End-Scan Using End Targets

How to perform super high accuracy end-scans using an end target. Back to VTube-LASER

Why the End-Scan technique is important

The quick End-Scan Using the Scissor Motion technique is not always precisely repeatable if you use any of the AUTO exposure settings to set the LASER exposure in real-time. The reason is that as he laser drops off the end of the tube, the automatic exposure feature impacts which of the points are kept where the tube drops off (at the end). The solution to this issue is to use the End-Scan Using the End Wall technique - which works well for tubes that have end-walls that are easy to aim at - AND end-walls that are not highly reflective with deformations like burrs. For tubes that don't qualify for either of the above techniques, we recommend end targets for ultra-precise measurements.

Measure Setup

Set System Options, Measure 2 Tab, "Maximum Number of LLP Points in String" to 3 Set Measure Setup - LASER Tab: The LASER defaults to ON for CYLINDERS and END-SCANS. Set Measure Setup - LASER Tab: Cylinder stripes = 3 to 5 Set Measure Setup - LASER Tab: End-scan stripes = 5 Set Measure Setup - LASER Tab: Split bend stripes = 5 Set Measure Setup = Scan Rates Tab: Set all rates to TIMER for all scan types. Set Measure Setup = Scan Rates Tab: Set the Scan Rates TIMER is set to 0 for all TIMERS.

Apply the Target

The image at the right shows the end of a copper tube with a sharp burr and a highly reflective end-wall. It is very difficult to aim the laser at this end wall and ensure no outliers at the same time. The solution is to use white targets on the end of the tubes. The example here shows white poly labels that measure at 0.004" thick and provide an excellent flat target for the laser. (Note: Use the Plane-Point measurement in the built-in computer of the FARO Edge to confirm the thickness of the target.) The offset from the target to the tube end is entered as a negative value in the Part Setup menu for either end. In this case, we use -0.004" offset. Any shape of target works well as long as it is LARGER than the diameter of the tube. Apply the target so that none of the end-wall can be scanned by the laser.

Measure the Target

When it is time to perform and end-scan, use the following technique to scan the target: Aim the laser at the target so that it strikes the target as perpendicular to the surface as possible. Avoid returning any points other than the target. Attempt to hold the laser motionless when collecting the stripes across the target to increase repeatability. Consistently place the line across the same area of the target from measure to measure.

Approve the Measurement On the Screen

The resulting geometry on the screen should appear like the image at he right. The end point generated on the screen should perfectly coincide with the stripes.

Using End Target Adapters

If you prefer using more durable end target adapter that plugs into the end of the tube, then they can be manufactured for repeatable measurements. The end target surface should be painted or covered with a flat white or near-white target. The offset from the target to the tube end is entered as a negative value in the Part Setup menu for either end.

Other Pages

• See also End-Scan Using the Scissor Motion
• See also End-Scan Using the End Wall
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