Increase number of force control schedules

    $CCG_CONFIG.$CCSCHN is the variable you're looking for. Use controlled start to change. I have a controller with 60 schedules-no idea what the max allowed would be.


    I'm not sure on the other items though. A method other than copy/paste of other schedules and manually modifying them would be helpful.

    How many schedules do you need to set up? Because each fc schedule is associated with a specific user frame and many of the schedules involved the same processes, tweaking the user frames on the fly was necessary in my case. If you use fc relative to a tool frame you could do the same but modify the tool frames instead. I found that I could use a single schedule in multiple areas of a cell while writing new values to the user frame associated with that fc schedule. This reduced my total schedule count by a third or so. I found that different mechanical unit postures had quite an effect on how well the force control would work, even though the same parts were being handled and the same gravity comp was being used.

    The customer eventually plans to run a large variety of parts on this cell (30+), so they would like to dedicate a chunk of force control schedules to each part type.


    Would you be able to elaborate on how the mechanical unit postures effect how well the force control works? We've enabled gravity comp and have done the auto tuning, but are having some difficulties getting the robot to produce light forces (~5N or so).

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    My apologies if this gets long... The first application I set up with force control was an R-2000/165F picking and placing dried clay pieces (extremely fragile) that weigh approximately 10kg each. Why such a big robot? The reach of the R-2000 was required for this application while the robot was more than capable from a payload perspective.


    Each piece has to go into a rack to dry for a specified amount of time and face match is used to get the pieces set into one of 18 drying racks without breaking them. If the pieces drop more than 12mm when the gripper releases them, the odds of part breakage are high. The racks are arranged around the robot as three identical stacks of six positions for a total of 18. The highest rack position is about seven feet off the floor and and the lowest is around a foot.


    When the robot picks and places at some of the rack positions, J4 might be close to zero degrees with the J5 axis of rotation approximately parallel to the floor. Other positions might find J4 rotated around +/- 90 degrees. At the highest rack positions, J5 is at +/- 10 degrees while it is around 90 degrees at the lower rack positions.


    While getting the face match to work, I found the results were sporadic depending on which rack position was being tended. The mechanical unit posture and configuration were the only differences being that I was trying to use the same fc schedule and parts at each position. I talked to my favorite Fanuc sales engineer and he confirmed that posture can play a role in force control effectiveness.


    In hopes of solving the problem, I made 3 new user frames, one for each rack so I have 6 rack positions tied to one of 3 new user frames. The posture changes quite a bit from the top positions to the bottoms, but not enough to keep one schedule from working with one part on one rack. In other words, there is one schedule for part A on rack 1, a schedule for part B on rack 1, a separate schedule for part A on rack 2, etc. Each part uses its own gravity comp parameters based on which tool is on the end of arm and which part number is being processed. It took some fooling around to tweak the gain to work for all positions in a user frame but it works very well. Warped pieces aren't a problem either.


    Also, if you haven't already, be sure to find the steps to use auto gain tuning in the edocs as this allows the robot to figure out some rough tuning parameters on its own. Very cool to watch. It's available on contouring schedules and some others but not all, and it saved me a lot of time. Run it until you see the "no change" in the schedule. If it changes you'll see "parameters updated" or something similar. Be sure to follow the directions exactly. 5N shouldn't be too tough to achieve.


    Fanuc put some serious thought into the fc system and it allows for the automation of many processes that weren't previously possible.

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