Determine the relative position of the tool and the workpiece (Figure)

/ October 19, 2018

For CNC machines, it is important to determine the relative position of the tool to the workpiece at the beginning of the machining. This relative position is achieved by confirming the tool point. The tool point is the reference point that determines the relative position of the tool to the workpiece by tool setting. The tool point can be set on the machined part, or it can be set at a certain position on the fixture that has a certain size relationship with the part positioning reference. The tool point is often the machining origin of the part. The principle of selection of the tool point is as follows:

(1) The selected tool setting point should make the programming simple;
(2) The tool point should be selected in a position that is easy to find and easy to determine the origin of the part processing;
(3) The position of the tool point should be convenient and reliable during processing;
(4) The selection of the tool point should be beneficial to improve the machining accuracy.

1

Figure 1

For example, when machining the parts shown in Fig. 1, when the NC machining program is programmed according to the illustrated route, the intersection of the center line of the cylindrical positioning pin of the clamp positioning element and the positioning plane A is selected as the machining tool setting point. Obviously, the tooling point here is also the origin of processing.

When using the tool setting point to determine the machining origin, a "tool setting" is required. The so-called tool setting refers to the operation of overlapping the "tool point" and the "tool point". The radius and length of each tool are different. After the tool is mounted on the machine, the basic position of the tool should be set in the control system. “Tool location” refers to the positioning reference point of the tool. As shown in Fig. 2, the cutter point of the cylindrical milling cutter is the intersection of the tool center line and the bottom surface of the cutter; the cutter point of the ball end mill is the center point of the ball head; the cutter point of the turning tool is the tool tip or the knife The center of the pointed arc; the location of the bit of the drill is the apex of the drill. The tool setting method for all kinds of CNC machine tools is not exactly the same. This content will be discussed separately with various machine tools.

Tool position of the drill bit, cutter point of the turning tool, cutter point of the cylindrical milling cutter, the cutter point of the ball end mill
Figure 2 knife location

The tool change point is set for machine tools that use multiple knives for machining centers, CNC lathes, etc., because these machines are automatically changed during machining. For CNC milling machines with manual tool change, the corresponding tool change position should also be determined. To prevent damage to parts, tools or fixtures during tool change, the tool change points are often placed outside the contour of the part being machined, leaving a certain amount of safety.

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