CNC lathes usually perform a variety of cutting operations. The difference between the tool position of the previous tool and the position of the newly changed tool at the time of tool change will be different. There are also errors in tool installation, tool wear, and arc radius of the tool tip. If you do not use the tool compensation function to compensate, you will not be able to cut the part that meets the required shape of the pattern. In addition, the rational use of tool compensation also simplifies programming. Tool compensation for CNC lathes can be divided into two categories, namely tool position compensation and tool radius compensation. 1 Tool position compensation In the machining process, if multiple tools are used, the center position of the tool holder is usually taken as the programming origin, ie, the center of the tool holder is the starting point of the program, as shown in FIG. 1 , and the actual movement path of the tool is controlled by the tool position compensation value. As can be seen in Figure 1(a), tool position compensation includes tool geometry compensation values ​​and wear compensation values. Fig. 1 Tool position compensation Because there are two forms of offset, tool position compensation uses two methods. One method is to set the geometric compensation value and the wear compensation value to the storage unit to store the compensation value. The format is: Another method is to compensate the geometric offset and the wear offset together, as shown in (b). The format is: The total compensation value storage unit number has two functions. One function is to select the compensation value corresponding to the tool number and perform the tool position compensation function; the other is to cancel the position compensation when the memory unit number is 00, for example T0100, which means to eliminate + No. Tool current compensation value. Figure 2 shows the role of position compensation. The solid line in Figure 2 is the programmed trajectory of point A in the center of the tool post. The dashed line is the actual trajectory of point A at the time of performing position compensation. The azimuth of the actual trajectory and the compensation values ​​of X and Z axes Relevant, its procedure is: N010 G00 X10 Z-10 T0202; Figure 2 Tool position compensation CNC lathe system tool structure shown in Figure 3, P in Figure 3 is the imaginary tip, S is the arc center of the cutter head, r is the radius of the cutter head, A is the reference point of the tool holder. Figure 3 turning tool structure The control point of the lathe is the toolholder center, so tool position compensation is always required. Tool position compensation is used to convert between the tool nose circular arc center track and the toolholder reference point. It corresponds to the transition between A and S in Fig. 3, but actually we cannot directly measure the two center points. The distance vector, and only the distance between the imaginary tool nose! and the toolholder reference point $ is measured. For the sake of simplicity, it may be assumed that the cutter head radius r=0, and the tool length measuring device may be used to measure the coordinates of the imaginary cutter point P with respect to the toolholder reference point. In the formula: The coordinates of the imaginary tip P in the formula 2 Tool radius compensation When programming a machining program, the tool tip is generally regarded as a point. However, in practice, the tool tip has a circular arc. When cutting the inner hole, outer circle, and end face, the tool nose arc does not affect the machining size and shape, but When cutting cones and arcs, the tool's walking trajectory does not coincide with the programmed trajectory, and there is a difference. Fig. 4 shows the trajectory of the radius tool nose with and without radius compensation. As can be seen from the figure, when using the imaginary tool tip P programming, the tool center arc trajectory is shown by the two-dot chain line in Fig. 4. The actual tool trajectory of the tool and the contour shape of the workpiece require errors, error size and arc radius. r related. If the tool arc center programming and the radius compensation function are used, the trajectory of the center of the tool arc is a thin solid line in Fig. 4, and the machining trajectory is equal to the contour required by the workpiece. Fig. 4 Trajectory with radius compensation and without radius compensation Because of the more complex installation and geometry of turning tools, the following further elaborates on several aspects. 2.1 Assuming that the orientation of the tool nose P determines that the orientation of the tool nose P with respect to the center of the arc is related to the tool movement direction, it directly affects the calculation result of the tool compensation for the circular tool. Fig. 5 is the arc cutter's imaginary nose orientation and code. It can be seen from the figure that there are eight kinds of azimuths of the tool tip P, which are represented by 1~8 eight-digit codes respectively. It is also stipulated that when the tool tip takes the center position of the arc, the code is 0 or 9, which can be understood as no circle Arc compensation. Figure 5 Arc tool imaginary tool nose orientation and code 2.2 Arc radius compensation and position compensation If the tool center A is used as the programming starting point and arc radius compensation is not taken into account, then the tool's compensation values ​​in the X axis and Z axis are determined as shown in Figure 1(b). . It is necessary to consider the position compensation of the turning tool and the arc radius compensation. In this case, the position compensation value of the turning tool on the X axis and Z axis can be determined according to the method shown in FIG. 6, and the arc radius r of the tool can be added. In the corresponding storage unit, the numerical control device automatically performs arc radius compensation during processing. In the storage unit corresponding to the compensation number in the tool code T, a set of data is stored: the length compensation value of the X-axis Z-axis, the arc radius compensation value and the imaginary tool nose orientation (0 to 9). During operation, the four data of each tool can be input into the storage unit corresponding to the tool compensation number, and automatic compensation can be realized (Table 1). Figure 6 Arc Tool Position Compensation Table 1 tool compensation value 2.3 Automatic Compensation of Arc Radius Tool radius is compensated by G40, G41, G42 in G command. G40__; Elimination of compensation; Figure 7 Tool compensation process As can be seen from Fig. 7, in the initial block, the tool gradually adds the compensation value during the movement. When the initial block ends, the center of the arc of the tool stays on the vertical line of the programmed coordinate point. The distance is the radius compensation value. 3 Tool compensation calculation when CNC lathe does not have tool radius compensation function When CNC lathes do not have the function of tool radius compensation, when machining workpieces with round turning tools, the calculation method is used to solve the tool radius compensation amount. 3.1 According to the imaginary tool nose programming machining cone surface as shown in Figure 8, if the imaginary tool nose moves along the workpiece contour AB, ie Where: r is the radius of the tool arc; θ is the taper angle. 3.2 Programming an Arc Based on an Imaginary Tool Tip When turning an arc surface, the condition shown in Figure 9 will appear. Fig. 9(a) is a convex arc with a turning radius R. Because of the presence of P, the arc trajectory of the # point of the tool nose is not the arc shape required by the workpiece. Its center is " Fig. 9 Sketch map of circular arc cutter compensation 3.3 Programming by tool nose arc center trajectory The part shown in Fig. 10 is composed of three convex arcs and concave arcs. At this time, the three segmented equal distance lines shown in dotted lines can be used for programming. Fig. 10 Programming by center of tool nose arc 4 Conclusion The function of the tool compensation function mainly lies in the simplification of the program, ie programming according to the contour size of the part. Before processing, the operator measures the actual tool length, radius, and determines the sign of the compensation. It is used as a tool compensation parameter to input the CNC system. When the tool size parameter changes due to tool change or tool wear, the original program is used. Parts that meet the dimensional requirements can still be machined. In addition, the tool compensation function can also meet some special requirements for programming and machining processes. A spare part, spare, service part, repair part, or replacement part, is an interchangeable part that is kept in an inventory and used for the repair or replacement of failed units. Spare Parts are an important feature of logistics engineering and supply chain management, often comprising dedicated spare parts management systems. Spare Parts Cone Pulley Drive,Crane Spare Parts,Crawler Crane Parts,Flat Belt Drive Pulley FUWA HEAVY INDUSTRY CO.,LTD , https://www.fuwacraneparts.com
N020 G01 Z-30;
N030 X20 Z-40 T0200; 
with 
, and stored in the tool parameter table. 
——— imaginary tip P coordinate;
(X, Z) ——— Coordinates of toolholder reference point A.
It is very easy to write the tool position compensation calculation formula 
In fact, it is the coordinate of the track point of the machined part, which can be obtained from the NC machining program. At this point, after the part contour trajectory is compensated by Formula (2), it can be achieved by controlling the toolholder reference point A.
For the case of r≠0 in Fig. 3, in the tool position compensation, not only the compensation of the arc radius of the cutter head but also the installation method of the cutter must be taken into account (see 2.2). 
G40 -- Tool radius compensation is canceled, that is, after using this instruction, G41 and G42 commands are invalid.
G41————Tool radius compensation left, that is, tool radius compensation when the tool is located on the left side of the workpiece viewed in the tool movement direction.
G42———Right tool radius compensation, that is, the tool radius compensation when the tool is located on the right side of the workpiece viewed in the tool movement direction.
Figure 7 shows the tool compensation process using arc radius compensation.
The program format of the tool compensation in Figure 7 is:
G41__; radius compensation start program segment;
__; 
Coinciding with AB and programming according to AB size will inevitably produce ABCD residual error in Figure 8(a). Therefore, as shown in Fig. 8(b), the cutting point of the turning tool is moved to AB and moved along AB, so that the residual error can be avoided, but at this time the imaginary cutting edge trajectory is assumed. 
The difference in the Z direction from the contour is Δz. 
So you can directly follow the imaginary tip trajectory The coordinate values ​​are programmed to compensate Δz in the x and z directions. 
Figure 8 Cone Cutter Compensation 
The radius is “R+râ€. At this time, the programmer still performs the programming according to the imaginary tool nose P point, regardless of the influence of the tool nose arc radius, but it is required to give Z direction and X direction to the tool compensation value before machining. Add a compensation amount r. Similarly, when cutting a concave arc, as shown in Fig. 9(b), subtract a compensation amount r in the X direction and Z direction. 
Circle radius is 
Circle radius is 
Circle radius is The coordinates of the end points of the three arcs are obtained from the equidistant tangent point relationship. This method is more intuitive to program and is often used. 
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