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Tonnage Monitors-101 - A Basic Guide for Stamping Press Load Monitoring

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This presentation explains the function, features, and benefits of Tonnage (Load) monitors applied to metal stamping (punch) presses. This presentation explains how tonnage monitors work, the proper application of high, low, and repeatability setpoints, and the ideal mounting locations for tonnage strain link sensors.

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Tonnage Monitors-101 - A Basic Guide for Stamping Press Load Monitoring

  1. 1. © 2018 - Wintriss Controls Group - All rights reserved Tonnage Monitors 101 Jim Finnerty Product Manager – Wintriss Controls
  2. 2. Tonnage Monitoring  What is it?  A system that monitors the force being exerted by a press during the working portion of the cycle  Compares the actual working force to preset limits, and stops the machine when the limits are exceeded © 2018 Wintriss Controls Group LLC- All rights reserved
  3. 3. Tonnage Monitoring  How do Tonnage Monitors work?  Sensors called strain links are mounted on the frame of the press in known locations where strain is proportional to load  The strain links measure the deflection of the press frame under load  A calibrated controller converts the strain link signal to a tonnage value © 2018 Wintriss Controls Group LLC- All rights reserved
  4. 4. Deflection  When the press is under load, the frame deforms  It will either stretch or compress depending on the shape of the frame and the location on it  The columns of straight side presses get longer under load  The inside front portion of a gap frame press stretches under load  The back of a gap frame press compresses under load  Deflection is measured in “microstrain” (parts-per-million) © 2018 Wintriss Controls Group LLC- All rights reserved
  5. 5. Straight Side Presses  A straight side press is constructed like a sandwich  The base and crown are the “bread”, and the columns are the “meat”  There are big threaded rods called tie rods inside the columns that hold the whole thing together  The tie rods have nuts at each end that are tightened to pre-stress the whole machine  The columns are permanently compressed when the press is assembled  Tonnage monitors measure the columns “relaxing” slightly under load © 2018 Wintriss Controls Group LLC- All rights reserved
  6. 6. Calibration © 2018 Wintriss Controls Group LLC- All rights reserved  Calibration is the process that enables the tonnage monitor to read the actual force being exerted by the press  Load cells are used to measure the actual force under the ram, then the tonnage monitor’s output is dialed in to match  Once the tonnage monitor is calibrated, the press itself becomes a force-measuring instrument  Calibration isn’t 100% necessary, but it provides some benefits
  7. 7. Zero Cam  The press frame expands and contracts with changes in temperature  The strain links measure this change, but we really wish they wouldn’t  The load monitor cancels out the temperature change by reading the strain link output during a non-load generating portion of the stroke (i.e. TDC), and subtracting this reading from the overall load  The “Zero Cam” is a latching magnetic limit switch (LMCS) that provides a timing signal to the tonnage monitor through the top of the stroke  The LMCS tells the load monitor where in the stroke to zero out the tonnage © 2018 Wintriss Controls Group LLC- All rights reserved
  8. 8. Setpoint Limits  Setpoint limits are thresholds that are set for each tool  When a setpoint limit is exceeded, the tonnage monitor stops the machine  High Tonnage Limit – If the peak tonnage exceeds this limit, the press will stop  Low Tonnage Limit – The peak tonnage must exceed this level or the press will stop © 2018 Wintriss Controls Group LLC- All rights reserved
  9. 9. Setpoint Limits © 2018 Wintriss Controls Group LLC- All rights reserved High Tonnage Limit Press Stops!
  10. 10. Setpoint Limits © 2018 Wintriss Controls Group LLC- All rights reserved Low Tonnage Limit Press Stops!
  11. 11. Nuisance Stops  It’s normal to see gradual changes in the peak tonnage value thought the day  Your high and low setpoints must allow for this variation or nuisance stops will result  This makes it impossible to monitor small tonnage variations with only high and low setpoints  Fortunately, there is a 3rd setpoint type © 2018 Wintriss Controls Group LLC- All rights reserved
  12. 12. Repeatability Limit  Gradual changes in tonnage are normal, but abrupt changes usually mean trouble  The Repeatability Limit is the maximum allowable variation in tonnage from one stroke to the next  High and low limits can be relaxed to prevent nuisance stops, but still protect the machine and die  The Repeatability Limit can be set to a very precise value (often in the tenths of tons) without causing nuisance stops © 2018 Wintriss Controls Group LLC- All rights reserved
  13. 13. Repeatability Limit © 2018 Wintriss Controls Group LLC- All rights reserved Press Stops!
  14. 14. Reverse Load  As regular (forward) load increases, the press frame loads up like a giant spring  When the punches break through, the spring suddenly releases, and the load direction reverses  Presses are designed to withstand forward load, but not reverse load (20% of capacity max).  Excessive reverse load damages bearing cap bolts, and the ram adjust mechanism © 2018 Wintriss Controls Group LLC- All rights reserved
  15. 15. Tonnage Monitor Benefits  More repeatable setups  Reduce off-center loading  Detect loss of lubrication  Detect material variations  Detect tool wear © 2018 Wintriss Controls Group LLC- All rights reserved
  16. 16. Your Insurance Policy  Even if you utilize other forms of monitoring such as die protection sensors or in-die measurement systems, tonnage monitors are still an important part of the overall monitoring package  Unlike those other devices, a tonnage monitor requires no tool- specific sensors or programming  The tonnage monitor becomes your “insurance policy” against machine or tool problems that are unusual or unforeseen – the things you would never install a specific sensor to detect © 2018 Wintriss Controls Group LLC- All rights reserved
  17. 17. AutoSet Load Monitors  Wintriss Controls offers a series of accurate and reliable stand-alone press tonnage monitors suitable for any application  The basic model 1500 provides economical protection for any machine  The 1500 Plus and 1504 Plus models provide advanced features that are extremely easy to use © 2018 Wintriss Controls Group LLC- All rights reserved
  18. 18. AutoSet Load Monitors  AutoSet 1500  2 inputs, high tonnage limit only  AutoSet 1500+  2 inputs, high and repeatability limits, reverse load display  AutoSet 1504+  Same as the 1500+ but with 4 inputs © 2018 Wintriss Controls Group LLC- All rights reserved
  19. 19. AutoSet 1500  This is the simplest and cheapest tonnage monitor we make  Available with either an enclosure or panel mount  The AutoSet 1500 uses auto-setpoints  It reads the tonnage during a sample period, and sets the high limit “X” percent above the highest reading © 2018 Wintriss Controls Group LLC- All rights reserved
  20. 20. AutoSet 1500  Setpoint limit percentage is set by the user with a rotary switch on the board  The sample period is either 1 or 15 strokes. © 2018 Wintriss Controls Group LLC- All rights reserved
  21. 21. AutoSet 1500/1504 Plus  The “Plus” models have both high and repeatability setpoint limits  There’s a momentary pushbutton on the front panel that allows the user to display reverse load  The AutoSet 1500+ has two inputs  The AutoSet 1504+ (shown) has 4 inputs © 2018 Wintriss Controls Group LLC- All rights reserved
  22. 22. Contact Us Backed by 60+ years of manufacturing experience, Wintriss has the expertise to help you protect your presses and keep your stamping operation performing smoothly and efficiently. Contact us by:  Calling (800) 586-8324  Submitting this simple form © 2018 Wintriss Controls Group LLC- All rights reserved

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