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1 Introduction Spiral cutters are cutting tools with a helical cutting edge, such as cylindrical milling cutters, end mills and spiral groove reamer. The sharpening of such tools is generally done manually by the process operator on the tool grinding machine by means of accessories. According to the spark, the grinding wheel is in contact with the teeth, and the amount of the backing knife is mastered by the hand feeling, and one tooth must be sharpened once. Therefore, the operator is required to be high, and it is difficult to ensure the quality of the sharpening, and the sharpening efficiency is not high. In this paper, the numerical control grinding method of helical tooth cutter is studied, and a small economical numerical control tool grinding machine is designed according to this, so that the numerical control sharpening problem of helical tooth cutter with unknown parameters can be solved.
2 CNC tool grinding machine transmission system CNC machine tool grinding machine mechanical part of the transmission system diagram, Y, Z axis for the table horizontal and vertical movement; X axis for the grinding head lifting movement; C axis for the tool (workpiece) rotary motion. The grinding head can be adjusted to rotate around the X axis by hand; the grinding wheel and the tool are tilted up and down; the tool gearbox rotates in the horizontal plane.
3 control system hardware structure control system hardware structure with single-chip 8031 ​​as CPU, through the lower 7 bits of P2 port and P0 port extended 32KBEPROM27256 to store the system program, the lower 3 bits of P2 port and the P0 port expand 2KBRAM6116 to store data, P2 port high Five bits are used for address decoding to gate LED display circuit, interface chip (8155, 8255), data memory (6116) and latch (273), P1 port is connected to stepper motor manual control circuit, stepper motor The drive pulse signal is sent from the P0 port output to the stepper motor driver via the latch (273); the 8255 PA port is connected to the system program start, pause button and working mode (parameter input mode, measurement mode, tool setting mode and automatic mode) ) Transfer switch, PB port is used for tool spiral tooth measurement signal and other auxiliary function signal input, PC port is used to output auxiliary function signal; 8155 PA port and PC port are respectively connected to keyboard row and column lines, PB port blade Grinding tool type selection switch.
4 helical tooth geometry parameter measurement CNC grinding, the need to determine the corresponding relationship between the tool axial feed and circumferential feed, due to the spiral angle of the helical tooth cutter and the guide are generally unknown, so in Before sharpening, the relevant parameters of the helical teeth need to be measured. To this end, the helical teeth are unfolded in a straight line. Set the axial feed length (including the length of the grinding l1, the length l2 of the cutting edge and the length l of the grinding) to l, then the corresponding circumferential feeding arc length (including the grinding arc length s1, the cutting edge arc length s2 and the grinding arc length) S3) is s0. To determine the arc length s, the geometric parameters of a spiral line can be measured first, and then the arc length can be obtained according to a similar triangle.
For this purpose, before the sharpening, a measuring head is mounted on the grinding head, and the measuring circuit of the measuring head and the tool form a closed loop. In the measurement mode, in the measurement mode, the manual function is used to first make the measuring head contact with the cutter teeth, and then the tool is moved or rotated linearly, and 1 or 2 of the movement track of the measuring head relative to the tool is automatically recorded by the control system. The tool linearly moves the step number Z1 and the number of rotation steps C1, and converts the feed length input from the operation panel to the stepping motor number Ze according to the pulse equivalent of the Z axis, and uses the measured geometric relationship of Z1 and C1. The number of rotation steps of the C-axis Ce is obtained, and (Ze, Ce) is the end point coordinate of the straight line, and the linear interpolation and the rotation of the tool are linearly interpolated by the two axes.
In order to prevent the measurement of the C-direction overtravel error (since the distance between the tooth and the measuring head is less than one pulse equivalent, the error is less than one pulse equivalent) affecting the accuracy of the spiral lead, on the one hand, the stepping motor should be reduced as much as possible. The arc length equivalent δ of each step of the tool. A stepping motor with a small step angle is used, and the δ value can be reduced with a small gear ratio when sharpening a larger diameter tool. On the other hand, increasing the Z-direction measurement length also reduces the effect of the C-direction overtravel error on the accuracy of the spiral lead.
5 Control system software The software adopts a modular structure, and the execution of the module depends on the mode switch state on the operation panel. After the main program of the system completes the setting of the I/O port and clears each data storage unit, it enters one of them according to the state of the mode switch. The main working methods are as follows:
(1) Parameter input method. According to the system prompt, input the number of teeth, the direction of the tooth, the length of the feed, the amount of sharpening, the number of feeds, the feed rate, the lower limit of the Z-axis and the C-axis, and the control parameters Z1min and C1min. .
(2) Measurement method. The measurement program flow utilizes the manual functions of the Z-axis and the C-axis to bring the teeth into contact with the measuring head and determine the starting point of the measurement. When measuring, the system determines the axial direction of the tool and the direction of circumferential feed according to the direction of the tooth rotation. When the measured value reaches or exceeds the preset Z1min and C1min, press the C key to turn the cutter to the measuring head. When the two are touched, the Z and C keys are pressed ineffective to avoid artificial overtravel error and damage measurement. The device then completes the calculation and returns to the main program.
(3) Tool setting method. When sharpening the front and rear flank, first turn the wheel frame dial so that the spark at the contact point is in line with the tangential direction of the point. Adjust the tool point in the manual mode. At this time, the system automatically records the tool movement from the starting point to the tool point. The number of steps is Z2, and then the mode switch is the tool setting mode. After starting the tool setting program, the system first takes out the internal recorded parameters Z1, C1 and Z2. According to the calculation, when the tool returns to the starting point, the tool rotates the number of steps C2, and finally (Z2, C2) as the starting point, the linear interpolation, the tool returns. To the starting point of the sharpening (0,0).
(4) Automatic mode. In the automatic sharpening program flow chart, i is the number of times of grinding each tooth; n is the number of teeth.
In the cycle, the teeth are internally looped, and the number of feeds is the outer loop, that is, each feed is once, and all the cutters are sharpened once, so that the cutter teeth are evenly deformed by heat, and the remaining amount of grinding is the same, and the sharpening knife can be guaranteed. The teeth are on the same circumference. When the number of steps is m with a decimal, it is rounded up and the decimal is added to the next step.
6 Conclusions (1) Using CNC cycle grinding, the effect of grinding temperature on sharpening accuracy can be reduced, the sharpening accuracy will be higher than manual sharpening, and the quality is stable.
(2) After measuring one time, all the teeth of one knife can be sharpened, and the sharpening efficiency and automation degree are high.
(3) Batch sharpening, no need to repeat measurement, just select the same clamping reference, the operation is simple and convenient.
(4) Only applicable to sharpening of unequal helical cutters.
Research on NC Sharpening System of NC Tool Spiral Tooth Tool
Based on the research of the NC sharpening method of the helical tooth cutter, the method of obtaining the geometric parameters of the helical cutting edge is proposed. The design and development of the hardware and software of the economical CNC tool grinding machine control system for sharpening the helical tooth cutter are carried out. The technology was introduced.