Scanning Offset Adjustment for Laser Engraving Precision

Overview Scanning Offset Adjustment

Modern laser systems are incredibly fast and precise, but even slight delays in firing the laser beam or mechanical movements can lead to misalignments during engraving. Understanding and addressing these scanning offsets is crucial for achieving accurate results.

What Causes Scanning Offset?

At higher engraving speeds, several factors can contribute to scanning offsets:

• Laser Firing Delays: Power supplies and tubes might take milliseconds to fire.
• Mechanical Stretch: Belts can stretch slightly under tension at high speeds.
• Speed and DPI Interaction: At 100 mm/sec and 254 DPI, a 1 millisecond delay shifts engraving by one dot. At 500 mm/sec, the same delay causes a 5-dot (0.5 mm) offset, which becomes noticeable.

The result often appears as ghosted or skewed edges in your engraving work.

LightBurn has a setting to counter this, called Scanning Offset Adjustment, in the Device Settings.

Using LightBurn’s Scanning Offset Adjustment

LightBurn offers a Scanning Offset Adjustment feature to counteract these misalignments. Other software may refer to similar features as "Reverse Interval" or "Reverse Compensation."

Steps to Determine and Apply Scanning Offset Adjustments:

1. Create a Test Rectangle:

   • Draw a rectangle 50 mm wide and 10 mm high in LightBurn.
   • Assign a layer in Fill Mode with appropriate power settings to engrave the material without charring.
   • Set the Line Interval to 0.5 mm.

2. Prepare for Testing:

   • If using a GCode-based device, enable Overscanning and set it to 5% or higher to ensure consistent speed across the engraving area.
     
   • For Ruida devices, overscanning is automatic.

3. Run Tests at Different Speeds:

   • Test engraving at multiple speeds, such as 100 mm/sec, 200 mm/sec, and 300 mm/sec. Use speeds your laser can handle, considering the units of distance and time.
     

4. Measure Line Misalignments:

   • Measure the distance between the ends of the engraved lines at each speed.

5. Enter Offset Values:

   • In the Device Settings window, click "Add" to input the measured speed and line shift values into the Scanning Offset Adjustment table. Enter half the measured misalignment value, as LightBurn adjusts each line pair by this amount.

6. Enable the Adjustment:

   • Toggle Enable Scanning Offset Adjustment, click OK, and save your changes.

Repeat the process with minor adjustments until you achieve clean results. With proper measurements, the corrected output should be precise and free of ghosted edges.

Line Wobble: A Related Issue

If you notice wobbling lines during the engraving process, the issue might be high acceleration settings. This "bounce" effect in the gantry can be resolved by lowering the acceleration for the Y-axis in your machine settings.