Gear Training Timing issues cause the slide to walk out of a parallelism condition with the bolster plate at approximately 90 and 270 degrees. See the following chart;
Detection of this condition is the first step. We will walk through a fail safe method of detection.
With the slide in a counterbalanced state, cycle the slide to the bottom dead center position. This applies to both (2)
point and (4) point presses.
Measure from the face of the slide down to the top of the bolster plate directly under the left and right connection
Assemblies and record. If inspecting (4) point, measure on the centerline of the press front to rear and directly under
Upper connection assemblies.
After recording your readings on BDC, if the slide face is not parallel with the top of the bolster plate, then adjust
parallelism between face of the slide and top of the bolster plate.
Once parallelism is established on bottom dead center, cycle the press to 90 degrees and record readings under the
Upper connection assemblies to the top of the bolster again and record them. If the measurement are more that .003”
Per foot of span of the bed left to right, the gear train timing is an issue and needed to be corrected.
Example: If the press bed measure 120” or 10’ feet left to right, the maximum allowable out of parallel at 90 degrees
10’ x .003” per foot or .030”. Conditions outside of this tolerance will require correction or damage will occur at the press
and at the tool.
Correction of Out of Gear Train Timing Issues
Place the press at the 90 degree position in the press cycle. With proper counterbalance air pressure applied.
Place a jack under the low side of the slide placing a piece of paper on top of the jack and raise the jack until the paper
will no longer move.
Now place a second jack under the high side of the slide under the connection assembly and raise the jack height until
It is the same height as the opposite jack.
At the point where the intermediate gears mesh, there will be some type of the locking device; keys or taper lock that
holds the intermediate gear’s relationship to the shaft.
Remove the key or loosen the taper lock to allow the shaft to rotate and lower the high side of the slide down until the
face of the slide is resting on both jacks. Make sure that the backlash is adjusted so that the clearance is on the opposite
side of the gear tooth away from the load. Make and fit a new step key or tighten taper lock between intermediate gear and
- Recheck parallelism in the die space with both jacks removed. Cycle press to BDC and recheck/record parallelism.
- Cycle the press several times and recheck die space parallelism at each of the (4) positions.
If your gear train is in time at 90 degrees or ¼ down and is out of parallelism at 270 degrees,
It is the result of gear tooth wear and there is not much you can do. The most important in
relation to gear train timing is die space parallelism at BDC and at 90 degrees. If you are within
Tolerance at these two positions, you should be able to run your machine without difficulty.
For more information, contact Jeff Fredline at 423-278-1450 or 423-278-4244; [email protected]
HOW TO MEASURE AND ADJUST PARALLELISM BETWEEN THE SLIDE FACE AND TOP OF THE BOLSTER PLATE/PRESS BED
To maintain a profitable working relationship between the press and the die, parallelism is up most importance. The goal is to maintain a perfectly square and parallel die space within the press for the tool. On (2) point mechanical metal stamping press Left to Right parallelism is controlled by the adjusting screw drive. Front to rear parallelism is controlled by the slide guiding. There are other conditions that can affect left to right parallel, which we will discuss in later issues.
This month we will examine a step by step process to make the necessary adjustments to maintain die space parallelism.
Steps: Prior to beginning the process, remove the die from the machine and clean the top of the bolster plant and the face of the slide. Check the tightness of the bolster plate hold down bolts to ensure that the bolster is tight to the press bed.
- Under power cycle the machine several times. Adjust counterbalance pressure so that the slide is properly counterbalanced. See the August 2018 addition of Monthly Press Tips on our Blog Site at MECO.
- Rotate the machine to the 180 or BDC position in the stroke of the machine.
- Turn off the main motor and allow the flywheel to come to a full and complete stop. Insert the safety blocks into the die space.
- Measure between the bed/bolster plate to the face of the slide locating the measuring tools directly under the LH and RH upper connection assemblies. Record the findings from both sides.
- For purposes of our discussion today we will say that the parallelism between the slide face and bolster show a .030” difference left to right with the RH side high or greater than the LH side. The allowable tolerance for parallelism between the slide face and the bolster is .001” per foot of span in both the left to right and front to rear orientations. At this point do not worry about the front to rear readings, we will correct those later.
- It is recommended that the higher side of the slide always be lowered using the slide adjusting mechanism to bring the slide back into a parallel condition with the bolster plate. On a (2) point press with slide adjusting capability there will be a drive unit inside the slide assembly. Normally there will either be chains or driveshaft connecting RH and LH sides. In this case if the RH side of the slide is high we will need to adjust it downward to bring the RH and LH sides back into a parallel condition. Disconnect the LH side of the adjusting mechanism so that it does not move during adjustment. Place a dial indicator under the connection assembly on the RH and using the slide adjusting mechanism lower the slide on the RH .030” to bring the slide face back into a parallel condition with the bolster.
- Once parallelism has been obtained between the RH and LH side of the slide using the slide adjusting mechanism, reconnect the drive unit to both sides.
- Now it is time to measure and machine adjustments in the front to rear orientation.
- The first step is to take measurements on the center line of the press bed left to right running front to rear. Remember on a (2) point press: left to right parallelism is controlled by the adjusting screw drive and front to rear parallelism is controlled by the slide guiding system.
- For our discussion after taking measurements we find that the slide is out of parallel with the top of the bolster plate by .040” front to rear. You may need to loosen the gib bolts front to rear to allow for clearance to adjust the slide back into a parallel condition. Place a jack under the side of the slide that is low either in the front or rear of the machine. Place an indicator on the side of the slide opposite the jack. If the slide is .040” out of the parallel front to rear then you will need to use the jack under low side and watching the indicator on the opposite side move the low side up the slide up .020” or half of the .040” to bring the front and rear back to a parallel state. Once parallelism is obtained, now adjusting the gibbing to the correct clearance level. We will discuss how to adjust the gibbing clearances in our next issue in October 2018.
Counterbalancing Cylinders can greatly increase the productive life and output of your press. You can expect to:
- Hide all excessive vertical lift clearances within the drivetrain
- Reduce the drivetrain load on the motor and flywheel
- Improve safety of the machine
- Assists the slide adjusting mechansim
Below are Four Steps on how to adjust the counterbalance cylinder pressure
- Check parallelism between the slide face and bolster. Adjust as required.
- Rotate the slide through the stroke of the machine and stop slide assembly at the 90 degree position and stop the press. If there is a tool in the press, set pressure at 60 PSI. Without the tool, set pressure at 50 PSI.
- Turn the press off and allow flywheel to stop.
- This step will require (2) people, release the brake and allow the slide to drift. If the slide moves up, then decrease the air pressure and if the slide drops increase the air pressure until the slide holds at 90 degrees. Once you have found this balance point, add an additional 3-5 PSI to slightly over counterbalance the slide.
You may ask the question: How often should the counterbalance be adjusted?
MCM Answer: It should be checked and adjusted with each die change.
Always follow your safety guidelines during any maintenance work!
For further information contact Jeff Fredline, Meco Contract Manufacturing, 423-278-4244