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GB2064134A - Monitoring press forces electrically - Google Patents

Monitoring press forces electrically Download PDF

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Publication number
GB2064134A
GB2064134A GB8037552A GB8037552A GB2064134A GB 2064134 A GB2064134 A GB 2064134A GB 8037552 A GB8037552 A GB 8037552A GB 8037552 A GB8037552 A GB 8037552A GB 2064134 A GB2064134 A GB 2064134A
Authority
GB
United Kingdom
Prior art keywords
press
strain
monitoring
circuit
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8037552A
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GB2064134B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rover Co Ltd
Original Assignee
Rover Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rover Co Ltd filed Critical Rover Co Ltd
Priority to GB8037552A priority Critical patent/GB2064134B/en
Publication of GB2064134A publication Critical patent/GB2064134A/en
Application granted granted Critical
Publication of GB2064134B publication Critical patent/GB2064134B/en
Expired legal-status Critical Current

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/0061Force sensors associated with industrial machines or actuators
    • G01L5/0076Force sensors associated with manufacturing machines
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B30PRESSES
    • B30BPRESSES IN GENERAL
    • B30B15/00Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/0094Press load monitoring means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/0061Force sensors associated with industrial machines or actuators
    • G01L5/0071Specific indicating arrangements, e.g. of overload

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Presses (AREA)

Abstract

A method of monitoring power presses for detecting malfunction which includes obtaining an amplified signal from a strain responsive device fitted to the press and digitising the peak value of the signal for comparison with known acceptable peak value signal levels; the output of the amplifier being automatically zeroed when the press is not under strain to compensate for variations due to temperature changes and gauge hardening.

Description

SPECIFICATION Method of monitoring the operation of a power press This invention relates to a method of monitoring the operation of a power press during operation, and includes both means for monitoring power presses and power presses that include such means.
According to the invention a method of monitoring the operation of a power press during operation includes:- a) fitting a strain responsive signal generating device to a member of the press that is subject to strain during operation of the press; b) amplifying the signal generated by the device and calibrating the amplified signal such that it represents the press loads during operation; c) storing the peak value of the amplified signal for each press cycle; d) digitising the peak value after detecting that the pressing operation is complete; e) feeding the digital value to a visual display or recording/monitoring system; and f) zeroing the output of the amplifier with the press not under strain to compensate for gauge hardening, temperature changes and any other long term system variation.
Thus the invention provides an accurate means for monitoring press loads during operation which can be utilised not only to reduce the peak press loads to a value necessary to produce a satisfactory product but also to detect any malfunction of the dies, two blanks being pressed or any other fault that causes variations in the press load to occur.
In practice several strain responsive signal generating devices may be employed on each press and each strain responsive signal generating device may comprise a strain gauge bridge network; and the devices may be attached to convenient parts on the press structure such as the frame and press connecting rods.
The signal from the strain responsive device may be calibrated using a load cell or from known press data.
The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a block diagram of a press monitoring arrangement according to the invention; and Figure 2 is an example of a typical trace obtained during press operation.
Referring to Figure 1, strain gauge bridge networks 11 are fitted to members of a press that are subject to strain during operation such as the connecting rods and/or to other parts of a power press (not shown), and the signals derived therefrom are fed to a pre-set gain sensing amplifier 12 which has the gain set by reference to a load cell or known press data such that the amplifier output represents the actual instantaneous press load.
The output of the amplifier is fed to a suitable recorder 1 3 and to a peak hold circuit 14 whose output signal is proportional to the peak press load. A timing control logic circuit 20 triggered by either a predetermined strain level fed from a press stroke detector 19, or by a suitable signal derived from switching device (not shown) activated by rotation of the press at the appropriate time during the press cycle, resets circuit 14 and initiates sequential operation of the circuits 1 5 and 1 6 as follows; the output signal of the circuit 1 4 is digitised in the analogue to digital converter 1 5 and fed in a serial or parallel via a necessary output buffer circuit 1 6 to a monitoring system (not shown) such as a visual display unit, programmable controller or a mini-computer; the peak hold circuit and timing control circuit being reset by the monitoring system after receipt of data.
The amplifier 12 is provided with a closed loop stabilizer feedback circuit consisting of an integrator 1 7 and error detection circuit 1 8 for automatically zeroing the output of the amplifier with the press under no strain. During press operation with the press stroke detector 1 9 detecting press strain above the predetermined strain level the integrator circuit 1 7 is suppressed by a signal from the detector to prevent self compensation action of the stabilizer circuit taking place.
Figure 2 illustrates a typical trace of press load plotted against time during a single operation of the press. The peak load is indicated by the letter 'A', and it has been found that such a trace is consistently produced during normal operation.
Thus the digital value of the peak load when fed to a visual display unit, or to a recording/monitoring system allows, a) the press to be set up efficiently without excessive loads being produced, b) a true stamping count to be made without free runs, which produce a reduced peak load, being recorded, and c) a safety cut out to be actuated if the load becomes excessive during operation.
1. A method of monitoring the operation of a power press during operation which includes:- a) fitting a strain responsive signal generating device to a member of the press that is subject to strain during operation of the press; b) amplifying the signal generated by the device and calibrating the amplified signal such that it represents the press loads during operation; c) storing the peak value of the amplified signal for each press cycle; d) digitising the peak value after detecting that the pressing operation is complete; e) feeding the digital value to a visual display or recording/monitoring system; and f) zeroing the output of the amplifier with the press not under strain to compensate for gauge hardening, temperature changes and any other long term system variation.
2. A method of monitoring the operations of a
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method of monitoring the operation of a power press This invention relates to a method of monitoring the operation of a power press during operation, and includes both means for monitoring power presses and power presses that include such means. According to the invention a method of monitoring the operation of a power press during operation includes:- a) fitting a strain responsive signal generating device to a member of the press that is subject to strain during operation of the press; b) amplifying the signal generated by the device and calibrating the amplified signal such that it represents the press loads during operation; c) storing the peak value of the amplified signal for each press cycle; d) digitising the peak value after detecting that the pressing operation is complete; e) feeding the digital value to a visual display or recording/monitoring system; and f) zeroing the output of the amplifier with the press not under strain to compensate for gauge hardening, temperature changes and any other long term system variation. Thus the invention provides an accurate means for monitoring press loads during operation which can be utilised not only to reduce the peak press loads to a value necessary to produce a satisfactory product but also to detect any malfunction of the dies, two blanks being pressed or any other fault that causes variations in the press load to occur. In practice several strain responsive signal generating devices may be employed on each press and each strain responsive signal generating device may comprise a strain gauge bridge network; and the devices may be attached to convenient parts on the press structure such as the frame and press connecting rods. The signal from the strain responsive device may be calibrated using a load cell or from known press data. The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a block diagram of a press monitoring arrangement according to the invention; and Figure 2 is an example of a typical trace obtained during press operation. Referring to Figure 1, strain gauge bridge networks 11 are fitted to members of a press that are subject to strain during operation such as the connecting rods and/or to other parts of a power press (not shown), and the signals derived therefrom are fed to a pre-set gain sensing amplifier 12 which has the gain set by reference to a load cell or known press data such that the amplifier output represents the actual instantaneous press load. The output of the amplifier is fed to a suitable recorder 1 3 and to a peak hold circuit 14 whose output signal is proportional to the peak press load. A timing control logic circuit 20 triggered by either a predetermined strain level fed from a press stroke detector 19, or by a suitable signal derived from switching device (not shown) activated by rotation of the press at the appropriate time during the press cycle, resets circuit 14 and initiates sequential operation of the circuits 1 5 and 1 6 as follows; the output signal of the circuit 1 4 is digitised in the analogue to digital converter 1 5 and fed in a serial or parallel via a necessary output buffer circuit 1 6 to a monitoring system (not shown) such as a visual display unit, programmable controller or a mini-computer; the peak hold circuit and timing control circuit being reset by the monitoring system after receipt of data. The amplifier 12 is provided with a closed loop stabilizer feedback circuit consisting of an integrator 1 7 and error detection circuit 1 8 for automatically zeroing the output of the amplifier with the press under no strain. During press operation with the press stroke detector 1 9 detecting press strain above the predetermined strain level the integrator circuit 1 7 is suppressed by a signal from the detector to prevent self compensation action of the stabilizer circuit taking place. Figure 2 illustrates a typical trace of press load plotted against time during a single operation of the press. The peak load is indicated by the letter 'A', and it has been found that such a trace is consistently produced during normal operation. Thus the digital value of the peak load when fed to a visual display unit, or to a recording/monitoring system allows, a) the press to be set up efficiently without excessive loads being produced, b) a true stamping count to be made without free runs, which produce a reduced peak load, being recorded, and c) a safety cut out to be actuated if the load becomes excessive during operation. CLAIMS
1. A method of monitoring the operation of a power press during operation which includes:- a) fitting a strain responsive signal generating device to a member of the press that is subject to strain during operation of the press; b) amplifying the signal generated by the device and calibrating the amplified signal such that it represents the press loads during operation;
c) storing the peak value of the amplified signal for each press cycle; d) digitising the peak value after detecting that the pressing operation is complete; e) feeding the digital value to a visual display or recording/monitoring system; and f) zeroing the output of the amplifier with the press not under strain to compensate for gauge hardening, temperature changes and any other long term system variation.
2. A method of monitoring the operations of a power press substantially as hereinbefore described with reference to the drawing.
3. A power press including monitoring means adapted to monitor the operation of the press in accordance with the method claimed in any one of the preceding claims.
GB8037552A 1979-11-24 1980-08-26 Monitoring press forces electrically Expired GB2064134B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8037552A GB2064134B (en) 1979-11-24 1980-08-26 Monitoring press forces electrically

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7940697 1979-11-24
GB8037552A GB2064134B (en) 1979-11-24 1980-08-26 Monitoring press forces electrically

Publications (2)

Publication Number Publication Date
GB2064134A true GB2064134A (en) 1981-06-10
GB2064134B GB2064134B (en) 1984-02-08

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2127973A (en) * 1982-10-05 1984-04-18 Bl Tech Ltd Monitoring a power press electrically
FR2594223A1 (en) * 1986-02-13 1987-08-14 Bobst Sa METHOD FOR MEASURING THE CUTTING STRENGTH AND LIMITING THE OVERLOADS IN A PLATINUM PRESS AND DEVICE FOR CARRYING OUT THE METHOD
EP0612992A2 (en) * 1993-02-25 1994-08-31 Toyota Jidosha Kabushiki Kaisha Method of diagnosing pressing machine based on detected physical value as compared with reference

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2127973A (en) * 1982-10-05 1984-04-18 Bl Tech Ltd Monitoring a power press electrically
FR2594223A1 (en) * 1986-02-13 1987-08-14 Bobst Sa METHOD FOR MEASURING THE CUTTING STRENGTH AND LIMITING THE OVERLOADS IN A PLATINUM PRESS AND DEVICE FOR CARRYING OUT THE METHOD
GB2186696A (en) * 1986-02-13 1987-08-19 Bobst Sa Method and device for measuring the cutting force and limiting the overload
GB2186696B (en) * 1986-02-13 1990-10-24 Bobst Sa Process for measuring the cutting force and limiting the overloads in a platen press and apparatus for carrying out the process
EP0612992A2 (en) * 1993-02-25 1994-08-31 Toyota Jidosha Kabushiki Kaisha Method of diagnosing pressing machine based on detected physical value as compared with reference
EP0612992A3 (en) * 1993-02-25 1995-04-05 Toyota Motor Co Ltd Method of diagnosing pressing machine based on detected physical value as compared with reference.
US5692404A (en) * 1993-02-25 1997-12-02 Toyota Jidosha Kabushiki Kaisha Method of diagnosing pressing machine based on detected physical value as compared with reference

Also Published As

Publication number Publication date
GB2064134B (en) 1984-02-08

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PCNP Patent ceased through non-payment of renewal fee