What is the function of a 'dry run' in CNC machining, and what potential problems can it help identify before machining a workpiece?

The function of a 'dry run' in CNC machining is to simulate the execution of a CNC program without actually cutting any material. During a dry run, the machine moves through the programmed toolpath, but the spindle does not rotate, and the cutting tool does not engage the workpiece. This allows the operator to verify the program's correctness and identify potential problems before risking damage to the machine, the tool, or the workpiece. A dry run can help identify several potential problems. First, it can reveal programming errors. These errors could include incorrect coordinates, incorrect toolpaths, or incorrect use of G-codes and M-codes. Second, it can detect collisions. The dry run allows the operator to visually check for any potential collisions between the cutting tool, the toolholder, the workpiece, the fixture, or any other machine components. Third, it can verify toolpath clearance. The dry run ensures that the toolpath has adequate clearance around the workpiece and the fixture, preventing the tool from running into any obstructions. Fourth, it can confirm machine limits. The dry run ensures that the program does not command the machine axes to move beyond their physical limits, which could damage the machine. Fifth, it can validate the work coordinate system (WCS). The dry run verifies that the WCS is correctly set and that the program is using the correct coordinate system. Most CNC controls have a dry run mode that can be activated from the control panel. In this mode, the machine typically moves at a reduced speed, allowing the operator to closely monitor the toolpath and identify any potential problems. Adjustments to the program or machine setup can be made as needed before running the program for real.