Tool calibration for cnc machine

Tool calibration

Tool calibration consists of lowering a tool until its bottom reaches a fixed reference point and then having the CNC memorize the Z-coordinate. This reference point must be the same for all tools used to make a specific part. Since no universal vertical reference point has been setup on the mill one has to be improvised. Often a flat surface on the part being machined is selected. This surface then becomes the point defining Z=0.

Here are practical pointers:

• Turn on the spindle during the calibration process. In this way, should the tool be accidentally driven into the workpiece it will hopefully machine away the material and pose a lesser risk of damaging the tool or the machine.
• Step in the Z-direction with low speed. (Practice manipulating the tool with the tool away from objects so as to avoid collisions. Lower the table if necessary to create clearance.)
• Control step size using the jog control and use smaller discrete steps when nearing the reference surface.
• The tool height is noted when the tool just scratches the reference surface.