How the Alignment Systems Work
Horizontal Roll Parallelism
When aligning rolls for paper mills, printing presses or film lines, the most difficult alignment is the horizontal parallelism (vertical parallelism or levelness can easily be checked using a machinist level. The following section provides sugges¬tions for choosing a reference and step-by-step procedures for equip¬ment setup and performing an alignment.
Choosing a Reference on Process Mills
Conventional methods of roll alignment usually use floor benchmarks (monu¬ments) at the side of the machine as ref¬erences. The L-742W (or L-732W) offers the versatility of using these benchmarks or of picking up a reference roll, such as a cooch roll on paper mills. We strongly believe that using a reference roll pro¬vides the most accurate reference and results in better alignments.
Benchmarks are usually set in a thin concrete floor, are rarely covered, and are routinely run over and nicked. More importantly, they move with the slab of concrete and rarely hold their position relative to the mill itself. Most floors in a typical plant have multiple slabs and are usually cracked throughout, creating instability of the monuments. Unless checked every time they are used, the use of the benchmark probably will result in significant alignment errors.
Here's how the process works for picking up a reference roll: (keep in mind that using the L-742W or L-732W is like having 2 walls, both perpendicular to each other, 100 feet (30.5 M) in radius and very flat).
- The L-732 / L-742 is placed on the L-106 stand outside the machine near the reference roll at the side of the machine and leveled.
- A-1519-2.4ZB Target #1 is placed on the reference roll horizontally at the closest point to laser, is leveled and zeroed in Read9 PDA software. Target #1 is then moved to the far end of the roll.
- Laser Plane #1 (LP#1) is then “Bucked-in” or tilted until Target #1 reads zero at the far point. Target #1 is then moved back to the near point and re-zeroed and the process is repeated until the target reads zero at both locations.
- The laser plane is now parallel to the reference roll.
- Since the LP#2 is perpendicular to LP#1, LP#2 becomes the offset centerline of the mill. This offset centerline has a range of 100 feet (30.5 meters) on both sides of the laser.
- Now we place Target #2 & #3, on floor fixtures at both ends of the machine and are adjusted until the laser hits the middle of the target windows. The targets are then zeroed, establishing the offset centerline, and are not touched during the remainder of the alignment.
- To check the parallelism of a section of rolls, the L-732 / L-742 and L-106 stand are moved along the offset centerline to the desired section and the laser is positioned so LP#1 is about 4-5” from the roll to be measured. The L-732 / L-742 is then leveled.
- Then the yaw adjustment on the laser base is adjusted to tilt LP#2 until both Target #2 & #3 show the same readings, which means LP#2 is now parallel to the offset centerline.
- Now to measure one of the rolls for parallelism, Target #1 is placed horizontally on the roll closest to the laser and zeroed. It is then moved to the far end of the roll to measure the alignment. A +.025” reading means the far end of the roll is pointing to the right relative to the reference roll.
- With targets producing live readings, the roll can then be adjusted until the target reads zero, which means the roll is aligned and parallel to the reference roll. Since the laser generates a plane, rolls up to 100 feet (30.5 m) in elevation in that section that are within 2 feet (610 mm) of the laser plane can be measured for parallelism without changing the setup of the laser.
For checking level on applications with multiple rolls in the same horizontal plane, the L-743 or L-733 must be used since they have a horizontal laser plane in addition to the two vertical planes of the L-742W or L-732W. The laser is leveled and a target is placed on one end of the roll and zeroed. The target is then moved to the other end of the roll and the deviation from level is measured. If both readings are zero, then the roll is level. If not, it can be adjusted using the target as an electronic indictor.
Checking Drive Shaft Alignment
To check the drive shaft alignment, the L-742W or L-732W is placed either at the end of the drive shaft or in the middle, depending on the how long it is. The horizontal plane is made parallel to the top of the closest drive shaft using vertically mounted targets and the vertical scan plane is made parallel to the side of the same shaft.
Each shaft is checked for parallelism to the reference shaft and aligned accordingly. To check a shaft for parallelism/colinearity, a target is moved from the reference shaft without re-zeroing, and two measurements are made, one at either end of the shaft. The difference between the two readings is the angle of the shaft relative to the reference shaft and the average is how far off center it is from the reference shaft. Up to 200 feet of drive shafts can be checked with one setup.
The T-1600 Non-Magnetic Roll Fixture for the A-1519-2.4ZB Targets
T-1600 Non-Magnetic Roll Fixture
The T-1600 Non-Magnetic Roll Fixture is used for aluminum, rubber and stainless steel rolls. Also available is the T-1601 Tight Space Roll Fixture/Tram Bar, which uses two A-1519-2.4ZB Targets to measure alignment in tight spaces. The following procedure describes the setup and procedure for using the T-1600.
Sweeping Through the Arc
Finding Top Dead Center (TDC) on rolls when using long target posts or when the roll diameter is greater than 2 feet (0.6 M).
Slowly rotate the roll (or slide the V-block mag base or T-1600 Fixture around the roll) and watch the display on the R-1355 Readout. The highest number (most +) will be at TDC and this is the measurement value to record.
Note that the level vials on the target mag base or the T-1600 Non-Magnetic Roll Fixture will find TDC for most applications where the roll diameter is less than 2 feet (0.6 M) and when the target post is also less than 2 feet (0.6 M). However, when performing roll alignments on large-diameter rolls or when using long target posts, use the Sweeping Through the Arc Method.
- Set up the T-1600 and T-1601 as shown in the photograph (or set up the target magnetic base). Make sure that the level on the fixture is centered, indicating you are close to TDC.
- If using the T-1600, slowly slide it around the roll while watching the R-1355 display. You will see the readings start to increase you get closer to true TDC. When you get to TDC, the readings will stay the same for a short time as you rotate the roll and then start to decrease as you pass TCD.
- If using the mag base, slowly rotate the roll in the same manner. For large diameter rolls that do not rotate, you will need to slide the mag base in the same way as the T-1600 fixture.
- The highest reading (most positive) will be at the TDC and this is the value to record.
The R-1355-2.4ZB Readout
Read9 ALIGN Screen
showing the difference
between Target 1 and Target 2
relative to the laser plane
The R-1355-2.4ZB Readout uses Hamar Laser's Read9 alignment software on a wireless, ruggedized PDA data receiver. The R-1355-2.4ZB can display data for up to eight A-1519-2.4ZB Single-Axis Wireless Targets, (four targets in two user-selectable screens) making multiple readouts unnecessary and allowing the user to perform many alignment functions with the convenience and portability of a handheld computer. The display screen shows a measurement value for each of the connected targets. Each value represents the position of the laser plane relative to the target centerline. A positive reading indicates that target is above the laser plane, while a negative reading indicates that the target is below the laser plane.
The Read9 software can toggle between Absolute (indicating exactly where the laser plane hits the target cell) and Relative modes. In Relative mode, the readout shows the measurement relative to the user-determined zero point. It also shows a display of the difference between two target measurements, a very useful feature for buck-in, roll alignment and angular measurements, and a graphical display of each target's position relative to the laser plane.