JP2000267718A - Inter-block speed control method for numerical controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an inter-block stop state without increasing the total machining time via a smooth speed reduction operation among a series of continuous machining operations by comparing an allowable speed with the feeding speed of a block and clamping the feeding speed of the block to the allowable speed when the former speed is higher than the latter speed. SOLUTION: The length, the feeding speed F, etc., of the next block n are confirmed in the preceding block, e.g., an n-1 section, and the mean length is calculated by a statistic technique among the blocks n-2, n-1 and n. Then, a feeding speed, i.e., the allowable speed Vn' of the block n is calculated from the mean block length to prevent an inter-block stop state that is caused when the execution of the next block n+1 is over in the block n. The feeding speed F of the block n is compared with the speed Vn', and the speed F is clamped by the speed Vn' if the former is higher than the latter. In other words, the speed F is reduced down to a speed V' to prevent the inter-block stop state of the block n.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed rate control method for a numerical controller, and more particularly, to a method for controlling an inter-block speed in a machining program or the like composed of continuous minute blocks to suppress occurrence of inter-block stop. is there.

[0002]

2. Description of the Related Art A numerical controller (CNC) performs machining by moving a tool at a feed speed specified by a machining program. FIG. 3 shows a block diagram of such a numerical controller, for example. The CPU 111 of the numerical control device shown in FIG. 3 controls the entire numerical control device according to a system program stored in the ROM 112. The RAM 113 and the non-volatile memory 114 store various data, a machining program 114a, parameters, Stores parameters etc. PMC
(Programmable machine controller) 115
The machine tool is directly controlled based on commands such as the M function, the S function, or the T function, and the graphic control circuit 116 displays data stored in the RAM 113 such as the current position of each axis and the movement amount. The axis control circuit 118 receives a position command from the CPU 111 and controls the servomotor 120 via the servo amplifier 119.

FIG. 4 is a view showing a state of controlling the feed speed of a tool of a conventional apparatus in such a numerical control apparatus. That is, when the tool moves on the XY plane according to the blocks N1 to N8 of the machining program trajectory as shown in FIG. 4A, for example, if the block N2 is a small block having a small tool movement amount, As shown in FIG. 4 (b), the next block N
The execution of the block N2 is completed before the pre-processing of No. 3 is not completed, and a section of the speed 0 between the blocks N2 and N3, that is, a stop between the blocks of the tool occurs to give a shock to the apparatus. Since an inconvenience occurs, block N
2, the speed of the execution of the block N2 is controlled so that the execution of the block N2 is not completed before the preprocessing of the block N3 is completed. As the degree of the deceleration of the block N2, the allowable maximum speed is obtained by dividing the moving amount of the tool in the block N2 by the allowable minimum time, and is compared with the feed speed of the block N2. , The feed rate is clamped to the maximum allowable
The allowable minimum time is a time for deceleration provided to prevent a temporary stop of the tool movement due to the tool moving speed being too fast, and is a block. This is a time corresponding to the time required for the pre-processing of the block N3 in the section N2. Specifically, for example, if the pre-processing time is 80 ms shown in FIG. 4B and the moving amount of the block N2 is 1 mm, the allowable maximum speed is 1/80 × 60 = 750 mm / min. As shown in the figure, in the small block N2, the moving speed of N1 is 4
The deceleration from 000 mm / min to 750 mm / min prevents inter-block stop.

[0004]

However, in the above conventional example, in order to suppress the inter-block stop, the maximum allowable speed obtained from the block length of each block is compared with the maximum allowable feed speed. Is exceeded, the feed speed (command speed) is clamped to the maximum allowable speed, so even if only one microblock exists in the program, the maximum allowable speed (for example, 4000 mm)
/ Min → 750 mm / min), and the processing time is unnecessarily extended. Therefore, the present invention provides an inter-block speed control method of a numerical control device capable of preventing inter-block stop without increasing the entire machining time by smooth deceleration operation by avoiding extreme deceleration in a series of continuous machining operations. It is intended to provide.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, when the feed speed of each block is higher than the allowable speed obtained from each block length, the feed speed is set to the allowable speed. In the inter-block speed control method of the numerical controller for preventing the inter-block stop by clamping to, an allowable speed is obtained from an average block length up to an arbitrary block n, and the allowable speed is compared with the feed speed of the block n. When the feed speed is higher than the allowable speed, the feed speed is clamped at the allowable speed. With this configuration, even when a small block is specifically present in a program, unnecessary deceleration is not required, and stoppage between blocks can be prevented. Further, in the invention according to claim 2, the allowable speed Vn 'of the arbitrary block n is such that when an average book length up to the block n is Ln' and a block analysis time is T, Vn '= Ln'. / T). According to this configuration, the permissible speed Vn '= Ln' / T is calculated using the average block length Ln 'up to the block n instead of the block unit as a basis for calculating the permissible speed. Clamps the feed speed of the minute block n to Vn ', so that it is not extremely decelerated in the block n section, and the inter-block stop can be prevented without greatly increasing the entire machining time.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a clamp state by an inter-block speed control method of a numerical controller according to an embodiment of the present invention. FIG. 2 is a flowchart of the process of the inter-block speed control method of the numerical controller shown in FIG. In FIG. 1, reference numeral 1 denotes a locus of a machining program, n denotes a minute block therein, and n-1 and n-2.
Represents a previous block, and n + 1 represents a subsequent block. 2 is the feed speed F, and 3 is the allowable speed V '(or Vn'). V
(Or Vn) is the conventional permissible speed (permissible maximum speed) shown for comparison. Next, the operation will be described. When the program trajectory 1 as shown in FIG. 1 is executed, the block n is the smallest in the program, and is a speed control object of the present invention for preventing inter-block stop. Therefore, a description will be given with reference to the flowchart of FIG. First, when the processing starts (S100), in the previous block, for example, in the (n-1) -th section, the block length Ln and the feed speed F of the next block n are checked, and so on.
Assuming that the average block length of each block from 3, n-2, n-1, and n is Ln ', Ln' = ｎ... + (N-3)
+ (N−2) + (n−1) + n｝ / n. This is calculated by a statistical method or the like (S101). Next, during the feed forward processing of the next block n + 1 in the block n, the feed speed for preventing the inter-block stop that occurs when the execution of the block n is completed, that is, the allowable speed Vn ′ of the block n is determined. The calculation is performed from the average block length Ln '(S102). Vn '= Ln' / T A comparison is made between the feed speed F of the block n and the allowable speed Vn 'obtained in S102 (F>Vn'?). In the case of NO, there is no block stop, and the process skips to S105. And exit. F> Vn '? Is YES, the feed speed F of the block n is clamped at the allowable speed Vn '. That is, FIG.
Is reduced to V ′ (= Vn ′) to prevent the block n from stopping between blocks (S104). As for the clamping process S104, as shown in FIG. 1, since the acceleration / deceleration function (S-shaped acceleration / deceleration, asymmetric acceleration / deceleration, etc.) performed during the cutting of the CNC is performed simultaneously, it is performed in the middle of the block (n-1). Start deceleration and block n section is V
Speed control is performed such that the speed is reduced to n 'and accelerated again to F in block n + 1. Thus, the speed is controlled to be smoothly reduced and accelerated while avoiding a sudden change in speed as in the conventional example.
Thus, according to the present embodiment, in the case of the conventional speed control shown for comparison in FIG. 1, the allowable speed Vn (= V) of the block n is: Vn = Ln / T where Ln is Block length of block n, T is block n
Since the analysis time, Ln is very small and the feed speed is higher than Vn, the feed speed is clamped at the allowable speed Vn (V) as processing in units of block n, and Vn (V) in this case is used.
Is decelerated to the feed speed F / 2 or less, and the acceleration / deceleration function starts the deceleration in the first half of the block n-1, so that the entire machining time is greatly increased. I will. On the other hand, in the case of the present invention, the block length Ln 'is not the block unit but the average block length up to the block n. Therefore, when the block length Ln of the block n is the shortest in the program, Ln'> Ln,
Vn ′> Vn, the deceleration width is considerably reduced, the entire machining time can be shortened as compared with the conventional case, and the inter-block stop can be effectively prevented. This is extremely effective in reducing time.

[0007]

As described above, according to the present invention,
Instead of the block length of each block, the average block length of the blocks analyzed so far is used as a calculation condition of the clamp speed so as to prevent block-to-block stop. There is an effect that the processing time can be suppressed and the processing time can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state of clamping by an inter-block speed control method of a numerical controller according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process of an inter-block speed control method of the numerical controller shown in FIG. 1;

FIG. 3 is a block diagram of a numerical controller according to the present invention.

FIG. 4 is an explanatory diagram of a conventional inter-block stop.

FIG. 5 is a diagram showing a state of a conventional clamp.

[Explanation of symbols]

 1 Program locus 2 Feed speed 3 Allowable speed

Claims (2)

[Claims] An inter-block speed control method for a numerical controller for preventing a block-to-block stop by clamping a feed speed to an allowable speed when a feed speed of each block is higher than an allowable speed obtained from each block length. In, the permissible speed is obtained from the average block length up to an arbitrary block n, and the permissible speed is compared with the feed speed of the block n. If the feed speed is higher than the permissible speed, the feed speed is An inter-block speed control method for a numerical control device, characterized in that clamping is performed at an allowable speed. 2. The permissible speed Vn ′ of the arbitrary block n
2. The inter-block speed of the numerical control device according to claim 1, wherein, when the average block length up to the block n is Ln 'and the block analysis time is T, Vn' = Ln '/ T. Control method.