Definitions

• This application pertains to the art of press fabrication and more particularly to control of a pressing operation or run.
• the invention is particularly applicable to continuous, real-time monitoring of press operation and will be described with particular reference thereto.
• the invention has broader applications such as in any system in which stress or strain characteristics are advantageously measured or monitored continuously, accurately, and in real time.
• a substantial number of manufactures are formed through punching or press operations.
• raw material such as steel or other malleable metal is subjected to a high-force blow from a die.
• Application of insufficient force will result in underformed or malformed workpieces.
• Excessive force may damage the workpiece or the press itself.
• excessive force may be indicative that the press is being operated at too high a level. That is, the particular press operation may be more suitable for a press of higher capacity or force.
• the present invention contemplates a new and improved press monitor which provides not only intermittent or set-up press characteristics, that provides continuous, real-time and non- supervised monitoring and control of a press operation.
• a linear variable displacement transducer which includes a coil portion movably connected to a core portion such that the magnetic flux generated by current impressed on the coil is influenced by a position of the core relative thereto.
• a securing means is provided for securing the core portion and the coil portion to spaced apart portions of a housing of an associated press. This is accomplished such that compression and expansion of the housing will influence a relative position of the core to the coil.
• An alternating current is impressed on the coil and variations in the resultant magnetic flux, due to the relative position of the core, is monitored. A signal is generated representative of this relative position.
• the signal is digitized and filtered to provide a press deflection system which bears information on the force being imparted to a workpiece in the press.
• a means is provided for archiving or generating a printout of press characteristics.
• a system for automatically zeroing the same to achieve a consistent minimum output when a press is unloaded.
• An advantage of the present invention is the provision of a press monitoring system adapted for continuous, uninterrupted and unsupervised duty.
• Another advantage of the present invention is the provision of a system which allows for building a record of press characteristics associated with each workpiece fabricated therefrom.
• Yet another advantage of the present invention is the provision of a system by which compressed characteristics may be compared to preselected standards to determine acceptability thereof. Further advantages will become apparent to one of ordinary skill in the art upon a reading and understanding of the subject specification.
• FIGURE 1 illustrates a press machine and monitor/controller in accordance with the present invention
• FIGURE 2 illustrate a top and side view of the transducer array as utilized in connection with the monitor of FIGURE 1;
• FIGURE 3 illustrates a block diagram of the data acquisition/control unit as illustrated in FIGURE 1;
• FIGURE 4 provides a flow chart of the logical flow in connection with a press monitor/control system of FIGURES 1-3;
• FIGURE 5 provides a flow chart of an automatic zeroing function of the subject monitor/control system.
• FIGURE 1 illustrates a press A, a linear variable displacer transducer ("LVDT") mechanism B, and a data acquisition/controller unit C.
• the press A is suitably comprised of any, conventional press mechanism.
• Such a mechanism includes a ram 10 disposed adjacent to a platen 12.
• typical workpiece formation such as in a formation of a workpiece 14, is accomplished by provision of a die or tooling in at least one of ram 10 and platen 12.
• the press A is illustrated as a motor-driven system employing a motor/gear arrangement 16 to drive the ram 10.
• any ram such as a hydraulically driven ram, may suitably be utilized in connection with the subject system.
• the ram A includes a frame or housing portion 20 which links the ram 10 with the platen 12. It will be appreciated that operation of the press results in an induced stress or strain on the frame 20.
• the LVDT mechanism B is secured to the frame 20 in a fashion to be detailed below. Stresses and strains within the frame 20, induced by operation of the press A, are measured by the mechanism B. These signals are, in turn, communicated to the data acquisition/controller unit C which will also be detailed below.
• a second LVDT B' which is shown as encased in a metallic housing 22. Such a second LVDT may be utilized for complimentary data acquisition or redundancy, and is interfaced to either the data acquisition/controller C, or to a secondary, similar unit C (not shown) .
• the LVDT B is, in the preferred embodiment, also encased in housing to similarly isolate it from debris and particulate matter, although it is not shown for illustrative purposes.
• FIGURE 2 illustrates, in detail, a preferred fabrication of the LVDT mechanism B.
• FIGURE 2A illustrated a top view while FIGURE 2B illustrates a side view.
• a rod member 26 includes opposed, first and second spaced-apart ends 28 and 30.
• the elongated rod 26 is suitably formed of a relatively inflexible material, such as hardened steel.
• First end 28 is secured to the frame 20 ( Figure 1) with a fastener such as illustrated by bolt 34.
• the fastener or bolt 34 functions to secure the first end to the frame so as to allow axial displacement of the rod 26 corresponding to frame movement at a first mounting point, defined as that accomplished with fastener 34.
• the second end 30 is slidably received into a support member 36 which allows axial movement of the rod 26 with respect thereto.
• the support member 36 is, in turn, originally secured to a base plate 38 via fasteners 42.
• the base plate 38 is affixed to the frame 20 ( Figure 1) via fasteners 44 and further secured by a dowel pin 45.
• the system advantageously employs an intermediate support member 46 disposed between the first and second space apart ends 28, 30.
• Support member 46 is second to the frame 20 with fasteners 48. Like the support member 36, the member 46 allows axial movement of the rod 26 with respect thereto.
• a bolt mechanism 50 is secured coaxially to the rod 26 at an extreme of second spaced apart ends 30. This bolt is, in turn, connected to a movable portion of a linear variable displacement transducer 52.
• a suitable LVDT is manufactured by Lucas Schaevitz of Pennsauken, New Jersey. The LVDT 52 employs a coil mechanism, movable relative to a core mechanism.
• the LVDT 52 which is secured to the base plate 38 by fasteners 54, is adapted for generating a signal relative to longitudinal stresses and strains on the frame 20.
• the LVDT 52 includes a core 60 which is coaxially secured to the rod 26 ( Figure 2) .
• An oscillator/driver 62 imparts a current to a coil 64, thereby inducing a magnetic flux therefrom.
• the core 60 is ferrous and disposed physically approximate to the coil 64. Accordingly, flux generated by application of current form the oscillator/driver 62 is affected by relative position of the core 60 thereto.
• a sensor coil 68 of the LVDT 52 acquires information as to properties of the flux, and provide a signal from voltages induced therefrom to a demodulator 70.
• an analog signal from demodulator 70 is communicated to a filter 72.
• the signal is them communicated to a buffer/amplifier 74 and a programmable gain amplifier 76 through a summer pair to be described further below.
• the signal to the buffer/amplifier 74 is communicated to a continuous analog recorder output, such as a plotter at port 80.
• the signal from amplifier 76 which is an amplification from that of filter 72, is provided to a peaks detector 78.
• a first switch 86 is closed to provide an output from peak detector 78 to an analog to digital (A/D) converter 88.
• the A/D converter 88 serves to digitize this signal for communication to a microprocessor base controller 90.
• the switch 86 is opened and a switch 92 is closed to short out the peak detector 78. Accordingly, the switch 92 allows for zeroing of the system to stable conditions.
• the digitized signal from A/D converter 88 is provided to the controller 90, operating under software as detailed below.
• the controller 90 also includes an alarm output 94, a port for bi-directional serial link 96, an end of cycle signal receiving port 98.
• Common controllers also include means 100 for receiving data from additional channels such as from a second LVDT, as well as means for communicating data to such additional channels.
• the system also employs a key pad for manual data entry, as well as a display as illustrated by LCD readout area 106.
• An external display 110 has also advantageously employed to provide an indication as to monitored press characteristics outside of the actual controller area.
• a signal from controller 90 is communicated to a digital to analog ("D/A") converter 114 to a summer 116.
• the summer 116 sums the signal received from filter 72 to form a composite signal therewith.
• a feedback loop is provided for enhancing stability and accuracy of the system as determined by the controller 90.
• a bias voltage, generated from bias generator 120 is selectively applicable, via a switch 122 to a summer 120. This bias allows for additional controller and stabilizing of the signal from the filter 72 and for the purpose of maintaining an optimized signal range to peal detector 78. However, bias is not communicated directly to influence the buffer amplifier and, accordingly, the printout achieved from port 80.
• FIGURE 4 a flow chart of the instructions of the controller 90 is illustrated.
• the procedure for continuous monitoring is commenced at block 130. From this point, progress is made to block 132 which represents retrieval of data representative of a selected threshold. This data is advantageously user definable via user input from serial link port 96 or keypad 110.
• block 134 at which point strain gauge data, obtained in accordance with an output of the LVDT 52 ( Figure 3) is achieved.
• the strain gauge data is communicated to a recorder 138 which may be suitably formed of any non-volatile data storage mechanism such as a static memory. Strain gauge data is then compared to first and second threshold data at block 140.
• a negative determination in block 146 facilitates determination as to whether an end of cycle signal is present, as received from port 98 ( Figure 3) .
• a positive determination from the end of cycle signal at block 152 directs an end of procedure at block 154.
• a negative determination at block 152 directs the system to proceed back to block 134, at which point additional strain gauge data is obtained from the current press cycle.
• auto-zeroing is executed when the monitor device, such as the press, is idle. If the device commences a load cycle, the function is immediately aborted without adjustment so that load cycle data integrity may be maintained. The auto-zero procedure is commenced at block 200.
• a negative determination at block 202 causes a "wait loop" by repeating the test.
• a positive result at block 202 causes progress to block 204, at which point analog circuitry is setup. The peak detector 78 and bias generator 120 are disabled and the programmable gain amplifier 76 is reconfigured at this point.
• acquired data is compared to fixed (non-alterable) data.
• a determination is then made at to whether the mean value thereof is within preselected operational limits.
• a negative determination signifies an error condition which triggers an alarm at block 210 and an unconditional abort of the process at block 212.
• the alarm at block 210 includes the displaying of a message, on a liquid crystal display in the preferred embodiment, disclosing a nature of the malfunction to an
• a positive determination at block 208 causes progress to block 214. At this point, a digital value is calculated which will negate the data obtained in block 206. This value is then normalized and sent to the digital analog converter 114 in block

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• Control Of Presses (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)

Applications Claiming Priority (1)

Publications (2)

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Family Applications (1)

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• 1995
  • 1995-08-08 JP JP50839597A patent/JP2001524203A/ja active Pending
  • 1995-08-08 AU AU32412/95A patent/AU3241295A/en not_active Abandoned
  • 1995-08-08 EP EP95928782A patent/EP0870169A1/en not_active Withdrawn

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