Control Solution for Laser Cutting (Jan. 2016)
ACS controller shows superior performance over a competitor’s controller
The application which used the ACS controller is a glass cutting machine.
An XY stage is used to move a piece of glass under a laser, which was positioned using a Z and a tilt motor.
The laser cut the glass in the pattern traced by the XY stage.
The customer had a competitive controller which was being used to command motion on their stage. They were using a test program as a metric in order to evaluate the performance results of the ACS option compared to their current controller. The test program involved tracing a rounded rectangular path in XY at various velocities. They used their laser to put down dots on a test piece of glass showing the motion path of the controller. By adjusting the focus of the beam, multiple trials could be run at different velocities on the same piece of glass. With the current controller, they were seeing a large change in the corner radius as a function of velocity. Specifically, they saw that as the velocity increased the corners began to appear more and more linear, making what eventually appeared as a line segment to the 45o point in the arc and another line off of that to the end of the arc segment. This was not acceptable for their application as they needed a uniform path independent of velocity
Due to limited time onsite, it was decided that only the XY stage would be controlled in this demonstration. To control this XY stage, an MC4U was chosen. This MC4U was running firmware 2.27 in order to take advantage of the new enhanced automatic corner and curvature discontinuity points processing feature available in our extended segmented motion (XSEG) command. This new feature of XSEG is a standard option available to any unit running firmware 2.27.
ACS’ application support was onsite to implement the proposed solution. The total work involved setting up the MC4U and connecting adaptor cables to take the existing controller inputs into the ACS drive, tuning these motors for optimal performance, and writing a brief buffer program to implement the motion path of the test metric. The total time spent onsite to implement and test this solution was one and a half working days. The motors were set up and tuned using the Adjuster Wizard and FRF Analyzer. The customer then provided the specifications for the path to be followed. It entailed the rounded rectangle which was their required path, along with a grid to put down to be used as a reference when inspecting the results under a microscope. The rounded rectangle was handled using XSEG/y, LINE, and ARC1 commands. The reference grid was then commanded using PTP moves. All LINE moves were done at a constant velocity of 400 mm/s, while the corner velocities were varied. In order to accommodate the change in velocity, the LINE/F switch was used in order to have the line segments finish at the corner velocity. Tests were done with corner velocities ranging from 20 mm/s up to 700 mm/s. The corners were all 90o with a radius of 8mm.
The competitive advantage gained
Using the ACS XSEG motion to carry out the test path showed far superior performance to the competitor controller’s results. At the worst case, moving with a corner velocity of 700 mm/s, the peak following error in the path was 3.16 microns. When moving at the slowest velocity tested, 20 mm/s, the peak following error was 2.08 microns, showing that the ACS controller is able to achieve a path which varies approximately a micron as velocity is increased. While exact numbers were not provided, the competitor controller showed a following error on the order of tens of microns when executing the same path. The ACS controller also did not exhibit any of the linearization in the corners seen with the other controller.
This performance advantage will allow the customer’s machine to operate at much greater velocities without worry of unwanted changes in the cut of the part, increasing the possible throughput of their machine. Overall the ACS controller showed a clear performance advantage when executing the customer’s test path.
“Unbelievable performance advantage! Your controller was VASTLY superior to the (Competitors Motion Controller). Thanks very much for letting us test it. Drew did a great job and we ran a tool path sample program we had used with the (Competitors Motion Controller) to show the problems we had. So not just following error plots – we made and measured parts under a microscope……”
Sr. System Engineer
Laser Microprocessing OEM