Tool setting principle and tool setting method of numerical control lathe

Tool setting is the main operation and important skill in NC machining. Under certain conditions, the precision of tool setting can determine the machining accuracy of parts, at the same time, the efficiency of tool setting also directly affects the efficiency of NC machining.

1．Why should tool setting?

Generally speaking, the NC programming of parts and machining of machine tools are performed separately. According to the design drawings of the parts, the NC programmer selects a convenient programming coordinate system and its origin, which we call the program coordinate system and the program origin. The program origin generally coincides with the process reference or design criteria of the parts, hence the workpiece origin.

The CNC lathe is energized, shall return to zero (reference point), its purpose is to establish the CNC lathe for position measurement, control, display the unified datum, this is the so-called machine origin, its position is determined by the machine tool position sensor. Since the machine tool goes back to zero, the position of the tool (tool point) is fixed from the origin of the machine tool. Therefore, the location of the tool point is regarded as the origin of the tool for the convenience of tool setting and machining.

The essence of the tool is the offset between the origin of the program and the origin of the machine, and sets the coordinates of the origin of the program in the coordinate of the machine tool with the tool point as the reference.

2. Try cutting tool presetting principle

There are many kinds of tool setting method, according to the accuracy of the knife can be divided into rough tool and precision tool; according to whether using tool can be divided into manual and automatic tool setting; according to whether the standard cutter, and can be divided into absolute and relative positioning tool. But no matter what kind of tool setting method is adopted, it is impossible to test the cutting tool, and the cutting tool is the most fundamental tool setting method.

The procedure for cutting and cutting tools is as follows:

In manual operation, use the selected tool to cut the outer circle of the workpiece in the machining margin, and then write down the X coordinate value in the display screen, which is denoted as Xa. (Note: the X coordinates of NC lathe display and programming are generally diameter values).

The tool along the Z direction back to the workpiece face a margin (assuming a dot) cutting end, record the Z coordinate display value, denoted as Za.

Measure the diameter of the outer circle of the workpiece after cutting, and mark it as phi.

If the program origin O is located at the intersection of the workpiece face (usually the end face that has been finished) and the center of rotation, the coordinates of the program origin O in the machine coordinate system are

Xo = Xa- phi (1)

Zo = Za

Note: the coordinate values in the formula are negative. Set the Xo and Zo into the CNC system, then complete the tool setting.

3. Program origin (workpiece origin) settings

In the FANUC CNC system, there are several ways to set the origin of the program:

Setting tool offset compensation;

Setting the starting point of tool with G50;

Setting the origin of program with G54~G59;

Set the origin of the program with the workpiece shift.

Program origin setting is an integral part of the tool setting. Each setting method has different programming modes, different application conditions and different work efficiency. Various settings can be used in combination.