An electronically controlled substrate working apparatus, such as a CNC controlled milling machine, drill press or lathe. The apparatus comprises a tool configured to remove material from the substrate, a spindle motor coupled to the tool, a feed motor configured to cause relative movement between the tool and the substrate along a feed path, a controller configured to control the spindle motor and the feed motor and a tool load measurement structure configured to provide a tool load value to the controller. The controller is configured to compare the load on the tool with stored or calculated first compliance values for a first location along the feed path and second compliance values for a second location along the feed path. The controller is further configured to cause the feed motor, the spindle motor or a combination thereof to take an action selected from a first set of response actions for the first location in the event that the load falls outside the first compliance values and to take an action selected from a second set of response actions for the second location in the event that the load falls outside the second compliance values. A method of operating the apparatus is also disclosed.

An electronically controlled substrate working apparatus, such as a CNC controlled milling machine, drill press or lathe. The apparatus comprises a tool configured to remove material from the substrate, a spindle motor coupled to the tool, a feed motor configured to cause relative movement between the tool and the substrate along a feed path, a controller configured to control the spindle motor and the feed motor and a tool load measurement structure configured to provide a tool load value to the controller. The controller is configured to compare the load on the tool with stored or calculated first compliance values for a first location along the feed path and second compliance values for a second location along the feed path. The controller is further configured to cause the feed motor, the spindle motor or a combination thereof to take an action selected from a first set of response actions for the first location in the event that the load falls outside the first compliance values and to take an action selected from a second set of response actions for the second location in the event that the load falls outside the second compliance values. A method of operating the apparatus is also disclosed.