Creating a Flat Plane - 3 Point Buck-In

The 3 point buck-in procedure is the most common procedure used in geometry laser alignment. The 3 point buck-in allows the user to establish a laser plane that is parallel to three points in space, which in turn establishes a flat plane. The flat plane has been used throughout history for measurement in machining and machine building industries. From the flat plane evolve master straight edges, squares, scrapping masters, laps, and surface plates. By creating the laser plane to a surface we are actually using a portable surface plate to check any surface we need to measure. This procedure is also a prerequisite for performing the other geometry functions the geometry laser is capable of.

Three Point Buck-In using one target

Basically this procedure is nothing more than making the laser beam parallel to a surface that needs to be measured for flatness or used as a datum to measure another surface to.

Uses: Checking the flatness of a surface plate, ways, a machine bed, boring mill table & ways, mounting pads, transfer lines, any surface that is supposed to be flat.

Equipment needed: L-720 series laser, A-517 Target, R-308 readout or R-307 readout w/T-251 preamp or a computer and R-355 interface w/ T-251 preamp, tripod (if the surface needs to be aligned/adjusted the laser should be independent of the surface), felt marker.

Set up of the equipment

• Place the laser either on the surface to be measured or on the tripod. Position the laser so that the pitch or roll axis is parallel with the long axis of the surface you are measuring. There is a tooling ball in the base that the laser pivots from. By aligning the laser with the surface, the buck-in procedure will go much easier.
• Pick out three points on the surface that are going to be the reference points for the laser plane. These points (when possible) should consist of a near target position (as near to the laser as possible), a far target position (preferably in a straight line from the near target position), and a third point at 90° to the laser. Remember any three points will determine a plane, this set up will allow for an easeir buck-in.
• Turn on the laser and set the readout to (fast) and to the desired tolerance setting.

Example:

• With the target in the near position (#1) - zero the readout by adjusting the target micrometer, and mark the target base with a felt marker. This is so the target can be set back into the same position.
• Move the target to the far target position (#2), mark the base with the felt marker and observe the reading. Using the correct axis adjustment on the laser pitch/roll/yaw base adjust the laser until zero is being read on the readout.
• Move the target back to the near target position (#1) and zero the readout by adjusting the target micrometer.
• Move the target back to the far position (#2) and adjust the laser to zero the target once again. Repeat this procedure until zero is observed at Points #1 and #2 without adjusting the laser or target.
• Now move the target to the 90° target position. Note: Keep the target base in the same orientation as in the first two points and rotate the target head. This keeps the measurement procedure consistant. Do not forget to mark the base with the felt marker.
• Observe the reading and adjust the laser with the axis that is in line with the target, so that the readout is zero.
• When the readout reads zero at all three target positions with no adjustments being made to the laser or the target the procedure is completed. A laser plane has now been created that is parallel to the three chosen points on the surface.
• The flatness of the surface can now be checked to itself to determine flatness or another surface can be checked for parallel to this surface.

Notes:

These are some tips that may help in the roughing in of the laser to a surface.

1. Always adjust the target in the near position, Aim the laser in the far positions.
2. Using earth level as a starting point. This is usually a good place to start, since most people set up equipment to earth level. Simply level the laser in both axes and begin the procedure.
3. If the surface is not level or you have no idea where to start, a tape measurer is a handy tool to use. It works best if two people are working together, one to adjust the laser, the other to see where the beam is at on the tape.
   • On the laser put the # 1 turret switch all the way down, this puts the turret in a manual mode - we can turn the turret by hand. With the tape extended in the near target position observe where the center of the laser beam strikes the tape.
   • Now move the tape to the far target position and point the laser so it strikes the tape and adjust the center of the laser beam to be striking the tape at the same point as in the near position. You are doing the same procedure as in the buck-in only using a tape measurer instead of a target. In many instances this saves a lot of time.