Calculating Press Reaction

Table of Contents

Collect a notebook, pen, and calculator. During this procedure, the line speed displayed on the controller must be noted. Measurements must be taken in the order parts are produced from the machine. It might be helpful to have support personnel available to observe and record.

  1. Set Press Reaction Time to zero.
  2. Program two press operations (in the case of a shear, two part lengths). Be sure to program them at a distance that is long enough so that when the XL200 fires the press in automatic, the line is at speed. If the line is still accelerating up to speed, the test will be invalid. (If the machine supports in-line punching, program the shear and punch tool at the same offset distance for the purpose of the test. After the test, reprogram the punch tool to the correct physical distance).
  3. Perform a standing press operation (fire the press manually while the material is halted).
  4. Run the line.
  5. After the controller has fired the press twice, measure the distance from the standing press hit to the first automatic press hit. Then measure from the first automatic press hit to the second.
  6. Subtract the second length from the first.
  7. Divide the result by the line speed in feet per minute (meters per minute).
  8. Multiply the result by 5 (0.06 if using the metric system).
  9. The result is the Press Reaction Time.

If part lengths are inconsistent due to encoder tracking problems or press reaction variances, this test is a waste of time. Inconsistencies must be eliminated first before measurements to eliminate constant errors can be performed. To entertain any other methodology is an exercise in futility and frustration.

When performing the Press Reaction Calculation Procedure for the first time, it is often helpful to run at least 5 parts in a row. The first two can be used to calculate reaction time, if the last 4 parts are consistent.

Example:

Maintenance (Joe) is called to examine an open loop flying die machine. Larry, the machine operator, complains that the machine produces varying lengths on startup and sometimes during the production run. Upon examination, Joe can see that the XL200 was never programmed with a Shear Reaction value (or he suspects the value has been changed).

Joe begins by programming 5 parts at 60” (1524 mm). It is well known that this machine reaches speed after a short distance, so there is no need to program a longer part that might potentially become scrap. He sets the line to run at 150 fpm (46 mpm) for the purpose of the test.

Joe performs a Manual Shear operation to reference the cutoff, and then he runs the line. After 5 parts are produced, he halts the line and measures the parts in the order they were produced, first to last. His results are:

Based on the numbers, Joe can see that there is an overall length variance that he must address before he continues with any other efforts. He knows how critical the material encoder tracking is to the accuracy of the process, so he begins by checking the alignment of the encoder wheel and bracket to the material.

Joe finds the wheel to be significantly out of alignment and corrects the problem. He programs another 5 parts, performs a Manual Shear, and runs a second set of 60” (1524 mm) parts. This time, his results are:

From the results, Joe is satisfied that the machine is performing consistently enough that he can now use the features built into the XL200 to eliminate the rest of the length issues. He runs through the procedure for calculating Press Reaction, using the average of the last 4 parts as his “second length”:

1st length – 2nd length = 4.235” (107.6 mm)
4.235” (107.6 mm) / 150 fpm (46 mpm) = 0.02823 (2.3528)
0.028233 (2.3528) · 5 (0.06) = 0.1412 s

Joe enters the value 0.1412 s into the Shear Reaction parameter in the XL200 controller. He also knows he can use the Calibrate Trim feature to remove the consistent 0.265” (6.73 mm) error from his overall length.

Now, when Joe turns the line over to Larry, production can expect part lengths to be consistent and accurate from first-to-last, even when Larry changes speeds during production.

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