BUILDER: Mori Seiki
MODEL: SL-25B
CONTROL: Fanuc 16-T
TITLE: TURRET ALIGNMENT (SIMPLE ROTATIONAL ALIGNMENT)
SUMMARY: THIS PROCEDURE EXPLAINS A SIMPLE ROTATIONAL ALIGNMENT OF THE TURRET AFTER AN IMPACT.
DETAILS:
After a crash, several items should be checked and noted. These are:
- Headstock alignment (parallelism of the spindle centerline with the Z axis). This is done either with a test bar mounted to the spindle or more typically by cutting a part and checking the part for taper. If correction is necessary, align the headstock before performing the turret alignment. We prefer to use a part at least 1 inch in diameter (to avoid excessive part deflection) and at least 5 inches in length.
- Rotational alignment of the turret. This can be done using one of two methods:
- Parallelism of a turning tool pocket to the X axis movement.
- Centering the bore of a boring bar holder to the spindle rotational center in the X axis plane and looking for deviation in the Y axis plane. Mount an indicator to the chuck and rotate the chuck with the indicator stylus inside the boring bar holder. (See picture 1 below).
- Be sure to note the machine position of the X axis when you have positioned the X axis so that the boring bar holder is centered on the spindle. We prefer this method because if the alignment is done using this check (as opposed to aligning the turning tool pocket with the X axis movement), you will end up with the tool tips centered better on the spindle. Facing will be better as well as drilling on center. It is best to hold the indicator in a piece that is clamped in the chuck, but often times this will not be available. It is possible to use an indicator and magnetic base to do this check (see picture 1 below), but the length of this setup should be kept to a minimum to reduce sagging and only a high quality base should be used.
- Parallelism of the turret bottom with the Z axis movement
Picture 1
Write down the amount and direction of any deviations from “0”.
In the case documented in this procedure, the headstock alignment and the Z axis parallelism of the turret were ok and no adjustment was necessary. However, the turret had been rotated by the impact and needed to be aligned. This is done as outlined below:
1. Position the turret so that the boring bar holder (use the best, least beat up one you can find, preferably without impact marks or scoring, rust or dents in the bore) is centered on the spindle rotational center. Make a note of the machine position in the X axis. Note the amount of deviation from “0” in the Y axis plane. (See picture 1 above)
2. Mark and remove the number plate around the center hub of the turret by taking out the Phillips screws. (See picture 2 below).
- PICTURE 2
3. Remove the 4 M8 cap screws in the turret center cover and remove the cover. (See picture 3 and 4). You may need to tap the cover in the CW and CCW direction to get it loose enough to pull out. This will expose the turret.
Picture 3
PICTURE 4
4. Remove the 2 M8 taper pins in the turret. These are located 180 degrees from each other. They are 90 degrees from the “master” pin hole. This is the hole with the small counter-bore. (See picture 5).
Picture 5
5. Loosen the (12) 8mm cap screws on the outer bolt circle. These are the bolts that hold the turret-side of the curvic coupling in place. Retighten the screws slightly (a little more than finger tight) to prevent excessive turret movement. (See picture 6).
- Picture 6
6. While watching the indicator, strike the turret to rotate it in the needed direction (CW or CCW) with a soft hammer or a piece of sturdy wood. (See picture 7) As you do this, check and adjust the X axis position back to center after seeing any change in the Y axis direction as the centerline will keep changing as the turret is rotated. Continue this process until the indicator reads “0” all the way around the inside diameter of the boring bar holder.
- Picture 7
7. Tighten the12 screws on the outside bolt circle in a cross pattern until all are fully tightened. We prefer at least 3 times around the pattern, tightening a little more each time.
Picture 8
8. Check your indicator again to make sure that the tightening of the screws did not move the turret. If you still have “0” all the way around the inside diameter of the boring bar holder, you can proceed. If not, loosen the screws and repeat from step 5. After achieving “0”, note the resulting machine position in the X axis9. After all screws are tight and your indicator reading is “0”, you will need to lightly ream the taper pin holes to remove any bur cause by the pin when the turret was impacted. (See Picture 9)
Picture 9
9. Install new taper pins. Use only the correct size metric taper pin with a tapped hole for later removal. Put a screw into the tapped hole in the pin and lightly strike the screw with a small hammer to seat the pin.
10. Check the rotational alignment with the indicator one more time with the indicator to make sure the turret is still correctly aligned.
11. Reinstall the center cover and the number plate.
12. Using the machine position of the X axis from step 8, calculate the difference between the current X centerline position and the machine specification distance. You will need to adjust the X axis grid shift to get the distance from X zero-return (home) position to the spindle centerline back to the specification distance. The specification distance may vary depending on the machine model and number of turret stations.See below:
Model: SL-25A, 25B, 25MC
10 Station Turret: 250mm or 10 inches
12 Station Turret: 250mm or 10 inches
Using the calculation from step 13, calculate the X axis grid-shift needed to put the machine back to specification. Use the following as a guide and you can be successful on your first attempt:
GRID SHIFT
Grid Shift is another element that must be considered to fully understand how the CNC establishes axis home position. Grid shift is a value entered into a CNC parameter that electronically phase-shifts the data coming from the motor’s encoder.
When a grid shift value is entered, the reference counter in the CNC no longer “sees” the native encoder data. The reference counter “sees” only the phase-shifted data.
By using this parameter, the machine’s ZRN stop position can be easily adjusted.
INCH-TO-METRIC CONVESIONS
| Millimeters (mm) | Microns (m) | Inches (in) |
| 25.4 | 25,400 | 1 |
| 1 | 1000 | 0.0394 |
| .001 | 1 | 0.0000394 |
| .0254 | 25.4 | .001 |
| .00254 | 2.54 | .0001 |
| Value in prm #1820 | D.U. | Multiplier to get 1 micron value |
| 10 | .2 | 5 |
| 20 | .1 | 10 |
| 4 | .5 | 2 |
| 2 | 1 | 1 |
DETECTION UNIT CALCULATION
Since the parameters for grid shift and backlash are in detection units, it is important to know how to calculate the detection units for each axis on the machine. Note that the detection unit may not always be the same for all axes on a machine.
To do this, check parameter #1820 (CMR – command multiply ratio), and use it in the following formula:
2m /prm1820 = detection unit (D.U.)
EXAMPLES:
| Value in prm #1820 | D.U. | Multiplier to get 1 micron value |
| 10 | .2 | 5 |
| 20 | .1 | 10 |
| 4 | .5 | 2 |
| 2 | 1 | 1 |
GRID SHIFT CALCULATION EXAMPLE
Example:
Suppose you have determined that an axis needs to be grid-shifted in the positive (+) direction by 0.030in. First, you must convert this error into a micron value.
30 X 25.4 = 762m
Then, you must determine the detection unit. Let’s say that parameter #1820 = 10.
2m/10 = .2m
Thus, the detection unit is .2m
To find the number to be added to parameter #1850 which would equal 762 microns, solve for “A” in the formula below:
762m = A X .2
762m/.2 = A
3810 = A
Thus, we would add 3810 to the existing grid shift value.
PWE (parameter write enable) will need to be on to change the parameter and the machine must be in M.D.I. After changing the grid-shift parameter (1850 for X axis), you will be prompted to shut off the control. Do this and wait several seconds and turn it back on. Let the machine power on fully. You should see and “alarm 300 X axis needs zero return”.
Zero-return the X axis then bring the boring bar down in the X axis until the machine position is the specification distance (X -10.0000”). When the indicator mounted to the chuck is rotated inside the boring bar at this position, your indicator should read “0” as in step 8. If not, adjust the X axis position until the boring bar holder is concentric with the spindle rotation (indicator reads “0” all the way around) then recalculate the grid shift based on the new X axis machine position. If you achieve “0” all the way around the boring bar holder at the machine specified distance (X-10.0000”) the turret alignment is complete.
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