Analysis on the processing application of NC machi

Analysis on the processing application of NC machine tool end milling cutter

machining workpiece with end milling cutter on NC machine tool, it can be clearly seen that the tool center motion gauge does not coincide with the workpiece contour, because the workpiece contour is formed by the motion envelope of end milling cutter

the center of the end milling cutter is called the tool position of the cutter (4 and 5 coordinate CNC machine tools are called the tool position vector), and the motion trajectory of the tool position represents the motion trajectory of the cutter. In numerical control machining, whether to program according to the outline size of the workpiece or the moving track size of the tool location should be handled according to the specific situation

in the full-function CNC machine tool, the CNC system has the function of tool compensation, which can be programmed according to the contour size of the workpiece. After the tool compensation is established and executed, the CNC system automatically calculates and the tool position is automatically adjusted to the tool motion path. Directly use the workpiece size to compile the processing program, the tool wear, change the processing program unchanged, so it is simple and convenient to use

economical CNC machine tools have simple structure and low price, and have a certain amount of ownership in manufacturing enterprises. In the economical CNC machine tool system, if there is no tool compensation function, the processing program can only be compiled according to the motion path size of the tool location, which requires that the external wall insulation material is pushed to the top of the wind and waves. First, calculate the path size of the tool location according to the workpiece outline size and tool diameter. Therefore, the calculation is large and complex, and the tool wear and replacement need to recalculate the trace size of the tool location and re compile the processing program

tool compensation in full function CNC machine tool system:

1 NC lathe tool compensation

NC lathe tool compensation function includes tool position compensation and tool arc radius compensation. Use the t function to specify in the machining program. The first two XX in t * * x are tool numbers, and the last two XX are tool compensation numbers, such as t0202 If the tool compensation number is 00, it means that the tool compensation is cancelled

(1) tool position compensation tool wear or tool position changes caused by reinstallation of the tool, after the establishment and implementation of tool position compensation, its processing program does not need to be re compiled. The method is to measure the position of each tool and input it into the specified memory. After the program executes the tool compensation command, the actual position of the tool will replace the original position

if there is no tool compensation, the tool moves from point 0 to point 1, and the corresponding program segment is n60g00c45x93t0200. If the tool compensation is x = 3, z = 4, and stored in the corresponding compensation memory, after performing tool compensation, the tool will move from point 0 to point 2 instead of point 1, and the corresponding program segment is n60g00x45z93t0202

(2) tool arc radius compensation when compiling the NC lathe processing program, the turning tool tip is regarded as a point (imaginary tool tip P point), but in fact, in order to improve the service life of the tool frugal tool and reduce the surface roughness of the workpiece, the turning tool tip is ground into an arc with a small radius (tool tip AB arc), which will inevitably produce the shape error of the workpiece. On the other hand, the position of the tool tip arc and the shape of the turning tool will also have an impact on the workpiece processing, which can be solved by tool arc radius compensation. The shape and position parameters of the turning tool are called the tool tip orientation, which is expressed by parameters 0 ~ 9, and point P is the theoretical tool tip

(3) tool compensation parameters each tool compensation number corresponds to a total of 4 parameters: tool position compensation (x and Z values) and tool arc radius compensation (R and T values), which are input into the corresponding memory and displayed on CRT before machining. In the process of automatic execution, the CNC system automatically corrects the position error of the tool and automatically compensates the arc radius of the tool tip according to the values of X, Z, R and T in the memory

2. Machining center, NC milling machine tool compensation

NC system of machining center and NC milling machine, tool compensation functions include tool radius compensation, included angle compensation, length compensation and other tool compensation functions

(1) tool radius compensation (G41, G42, G40) the radius value of the tool is stored in memory hxx in advance, and XX is the memory number. After the tool radius compensation is performed, the CNC system automatically calculates and makes the tool automatically compensate according to the calculation results. Tool radius left compensation (G41) refers to the left side of the tool's deviation from the movement direction of the programmed machining path, and tool radius right compensation (G42) refers to the right side of the tool's deviation from the movement direction of the programmed machining path, which is the area surrounded by the stress-strain curve to the specified strain. G40 is used to cancel tool radius compensation, and H00 is also used to cancel tool radius compensation

note in use: when establishing and canceling tool compensation, that is, the program segment using G41, G42, G40 instructions must use G00 or G01 instructions, and G02 or G03 must not be used. When the tool radius compensation takes a negative value, the functions of G41 and G42 are interchanged

tool radius compensation has two compensation forms: B function and C function. Because the B-function tool radius compensation is only calculated according to the program of this section, it can not solve the transition problem between program sections, and it is required to treat the workpiece contour as fillet transition, so the processability of the sharp corner of the workpiece is not good. The C-function tool radius compensation can automatically process the transfer of the tool center path of the two program sections, and can be programmed completely according to the workpiece contour. Therefore, almost all modern CNC machine tools use C-function tool radius compensation. At this time, it is required that the next two program segments that establish the tool radius compensation program segment must have the displacement instructions (G00, G01, G02, G03, etc.) that specify the compensation plane, otherwise the correct tool compensation cannot be established

(2) included angle compensation (g39) the intersection of two planes is an included angle, which may cause over travel and over cutting, resulting in machining errors, which can be solved by included angle compensation (g39). When using the included angle compensation (g39) command, it should be noted that this command is non modal and can only be used after G41 and G42 commands. The experimental torque and change angle are effectively displayed in the program segment of the command

(3) tool length offset (G43, g44, G49) using the tool length offset (G43, g44) command, the change of tool length can be compensated at any time without changing the program, and the compensation amount is stored in the memory of the H code command. G43 indicates that the compensation amount in the memory is added to the end coordinate value of the program instruction, g44 indicates subtraction, and G49 instruction or H00 instruction can be used to cancel the tool length offset. In program segment n80g43z56h05 and, if the median value of 05 memory is 16, it means that the end-point coordinate value is 72mm

the value of the compensation amount in the memory can be pre stored in the memory with MDI or DPL, or the program segment instruction g10p05r16.0 can be used to indicate that the compensation amount in the memory No. 05 is 16mm

calculation of tool path in economic NC machine tools:

Economic NC machine tool system, if there is no tool compensation command, can only calculate the motion path size of the tool location, and then program according to this, or carry out local compensation processing