DE2313707A1 - FEED CONTROL IN A NUMERICAL CONTROL UNIT FOR A MACHINE TOOL - Google Patents

Description

Feed circuit in a numerical control unit for an efkzeuemschine Machine tool The invention relates to a feed circuit in a numerical one Control unit for a machine tool, through whose operation e.g.

Thread with gradually varying pitches by electrical Control of a servo motor, and it relates in particular to one Operation generator part of the numerical control unit.

Sin system for cutting a thread with a constant pitch af a lathe controlled by a numerical control unit is dem Known to those skilled in the art. However, it is impossible to have a thread with a mutable Cut slope with this system.

furthermore there is also a cutting device for cutting a Thread with a variable pitch known by a mechanical method. However, this cutting device requires a guide plate, the one Has second order surface, and a manual transmission mechanism to a Advance a steel holder or tool holder at a speed which depends on the square of the feed rate of a support. The manufacturing the circuit board requires a lot of work. In addition, it is uncomfortable that the gearbox must always be changed if there is a change in the thread pitch required when producing a screw with a varying thread pitch is. A thread produced in this way is therefore relatively expensive with himself.

It is accordingly the object of the invention to provide an improved numerical To deliver control unit for machine tools, in which the difficulties described above, associated with conventional numerical control units are eliminated. Included should not be a guide plate that has a surface with a second order curvature owns, and no longer a gearbox mechanism for producing a thread with varying thread pitch may be required.

Furthermore, the feed circuit should be in a numerical control unit be simple in construction for a machine tool, cause low costs and only work electronically.

There should continue to be a very small change in pitch per thread turn can be supplied by a shift register that has one pitch change per thread turn stores; the very small changes in pitch per thread turn obtained in this way are then always consecutively an accumulator or arithmetic unit register when a pulse made by the rotation of a main shaft is fed to it is supplied # to thereby obtain a very small change in slope; the so The very small change in gradient obtained is stored in a different arithmetic unit register processed when the pulse is applied to it; and the content of the last arithmetic logic unit register is presented as a signal representing a position. which are run by a support should, fed to an arithmetic unit.

Furthermore, an advance circuit should be integrated into a numerical control unit for machine tools an operating generator part for smooth control the operation of a machine tool. It should go through the Feed circuit in the numerical control unit accelerates and decelerates a tool part3 to be controlled such as a support table or slide can be achieved in the machine tool in a smooth, frictionless manner, whereby the tool part is controlled easily and with low impact loads.

The invention will now be explained in more detail with reference to the accompanying drawings. In these figures: Fig. 1 shows a block diagram showing a numerical control unit represents for a lathe; Fig. 2 is a block diagram showing an example of a operating generator according to the invention in a numerical control unit for machine tools represents; Fig. 3 is a block diagram showing a conventional numerical control unit for machine tools that is used to describe another exemplary embodiment the operating generator is used according to the invention; 4 is a block diagram, this is another embodiment of an operating generator according to the invention in a numerical control unit for machine tools, and FIG. 5 graphically Graphs showing the relationships between the speed of a controlled vehicle Illustrate tool part of a machine tool and the position of the tool part.

As an aid to a better understanding of this invention, first briefly with reference to Fig. 1, a thread cutting system by means of z.fl. a lathe described with numerical control.

Control signals, the pitch Fo of a Cewindeganges and a length L represent a threaded part are read by a tape reader 1 stored in register 2. The content of the register and an output pulse N by a pulse generator 11 which is directly connected to the main shaft or spindle 13 of the Lathe is coupled, are fed to an operating generator 3, this Operation generator 3 successively a location signal P of a thread function that creates itself exactly with that given by the control signal The pitch per revolution of the main spindle 13 changes. A position detector 10 has a current position of a support or tool slide 9 of the lathe # nac #. and thereby generates an output signal B1. The location signal P is with the output signal B1 of the position detector 10 compared in an arithmetic unit 1, and the The difference P-B between these two is determined by a digital-to-analog converter 5 converted into an analog signal, i.e. a voltage; this tension then becomes one Motor control unit 6 supplied to control a servo motor 7, which thereupon a feed spindle e and accordingly the support 9 drives.

When the feed screw 8 rotates, the output signal becomes B1 of the position detector 10, which is directly coupled to the feed screw 8 ', progressively changed. In this way, the threading system becomes in one changed in such a way that the difference P-B1 is always controlled so that it remains 0.

The present invention is directed to improving the above System by creating a new operating generator in the numerical control unit.

In Fig. 2 an embodiment of the operating generator is gemaos of the invention applied to the system described above.

The operation generator has a shift register 31 which is a Sig al fir receives a change in slope per slope H and an output signal of a tiny change in pitch per pitch PR = H / N generated (if N equals the number of the pulses generated by the pulse generator 11 is those generated by the shift register is limited).

The operating generator also has an arithmetic unit 32, which shows the tiny change in slope per slope via a gate circuit 36 is supplied, which only opens when the pulse generator 11 is off # 'angssignal generated, and a shift register 33 which is the output of the arithmetic unit 32 receives. A content X of the shift register 33 is sent to the arithmetic unit 32 fed back, creating a closed loop circuit. The arithmetic Unit 32 and shift register 33 form an accumulator or an arithmetic unit register 301

The shift register 33 initially receives the control signal that dtt Represents thread pitch Fo from the tape and creates a tiny thread pitch change = X / N.

The operating generator also has an arithmetic unit 34, to which the tiny thread pitch change AX is fed via a gate circuit 37 which only opens when the pulse generator 11 generates its output signal, and a shift register 35 which receives an output from the arithmetic unit 34 receives. A content P of the shift register 35 is sent to the arithmetic unit 34 fed back, thereby forming a closed loop circuit. The arithmetic Unit 34 and shift register 35 form an accumulator or arithmetic unit register 3 (J2. The shift register 35 initially stores an output from the position detector 10, i.e. a signal representing a current position of the support, and its content P represents a value for the next position to which the support should move, represent.

The operation of the system organized as described above is as follows. When the numerical control unit and the lathe put into operation in order to cut a thread, the pitch of which turns progressively to: ^ hst the main spindle 13 and the pulse generator 11 generates pulses to thereby the gates 36 and 37 to open.

As a result, the tiny thread pitch change per pitch becomes aH supplied from the shift register 31 to the arithmetic unit 32 and the arithmetic unit Processing for generating the content X of the shift register 33 is subjected, wherein the content X is initially equal to the slope Fo.

The tiny thread pitch change # X from the shift register 33 is through the gate circuit 37, which is open to the arithmetic unit 34, to this arithmetic unit 34, which the contents P in the shift register 35 generated by arithmetic operations. The content P is in the arithmetic Unit 4 transferred.

Whenever such a pulse from the pulse generator 11 by rotation the main scramble 13 is generated, the content of the shift register 33 increases by H and the contents of the helper 35 us QX.

After the generation of N pulses by the pulse generator 11, ie after one revolution of the main spindle, the contents of these shift registers are as follows: Shift register 31 -------------- H (unchanged) 33 ---- ---------- X = Fo + H 35 1> -------------- P = Bo + Fo + H After two rotations of the main spindle, the contents of the shift register are like follows: Shift register 31 ------- * H (unchanged) 33 --------------- XX = Fo + 2H 35 P ----------- ---- P = Bo + Fo + H + Fo + 2H After M revolutions of the main spindle, the contents of the shift registers are as follows: Shift register 31 -------------- H (unchanged) In this way, the content of the arithmetic unit register 302 has the function of a thread, the pitch of which increases progressively. The system according to the invention can therefore cut a thread in which the pitch increases by H between adjacent thread turns.

The above descriptions refer to a thread with progressive increasing thread pitches. However, the principle described above can be easily implemented in the case of thread cutting with a progressively decreasing thread pitch be applied. In this case or in the case when the thread cutting direction is changed, the signs of the equations given above are changed.

In this way, according to the invention, it is possible to cut threads with variable thread pitches, which was previously considered difficult is easy to do.

In order to have a full understanding of another aspect of the present In order to achieve the invention, referring to FIG. 3, a conventional numerical one becomes Control system and a machine tool controlled thereby briefly described.

A numerical value A1 of the end position A of a tool part to be controlled, e.g. a support or a tool slide 9 is read via a tape reader 1 fed to a register 2. With the help of an output signal from register 2 an operating generator 3 generates an output signal P that the next position, to which the support 9 is to be moved includes. On the other hand, a position detector generates 10, which is coupled to a feed spindle 8 for advancing the support 9 Output signal that represents the current actual position B of the support.

In the case when the support 9 quickly moves from the actual position B in Direction towards the end position; A is moved, the output signal P of the operation generator becomes 3 is initially set to the value that represents position B, but it receives finally a value that represents position A. That is, the output signal P changes kept constant in such a way that the support feed speed is accelerated is and is braked.

The output signal P is identical to the output signal B1 of the position detector 10 compared with an arithmetic accuracy of 4, the difference iP-B11 between both is generated as a digital value. This digital value is represented by a Digital-AnsJog-converter 5 into an analog signal i.e.

a tension, implemented. This voltage becomes a motor controller 6 for controlling a Sprvomotors 7 supplied. As a result, the feed screw twists 8 rotated by the servo motor 7, whereby the support 9 is controlled while the output signal B1 of the position detector, which is directly linked to the feed spindle 8 is coupled, is changed so that the difference U-B1l is regulated so that it approaches the value 0.

With this operating mode, the simplest change of the exit signal is P of the operating generator 3 obtained when the (speed of the support 9 suddenly increases to a speed V at position B, and suddenly to 0 at the Position A falls as it is in (a), Fig. 5 'is shown.

However, it is opposite to a mechanical system and a system with servomechanism in it advantageous, in it support feed speed smoothly and is regulated smoothly by acceleration and deceleration, as shown in (bl Fig. 5, is shown.

Referring to Fig. 4, there is another embodiment of the feed control system or an operation generator section in the numerical control unit for tool machines shown according to the invention.

The operation generator section has a unit 431 for setting a gradient of an acceleration or a deceleration (hereinafter referred to as "gradient setting unit" designated). A constant value VT is set in this gradient setting unit 431 set and fed to a gate circuit 432, which is only open when you, as described below, a gate signal is supplied.

On the other hand, a numerical value oV is determined by a maximum speed max speed setting unit 1, 433 set. This value becomes a max unit of 434 to check whether the support 9 is within an acceleration range is located (hereinafter referred to as "Acceleration Control Unit 434").

In this acceleration control unit 434, the values V and a max content V of a first arithmetic logic unit register 501, which will be described later, subjected to the comparison to determine whether the support is within the acceleration range is. After the supply of an additional command, the acceleration control unit generates 434 an output signal which is fed to the gate circuit 432.

The operating generator part also has a unit 435 for testing, whether the support 9 is within an Ah XIT msungsbereiches (in the following referred to as "deceleration controller 435"}. This Breathing brake: control unit 435 receives signals C and D, which are described in more detail below.

After applying a subtractlon control signal to this unit the deceleration control unit 435 generates an output signal that the gate circuit ' 432 is fed to open it.

Thus, when the gate 432 has been opened, the becomes constant S ~ ert VT is fed to an arithmetic unit 436.

The addition control signal and the subtraction control signal become supplied not only to gate # 32 but also to an arithmetic unit 436. In this regard, the arithmetic unit 436 is designed to that, when these control signals are supplied to it, the subtraction control signal priority is given to the addition control signal.

That is, the subtract operation is carried out first.

The arithmetic unit 436 is connected to a shift register 437, the content of which is fed back to the arithmetic unit 436, whereby a closed loop circuit is formed. In this way form the arithmetic Unit 436 and the shift register 437 the first arithmetic unit register 301.

The content V becomes an arithmetic unit 438 as well the acceleration control unit 434 is supplied. The arithmetic unit is 438 connected to a shift register 439, the content of which P to the arithmetic unit 438 is fed back, creating a closed loop circuit. In this way, the arithmetic unit 438 and the shift register form 439 a second arithmetic unit register 302.

The content bV of the shift register is successively in the Arithmetic logic unit register 302 collected while the contents of the arithmetic unit register 302 is supplied to the arithmetic unit 4. Each shift register 437 and 4) 9 has a capacity or capacity rusty enough to support the maximum To store control signal value A1 supplied by the tape reader.

It is assumed that in the operation generator part programmed in this way the value VT from the gradient setting unit 431 is not passed through the gate circuit 432 can go because it is closed that the content V of the shift register 437 unchanged remains, and that the value of the support position B, which was initially set is stored in the shift register 439. Under these conditions will be the content P of the shift register 439 just increases by ~ V with each revolution of the shift register change. Accordingly, this value ~ V will determine the support feed rate.

In the event that the support is at a maximum speed is forwarded is OV. EV, and it is therefore necessary to go through this value the maximum speed £ - setting unit 433 for the Zumax guide to the Adjust acceleration control unit 434.

On the other hand, shift register 437 is initially reset has been found that its content is 0, the value AV will also be 0. In this In this case, the condition of the shift register 439 will remain unchanged and therefore will its content P also remain unchanged.

In the acceleration control unit 434 EVmax and ZV are compared, and as a result of this, the addition command signal is output from this unit, if #V> EV, and the gate circuit 432 is opened max and the arithmetic Unit 436 becomes ready for the add operation.

If under these conditions the normal operation of the support feed speed.

speed has been initiated, the content of the shift register grows 437 by VT with each cycle of the shift register, i.e. the content av of the same grows gradually increasing As a result, the content P of the shift register 439 grows as it increases Speed from its unchanged position, with the support bescle nigt will. This acceleration continues until VV reaches the value #Vmax, so that the supply of the addition command signal from the acceleration control unit 434 is ended in order to close the gate circuit 432.

When AV reaches the value CIV, the accumulation in the shift register 437 and its contents are fixed at AV. Therefore the max content changes of the shift register 439 at a constant speed and the support becomes therefore pushed forward at a constant speed.

When the support is moved in an area where it is slow should beren, the subtraction command signal from the deceleration control unit 435 submitted. Accordingly, the gate circuit 432 is opened and the arithmetic Unit 436 becomes ready for the subtract operation.

As a result, the content LV of the shift register 437 takes successively by EVT, and the input signal of the second arithmetic unit register 302 also decreases consecutively. That is, the content P of the shift register 439 brakes the movement of support.

In this operation it is very important to determine which one position of support should begin at the braking area. There may be moments in which the Stlpport feed rate of Acceleration to deceleration must be changed, as shown in (c) JFig. 5) shown is.

The determination of the deceleration range is also taken into account in this regard described.

(i) In the case of Fig. 5 (b), the gradients are Vt of acceleration and the deceleration are the same: Because of the same gradients, the acceleration feed rate is distance E is equal to the deceleration feed distance C. Therefore, the time of Start deceleration at the point in time at which the distance D between the the present position B1 and the target position A equal to the acceleration / feed distance E will. At this point in time, braking begins.

(2) In the case of Fig. 5 (c) is the distance between the starting positions B and the objective A relatively short.

In this case, braking must be carried out before the Acceleration to the end has been carried out. Similar to the case of the Fig. 5 (b) is the timing of the start of deceleration equal to the timing at that the acceleration feed distance E is equal to the deceleration feed distance is.

From the above description it can be seen that the function generator part to control the speed of the support or the tool part that is controlled is to be provided with first and second arithmetic logic unit registers that the first arithmetic unit register as an input signal a numerical value for determination records a gradient for acceleration and deceleration in order to carry out the control, causes the addition and subtraction of this numerical value, and the content Aer To supply the addition and subtraction operation to the second arithmetic unit register. The acceleration and deceleration of the tool part to be controlled can accordingly be adjusted very smoothly and smoothly, which leads to the result that this tool part can be controlled easily and without impact.

- patent claims -

Claims (6)

Claims @ feed circuit in a numerical control unit for a machine tool, characterized in that it has a reading circuit (tape reader 1) for reading command signals according to a predetermined program, a register (2) for storing the command signals, one with a feed mechanism @@@ die Cutting devices coupled position detector (10) for the detection of the actual position these cutting devices and for generating a corresponding output signal (B1), an operating generator (3), which according to an output signal from the register (2) works and successively generates an output signal (local signal P), which corresponds to a location that follows a predetermined numerical function, and an arithmetic unit (4) for comparing the output signal (1>) @@@ the output signal (B1)) of the position detector (10), and that by the latter the cutting devices are controlled so that the output of the arithmetic Unit (4) becomes zero that the operation generator (3) has a first arithmetic unit register (2 and a second arithmetic unit register (302), which are switched so that the second arithmetic unit register (302) as input signals the content of the first Arithmetic unit register (301) receives the second arithmetic unit register (302) Output signal generated by which the cutting devices with a desired Speed can be moved to a predetermined position by using a numeric Value of a feed rate of the feed mechanism for the thread cutting device or a tiny change in the acceleration or deceleration of the cutting devices corresponding to the first arithmetic unit # register (301) and that the output signal of the second arithmetic logic unit register (302) is introduced into the arithmetic unit (4) is to smooth-nF smooth and accurate speed control of a steerable To effect tool part. 2. Feed circuit according to claim 1 for cutting servants, characterized in that it also has one with the main spindle (8) of the machine tool coupled pulse generator (11) for generating N pulses per revolution of the main spindle (8) and a shift register (31) and that the shift register (31) stores a change in pitch per thread turn H and a tiny change in pitch per thread # H = H / # generated by receiving the pulses from the pulse generator (11), that the first arithmetic unit register (30t) is a circuit that initially has a Stores a value that determines a thread pitch Fo, and successively each receives a value for a thread pitch that varies over time by using the Pulse generator (11) for the purpose of generating a tiny pulse Slope change #X = r x / N are fed that the tiny slope change per thread turn & H is introduced into the first arithmetic unit register (301) in order to to be picked up in it, and that the tiny thread pitch change ßX always the second arithmetic unit q register (302) and stored therein if a pulse is generated in and supplied by the pulse generator (ii) to to generate a function of a thread turn with a variable pitch. 3. Feed circuit according to claim 2, characterized in that the first arithmetic unit register (301) an arithmetic unit (32) and a shift register (33) contains that the arithmetic unit (32) as the input signal the tiny Change in pitch per thread from the register (31) by a gate circuit (36) which is only open when the pulse generator (ii) has its output signal generates that the shift register (4) as its input signals an output signal the arithmetic unit (32) and the value Fo determined as the slope, that a content of the shift register (33) is fed back to the arithmetic unit (32) is, thereby forming a closed loop circuit, and that the Tiny slope change AX = I X / N introduced into the second arithmetic unit £ register (302) will. 4. Feed circuit according to claim 2, characterized in that the second arithmetic unit register (302) an arithmetic unit (34) and a shift register (35) contains that the arithmetic unit (34) as the input signal the tiny Slope change # X from the shift register (33) via a gate circuit that only is open when the pulse generator (is) generates and receives its output signal, and that a content of the shift register (35) is fed back to the arithmetic unit (34) thus forming a g? closed loop circuit. 5. Feed circuit according to claim 1, characterized in that the first arithmetic unit register (301) with the second arithmetic unit register (302) is connected in such a way that the #wide arithmetic unit register (302) as an input signal a content of the first arithmetic logic unit register receives that the first arithmetic unit register (301) as an input signal a constant numerical value (VT) for determining a Gradients of the acceleration or the deceleration of the tool part to be controlled receives that the numerical value (VT) by a unit (434, 435) for checking, whether there is an acceleration range (434) or a deceleration range (435), subjected to the addition operation when the tool part are accelerated should, or the subtraction operation is subjected when the tool braked part it should be that the second arithmetic logic register (302) also has an output signal for information about the next position to which the tool part will be moved should, that this output signal is generated by the arithmetic unit (4) with the output signal B1) of the position detector (10) indicating the current position of the tool part, for the purpose of smooth and smooth execution the speed control, the tool part is compared. 6. Feed circuit according to claim 5, characterized in that they a unit (431) for setting the gradient of the acceleration or deceleration to generate the constant numeric value (VT), a first arithmetic unit, which subjects an output of the unit (431) to the arithmetic operation and an output signal of the same to the first arithmetic unit register (301), and an acceleration range control unit (434) and a unit (435) for controlling the braking area, each according to their Test and control function open the gate circuit and close it further a shift register (437) contains that as an input signal an output signal of the first arithmetic unit (426) receives and an Atsgangssigiial generates that is fed back to the first erithmetic unit (436), whereby a closed loop circuit is formed that the arithmetic unit (436) and the shift register (437) form the first arithmetic unit register ~ (3 # i), that the arithmetic unit (436) performs the addition operation when a Acceleration of the tool part to be controlled is required, and the subtraction operation executes, if braking of the tool part to be controlled is required, that also an output signal AV of the shift register (437) of a second arithmetic Unit (438) to which a shift register (439) is connected is fed, that an output of the shift register (439) of the second arithmetic unit (438) is supplied, thereby forming a closed loop circuit, that the second arithmetic unit (438) and the shift register (439) a second Form arithmetic unit register (302) in which the output signal AV is collected, and that an output of the shift register of the arithmetic unit (4) is fed.