Dobot Magician Joint 1 resistance - won't rotate all the way

#1

Hello all,

I was hoping to get a response from Customer Support, but I thought I’d post here as well. I just recently purchased a Dobot Magician, and it’s a fantastic robot. However, I’m having a resistance issue with Joint 1 (base rotation). If I go more than 90° counter-clockwise from “home”, the robot arm experiences significant resistance and the stepper starts skipping. This, I believe, is from a large cable in the base making contact with the case itself…

If I shut off the robot, and the arm is in the “home” position, the cable causes the robot to twist clockwise about 10-30 degrees. In addition, most rotation motions cause a “rubbing sound” from the cable. I’ve tried to improve it with some machine oil on the cable, but it’s not enough to fix it.

People have said that opening the case is not advised, as it can cause damage. Has anyone else experienced this (I’ve seen videos from others with this problem), and does anyone have a fix? Because of this, I can only use 80-85% of the Joint 1 rotation range. In essence, I can only rotate 90° counter-clockwise from the “home” position.

In summary: cable causing a “rubbing” sound when rotating base joint, (Joint 1), and induces a resistance where you only get 80-85% of possible rotation angles. Would appreciate any feedback from community members and/or from customer service. Thanks!

#2

Update: Support was very helpful. They pointed out that the operating range for J1 is +/- 90°, so it is within specification. Has anyone been able to reduce the noise made by the cable rubbing against the case? Thanks!

#3

I have the exact same problem, although this does not cause me too much harm in programming since I don’t use such extreme angles.
Although the robots Y-coordinate seem to be resetting everytime I restart the robot. Meaning that each time I turn on the Dobot, the Y-coordinate is set wherever the joint 1 is “facing”.
Trying the “base calibration” in the dobot software would solve this problem but due to the limited range caused by the cable the dobot cannot calibrate itself this way.

How did you solve this problem?
Any support would be appreciated.

Having a non reliable y-axis causes alot of trouble with re-running saved programs.

#4

I was able to resolve the issue with white lithium grease. There are two black rubber-insulated cables that cause the noise in various contact points. I put the grease around each cable, and inbetween the two cables. This is hard to see, and even harder to show, but keep pushing it in and around until the rubbing noise stops. The robot will still rotate back when it shuts off. This is probably to be expected, as the cable tension itself is still there, though the resistance is much improved.

Joint 1 should be re-homed every time you turn on the robot. Every time I turn on the robot, I click the “Home” button, or add the instruction to the program. For this reason, either home it on startup (you can add this to your program) or keep it on.

#5

Hello,

you can use some grease or oil to fix the problem with the rubbing noise, like described from bytemaster0.
The cable in the bottom of the casing doesn’t cause the rotation back of Joint 1. There is a spring inside the robot arm, which - I guess - preloads the motor of Joint 1. Some robots rotate very strong other not or only a little bit after switching off the robot. This is due to the mechanic and can’t be fixed.

Kind regards