Why is it critical to accurately determine and input tool length offsets in CNC machining?

Accurately determining and inputting tool length offsets in CNC machining is critical because these offsets define the distance between a reference point on the machine (typically the spindle face or machine zero) and the tip of the cutting tool. Without accurate tool length offsets, the CNC control system cannot accurately position the tool relative to the workpiece. Incorrect tool length offsets will lead to inaccurate machining, resulting in parts that are the wrong size, shape, or depth. For example, if the tool length offset is too short, the tool will not cut deep enough, leading to features that are shallower than specified. Conversely, if the tool length offset is too long, the tool will cut too deep, potentially damaging the workpiece or the machine. Furthermore, accurate tool length offsets are essential for tool changes. During a tool change, the CNC control system uses the tool length offsets to compensate for the differences in length between different tools. This allows the machine to automatically adjust the tool position so that the new tool is positioned correctly relative to the workpiece. If the tool length offsets are not accurate, the tool change will result in a sudden and unexpected change in the tool's position, potentially causing a crash. The tool length offset is determined by using a tool presetter, an electronic edge finder, or by touching off on a known surface of the machine or workpiece. The measured value is then entered into the CNC control's tool offset table, where it is stored for future use.