Skip to content

Power vs Speed

Understanding the relationship between laser power, movement speed, and material interaction is crucial for achieving high-quality cuts and engravings.

The Fundamental Relationship

Energy delivered to material = Power x Time

When the laser moves more slowly, it delivers more energy per unit area. When it moves faster, less energy is delivered.

Key principle:

More power + slow speed = High energy (deep cuts, dark burns)
Less power + fast speed = Low energy (light marks, shallow cuts)

Balance is key: Different materials and operations require different combinations.

Understanding Power

What is Power?

Laser power is the intensity of the laser beam, typically measured in watts (W).

Power control:

  • Rayforge uses the S parameter (0-1000) to control power
  • S0 = 0% power (off)
  • S500 = 50% power
  • S1000 = 100% power (maximum your laser can produce)

Example:

M4 S250   ; 25% power
M4 S750   ; 75% power
M4 S1000  ; 100% power

Absolute Power vs Percentage

Your laser has a maximum power rating:

  • 5W diode laser
  • 40W CO2 laser
  • 80W CO2 laser

When you set 50% power:

  • 5W laser delivers: 2.5W
  • 40W laser delivers: 20W
  • 80W laser delivers: 40W

Implication: Settings that work on one laser won't directly transfer to a different wattage laser. You must adjust for your specific laser power.

Understanding Speed

What is Speed?

Feed rate (or cutting speed) is how fast the laser head moves across the material, measured in mm/min or inches/min.

Speed ranges:

  • Very slow: 50-300 mm/min (deep cuts, thick materials)
  • Moderate: 500-1500 mm/min (general cutting, engraving)
  • Fast: 2000-5000 mm/min (light engraving, travel moves)

Example:

G1 X100 F500   ; Move at 500 mm/min (slow cut)
G1 X200 F3000  ; Move at 3000 mm/min (fast travel)

Speed Affects Energy Density

Slower movement = More time at each point = More energy delivered

Example:

  • Laser power: 40W
  • Speed 1: 100 mm/min
  • Speed 2: 1000 mm/min

At 100 mm/min, the laser spends 10x longer at each point compared to 1000 mm/min, delivering 10x more energy.

The Power-Speed Matrix

Different combinations of power and speed produce different results:

Power Speed Result Use Case
High Slow Very deep cuts, charring Cutting thick materials
High Fast Moderate cuts/engraving Fast cutting, efficient production
Low Slow Deep engraving, controlled burns Detailed engraving, dark marks
Low Fast Light engraving, surface marks High-speed raster engraving

Visualization:

Power
  ^
  |  Charring/   |  Through-cut
  |  Too deep    |  (ideal)
  |              |
  |------------- +-------------
  |  Good        |  Too fast/
  |  engraving   |  Not cutting
  |              |
  +-----------------------------> Speed

Material-Specific Considerations

Wood

Cutting:

  • Medium to high power
  • Moderate speed
  • Multiple passes for thick wood

Example (3mm plywood, 40W CO2):

  • Power: 70-80%
  • Speed: 200-400 mm/min
  • Passes: 1-2

Engraving:

  • Low to medium power
  • High speed for raster
  • Lower speed for deeper marks

Example (wood engraving, 40W CO2):

  • Power: 20-30%
  • Speed: 2000-3000 mm/min

Acrylic

Cutting:

  • High power
  • Very slow speed
  • Produces clean, flame-polished edges

Example (3mm cast acrylic, 40W CO2):

  • Power: 80-100%
  • Speed: 100-200 mm/min
  • Passes: 1 (through-cut)

Engraving:

  • Low power
  • Fast speed
  • Produces frosted appearance

Example (acrylic engraving, 40W CO2):

  • Power: 15-25%
  • Speed: 2500-4000 mm/min

Cardboard / Paper

Cutting:

  • Very low power
  • Fast speed
  • High fire risk - monitor constantly

Example (cardboard, 40W CO2):

  • Power: 10-20%
  • Speed: 1000-2000 mm/min

Engraving:

  • Extremely low power
  • Very fast speed

Example (paper engraving, 40W CO2):

  • Power: 5-10%
  • Speed: 3000-5000 mm/min

Leather

Cutting:

  • Medium power
  • Moderate speed

Example (leather, 40W CO2):

  • Power: 40-60%
  • Speed: 300-600 mm/min

Engraving:

  • Low power
  • Fast to moderate speed
  • Creates dark, detailed marks

Example (leather engraving, 40W CO2):

  • Power: 15-25%
  • Speed: 2000-3000 mm/min

Multi-Pass Strategies

When to Use Multiple Passes

Reasons:

  1. Material too thick for single pass
  2. Preventing excessive charring
  3. Achieving cleaner cuts
  4. Reducing heat buildup

How it works: Instead of one deep cut, make several shallower cuts:

  • Pass 1: Cuts 30% through
  • Pass 2: Cuts 60% through
  • Pass 3: Cuts 90% through
  • Pass 4: Cuts fully through

Benefits of Multi-Pass

Cleaner cuts:

  • Less charring on edges
  • Less heat stress on material
  • Better edge quality

Thicker materials:

  • Cut materials beyond single-pass capability
  • Safer than maxing out power

Heat management:

  • Allows material to cool between passes
  • Reduces warping and melting

Multi-Pass Settings

General approach:

  1. Determine total energy needed to cut through
  2. Divide into multiple passes (2-5 passes typical)
  3. Adjust speed or power to deliver energy gradually

Example (6mm plywood, 40W CO2):

Single pass (may fail or char heavily):

  • Power: 100%
  • Speed: 100 mm/min
  • Passes: 1
  • Result: Excessive charring, incomplete cut

Multi-pass (better):

  • Power: 80%
  • Speed: 200 mm/min
  • Passes: 3
  • Result: Clean cut, minimal charring

Configuring Multi-Pass in Rayforge

In operation settings:

  1. Select Contour operation
  2. Set Passes to desired number (e.g., 3)
  3. Adjust power/speed as needed
  4. Rayforge will automatically repeat the cut path

G-code result:

; Pass 1
G0 X10 Y10
M4 S800
G1 X50 Y10 F200
; ...path...
M5

; Pass 2 (same path repeated)
G0 X10 Y10
M4 S800
G1 X50 Y10 F200
; ...path...
M5

; Pass 3
; ...

Reading Burn Marks and Adjusting

Visual Feedback

Material tells you if settings are correct:

Too much power or too slow:

  • Heavy charring (black edges)
  • Excessive smoke
  • Melted/deformed edges
  • Material warping

Too little power or too fast:

  • Incomplete cuts
  • Light surface marks only
  • No visible change

Just right:

  • Clean cuts all the way through
  • Minimal charring
  • Smooth edges
  • Consistent depth

Adjusting Based on Results

If cut doesn't go through:

  1. Increase power by 10-20%
  2. OR decrease speed by 20-30%
  3. OR add another pass

If too much charring:

  1. Decrease power by 10-20%
  2. OR increase speed by 20-30%
  3. OR switch to multi-pass with lower power

If engraving too light:

  1. Increase power by 10-15%
  2. OR decrease speed by 15-25%

If engraving too dark/burned:

  1. Decrease power by 10-15%
  2. OR increase speed by 15-25%

Diode Lasers vs CO2 Lasers

Diode Lasers (Typically 5-20W)

Characteristics:

  • Lower power output
  • 445nm wavelength (blue light)
  • Absorbed differently by materials

Power/speed considerations:

  • Slower speeds needed (lower power)
  • Multiple passes often required
  • Struggles with thick materials
  • Excellent for wood engraving

Example (wood engraving, 5W diode):

  • Power: 60-80%
  • Speed: 500-1500 mm/min

CO2 Lasers (Typically 40-150W)

Characteristics:

  • Higher power output
  • 10,600nm wavelength (infrared)
  • Efficiently absorbed by organic materials

Power/speed considerations:

  • Faster speeds possible
  • Clean through-cuts on thicker materials
  • Better for cutting acrylic, wood

Example (wood cutting, 40W CO2):

  • Power: 70-90%
  • Speed: 200-500 mm/min

Material Testing Workflow

Using the Material Test Grid

Rayforge's Material Test Grid automates power/speed testing:

  1. Create grid: Features > Operations > Material Test Grid
  2. Set ranges:
  3. Power: 20% to 80% (or appropriate range)
  4. Speed: 500 to 2000 mm/min (or appropriate range)
  5. Run grid on scrap material
  6. Inspect results:
  7. Find the cell with best cut quality
  8. Note the power/speed values
  9. Use those settings in your actual job

Example grid result:

        500mm/min  1000mm/min  1500mm/min  2000mm/min
20%     Too light  Too light   Too light   Too light
40%     Good       Too light   Too light   Too light
60%     Too dark   Good        Light       Too light
80%     Charred    Too dark    Good        Light

Conclusion: Use 60% power at 1500 mm/min for this material.

See Material Test Grid for details.

Advanced Topics

Kerf Compensation

Kerf is the width of material removed by the laser beam.

Power/speed affect kerf:

  • Higher power = Wider kerf
  • Slower speed = Wider kerf (more material burned away)

Adjust kerf compensation if parts come out wrong size:

  • Parts too small: Reduce kerf compensation
  • Parts too large: Increase kerf compensation

See Kerf for details.

Raster Speed Variation

For raster engraving, Rayforge varies speed to create different gray tones:

How it works:

  • Light areas: Fast speed, low power
  • Dark areas: Slow speed, higher power (or just higher power at constant speed)

Bidirectional raster:

  • Laser engraves left-to-right, then right-to-left
  • Must maintain consistent power at varying speeds
  • M4 (laser mode) ensures constant power

Air Assist and Cooling

Air assist affects results:

  • Reduces charring
  • Cools material
  • Blows away smoke/debris

Settings interaction:

  • With air assist: May need slightly higher power
  • Without air assist: More charring, may need lower power/faster speed

Common Mistakes

Mistake 1: Maxing Out Power

Problem: Using 100% power for everything.

Why it's bad:

  • Excessive charring
  • Accelerated wear on laser tube
  • Less control and precision

Solution: Use appropriate power (usually 60-80% for cuts).

Mistake 2: Ignoring Material Variation

Problem: Using same settings for all "wood" without testing.

Why it's bad:

  • Different wood species vary significantly
  • Plywood vs solid wood behaves differently
  • Moisture content affects results

Solution: Test each new material type with a Material Test Grid.

Mistake 3: Not Adjusting for Thickness

Problem: Using same settings for 3mm and 6mm material.

Why it's bad:

  • 6mm needs much more energy (lower speed or more passes)
  • 3mm settings won't cut through 6mm

Solution: Adjust speed (slower) or passes (more) for thicker materials.

Mistake 4: Focusing on Power Only

Problem: Only adjusting power, never speed.

Why it's bad:

  • Speed is equally important
  • Sometimes speed adjustment is more effective

Solution: Adjust both power AND speed to find optimal settings.

Quick Reference

Starting Points (40W CO2 Laser)

Material Thickness Power Speed Passes
Plywood 3mm 70% 300 mm/min 1-2
Plywood 6mm 80% 200 mm/min 2-3
Acrylic 3mm 90% 150 mm/min 1
Acrylic 6mm 100% 80 mm/min 1-2
Cardboard 2mm 15% 1500 mm/min 1
Leather 2mm 50% 400 mm/min 1

Note: These are starting points only. Always test on your specific machine and material.

Starting Points (5W Diode Laser)

Material Thickness Power Speed Passes
Wood engrave - 70% 800 mm/min 1
Wood cut 3mm 90% 100 mm/min 3-5
Cardboard 2mm 50% 500 mm/min 2
Leather engrave - 60% 600 mm/min 1

Note: Diode lasers struggle with thick materials. Multi-pass is often required.

Best Practices

  1. Always test new materials with Material Test Grid
  2. Start conservative (lower power, moderate speed) and increase gradually
  3. Use multi-pass for thick materials rather than maxing out power
  4. Adjust one parameter at a time (power OR speed, not both)
  5. Document successful settings for future reference
  6. Account for material variation (different batches may need adjustment)
  7. Monitor first few cuts of any job to catch issues early