JPS6236825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a main shaft transmission of an NC lathe.

Conventionally, NC lathes have generally used variable speed motors (DC or AC) as the spindle drive motors, but this has the disadvantage that the output decreases in the low speed range.

To solve this problem, a method has been adopted in which a transmission is inserted between the motor and the main shaft.

However, when using a transmission with multiple gears, it is necessary to select the optimal gear. With conventional NC lathes, this task is left to the operator, but this task is extremely time-consuming. It is troublesome and has the disadvantage that input errors are difficult to avoid.

Therefore, the present invention is designed to automatically select the optimum gear stage based on the processing information of the workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the structure of the present invention shown in the drawings will be described below.

First, an NC lathe is equipped with a computer consisting of an input device, a storage device, a calculation device, a control device, and an output device. Machining information, tool information, etc. are input through the input device, and the workpiece checked on the spindle is automatically processed. It is something to be processed.

The above machining information includes the shape of the workpiece (outer diameter milling, inner diameter milling, thread cutting, grooving, rough machining, rough finishing machining, finishing machining, etc.), dimensions (dimensions in the spindle direction and radial direction), and cutting conditions. (Cutting speed, depth of cut,
(whether the peripheral speed is constant or not) are input for each machining process.

As shown in Figure 1, the target NC lathe transmission has two gear stages, high and low, and each main shaft rotation speed range is M/g ₁ to M/g ₁ . It is assumed that the K high-speed stage is defined as M/g ₂ to M/g ₂ ·K.

However, M: Maximum motor rotation speed (rpm) g ₁ : Gear ratio of low gear
(Motor rotation speed/spindle rotation speed) g ₂ : High-speed stage 〃 〃 (However, g ₁ > g ₂ ) K: Ratio of the maximum and minimum rotation speed of the motor in the constant output range (minimum motor rotation speed = M /K).

Then, the NC calculation unit calculates the required rotational speed of the spindle necessary for machining from the input machining shape of the workpiece, radial dimension of the machining position, and cutting speed.

The procedure will be explained below using the flowchart shown in FIG.

First, in the process number initial setting step 1, the process number N is set to N=0, then in the process number setting step 2, the process number is set to N=N+1, and then, in the confirmation step 3, data is assigned to the process. If the answer is "NO", the end signal (RET) is sent, but normally it is "yes", so if "constant circumferential speed" is specified for the N process in confirmation step 4, the end signal (RET) will be sent. Confirm whether or not. In other words, when the machined shape is a tapered shape or an arc shape, if the spindle rotation speed is constant, the circumferential speed will change in proportion to the size of the radius, and in order to prevent the machining accuracy from changing in each part, For these shapes, the peripheral speed is specified to be constant.

If the answer is "yes" in the above confirmation step 4, the maximum value (r _nax ) and minimum value (r _nio ) are selected from the radial dimension of the N process in the selection step 5 and temporarily stored, and then the next confirmation step 6 is performed. If ``yes'' in the calculation step 7, r _nax and r _nio are calculated and stored as r _nax , r _nio =r _nax +r _nio /2, and the process moves to the next calculation step 8. Incidentally, if "NO" in the above confirmation step 6, the process immediately proceeds to calculation step 8.

In the above calculation step 8, the minimum rotation speed n _L (rpm) and maximum rotation speed n _H (rpm) of the N process are calculated and stored as n _L = 500V/π・r _nax n _H = 500V/π・r _nio , respectively. .

However, V: input peripheral speed (cutting speed) m/
min π: Pi Percentage Then, in confirmation step 9, it is confirmed whether the previous process, ie, the "N-1" process, is in the same group.

The above-mentioned same group means the same processing mode, and is divided into groups such as "outer diameter cutting,""inner diameter cutting,""frontcutting,""groovecutting," and "thread cutting," for example.

Note that if "NO" is determined in step 4 to confirm constant circumferential speed, that is, if constant circumferential speed is not specified for the N process, both n _L and n _H are input in setting step 10. Rotation speed n(r・
p.m) is set, and the process moves to confirmation step 9.

If “NO” in confirmation step 9, set the minimum rotation speed n _L in the same group in setting step 11.
(M) and the maximum rotation speed n _H (M), respectively, M _L
Set as (M)=n _L and n _H (M)=n _H.

However, if the answer is "yes" in confirmation step 9,
In confirmation step 12, the minimum rotation speed n _L (M) of the N process and the previous time in the same group is compared with the minimum rotation speed n _L of the N process, and n _L
If (M)>n _L is "yes", that is, the current n _L is smaller, then in the next setting step 13, n _L (M) = n
If _the answer is "NO", the setting step 13 is skipped and the process immediately proceeds to the next confirmation step 14.

In confirmation step 14, the maximum rotation speed n _H (M) up to the previous time in the same group as the N process is compared with the maximum rotation speed n _H of the N process,
If n _H (M)<n _H is "yes", that is, the current n _H is larger, then in the next setting step 15, n _H (M) =
_nH , and if "NO", skip setting step 15 and immediately proceed to the next pseudo process number setting step 16, and set N'=N.

Then, in the next confirmation step 17, it is confirmed whether the next process, that is, the (N'+1) process, is in the same group. If "yes", the process returns to the first process number setting step 2 and the same process is performed. Repeat the process.

That is, from step 2 to step 17, the maximum rotation speed n _H (M) and minimum rotation speed n _L (M) (in other words, the required rotation speed range of the spindle) within the same group are calculated. be. Therefore, in the process of calculating the maximum rotational speed _nH and minimum rotational speed _nL for each machining process, if the same group of processes is continuous, the above process is repeated.
As a result, the maximum rotation speed n _H for each group
(M) and the minimum rotation speed n _L (M) will be calculated.

When one group is completed, a determination of "NO" is issued in the confirmation step 17, and the process moves to the next mission selection step 18, where the requested rotation speed range n _H (M) to n _L
The optimum gear position for (M) is selected.

When the transmission speed of the group is selected in the mission selection step 18, the selected transmission speed is written in the N' step (i.e. N′-1) process (i.e. 1 of N process
It is confirmed whether the previous process) is in the same group.
If “yes”, in step 21 to set the process number.
N'=N'-1 is set, and the same number of mission stages is written in the previous process in step 19, and this is repeated for all the same group. That is, when processes in the same group are consecutive, the number of stages of the processes in the group is all set to be the same. The reason for this is that machining within the same group is often performed continuously, and in the case of a transmission that takes time to change gears when moving from one process to the next,
This is because the speed change operation may be delayed and machining accuracy may deteriorate.

When the writing of the number of mission stages for all the processes in the same group is completed, a "NO" determination will be made in the confirmation step 20, and in order to perform the same process again for the next group, the first process number will be written again. The process returns to setting step 2, and the above operations are repeated until all processes are completed. When all processes are completed, the process returns to the next process and confirmation step 3 is reached, and the data for the next process is displayed. No termination signal (RET)
appears and ends.

The above explanation is for the case where the required rotation speed range of the spindle is calculated for each group.
In the case of a transmission in which gear shifting operations are performed at high speed, the number of transmission stages can be selected each time depending on the required rotational speed range for each process.

Next, the procedure for selecting the number of mission stages in the mission selection step 18 will be explained with reference to the flowchart of FIG.

First, the maximum rotation speed n input in step 22
A comparison is made between _H (M) and the maximum spindle rotation speed M/g ₁ in the low speed gear (n _H (M)≦M/g ₁₎ , and if "yes", a low speed shift is performed in low speed instruction step 23. A row is selected.

If “NO” in step 22, proceed to step 24 to set the minimum rotation speed n _L (M) obtained earlier.
A comparison is made between n _L (M) < M/g ₂・K between the minimum spindle speed M/g ₂・K in the high speed gear, and if “yes”, a low speed gear is selected. If "NO", it is confirmed in a confirmation step 25 whether the machining of the group (or process) is finishing machining, and if "yes", a high speed gear is selected in a high speed instruction step 26. However, if “NO” is determined in the confirmation step 25, then in the comparison step 27, {n _H (M) − M/g ₁ }×C≦M/g ₁ −n _L (M
) is compared, and if ``yes'', a lower gear is selected, and if ``no'', a higher gear is selected. In the above formula, C is a high speed/low speed selection coefficient; when C is increased, priority is given to high speed gears, and when C is decreased, priority is given to low speed gears.

This means that if the machining of the group (or process) is not finishing but rough machining or rough finishing, the ratio at which the required spindle speed range overlaps with the speed range of the gear is higher than the predetermined value. In rough machining and rough finishing machining, even if the required rotation speed range is not satisfied in the high speed range, depending on the degree, it is better to rotate the spindle at a low speed. This is because the torque increases, which is preferable.

In short, in this embodiment, the transmission selection criteria are as follows: 1. Do not rotate faster than the input circumferential speed/rotation.

2. Use a constant output range as much as possible (give priority to low speed gears).

(3) When either is acceptable Rough cutting/rough finishing...output (torque) priority (low speed gear priority) Finishing...high speed priority (high speed gear priority) (4) Mission shifting is not performed within the same group. (For transmissions that take time to shift) The following four items are taken into consideration.

In response to a gear change command based on the gear position set in this manner, an appropriate actuator such as a hydraulic pressure, a motor, or an electromagnet is operated to automatically change the gear position of the transmission.

As explained above, the present invention is a method for controlling the spindle transmission of an NC lathe in which a transmission consisting of two stages, high and low, is inserted between the motor and the spindle. The rotation speed range is calculated based on the input machining information, and if the maximum value of this required rotation speed range is smaller than the main shaft rotation speed range of the low gear of the transmission, or the minimum value of the required rotation speed range is high. If it is smaller than the spindle rotation speed range of the stage, the low speed gear is set as the gear for the relevant machining, and the maximum value of the required rotation speed range is greater than the maximum value of the spindle rotation speed range of the low speed stage, and the required rotation speed range is If the minimum value is larger than the minimum value of the spindle rotation speed range of the high speed gear, and if a predetermined ratio or more of the required rotation speed range overlaps with the spindle rotation speed range of the low speed gear, the low gear will be used as the gear for the relevant machining. If the overlap is less than a predetermined value, the high speed gear is set as the gear for the machining process, so unlike variable speed motors, there is no problem of output drop in the low speed range. In addition, the optimal gear stage can be automatically selected based on the shape, dimensions, and cutting conditions of the workpiece, reducing the burden on the operator.
In addition, input errors can be prevented, and this type of method can exhibit excellent performance as a control method for the main spindle transmission of an NC lathe.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the high and low gear ratios of the present invention and the main shaft rotation speed, Fig. 2 is a flowchart showing a specific example of the control method of the present invention, and Fig. 3 is a FIG. 3 is a flowchart showing the procedure for selecting the mission shown in FIG.

Claims (1)

[Claims] 1. A method for controlling a spindle transmission of an NC lathe in which a transmission consisting of two high and low stages is inserted between a motor and a spindle, which method includes controlling the required rotation of the spindle when machining a workpiece. If the maximum value of this required rotation speed range is smaller than the main shaft rotation speed range of the low speed gear of the transmission, or the minimum value of the required rotation speed range is calculated based on the input machining information, If the spindle rotation speed is smaller than the spindle rotation speed range of If the value is larger than the minimum value of the spindle rotation speed range of the high speed gear, and if a predetermined ratio or more of the required rotation speed range overlaps with the spindle rotation speed range of the low gear gear, the low gear will be set as the gear for the relevant machining. However, if the overlap is less than a predetermined value, a high-speed gear is set as the gear for the machining process. 2. The spindle transmission control method for an NC lathe as described in paragraph 1, wherein the maximum value of the required rotation speed range is greater than the maximum value of the spindle rotation speed range of a low speed stage, and the minimum value of the required rotation speed range is high. If it is smaller than the minimum value of the spindle rotation speed range of the stage, it is further determined whether the machining is finishing machining, and if it is finishing machining, it is determined whether the required rotation speed range overlaps with the spindle rotation speed range of the low speed stage. 1. A method for controlling a spindle transmission of an NC lathe, characterized in that a high speed gear is set as a gear gear for the machining process regardless of the process.