Mg400 payload settings

#1

Hi

I’m trying to implement a glue dispense function alongside a pick and place function. We have a 3d printed adaptor that weighs approx. 30g, where the pick and place nozzle sits at 0mm and a ptfe syringe that fits in the end weighing a further 35g. The syringe is 100mm from the centre point (0mm) and ive currently set the payload at 40g, and the x offset to 40mm. This works fine for simulating the glue dispense part of the program, but when it runs in to the pick and place part of the program i get a very loud vibrating sound. I cant seem to figure out how to set the payload and x/y offsets correctly. Is there a formula to use that will help with this? When i simply input the actual weight of the end-effector and syringe and put an x offset of 100mm, which are all the actual parameters and then activate the Dobot, i immediately get the same loud vibrating sound like a fog horn.

Any help would be much appreciated

Thanks

Steve

#2

I have the same vibrations problem. The R-axis goes completely nuts as soon as I enable the robot. Strange this is that it used to work fine before :frowning:
Hoping you found a solution or dobot responds.

#3

I managed to stop it (more by luck than judgement) by adjusting the weight and “x” distance of the end effector in settings. It still whines ever so slightly, but is no longer losing control. I feel like there must be some way of calculating these values properly though, hopefully someone has a formula for this…

#4

Hi Steve,
thanks for the tip. It really had to do with the end loading. It is immensly important to get those values right when there is any problem to do with the R-axis.
I had so far had two issues:

  1. slow twitches with an eccentric end load
  2. super high frequency vibrations which made the robot sound terrible and uncomfortable

The R-axis seems to be equipped with a very aggressively tuned pid controller that counteracts any eccentricity. If the values provided by the user are incorrect (i.e. wrong weight and/or x,y distance of the centre of gravity from the axis) the robot tries to overcompensate.
i found that the slow twitches occur when the distance provided by the user is too small and the high frequency when the weight is too high). Obviously distance and weight are directly connected so always look at them in conjunction.

#5

As far as tips go for estimating: I used a CAD package to estimate the position of the centre of gravity away from the R-axis. Most of these packages are equipped with this functionality. Just use the model of your end load at 0 degree R and apply the density of the relevant materials to calculate the weight and position of the centre of gravity

#6

Thanks so much for these responses, both really helpful and ill be sure to apply what you’ve said and let you know if i have any joy.

All the best