The L-743 and L-733 require a simple set up process for finding and fixing most geometry errors. In most cases, one setup is all that is required to completely measure the geometry errors of machining centers.
When envisioning how the system works, keep in mind that the L-743 and L-733 systems are like having a ceiling and two walls, each 100' (30.5 meters) in radius and mutually perpendicular to each other.
Setting Up (Bucking-in) the Laser
When setting up the laser to measure either straightness or flatness, the user must first position the laser plane(s) so that they are parallel to the reference points on the machine. This process is called "bucking in" the laser. In cases where only one target is used to set up the laser, the user must first determine what type of setup exists: close or remote. To speed up the setup process, the use of three reference target is highly recommended.
- For measuring straightness, two reference points are needed.
- For measuring flatness, three reference points are needed.
- For measuring the squareness (three areas) of a machining center, five reference points are needed.
Once the laser has been set up to its reference points, the targets can be repositioned to measure the various surfaces or lines of motion for deviation from the references. A plus (+) reading indicates the target is higher than the reference points, and a minus (-) reading indicates they are lower.
Measuring Horizontal Straightness
To measure horizontal straightness of a surface or machine axis, two reference points and one vertical laser plane are needed.
- Mount a target horizontally at the closestreference point to the laser, either on the side of the table or fixtured into the spindle. Adjust the target so that it detects the laser.
- Zero the target and move it to the farthestreference point from the laser until the target reads zero. Re-measure the initial reference point, re-zero the target, and repeat the procedure until the same reading is produced for both reference points.
The laser is now parallel or “bucked in” or adjusted to the reference points.
- Place the target at intervals along the surface or machine axis. Any deviations from zero are a measure of straightness relative to the reference points. If the target is mounted so that its top is to the left of the laser plane, then a "+" reading means the measured point is to the "left" of the reference points and a "-" reading means the point is to the right of the reference points.
To measure flatness, a horizontal, continuously rotating laser plane is “bucked in” or adjusted so that it is parallel to three reference points on a table, set of ways, or a surface. The diagram below shows the setup for a 3-point buck-in using one target and multiple targets. The following procedure describes a 3-target buck-in:
- Place all the targets on one reference point one at a time and adjust them up or down so they detect the laser plane.
- Zero the targets, one-by-one, on the same reference point.
- Reposition the targets so that one target sits on each reference point, usually in an “L” pattern (see Figure 2).
- Using the PITCH and ROLL adjustments, adjust the laser scan plane until all three targets produce the same value, thus making the laser parallel to the reference points.
Note: This may also be accomplished by using one target, zeroed on the closest reference point to the laser, and moving it back and forth from the reference points until it produces a reading of zero at all three points (see Figure 1).
- Re-zero one target on a reference point and move it to desired measurement points on the surface.The resulting reading is a measure of the deviation from the reference points, helping to produce a flatness profile. The measurement will show either a plus (+) or a minus (-) sign. A plus reading indicates that the target is higherthan the reference points and a minus reading means the target is lowerthan the reference points.
- Use Plane5 or 3DPlot Software to record and analyze the data.
After bucking in the laser to the five reference points described in Measuring Straightness and Measuring Flatness, (to determine the straightness and flatness of the machine's axes) measuring squareness is a simple processof positioning targets on the column or the table, zeroing them and noting the deviations as the axis traverses. It should be noted that totrulymeasure squareness, one must compare the least-squares, best-fit line of the one axis to the other axis. If this is not done, bad reference points or severely worn ways might produce what looks like a squareness error, but in fact is not. To facilitate this type of analysis, our software programs may be used to automatically calculate the best-fit line.
To measure Y-to-Z squareness (see figure above):
- Lower the column/spindle to its lowest Z position and position a target horizontally to pick up the vertical laser plane that is parallel to the X-axis (perpendicular to the Y-axis).
- Zero the target and traverse (raise) the column along its axis.
The data produces a measurement of both the straightness of the Z-axis and the squareness of the Y-axis to the Z-axis.
To measure Z-to-X squareness (see figure above):
- Position and zero the target to detect the vertical laser plane that is parallel to the Y-axis.
Traverse the column upward.
The resulting data is a measure of the Z flatness and Z-to-X squareness.
To measure X-to-Y squareness (see figures above):
- Position and zero the target to detect the vertical laser plane that is perpendicular to the X-axis.
- Traverse the table or column (whichever is moveable) along the Y-axis. The result is a measure of both Y straightness and X-to-Y squareness.
- Level the laser using the built-in level vials.
- Place a target on one reference point, adjust it up or down so that it detects the laser plane, and zero the target.
- Move the target to any other point on the surface to see the deviation of that point from the reference point relative to the level laser plane.
- Buck in the laser plane to three reference points on the first surface (see Measuring Flatness).
- Place a target on the second surface on one reference point and adjust the target so it detects the laser plane.
- Zero the target.
- Move the target to other points on the surface.
Any deviation from the reference point is a measure of the parallelism of the first surface to the second.
Note: At least three points should be measured. The best way to determine parallelism is to measure both surfaces with the laser plane and enter the data into Hamar Laser’s Plane5software, which calculates the least-squares best-fit plane for both surfaces.
Checking Parallelism of Gantry WaysUsing the Laser Transfer Method
The two drawings on the following page illustrate the Laser Transfer Method used to check the parallelism of gantry ways. Because the ways are generally 5-20 feet apart, the most difficult and time consuming part of aligning a gantry is checking the ways for parallelism. By using the L-743 Machining Center Alignment System with the following procedure, however, the setup, transfer of references and measurement of surface #2 should take no longer than 35-45 minutes.
- Make the laser parallel to reference points #1-#5 on the reference surface, using the pitch and yaw adjustments in the laser base. This makes the laser parallel to three points on the top of the master and slave ways and two points on the side of the master rail.
- Set up temporary reference targets #1 and #2 to pick up laser plane #2 and zero. This creates the reference line for the rollaxis.
- Set up two more temporary (offset) reference targets to pick up laser plane #3 and zero. This creates the reference line for the yawaxis.
- Move the laser to the new location (laser position #2) and start turning the adjustment knobs until the laser plane #1 is parallel to reference points 1, 2 and 3 and laser plane #2 is parallel to offset reference points #3 & 4. This should take about 10-15 minutes.
- When the laser is in position #2 and the laser planes are parallel to their respective references, place a fifth target on the second surface and zero to the laser.
- Move the target to other points on the surface, and any deviation from zero is a measure of how far out of parallel surface #1 is to surface #2. Readingsare live so the surface can be adjusted while the user watches it move on the handheld readout device.
Analyzing Machine Geometry Data
Our Machine Tool Geometry Software analyzes lines of motion for a machine tool, similar to the methodology used in ASME's B5.54 Standard. Our Plane5 Software analyzes multiple planes and surface types (squares, rectangles, frames, ways, circles and rings) and presents the analysis in 3D graphics. Both sets of software automatically download alignment data, save data analyses and produce alignment reports.