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76 MMS April 2017 mmsonline.com FEATURE accuracy. Therefore, shops using high-speed c o a t e d w i r e m i g h t c o n s i d e r a n a l t e r n a t e probing method. For instance, Makino offers a manually loaded, touch-trigger probing system option for its wire EDM equipment consisting of a Renishaw MP250 probe and Erowa ITS air chuck. This system installs on the side of the machine's upper head, but is designed so the centerline of the probe is located at the centerline of the wire. That way, probing can be per formed within the entire available machine stroke. Probing accuracy using this method is ±1 micron. The touch-trigger probe is also valuable in that it can be used to touch off the top or the sides of a part to establish a Z-axis plane. By probing three points on the top of a part, three points on one side and two points on another side, the zero point on a corner can be established, the machine's U and V axes can be adjusted so the wire is normal to the workpiece surface, and the work coordinate system can be reset per the true location of the fixtured part. This is especially helpful for very large parts such as mold blocks that can be chal- lenging to level and position accurately using shims and other methods in an effort to precisely align the part to match the machine's native work coordinate system. This probing method is also necessary when wire-machining polycrystalline diamond (PCD) inserts brazed onto cutting tool bodies. Using a machine's wire as the probe isn't possible given the small area on the insert land available to align the insert in the linear X and Y and rotational C axes. Touch-trigger probing of a few points on the insert is required to establish the location of the insert land in the locked C-axis position before wire-machining the proper rake angle. Although touch-trigger probing systems offer high accuracy and might be necessary in cases such as PCD insert machining, they are pricey machine options. As a result, Mr. Pfluger says Makino has developed an alternate, lower-cost, albeit more manual means of probing called 3D Plane Find that instead uses a common dial indi- cator that most shops will already have to perform 3D part leveling to adjust the U and V axes per- pendicular to the workpiece surface. Users install the dial indicator in the machine's upper head and use it to find the location of three points on the workpiece surface just as the touch- trigger probe would. To do this, the setup person positions the indicator at one point, zeros the indicator and clicks a "get position" button on the machine's control to record that point location. The dial indicator is then moved to a second point on the part surface, the setup person adjusts the head's Z axis until the dial indicator goes back to zero, and that location is similarly recorded. After repeating this for the third point, the part surface plane is established after clicking a "compute angle" button on the control. The wire U and V This touch-trigger prob- ing system installed on a wire EDM unit can easily perform 3D part leveling to adjust the wire U and V axes perpendicular to the workpiece surface.