems like joint3 is not locked up, I think you can check one more thing: the A4988 driver board of stepper L on the main controller box. You can swap it with the stepper R one, see if the same thing happened on joint 2. If joint3 works great with joint2’s driver board, then the driver board might be defective. And remember to check the mechnical structure first, make sure all the screws are tight enough to hold the arms.


#9

Hi Eric,

I have swapped the cables and I see the same problem. I think joint 3 has a mechanical problem. If I do only joint 3 move, I hear the voice of motors but a few later arm acts.

There are only 2 screws that may effect moves and checked them, may be is there any screws inside that should I check?

In video you will see the gap, no gear move here.


#10

I remember there’s two screws between the coupler and the metal block, so I guess you need to disassemble the whole joint to tighten the two screws, but before you do that you should research into the structure in order to know how to assemble it.


#11

After long mails, it seems that my dobot have some mechanical problem, so the firm in my country where I bought the dobot has changed it. Finally problem is solved. :blush:


#12

Nice job! :thumbsup: Have fun with dobot!


#13

I have also noticed that it is not moving properly. Thinking it in the Epson Printer In Error State, I am in search of the fixing solutions. What shall I do and make it move properly?


#14

could you please help me with script coding that my dobot mg400 doesn’t move lineraly.