Loose Optic Presents As Mechanical Backlash And/Or Offset Issue

Preface: A Loose Optic (Mirror, lens) can present itself as excessive mechanical backlash and/or scanning offset value issue. This article will address the symptom and possible causes.

Example on a Rotary:

Client was in the middle of engraving a water bottle on a rotary an noticed the double image effect as shown in the image below:

The client then disabled their scanning offsets and bi-directional was set to off for the fill layer. The project was then sent from Lightburn again and re-engraved on the same tumbler. The results improved, as shown in the image below:  

The next test was to run some tests on the existing scanning offsets. The client set up a small rectangle engrave with a low LPI like 40 with bidirectional back on. The client adjusted the stock offset value from .105 to .8 with no noticeable improvement in the edge quality. The ends of each engrave line were also very curved which would not be an offset related issue.

The Root Cause:

While it looks like a scanning offset value issue, it was actually mechanical. The Focus Lens was not secure in the Laser Head. So, as the head traveled left and right to engrave, the Focus lens would shift in the head, shifting the beam and mimicking a large mechanical backlash or offset issue.

Example on Flat Material:

Mirror 3 was loose on the laser head.

What a Loose Lens may sound like:

In this video you will be able to hear what a loose Focal Lens sounds like.

What if it is not the lens:

Lets also check the mirror 3 retaining ring, bearings on the laser head, and the that laser head is secure to the trolley plate (Grab the head and try to wiggle it).

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