De-focusing engraved lines increases job time by 50%

Problems and Support
1

While performing some test engraving of 1/43rd scale architectural brickwork, and in order to get the required mortar thickness lines I determined that a ‘de-focused’ laser, with a Z Offset of -4 (up) gives a better scale mortar effect.
However, I noticed during these de-focused tests that the laser head moves down while moving, before being raised again to engrave the next line. Consequently, this job with a Z offset of -4, takes about 50% longer than the same file with a Z Offset of 0 (zero). Almost two minutes of extra time is spent unnecessarily moving the head up and down. This phenomenon appears to be exacerbated by the brick design having lots of very short unconnected lines in one direction. See attached image.

Z-Offset-4
Z-Offset-41349×882 211 KB

Using the 10W laser on my E2, this test takes about 4:37 with a Z offset of 0. But with a Z offset of -4, it takes 6:45 – almost 50% longer.

Any idea why the head needs to move down when moving de-focused, to engrave lines on the same layer?

Thanks

Mike

2

Hi Mike,

This action is primarily in place to prevent potential collisions if using a positive (down) offset.

The idea being that the normal (zero offset) height is safe for the laser to move around the workpiece, however a positive (down) offset may have been applied for a particular area where there is a lower surface height, such as a pocket or recess. Moving away from the cut/engrave path at this height has the potential to cause a crash, so LightBurn will return the laser to the standard height, then lower again once the next location is reached.

I can not think of any reason that this needs to apply to negative (up) offsets. Let me run it past the LightBurn Team and get back to you.

3

Hi Lliam,
It makes sense to move the laser head up when moving it in a positive Z offset situation to avoid collisions. But as you say it doesn’t need to apply the same rule when a negative Z offset is applied to a layer.
I await the response from the LightBurn Team.
Many thanks
Mike

4

Hi Mike,

OK - So LightBurn has recommended enabling ‘Optimised Z Moves’ in the Device settings. This should remove all Z-moves other than the essential ones.

Please let me know if this works for your application.

1 Like
5

Hi Lliam,
I can confirm that enabling “Optimize Z moves” in LightBurn has solved this issue on my E2. The head no longer moves down between engraving lines when deliberately de-focused. Now back to predicted job times.
Of course, when you hover over this Device Setting option with the mouse pointer, it tells you exactly what it’s going to do. I just hadn’t visited the Device Settings page. :blush:
Thank you for your help. And please pass on my thanks to the LightBurn Team for identifying the cause.
Mike

1 Like