Tool length compensation

The concept of tool length Tool length is a very important concept.

When we program a part, we must first specify the programming center of the part, and then we can set the part programming coordinate system. This coordinate system is simply the coordinate system of the workpiece, and the zero point is usually on the workpiece. Length compensation is only related to the Z coordinate. It is not like the programmed zero point in the X and Y planes. Because the tool is positioned by the taper hole of the spindle and does not change, the zero point of the Z coordinate is different. The length of each knife is different.

For example, we want to drill a hole with a depth of 50 mm, and then tap a hole with a depth of 45 mm using a drill with a length of 250 mm and a tap with a length of 350 mm. First, use the drill to drill a hole with a depth of 50 mm. At this time, the machine has set the zero point of the workpiece. When replacing a tap for thread cutting, if both tools start machining from the set zero point, the tap will be too long because it is longer than the drill, causing tool damage and artifacts. If tool compensation is set at this time, the length of the tap and drill will be compensated. After setting the machine zero point, even if the lengths of the tap and drill are different, due to the presence of compensation when calling during retraction work, the Z coordinate of the zero point automatically moves to Z+ (or Z) to compensate for the retraction length to ensure the correct machining zero point.

Tool length compensation work is achieved by executing commands containing G43 (G44) and H. This sets the Z coordinate value so that the tool moves to a distance of Z from the workpiece surface after compensation. Another G49 command cancels the G43(G44) command. Actually, we don’t need to use this command because each tool has its own length compensation. When changing tools, use the G43(G44)H command to set your own tool length compensation. The length compensation of the previous tool is automatically canceled.