Engraving speed settings. Lead in and lead out overcutting

LunarConcepts · October 17, 2022, 7:44pm

New to engraving but have been cutting for a few years . Pictured is an issues that appears to be scanning speed related and I am not sure what its called to try and search out the answer? I imagine there is a setting in Ruida or LB to compensate for the scan speed vs. the laser firing time? The engraving shown in the photo was run at a high speed. As I lower the speed the issues gets better but I have to bring it below 100mm/s before it gets close to what we want and that seems much slower than most examples I can find. Still, once the speed is that low there is a bit of a step in and out at the entrance and exit that is close to half of the actual engraving depth. You can see it the photo. This over run is making the cut larger than it is supposed to be. Actual engraving is

1"x.75" in Photo and shown by the darker outline.

jkwilborn · October 17, 2022, 8:26pm

It’s probably backlash, it usually gets worse at higher scan speeds…

Suggest you ‘fill’ a small box with a large lpi. You can see the backlash more easily with more room between scans.

Lightburn refers to it as ‘scanning offset’ and is in “Edit → Device Settings”

Good luck

LunarConcepts · October 17, 2022, 9:15pm

Thank you! Sometime the hardest part is learning what the problem is called so you can find the solution. After a found this articles it all made sense. Thanks for pointing me in the right direction.

github.com

LightBurnSoftware/Documentation/blob/master/ScanningOffsetAdjustment.md#scanning-offset-adjustment

[Return to main page](README.md)

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# Scanning Offset Adjustment

Modern lasers are capable of moving very fast, and with remarkable precision, however firing the beam still takes time.  Some power supplies and tubes may respond in less than a millisecond, but many take longer.

At 100 mm/second, 254 dots per inch means your dots are 0.1mm in length, fitting 1000 of them in 100mm. At 100 mm/sec, if your power supply and tube take 1 millisecond to fire, your engraving will be offset by a full dot width.

At 500 mm/second, that 1 millisecond delay means you'll be off by 5 dots, or 1/2 a millimeter. Still not very much, but visible. Many power supplies and tubes will take even longer to fire.

The result often looks like ghosted edges.  The image below is a 20mm square at 1000 mm/sec, with a 1ms delay, resulting in a full mm of skew between scans:

![](./img/ScanningOffset-Illustration.png)



LightBurn has a setting to counter this, called Scanning Offset Adjustment, in the [Device Settings](DeviceSettings.md):

This file has been truncated. show original

This helped me understand LINE SHIFT and INITIAL OFFSET which are the 2 adjustment under Scanning Offset Adjustment

system · November 16, 2022, 9:15pm

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