EP0524351B1

EP0524351B1 - Wire drawing machine with diameter watching-system

Info

Publication number: EP0524351B1
Application number: EP91201916A
Authority: EP
Inventors: Johan Samyn
Original assignee: Bekaert NV SA
Current assignee: Bekaert NV SA
Priority date: 1991-07-22
Filing date: 1991-07-22
Publication date: 1994-09-28
Anticipated expiration: 2011-07-22
Also published as: TR27144A; AU655385B2; ZA925481B; EP0524351A1; DE69104352D1; DE69104352T2; JPH05185143A; AU2035792A; BR9202800A

Description

The invention relates to a wire drawing machine having a watching system of the wire diameter at a watched location and to a method of watching the diameter of a wire at a watched location. A wire drawing machine comprises a number of passes, from one to ten or even more, the one downstream after the other, and in each pass the wire diameter is reduced. In order to watch over the good operation of the machine, it is desirable to watch the diameter at one or more specific locations, e.g. at the exit of one or more of the passes. Due to the wear of the drawing-die indeed, the wire diameter at the exit of such pass becomes greater and greater, and after a certain time, when the diameter exceeds the tolerance limit, the die has to be replaced. It is however not easy to continuously measure the diameter of a wire traveling at a speed of 2 to 12 m/sec, because mechanical systems are disturbed by the movement of the wire and optical systems are disturbed by dust or other pollution, or are very expensive. For that reason, in practice, the operator of the machine simply measures the wire manually at machine stop for whatever reason, and when the diameter appears to have somewhat approached the limit, he replaces the drawing-die as a precautionary measure. In this way, die consumption is higher than it should be, i.e. when the operator would be able to continuously watch the wire diameter and only proceed to the replacement when it is really necessary.
Although the need of watching the wire diameter at the exit of a drawing pass has been explained hereabove, and although the explanations hereinafter will refer to watching the diameter at the exit, it will be clear that the invention is not limited to a watched location at the exit side of a drawing pass, but can also be usable at an entrance side.
It is the object of the present invention to procure a watching system of the wire diameter at a watched location and a method of watching said wire diameter at said watched location, which allow to continuously follow the evolution of the wire diameter, without the need of an instrument that measures the diameter in a direct way by optical or mechanical or other means, and adapted to operate without human intervention during long periods, i.e. periods in which different wire coils are entered and treated in the machine, and still with high accuracy.
A first step towards the solution consists of the choice of the indirect method of measuring the diameter : via measuring wire speeds. In this method, the wire speed is measured, on one hand at the watched location, and on the other hand at a reference location where the diameter value is known and can be supposed to be nearly constant. As the passing steel volume per unit of time is the same at both locations, one has :

in which V_w and V_r are the speed at the watched and reference location respectively and D_w and D_r the wire diameter at the watched, respectively reference location. As D_r is considered to be a fixed value, the diameter D_w can continuously be calculated and a signal be generated, representing such value, without direct measurement of any wire diameter.
Such a method and the corresponding watching system are known for example from SU-A-933155.
For continuous measurement, measuring the wire speed is much easier indeed than measuring the wire diameter, e.g. by passing the wire over a slip-free pulley of which the rotation speed is measured.
A condition for the operability of this method is the presence somewhere of a location where the diameter can be supposed to be nearly constant. In wire drawing, this may constitute a difficulty because, due to wear of the drawing dies, the diameter is fluctuating everywhere. The entrance of the machine can however in general be used as a reference location. It has been observed indeed that the coils that are unreeled and entered into the machine, come themselves from other processes with narrow diameter tolerances at the output, and that they have a wire diameter that varies very slightly over a same coil (but can remarkably vary from coil to coil, because of different origins). Consequently, the method can be operable, at least for the period of treatment of a same coil. Another reference location can be the exit of a drawing pass with very small diameter reduction in a strongly wear resistant die, where the method can be operable, at least for the period between two replacements of such die. In principle, any location can be chosen where the diameter remains, or is made to remain constant during a certain period. The method must however serve for a longer duration of several such periods, and in a way that human intervention can be avoided. The way how the method will bridge the transition from one period to the other, constitutes the second step towards the solution, as explained later.
In using the method during the first period, the initial diameter D_o,r at the reference location at standstill before starting the machine is known (e.g. by manual measurement of the diameter, or by knowledge of the opening diameter of the drawing-die just before the reference location). This diameter is preset as a fixed value D_o,r in a register. With the use of such reference value in said register and the continuous measurement value signals of the speeds V_w and V_r, a continuously varying value signal D_o,w can be computed and generated according to formula (1) :

in which D_o,w represents the wire diameter at the watched location during said first period, i.e. the period before the first substantial change of the actual wire diameter at the reference location.
The next problem is now, that this method is only good for each single "quiet" period in which the wire diameter at the reference location does not remarkably vary. But between these quiet periods, there are transition periods of substantial change of the wire diameter, e.g. when a coil at the entrance is finished and followed by another coil (e.g. without machine stop, the tail of the former one being welded to the head of the latter), or when the reference drawing-die, just upstream the reference location, is replaced. Then a new quiet period starts with a new reference value D_1,r that has to be introduced in the register in replacement of D_o,r. And the problem is, how do this this, without any human intervention (measurement of diameter and introduction in the register).
The second step towards the solution consists of inverting, during the transition period, the roles of the reference location and the watched location. During the transition period, in which the diameter at the reference location is unreliable, and which period is relatively short, it is now supposed that the location where the diameter remains relatively constant, is now the watched location. One is allowed to suppose this, because this transition period is sufficiently short for neglecting die-wear or other influences.
As a consequence, the system proceeds to the inverted operation. it is now the last obtained value D_o,w for the watched position during the first quiet period that is stored as a fixed value in the register. And it is now the diameter value D_1,r for the reference location that is now continuously generated by means of the inverse formula :

When the transition period is now finished, the system is made to switch over from such inverse mode back to its direct mode. This means : the last obtained value D_1,r during the transition period is now stored as a fixed value in the register, and it is now again the diameter at the watched location, but now after the first transition period (D_1,w), that is generated by means of the direct formula (1) :

As soon as a following transition period is announced, the system is made to switch over again from direct mode to inverse mode, in order to continuously generate a signal

and to return then back to direct mode, in order to generate the signal

in which D_2,w is now the value, representative of the wire diameter at the watched location after the second transition.
This can so be repeated for n transitions, and each time the system switches over from direct mode to inverse mode and back.
The process can be started, either in direct mode or in inverse mode also. E.g., when the watched location is just downstream a drawing pass with a new drawing-die of which the opening diameter is accurately known, it is preferred to start the operation in inverse mode, and to have the diameter at the reference location be calculated first by the system, and then to switch over to the direct mode where this calculated value is then firstly introduced into the register.
In both ways of starting, the method of watching the diameter of the wire at said watched location consequently comprises, according to the invention (indexes a and b hereafter being equal to r, respectively w when starting in direct mode, and equal to w, respectively r when starting in reverse mode) :

(a) providing measuring means (1) (2) of the wire speed V_r and V_w at said watched location, and at a reference location respectively ;
(b) introducing a preset value signal D_o,a representative of the initial value of the wire diameter at one of said locations, in a register means (3) ;
(c) continuously generating a value signal D_o,b, representative of the value
in which V_a and V_b is the wire speed at said one location, respectively the other location ;
(d) before a substantial change of the actual wire diameter at said one side, storing a value in said register means, representative of said value signal D_o,b ;
(e) subsequently, continuously generating a signal D_1,a, representative of the value
(f) before a substantial change of the actual wire diameter at said other side, storing a value in said register means, representative of said value signal D_o,b;
(g) repeating steps (c) to (f) in which D_o,a, D_o,b and D_1,a are replaced by D_n,a, D_n,b and D_n+1,a, in which, for each repetition, n is the number of times the steps (c) to (f) have already been taken.

Besides the method, the invention provides a drawing machine with a watching system of the diameter of the wire at a watched location, and which comprises, according to the invention :

(a) measuring means (1)(2) of the wire speed V_r and V_w at a reference location and, at said watched location respectively ;
(b) register means (3) for storing a value D and comprising means (4) for presetting said register means to an initial value D_o, and further comprising a feedback signal entrance (5) for setting said register means (3), on receipt of a feedback value signal, to such feedback value D_n ;
(c) calculating means (6) adapted for continuously generating at its output (29) (30) a value signal
on one hand and
on the other hand ;
(d) a feedback control switch (8) having input means (7) for a switch signal, and input means (31) (32), connected to the output (29) (30) of said calculating means, and further having an output (33) connected to said feedback signal entrance (5) of said register means (3), the switch (8) being arranged for alternately sending, on receipt of a switch signal, one of said value signals present at said input means (31) (32) towards its output (33) ; and
(e) output means (34) connected to the output (29) of said calculating means (6).

The watching system provides a wide range of possible uses in a wire drawing machine, as shown hereafter. But, above this, the system also appears, rather unexpectedly, to perform with a reaction speed to diameter variations and with an accuracy, comparable to any optical system at least.
The invention will now further be explained with reference to the appended drawing, showing a schematic view of the wire drawing machine with its watching system.
In this drawing, the numbers 10 and 20 refer to the first and the second pass of a wire drawing machine. Each pass comprises a drawing capstan 11, respectively 21, that draws the wire 9 through a drawing-die 12, respectively 22. Upstream the drawing-die, there is a guiding pulley system with a pulley 13, respectively 23, driven by the wire 9 into rotation in a slip-free manner. The rotational speed of this pulley is consequently proportional with the linear speed of the wire on entering the corresponding drawing-die. In this example, the drawing-capstan is of the slip-free type, so that in this case the rotational speed of this capstan is proportional with the linear speed of the wire on the exit side of the drawing-die.
The wire travels in the direction of arrows 40, and comes from an unwinding station (not shown), where the wire is unreeled from a coil. The tail end of the wire of this coil is welded to the leading end of a next coil, so that, without stopping the wire drawing machine, the system can automatically proceed to a coil change where the next coil takes the place of the empty coil in the unwinding station. The triggering signal for coil change can be given by any mechanical, electrical or optical system for detecting that the treated coil is empty or nearly empty.
The example of Figure 1 shows a system for measuring the wire diameter at the exit of the drawing die 12 of the first pass. This exit is consequently to be considered as the "watched location", as referred to hereinbefore. The reference location is here the entrance of the drawing-die 12, i.e. the location of pulley 13. This pulley and the driving capstan ar each provided with an instrument for measuring the rotational speed, in this case, a pulse generator 1, respectively 2, delivering electrical pulses at a rate proportional to the rotational speed, generated by well-known optical, magnetic or electrical means. Each of said pulse generators sends its pulses towards a pulse counter 16, respectively 17, both being associated to a clock pulse generator 18, of which each odd output pulse resets the counters 16 and 17 to zero and each even output pulse stops the counting operation. In this way, the value stored in the counters between an even pulse and the next odd pulse, is proportional to the linear speeds of the wire, on one hand V_w at the watched location, in this case the exit side of the drawing-die 12, and on the other hand V_r at the reference location, in this case the entrance side of the same drawing-die. The outputs of both counters 16 and 17 are connected to the entrances, 26 and 27 respectively, of a calculator module 6, and transmits the content of the counter towards the calculator once just after each even clock pulse. These transmitted signals are digital coded signals, representing the content of the counters and consequently representing the linear speed values V_r and V_w.
The system further comprises a digital register 3, capable of storing a value D, representative of the diameter of the wire, and comprising an input 4 where a digital coded value signal D_o can be entered for presetting said register to an entered value. The output 28 of this register is connected to the entrance of said calculator module 6, and transmits the content D of the register towards the calculator module 6 at regular time intervals (e.g. at each even output pulse of said clock pulse generator 18). This transmitted signal is also a digital coded signal, representing the content D of the register or the value of the wire diameter, as lastly entered in the register.
The calculator module 6 is arranged to generate at its outputs 29, respectively 30, and with the use of the value signals V_w, V_r and D, received at its input, two other digital value signals, representing the values

on one hand and

on the other. Both outputs 29 and 30 of the calculator module 6 are connected to the inputs 31 and 32 of a feedback switch 8, of which the output 33 is connected to another input 5 of said register 3, for resetting said register to a feed back value D_n, entered via input 5.
Feedback control switch 8 has three entrances : one switch pulse input 7, and two value signal inputs 31 and 32. Input 31 is connected to output 29 of the calculator 6 and receives the value signal

and input 32 is connected to output 30 of the calculator module 6 and receives the value signal

The switch has three positions : one "start-direct-mode-position", and one "start-reverse-mode-position" in which it transmits the signal on input 32, respectively 31, towards the output 33 and to the register 3, and one "neutral" position in which it doesnot allow any signal at all towards the register 3. The switch stands in general in neutral position. On receipt of a switch pulse, it comes for a very short pulse time in one of both mode positions (direct or reverse) and then comes back to its neutral position, and on receipt of the following switch pulse it comes for a same very short pulse time in the other mode position. This means, that on receiving consecutive switch pulses at input 7, the switch sends alternately the momentaneous values at inputs 31 and 32 towards the register 3.
The output 29 of calculator module 6 is connected to the output 33 of the system. The output value signal can there be either visualized on a screen, or printed out or used in any other way for controlling the wire drawing machine and/or informing the operator.
In operation, the system works as follows. At standstill, the operator measures manually the wire diameter at the entrance 9 of the machine and introduces this value D_o,r into the register. This can be done, in dependence of the type of input means provided by the register, by means of manually setting a series of knobs to the digital value to introduce, or by a computer keyboard.
Then the machine is started and at each even output pulse of clock pulse generator 8, e.g. each half second the momentaneous values of V_w, V_r and D_o are sent to digital calculator. The system works now in direct mode, i.e. the calculator 6 immediately calculates

and sends this value, in the form of a coded value signal, via its output 29 towards the output 34 of the system. In dependence of the type of output means, this can be an optical display system on an operator's desk, or a computer screen, or any further data processing system, using the output signal for further processing into other information signals, e.g. "replace drawing-die".
After a certain time of operation, the unreeled coil becomes empty, and, without machine stop, the unwinding station produces a triggering signal for operating coil change, before the leading end of the wire, coming from the next coil, enters the machine. This triggering signal is transformed into two switch pulses, to send to the input 7 of feedback control switch 8. The first pulse is produced on occurrence of the triggering signal, and the other pulse, using an appropriate time delay circuit, about 20 seconds thereafter, when the heading end of the next coil has already passed the wire drawing machine. The first pulse will serve for setting the system in reverse mode, and the second pulse for resetting in direct mode.
On arrival of the first switch pulse at the feedback control switch 8, the signal at input 31 of the switch 8 is transferred to the output 33 for a short while, sufficient to pass the value signal D_o,w, coming from the output 29 of the calculator module 6, and to enter the value, represented by this signal, via input 5, into register 3, replacing the former value D_o,r. At this time, the system works in the reverse mode, i.e. the calculator 6 immediately calculates

and sends this value, in the form of a coded value signal, via its output 30 towards the input 32 of feedback control switch 8, that stands in neutral position and doesnot transfer this signal towards register 3. During this reverse mode, the output 29 of the calculator 6 is of no use, because it calculates a value

that doesnot correspond to the diameter at the watched position. For that reason, during this reverse mode, the output 34 is freezed by electronic means (not shown) to the last calculated value during the direct mode.
On arrival of the second switch pulse at the feedback control switch 8, the signal at the input 32 of the switch 8 is transferred to the output 33, sufficient to pass the value D_1,r, coming from the output 30 of the calculator module 6, and to enter this value into register 3, in replacement of the former value D_o,w. The system now again works in direct mode, i.e. that the calculator sends to the output 34 the value signal

that corresponds to the wire diameter at the watched location.
This short position in reverse mode is operated at each next coil change.
The system can also be used with start in reverse mode, when the operator accurately knows the opening diameter of drawing-die 12 at the start. Then, he doesnot need to manually measure the wire diameter of the first coil before machine start. He lets the system itself to calculate this, by starting the machine in reverse mode. Before machine start, he enters into register 3 the value D_o,w of the wire at the watched position (equal to the drawing-die opening), and at machine start, he triggers himself the switch pulses for the feedback control switch 8. In this way, the system starts in reverse mode, and output 30 delivers the diameter value D_r,1 at the entrance. When the second switch pulse arrives, this value is entered in register 3 and the system can start watching the diameter at the watched position via output 34.
It is clear that many different forms of execution of the same system can be designed without deviating from the essence of the invention.
In the first place : the signals that are transmitted forward towards the output, or in feedback, are "value signals". This means that they contain the information of a value, that can be derived therefrom with an adapted decoding system. Such signals can be of the analog type, e.g. voltages of which the value corresponds to the value to represent. They can also, as preferred for reasons of accuracy, be of the digital type, in the form of coded pulses, transferred in series or in parallel at regular time intervals. The measuring means 1,2, the register 3 and calculator 6 have then to be adapted to such signals : a tachymeter for speed measuring, condensator means for memorizing analog values, and digital memory means for registering digital values, and analog calculators, digital calculating means respectively for calculator 6. This value signals are "representative of the value" of a magnitude, but this doesnot mean that the value, contained in the signal, must be equal to or directly proportional to the value it has to represent. Then however, the calculator 6 shall have to take this into consideration. For instance : the value signal, stored in the register can be a coded value, not of D, but of D², and the value signal at the output 29 can be a coded value, not of

but of

but these are still value signals "representative of" the value they have to represent. The value decoder 34 shall have to be adapted thereto, and also the calculator 6, which has then not to calculate any square roots, but only to multiply the value entered at input 28 with the proportion of the values, entered at inputs 26 and 27.
Without deviating from the essence of the invention, one can also use other wire speed measuring means than those that give at their output a value signal that is equal to, proportional to, or representative of the measured speed. After all, the calculator is only interested in the proportion

and the inversed proportion

and any measuring means allowing to deliver a value, representative of such proportion, is usable, without having to pass through the values V_w and V_r themselves. For instance : pulse generator 1 can be used to open a switch for e.g. 1000 pulses and then close it again, whilst during the opening time the pulses coming from generator 2 are allowed to a counter. The value, stored in the counter when the switch closes again, corresponds then to

The calculator 6 has to be adapted for "continuously" generate at its outputs (29) (30) the said values D_w and D_r. This doesnot mean that the calculator must deliver a mathematically continuous signal, but this can also be a train of signal pulse combinations, in which each combination represents said values, and in which the combinations follow each other at sufficiently short intervals for being representative of the momentaneous values they have represent. Further, during the inverse mode, the signal D_w at output 29, is of no use, so that generation of this signal can be interrupted in inverse mode. And the same applies to the signal D_r at output 30 in the direct mode. The calculator can be conceived to have only one output instead of outputs 29 and 30, and only calculating and generating D_w during the direct mode and D_r during the inverse mode.
The output of the calculator is connected to the input of the feedback switch in order to operate the feedback of the values D_w and D_r towards the register 3. This doesnot mean that this feedback connection would be a direct connection, without any possible treatment of the values D_w or D_r between the outputs 29, 30 and the entrance of control feedback switch 11. It is more specifically desirable that the output of the calculator 6 passes through a data processor 35 (in dotted lines in the figure) making the average of the values D_w and D_r over the last few seconds. In such case, the system is protected against a feedback towards switch 3 of a momentaneous value just at a moment when there is some anomaly in the measured speed. Consequently, the generation or transmittal of value signals "representative" of certain values also means, in a broad sense : representative of the average of such value.
In dependence on the practical realization of the system, it may also be necessary to insert a time delay element in the system. The system must not operate so rapidly that, when a switch pulse occurs at the input 7 of switch 8, in order to admit a feedback signal into register 3, that the calculator already would have generated the new value at its output and sent it back to register 3 before the switch closes again. If necessary, this time delay system can be inserted either in the direct part or the feedback part of the loop, formed by elements 3, 6 and 8.
It is further clear that the preferred and most attractive way of realization of this invention is by way of a computer, programmed to store in its memory the values that have to be stored, to calculate in its processor the values that have to be calculated, and to transfer the values at the right times under control of the computer programme.
More specifically, the register 3 mustnot necessary be executed as a hardware element. The register function can be executed in a computer memory module, where the value to store is stored at a given address, where the programme knows where to find it back, and where the next value is stored at the same, or at another address, where the programme still knows where to find it.
Similarly : the calculator 6 mustnot necessarily be a calculator module, specially designed only to calculate the mentioned formulae. The calculating function can also be executed in a digital processor module, adapted for any sort of calculation or data processing, but that has been programmed to send the desired data at the desired moment towards the desired output or memory address. The same applies to the memory switch, and to any necessary calculator of average values.
This all means that the whole of registering, calculating and switching functions can be performed in a programmed manner in a digital computer. The diameter data at the watched location can then also further be processed, in the same computer, with other data towards a number of messages for the operator on the computer screen or on other warming apparatuses, or towards the command input of any automatically controlled part of the drawing machine.
The wire-drawing machine will in general comprise a number of watched locations, with each a watching system, e.g. a watching location at the exit of each drawing pass. These watching systems may all use the same reference location, at the entrance 9 of the first pass, or not. The watched locations are then "directly" downstream each drawing die : this means without any further diameter reduction between the drawing-die and the watched location where the wire speed is measured. It is not because, by wear, the opening of a drawing-die in an intermediate pass exceeds a limit, that this die has directly to be replaced. This may depend on the other diameters, and the message for the operator may result from processing the different obtained data in the computer.

Claims

A wire drawing machine having a watching system of the wire diameter at a watched location, said system comprising :
(a) measuring means (1) (2) of the wire speed V_r and V_w at a reference location where the diameter value is known and can be supposed to be nearly constant and, at said watched location respectively ;

(b) register means (3) for storing a value D, and comprising means (4) for presetting said register means (3) to an initial value D_o, and further comprising a feedback signal entrance (5) for setting said register means (3), on receipt of a feedback value signal at said entrance, to such feedback value D_n ;

(c) calculating means (6) adapted for continuously generating at its output (29) (30) a value signal
on one hand, respectively
on the other hand ;

(d) a feedback control switch (8) having input means (7) for a switch signal, and input means (31) (32), connected to the output (29) (30) of said calculating means (6), and further having an output (33) connected to said feedback signal entrance (5) of said register means (3), the switch (8) being arranged for alternately sending, on receipt of a switch signal, one of said value signals present at said input means (31) (32) towards its output (33) ; and

(e) output means (34) connected to the output (29) of said calculating means (6).
A wire drawing machine according to claim 1, in which said measuring means (1) (2) are each arranged to deliver at their output a digital value, representative of the measured speed.
A wire drawing machine according to claim 1, in which said register means (3) is in the form of a digital memory, programmed for storing subsequent entering values at programmed addresses in said memory.
A wire drawing machine according to claim 1, in which said calculating means (6) is in the form of a digital processor, programmed for generating instantaneous digital values of D_w and D_r at regular time intervals.
A wire drawing machine according to claim 1, in which said input means (31) (32) of said feedback control switch (8) comprise calculating means of the average of the value signals received from the output (30) (29) of the calculating means (6) of the value signals D_w and D_r.
A wire drawing machine according to claim 1, in which said register means (3), calculating means (6) and feedback control switch (8) are in the form of a programmed digital computer.
A wire drawing machine according to claim 1, in which said reference location is the entrance of said machine.
In the operation of a wire drawing machine according to claim 1, the method of watching the diameter of a wire (9) at a watched location where the diameter value is known and can be supposed to be nearly constant, said method comprising :
(a) providing measuring means (1) (2) of the wire speed V_r and V_w at a reference location and at said watched location respectively ;

(b) introducing a preset value signal D_o,a, representative of the initial value of the wire diameter at one of said locations, in a register means (3) ;

(c) continuously generating a value signal D_o,b, representative of the value
in which V_a and V_b is the wire speed at said one location, respectively at the other location ;

(d) before a substantial change of the actual wire diameter at said one side, storing a value in said register means (3), representative of said value signal D_o,b ;

(e) subsequently, continuously generating a value signal D_1,a, representative of the value

(f) before a substantial change of the actual diameter at said other side, storing a value in said register means (3), representative of said value D_1,a ;

(g) repeating steps (c) to (f) a number of times, in which D_o,a, D_o,b and D_1,a are replaced by D_n,a, D_n,b and D_n+1,a, in which, for each repetition, n is the number of times the steps (c) to (f) have already been taken.
A method according to claim 8, in which said one location is the reference location at the entrance of the machine on one hand, and said other location is the watched location directly downstream a drawing die (12, 22) on the other hand, and in which the storing operations of step (d) and (f) occur a few seconds before, respectively after each change of the entrance coil.
A method according to claim 8, in which said one location is the watched location directly downstream a drawing-die (12, 22) on one hand, and said other location is the reference location at the entrance of the machine on the other hand, and in which the storing operation of the first step (d) after starting the machine occurs a few seconds after said start, and in which the subsequent operations of steps (f) and (d) occur a few seconds before, respectively after each change of the entrance coil.