Accurate Cutting, Sealing, Welding with your Robot

Robotic applications such waterjet cutting, laser cutting, applying a bead of sealant, arc-welding, etc. are generally ‘path-intensive’, in that such applications require the Robot’s TCP to accurately follow a specific path along a part (located on a fixture), and that such path is often formed by a series of points at a rather close distance from one another (depending on the path’s shape).

Such paths are typically good candidates for Off-Line Programming: the part, and the desired path along it, are typically well-defined in CAD, and the amount of points to program along such path would generally make their manual teaching on the plant floor very time-consuming. The desired robot programs are thus often generated through Simulation, after proper modeling of the robot-cell, and also include the necessary end-effector-related commands (e.g. when to start/stop the flow of sealant).

However, the level of precision typically required at the robot’s TCP for such applications makes it unlikely that the robot programs generated through Simulation will be accurate enough when executed on the robot controller ‘just like that’: Absolute Accuracy robot-cell calibration is required, with the DynaCal™ system (see “Absolute Accuracy Robot-Cell Calibration” and “Off-Line Programming with No Touchup”).

More specifically, the measurement point used for calibration purposes will be located right at the desired TCP, i.e. coinciding with the point of interest on the end-effector (generally some fixed distance away from the nozzle’s end of the waterjet tool, or the sealant tool, etc.): a dedicated tool with the proper dimension will temporarily be affixed to the end-effector. On the other end, the measurement equipment will be referenced to the fixture holding the part.

That way, the DynaCal calibration procedure will accurately determine in one step all of the important parameters forming the entire ‘metrological chain’ between the desired path along the part and the TCP, without the need for any other (potentially inaccurate) mathematical manipulation. Following the ‘Identification’ of the parameters of the complete robot-cell, the robot programs generated through Simulation will be ‘Filtered’ through the DynaCal software prior to being executed on the robot controller – with the necessary accuracy at the robot’s TCP!

It would of course be wise to maintain the level of Absolute Accuracy initially obtained with the DynaCal system throughout production. An ideal solution therefore in these kinds of applications is the AutoCal™ system (see “Maintain your Robot’s Accuracy throughout Production”). The end-effector’s nozzle can generally be used ‘as is’ (no need for some additional measurement artifact) to record the necessary measurements within the AutoCal’s measurement area.

By running the AutoCal system systematically in between production cycles (i.e. after each part run), any accuracy issue that might occur throughout production with the robot and/or its TCP will automatically be caught and corrected for prior to the next production run. In these kinds of robotic applications, the TCP in particular is likely to change over time, either because the end-effector’s nozzle gets ‘bumped’, or it needs replacement (after wearing out), etc.

Finally, these robot applications are potential candidates for robot-cell ‘Cloning’ in certain situations. After Off-Line Programming of the first arc-welding station, for example, an end-user might want to use the DynaCal robot-cell ‘Cloning’ functions for the duplication of that first robot-cell towards additional ‘identical’ ones. In fact, some customers might go as far as to set up a plant-wide data server, allowing robot programs created/modified in any of these ‘identical’ cells to be automatically ‘cloned’ towards all the other ones (see “Targeted Robot Communication Solutions”).

 

 

>Case Study>Integrated OLP process at JCI using DynaCal
>Case Study>No Manual touch up with DynaCal at Ford - Genk
Related Topics:
>Product>DynaCal
>Product>AutoCal
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