End-Scan Using End Targets

How to perform super high accuracy end-scans using an end target. Back to VTube-LASER See End-Scan Technique Research

Why this 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.

Highly Reflective Ends with Concave Curves

Shiney tube ends with ragged or burred edges with CONCAVE curves facing the laser scanner camera can create an overload problem for the exposure. This can create flyers (points that are not on the surface) in any laser camera. The example on the right shoes a burred end wall on the left side. For this kind of cut, it is critical that you apply a target like the green dot stickers shown here. Colors that work well are white, yellow, green.

Measure Setup

In the Laser tab menu, we recommend that you use the standard setup of End Stripes per measure at from 10 to 20.
In the Separation Filter tab menu, we recommend that you set the End Scan Separation type to TIMER and set the TIMER to 0 milliseconds.

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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