JPH04360744A - Breakage prevention method of feed shaft bearing - Google Patents

Abstract

PURPOSE:To prevent breakage of a bearing due to thermal expansion of a feed shaft at a cheap price by obtaining the average speed of every shaft based on an accumulated moved distance during a decided time at every unit time, comparing it with the previously set safety speed and critical speed of a feed bearing, and correcting an override correcting ratio so that the speed is in the safety speed range. CONSTITUTION:The average speed of every shaft is obtained with a computing part 4 based on an accumulated moved distance in a decided time at every unit time. Next, the previously set safety speed and critical speed are compared with this obtained average speed in a speed judging part 5, and when the average speed is over the safety speed, an override ratio is corrected to make the speed not to be over the safety speed. If the average speed is over the critical speed, operation is stopped for alarm. Hereby, breakage of the bearing due to thermal expansion of the feed shaft is prevented at a low cost.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing damage to a bearing of a feed screw of an NC-controlled moving shaft due to thermal expansion.

0002

[Prior Art] Conventionally, as shown in FIG. 5, the feed axis control mechanism of an NC is roughly divided into three parts: a program analysis section 101, a function generation section 102, and an axis drive section 103. Multiply the feed amount per unit time (feed unit amount) determined according to the feed rate by the override ratio to obtain the actual feed unit amount, and distribute this to each axis component of each axis (X, Y, Z) of the program command. A function is generated based on the unit movement amount for each axis determined by
3 to process one unit of time and control the speed of the feed axis.

0003

[Problems to be Solved by the Invention] In the feed axis speed control method described in the prior art, the actual feed speed is determined by the speed command of the program and the override ratio set on the operation panel. If high-speed feeding is continued, there is a problem in that the bearing may be damaged due to thermal expansion of the feed screw. The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to monitor the actual feed speed and forcibly correct the override when the safe speed is exceeded. The purpose of the present invention is to provide a method for preventing damage to bearings.

0004

[Means for Solving the Problems] In order to achieve the above object, the method for preventing damage to a feed shaft bearing in the present invention involves determining the average speed of each shaft based on the travel distance accumulated over a certain period of time for each unit time. , Compare the average speed with a preset critical speed and safe speed for each axis, and when the average speed exceeds the critical speed, an alarm is stopped, and when the average speed exceeds the safe speed, an override ratio is set. This is to correct the above-mentioned safe speed so as not to exceed it.

[0005]

[Operation] The average speed of each axis determined based on the travel distance over a certain period of time accumulated for each NC specified unit time (sampling time) is calculated as the safe speed and critical speed of the feed shaft bearing that is set and stored in advance. By comparison, the override ratio is corrected so that the average speed does not exceed the safe speed, and in the event that the average speed exceeds the dangerous speed, an alarm is stopped.

[0006]

[Embodiment] An embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a block diagram of the circuit of this embodiment, in which the program analysis section 1 is the section that interprets the input program and outputs signals to the necessary parts, and the function generation section 2 is the section that interprets the input program and outputs signals to the necessary parts. Override ratio V to unit amount ΔF
Further, the override is corrected using the override correction ratio R sent from the override correction value determination unit 7, which will be described later, to obtain the actual feed unit amount ΔFV, and the command movement amount X, Y of each axis input in the program is calculated. , Z, the unit movement amount ΔX, ΔY, ΔZ for each axis is calculated by the following formula:
The axis movement shaft unit 3 is a unit that generates a function based on the determined unit movement amount, and drives each axis by a signal from the function generation unit 2.

[Math 1]

The average speed calculation unit 4 calculates unit movement amounts ΔX, ΔY, and
The average speed LMX, LMY of each axis is obtained by accumulating ΔZ for a certain period of time.
, LMZ, the speed determination section 5 calculates the safe speeds Lsx, LsY stored in advance in the safe speed/dangerous speed storage section 6.
, Lsz and critical speeds LDX, LDY, LDZ, and average speeds LMX, LM sent from the average speed calculation section 4.
A part that compares Y and LMZ and outputs a signal that causes the average speed to go below the safe speed when it exceeds the safe speed, and outputs a stop signal when the average speed exceeds the dangerous speed, and an override correction value determining part. Reference numeral 7 denotes a section that outputs an override correction ratio R based on a signal sent from the speed determining section 5 that causes the speed to become below the safe speed.

Next, the operation of this embodiment will be explained. First, the function generation process performed at sampling time intervals of, for example, approximately 1/30 seconds will be explained in the order of the flowchart in FIG. 2. In step S1, the feed unit amount (
In step S2, ΔF is multiplied by the override ratio V to obtain the feed unit amount ΔFV, which is multiplied by the override ratio V set on the operation panel. In step S3, the calculated feed is further calculated. The actual feed unit amount ΔFV is determined by multiplying the unit amount ΔFV by the override correction ratio R obtained by the feed axis protection subroutine described later.

Next, in step S4, the axial components ΔX, ΔY, and ΔZ of the movement unit vector, ΔFV, are determined using the movement amount of each axis X, Y, and Z according to the program command, and in step S5, the feed axis protection subroutine to be described later is executed. Execute. In step S6, a function is generated for each axis,
In step S7, the function is output to the shaft drive section 3.

Next, the feed axis protection subroutine of step S5, which is executed every time a function is generated, will be explained in the order of the flowcharts shown in FIGS. 3 and 4. In step S5-1, it is confirmed whether the counter C has been reset. If YES, the override correction ratio R is set to 1 in step S5-2. In step S5-3, variables LMX, LMY, and LMZ for accumulating the movement amount of each axis are all set to zero, and in step S5-4, the count C is set to zero.
is set to zero, and the first round of cumulative movement of each axis ends. However, no override modification is performed at this stage.

In the next unit time, step S5-1 becomes NO because it is the second time, and in step S5-5, the count C is incremented by 1, and in step S5-6, the function generator 2 calculates the axis component of the movement unit vector ΔFVi. ΔXi, Δ
Yi, ΔZi are read, and in step S5-7,
The cumulative value is updated by adding the currently read ΔXi to the previously stored LMX. Thereafter, the cumulative numerical values of LMY and LMZ are updated in the same way. Next, in step S5-8,
It is checked whether the count C has reached the count up Co, and if no, the process ends. Even at this stage, override correction is not yet performed.

The number of times the axis component of the moving unit vector is integrated each time this function is generated is 1800 times, for example, assuming that the time for counting up is one minute. If it reaches 1800 times and the answer is YES in step S5-8, then in step S5-9 the integrated variable LMX on the It is confirmed whether the speed is higher than the critical speed LDX.

[0013] If no, step S5-10
In step S5-11, it is checked again whether LMY on the Y axis is greater than the critical speed LDY, and if the answer is no, it is checked again in step S5-11 whether LMZ is greater than LDZ.
In the case of no, the process moves to the flowchart of FIG. Further, if the answer is YES in any one of steps S5-9 to S5-11, an alarm signal is outputted and feeding is stopped in step S5-12.

Next, moving to the flowchart of FIG. 4, in step S5-13, the average feed speed LMX/R converted to the value before override correction guarantees the safety of the bearings of each axis, which has been determined in advance through experiments etc. L expressed as the distance traveled while counting up the safe speed that represents the upper limit of
It is checked whether it is larger than SX, and if yes, in step S5-14, the calculation Rx = R・(LSX/L
MX), the X-axis override correction ratio Rx that does not exceed the safe speed LSX is determined, and in step S5-15, the override mantissa RT is made the same as the determined Rx.

[0015] Next, in step S5-16, LMY
It is checked whether /R is larger than the safe speed LSY, and if yes, the calculation RY = R is performed in step S5-17.
・(LSY/LMY) determines the Y-axis override correction ratio RY that does not exceed the safe speed LSY. In step S5-18, it is checked whether the obtained RY is the same as or larger than the override mantissa RT.

[0016] If yes, step S5-1
In step S9, it is confirmed whether LMZ/R is larger than LSZ, and if yes, in step S5-20, the safe speed LSZ is determined by the calculation Rz=R・(LSZ/LMZ).
The Z-axis override correction ratio RZ that does not exceed is determined. Next, in step S5-21, the obtained RZ
It is checked whether RT is the same as or greater than RT, and if yes, RT is set as the final override correction ratio R in step S5-22.

When the final override correction ratio R is determined in this way, the value of R in step S3 described above is rewritten and calculation is performed using the new override correction ratio R. Therefore, it is rewritten every minute, for example, when R is counted up, and the rewritten R continues to be used until the next time it is counted up.

If the answer is NO in step S5-13, the X-axis override correction ratio Rx is set to 1 in step S5-23, and step S5-23 sets the X-axis override correction ratio Rx to 1.
15, RT = Rx, that is, the override mantissa RT becomes 1. If the answer is NO in step S5-16, RY is set to 1 in step S5-24, and if the answer is no in step S5-18, the override mantissa is set to 1 in step S5-25. RT becomes 1.

Furthermore, if the answer is NO in step S5-19, Rz is set to 1 in step S5-26.
If the answer is NO in step S5-21, RT is set to 1 in step S5-27,
In step S5-22, the final override correction ratio R becomes equal to RT, that is, 1. In this way, when the override correction ratio R becomes 1, as a result, step S3
The override correction in is not performed, and the actual feed unit amount ΔFV is multiplied only by the override ratio V set on the operation panel.

[0020]

[Effects of the Invention] Since the present invention is constructed as described above, it achieves the following effects. The average speed of each axis is calculated based on the travel distance over a certain period of time accumulated for each unit time, and this is compared with the preset safe speed and critical speed of the feed shaft bearing, and the override is performed to keep it within the safe speed. Since the correction ratio is modified so that the feed is stopped in the event that the critical speed is exceeded, damage to the bearing due to thermal expansion of the feed shaft can be prevented at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a circuit of this embodiment.

FIG. 2 is a flowchart for explaining the operation of this embodiment.

FIG. 3 is a flowchart diagram for explaining the operation of this embodiment.

FIG. 4 is a flowchart for explaining the operation of this embodiment.

FIG. 5 is a block diagram representing a prior art circuit.

[Explanation of symbols]

4 Average speed calculation section 5 Speed judgment section 6 Safe speed/dangerous speed memory section 7 Override correction value determination section

Claims (1)

[Claims] Claim 1: Obtain the average speed for each axis based on the travel distance accumulated over a certain period of time for each unit time, and compare the average speed with a preset dangerous speed and safe speed for each axis to determine the average speed. A method for preventing damage to a feed shaft bearing, characterized in that an alarm is stopped when the speed exceeds the critical speed, and an override ratio is corrected when the average speed exceeds the safe speed so as not to exceed the safe speed. Method.