How to ensure robot constant speed during data matrix printing?

    Gents, I have a project with data matrix code printing using a robot.

    Robot will have a dedicated printer in the wrist and should move to the strictly defined positions (+/- 1mm) and when moving with constant speed send the signal to the printer to start printing. Robot speed during printing should be within the range: 5-30m/min.

    Everything would be fine, but there is a problem how to ensure the position where to print (send the signal in the proper place) and also being sure that the speed is constant and with the defined range?

    I could jog the robot eg. 100mm before the printing position, then move linear to printing start point, but how to be sure I have a defined speed eg. 500mm/s? How do I know that robot has finished its acceleration and has the defined speed?

    Have you meet any application like this? Any ideas how to solve it?

    Thanks a lot for help.

    Is the speed of the print head adjustable?

    ReaJet printers, for example, use an encoder wheel that rides along the surface being printed on, and the print head adjusts to that speed in real time.

    If you can program your print head to print at a different "feed rate," based on inputs from the robot, you could perhaps print at lower speeds in those areas where you can't get enough ramp-up distance.

    If your print head can only work with one "feed rate," you're a bit stuck -- the slowest, worst-case position is going to determine the print speed you can use anywhere in this application -- a chain is only as string as its weakest link.

    The acceleration a robot can manage is so dependent on payload, pose, and other variables, unless you want to invest in pretty expensive simulation time, trial-and-error with your actual robot and end effector is your best bet to determine your ramp-up distance.

    If you use a U-shaped path with some small CNTs on the corners, you might be able to put part of your ramp-up into the "approach" and "depart" legs of the "U". But that would be another trial-and-error process.

    Quote from SkyeFire

    Is the speed of the print head adjustable?

    ReaJet printers, for example, use an encoder wheel that rides along the surface being printed on, and the print head adjusts to that speed in real time.

    If you can program your print head to print at a different "feed rate," based on inputs from the robot, you could perhaps print at lower speeds in those areas where you can't get enough ramp-up distance.

    Yep... the printer doesn't have any encoder. I'd check how do they program the speed, because anyway it's constant, somehow it needs to be set what it is in order to make a good print. But it doesn't solve my problem at all.. so tests, tests and tests to adjust it :-((((

    The worse thing is the customer want's to have a receipe in HMI, where he could add new details himself, so it means also different printing positions... :loudly_crying_face:

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