Calibration Tests for CO2

Four tests every CO2 owner should run on a new machine and after major maintenance. Each takes 5-15 minutes and catches problems before they ruin a customer order.

1. The ramp test (focus calibration)

The ramp test reveals where the beam is actually focused, most precise way to verify the focal distance for any lens. Useful when:

• You install a new lens and want to verify the focus puck/stick is correct.
• Your engraves look soft and you suspect focus drift.
• You're switching between lenses (2" / 4") and need to re-confirm Z reference.

Setup

1. Cut a triangular wedge of stock material (matching the part you'll be engraving, wood for wood work, acrylic for acrylic, etc.). Wedge angle: 5-10° is ideal.
2. Mark the wedge with reference lines every 1mm along the slope so you can identify positions later.
3. Place the wedge on the bed. The thin edge aligned with X = 0 (or your origin), thick edge extending upward in Z.
4. Manually focus on a point near the middle of the wedge.

Run the test

1. In Lightburn, draw a single horizontal line spanning the wedge.
2. Set Line mode at engrave settings: 200-300 mm/s, 30-50% power. Single pass.
3. Run the line.
4. Inspect the engraved line under a loupe.

Interpret

• The thinnest, sharpest, deepest point on the line is true focus.
• Measure the distance from your reference origin (thin edge) to the sharpest point.
• Calculate Z offset: Z_offset = (distance × tan(angle)).
• Adjust your Z reference accordingly. Or just remember the new Z value for that lens.

Quick pin-method ramp test

Even simpler: tilt the material on a single pin (one corner raised by ~3-5mm). Engrave a line crossing the slope. Same principle, the sharpest part of the engraved line indicates focus.

2. Power test grid (Lightburn Material Test tool)

Lightburn has a built-in tool for this: Laser Tools → Material Test.

1. Open Material Test from the Laser Tools menu.
2. Configure: speed range (e.g., 5-30 mm/s for cuts, 200-500 mm/s for engraves), power range (e.g., 30-100%).
3. Set the cell Height and Width, and the settings every box shares (interval, passes) under Edit Material Setting.
4. Click Preview, then Frame, then Start. LightBurn runs the grid directly; there is no file to import.
5. Run on a sample piece of your target material.
6. Photograph in good lighting, identify the optimal cell.
7. Save those settings to your Material Library.

For ranges per material and goal, use the Material Test guide.

3. Speed-and-passes test (for cuts)

For cutting jobs, you want the FASTEST speed × FEWEST passes that achieves a clean cut. Test grid:

• Speed varies down columns (e.g., 25, 20, 15, 10 mm/s).
• Passes vary across rows (e.g., 1, 2, 3 passes).
• Power constant at 100%.
• Run on the actual production material.
• Pick the FASTEST + FEWEST combination that cuts cleanly through. Don't over-cut "to be safe", wastes time and builds char.

4. Bed levelness test

If your bed is tilted relative to the gantry rails, focus varies across the work area, engraves come out crisp on one side and soft on the other.

Quick check

1. Place a flat reference (granite tile, machined aluminum block, or even a flat sheet of MDF).
2. Use the focus puck/stick at four corners + center of the bed.
3. If puck contact varies by more than 0.5mm corner-to-corner, the bed isn't level.

Engrave-line-pattern check

1. Draw a 6×4 grid of small filled rectangles spanning the entire bed.
2. Engrave at consistent settings.
3. Inspect each rectangle under a loupe, depth and edge sharpness should be uniform.
4. If corners are softer than the center, your bed is bowed or off-level.

Fixes

• Adjust the bed leveling screws (most prosumer machines have these at the four corners).
• For heavy bows: replace the bed surface (honeycomb panels do warp over time).
• For minor variation: live with it but always focus at the WORK AREA, not the corner.

5. Mirror alignment quick check (recap)

Covered fully in the Mirror Alignment module, but here's the 30-second version:

1. Tape over each mirror in turn.
2. Pulse at low power.
3. Burn dot in tape should be CENTERED on the mirror at all four bed corners (front-left, front-right, back-left, back-right).
4. If centering varies by gantry position, that mirror needs adjustment.

6. Beam quality test (M² check by proxy)

You can't measure M² directly without specialized equipment, but you can compare beam quality between two lasers / before-and-after maintenance:

1. Engrave a thin line (1px wide vector) at known power on the same material.
2. Inspect under a loupe. Measure line width.
3. Sharper, narrower line = better beam quality.
4. Use as a baseline; if line widens after lens cleaning, the lens may be coated or scratched.

When to run each test

Test	Frequency	Trigger
Ramp test	After lens swap; quarterly	Soft engraves; new lens; new puck
Material test grid	Per new material lot	New supplier; new wood species; quote-time tuning
Cut speed/passes test	Before production runs	Production order > 50 pieces
Bed levelness	Annually; after move	Uneven engrave depth across bed
Mirror alignment (tape test)	Monthly	Drifting cut quality across the bed
Beam quality / line width	Quarterly	After major maintenance; before/after lens cleaning