BD-04a: Check Machine Geometry and Lost Motion

Transcription

1 Page 1 of 14 BD-04a: Check Machine Geometry and Lost Motion SAFETY FIRST o Follow all Caterpillar facility safety standards when performing this task. o A hoist will be necessary for moving the cube or cylindrical square. EQUIPMENT o cube o cylindrical square o adjustment wedge set o laser axis checker o dial indicator and associated mounting equipment o robot alignment disc, pin, and cross bar RESOURCES o laser equipment documentation Check Machine Geometry and Lost Motion 1. If a part has been machined out of tolerance, the machine or tool robot has wrecked, been disassembled, or repair epaired, ed, determine the best technique for checking the axes. o Use the laser when: a) the axis is long and movement must be checked over the full range of travel; b) the flatness of a surface must be checked. o In most cases, use the cylindrical square when the spindle unit or units move vertically, and can also rotate around the vertical axis. o Use the cube when the spindle unit or units move horizontally, the range of motion is relatively short, and all axes need to be checked for squareness. o Use the vertical bar and cross bar to check the tool robot alignment.

2 Using a Cube: Page 2 of Set up the cube. o Set the spindle unit(s) out of the way, the machine table to an accessible location, and machine control to manual. o Choose a flat surface in the middle of the machine table and clean it. o Clean the under side of the cube and carefully set the cube on the machine table or a pallet on the machine table. o Adjust the position of the cube with a soft hammer to align one face roughly parallel to the direction of table motion. 3. Referring to the figure e below,, establish the X axis as a refer eference. ence. Readings on a Cube o Mount a dial indicator on the spindle unit for reading X1. o Move the machine table to indicate along the full length of cube surface X1.

3 Page 3 of 14 o Align the cube with the direction of table motion so the reading is constant, or as near as practical; note the residual deviation in units that correspond to the measuring equipment, such as ten thousandths per foot. o Remount the dial indicator for reading X2. o Move the machine table to indicate along the full length of cube surface X2. o If the indicator reading is constant, the top of the cube is parallel to table motion. o If the indicator reading is not constant, note the deviation. Note: If the dial indicator has a plunger,, the plunger should be perpendicular to the surface being indicated. If the dial indicator has a lever,, mount the indicator so the lever is no more than 15 degrees ees from parallel with the surface being indicated. See the figure below. Mounting a Dial Indicator

4 4. Check the Y and Z axes. Page 4 of 14 o Remount the dial indicator for reading Y2. o Move the machine spindle vertically to indicate along the full length of cube surface Y2. o The indicator reading, if it is not constant, should be the same (magnitude and direction) as noted in X2. o Remount the dial indicator for reading Y1. o Move the machine spindle vertically to indicate along the full length of cube surface Y1. o If the indicator reading is not constant, note the deviation. o Remount the dial indicator for reading Z1. o Move the machine spindle horizontally to indicate along the full length of cube surface Z1. o The indicator reading, if it is not constant, should be the same (magnitude and direction) as noted in Y1. o Remount the dial indicator for reading Z2. o Move the machine spindle horizontally to indicate along the full length of cube surface Z2. o The indicator reading, if it is not constant, should be the same (magnitude and direction) as noted in X1. 5. If the machine has two spindle units, leave the cube in the same position and check the Y and Z axes of the second spindle unit. o If the opposing machines need to be aligned to each other, check the second machine with the cube referenced to the first machine. o If the spindle units or machines are parallel, the readings will be the same as in step 4. Using a Cylindrical Square: 6. Set up the cylindrical square. o Set the spindle unit(s) out of the way, the machine table to an accessible location, and machine control to manual. o Choose a flat surface in the middle of the machine table and clean it. o Clean the under side of the cylindrical square and carefully set it on the three wedge units on the machine table or a pallet on the machine table.

5 Page 5 of Referring to the figure e below,, establish the X axis as a refer eference ence because it will not be adjusted. X, Y,, and Z Readings on a Cylindrical Square o Mount a dial indicator on the spindle unit for reading X1. o Move the machine table to indicate at the two points at the end of diameter X1. o If both readings are the same, the top of the cylindrical square is parallel to the direction of table motion. o If the readings are not the same, adjust the wedges until the readings are the same. 8. Establish the Y axis as a refer eference. ence. o Remount the dial indicator for reading Y1. o Move the machine spindle unit horizontally to indicate at the two points at the end of diameter Y1. o If the readings are not the same, adjust the wedges until the readings are the same.

6 Page 6 of 14 o Recheck the readings at the ends of diameter X1 and adjust if necessary. o When the readings at X1 and Y1 are all the same, proceed to step Check the Z axis. o Remount the dial indicator for reading Z2. o Move the machine spindle unit vertically to indicate along the full length of the cylindrical square at Z2. o If the reading is constant, the Z axis is perpendicular to the X axis. o Remount the dial indicator for reading Z1. o Move the machine spindle unit vertically to indicate along the full length of the cylindrical square at Z1. o If the Z axis is perpendicular to the Y axis, the reading will be constant. 10. If the spindle unit can rotate about a rotary axis, check the rotational axis. o Line up the spindle unit rotational axis with the centerline of the cylindrical square.

7 Page 7 of 14 o Remount the dial indicator for reading on the top, outer rim of the cylindrical square, as shown below. Note: Any deviation in Z axis from om X and Y should also show up in C axis. Z and C should be square, e, 90 degrees, ees, to each other. Reading Spindle Unit Axis on a Cylindrical Square o Rotate the machine spindle unit about the Z axis a full turn. o If the spindle unit rotational axis is perpendicular to the X and Y axes (co-linear with the Z axis), the reading will be constant If the machine has a second spindle unit, check it as in steps 9 and 10 without moving the cylindrical square. 12. If the rotational axis of the spindle is vertical, check the spindle tram. o Line up the spindle with the centerline of the cylindrical square.

8 Page 8 of 14 o Mount the dial indicator on the spindle tool holder to read on the top rim of the cylindrical square, as shown below. Spindle Tram Reading on a Cylindrical Square o Rotate the spindle tool holder a full turn. o If the spindle axis is perpendicular to the X and Y axes (co-linear with the Z axis), the reading will be constant. 13. If the machine has a second spindle, check its tram as in step 12 without moving the cylindrical square. Using a Laser: 14. Set up the laser equipment. o Establish a solid, non-moving location for the laser where it can illuminate targets that move with the machine bed, the spindle unit, or other moveable equipment.

9 Page 9 of 14 o Clean the selected location, and set the laser in position. o Use the bubble for an approximate level setting. 15. Reference the laser to the horizontal axes X and Y (or X and Z on some machines). o Mount the laser target on the machine table or a pallet at a height where the horizontal plane laser strikes it, as shown below. Referencing encing the Laser to the Horizontal X Axis o The targets should be as close to the laser as possible and in a line along one axis from the laser. Otherwise, two directions have to align at the same time. o Move the machine table to take readings at each end of the X travel. o Adjust the laser or target heights so the readings are equal.

10 Page 10 of 14 o Mount the laser target on the spindle unit at the same height, as shown below. Note: Rule of thumb. If the target get is close to the laser,, adjust the target. If the target get is far from om the laser,, adjust the laser. Referencing encing the Laser to the Horizontal Y(Z) Axis o It is always best to use a configuration, as shown below, to align with the target(s) at X and the laser at 0. o Move the spindle unit horizontally to take readings at each end of the Y(Z) travel. o Adjust the laser or target heights so the readings are equal. o Recheck the readings on the table X axis to ensure that the Y(Z) adjustment did not affect the X adjustment. 16. Check the horizontal axes for sag. o Take one or more readings in the middle of the horizontal table and spindle unit travel. o Any difference between the readings at the end of travel and the middle indicates sag.

11 Page 11 of Check the vertical axis Y (or Z on some machines). o Mount the target on the spindle unit so the laser beam illuminating the target is parallel to the X axis, as shown below. Reading the Vertical Axis with a Laser o Take readings at the bottom and top of the spindle unit travel. o Remount the target on the spindle unit so the laser beam illuminating the target is parallel to the Z axis o Take readings at the bottom and top of the spindle unit travel. o If the readings do not vary, the vertical axis is perpendicular to the horizontal plane defined by the X and Z axes. Using the Vertical Bar and Cross Bar to Align an Ingersoll Tool Robot: 18. Check vertical alignment. o Set the robot to manual control.

12 Page 12 of 14 o Mount a dial indicator on the robot head to read the side of the vertical bar attached to the side of the tool cage, as shown below. Checking the Tool Robot Vertical Axis o Move the robot head the full range of vertical motion to check deviation from vertical in the Y direction. o Remount the dial indicator to read the front of the vertical bar, and move the robot head the full range of vertical motion to check for deviation from vertical in the X direction. 19. Check head rotational alignment. o Ensure all axis are in the home position. o Mount a special disk in one set of robot fingers. o Install the cross bar between the pad on each side of the tool cage.

13 Page 13 of 14 o Position the disk so the index pin slips through the mating holes in the disk and in the cross bar, as shown below. Do not move CT axis to align disk to bar. Move only XT, YT, ZT or BT axis. Checking the Tool Robot Rotational Alignment o Withdraw the pin and remount the disk in the other set of robot fingers. o Rotate the robot head 180 degrees with pendant function. o Align disc and pin. Again, do not move CT, only XT, YT, ZT or BT axis. o The index pin should slip through the mating holes as before. Checking for Lost Motion: Note: Lost motion is a problem only on machines that position the axes with resolvers on the axis drive motors.

14 Page 14 of Mount a dial indicator on the stationary machine way to read parallel to the axis to be checked, as shown below. Dial Indicator Reading Lost Motion 21. Increment the axis to drive the dial indicator almost to the high end of its travel. 22. Reverse the axis to release the dial indicator almost to the low end of its travel. 23. Zero the reading on the indicator,, and note the axis position readout on the machine. 24. Increment the axis to release the dial indicator farther in the same direction, past the low end of its travel. 25. Increment the axis back to the machine readout where e the dial indicator was zeroed. o The indicator should read zero. o Any deviation from zero is lost motion due to clearances in the positioning mechanism (drive gear backlash, ball nut looseness on the screw, ball screw endplay, etc.).