Path Programming and Force Mode

Tyler_Berryman 2016-08-25

We received an interesting question from @NicoHanstein who is experimenting with the path recording for deburring with their spindles.

After programming path, we would like to tell the system to follow the path with a specific (preset) force.

With our spindle we can adjust the force to e.g. 5 Newton with a certain air pressure.

That means, the spindle will not deflect/move to the side before you do not exceed a force to spindle higher than 5N.

However very often the force of 5N can be too strong. In this case it would be good to tell the system/software to apply a maximum force of e.g. 2 Newton.

Is this possible with the system?

The reason for this is that our spindles have limitation when it comes to very low forces against a work piece. Depending on the size and weight of a spindle, we need a certain air pressure to position / center it in the middle. This necessary air pressure results in a minimum force of deflection. With a bigger spindle it can be easily 6 – 8 N.

Alexandre_Pare 2016-08-19

@NicoHanstein I have seen people working on this kind of application before and the first issue you may want to look at is the variation of the force signal caused by the spindle rotation. 2N measurement is quite low and I am wondering how the signal fluctuates when you turn on the spindle. The best way to do this is to unplug the sensor for the Universal Robot controller and plug it in to the a PC. You can then use the FT150/300 sensor demo package (on our Robotiq Support Website) on your computer to graphically show force data on the PC. You can then get a screen recording device to save these in video format. The tests that you can do would be to have the robot just stand there and just start the spindle. In this case the spindle won't be loaded with any external forces so you will see the impact of only the spindle rotation on the signal. Then you can run your path and check the force graph data to see how the signal varies. Don't forget to record the path before unplugging the sensor from the UR!!!

I would be curious to see how the signal fluctuates and if we can get a 2N accuracy without too much disturbances caused by spindle rotation!

NicoHanstein 2016-08-22

@Alexandre_PareThank you for the instruction, I will take a video of the sensor data on wednesday and send it to you. I already took a short look at the variables in the sensor_data demo and there was no big difference to recognize apart from when the spindle initially started.

I have another question regarding the path programming: Since I need to unplug the sensors for the UR controller, do the FT300 sensors not send data to the robot while running a path? Are the sensors only required for recording paths via active drive?

Alexandre_Pare 2016-08-22

@NicoHanstein
The sensor can be unplug from the robot once the path has been recorded. No sensor data is used when the robot is running the path. However, you won't be able to modify path properties in the interface when the sensor is unplug. So you won't be able to adjust speed of the path, reverse it and so on. I will wait and see the data variation before making further recommendations!