How to Avoid burn Marks When Cutting?

Background

Burn marks and discoloration are common issues when laser cutting wood, especially for beginners. These unsightly yellow or brown stains can detract from the final product's appeal and are difficult to remove once they appear. In this blog, we'll share practical methods to prevent them for cleaner, more professional results.

Supported Materials

This advice applies to various types of wood commonly used in laser cutting, such as plywood, hardwood, and softwood. Note that denser woods may require more adjustments to settings, while lighter woods are more prone to scorching.

Steps to Prevent Burn Marks

1. Apply Masking Tape

Start by covering the wood surface with masking tape before engraving. Ensure the tape is applied smoothly, without bubbles or overlaps, to achieve even results. After cutting, simply peel off the tape to reveal a clean surface free from brown scorch marks. 

2. Place a Honeycomb Panel

Burn marks on the underside of wood are often caused by trapped smoke and fumes. To combat this, place a honeycomb panel underneath the wood. This accessory improves ventilation, allowing smoke to be efficiently exhausted through the hood while protecting your work surface.

3. Enable Air Assist

Air assist is a crucial feature in laser machines that delivers a strong airflow to disperse debris and fumes away from the workpiece. By cooling the surface and reducing heat buildup, it prevents discoloration and scorching. If conditions permit, it is recommended to use a high-pressure air pump(33 psi) for blowing.

4. Optimize Power and Speed Settings

Incorrect power or speed can lead to excessive heat and burning. Before starting your project, conduct a power-speed test on scrap wood to determine the ideal parameters. Lower power combined with higher speed often yields better results without charring.

5. Apply a Thin Layer of Water

Moistening the wood surface lightly with water can act as a barrier against fumes. The moisture helps dissipate heat and prevents particles from adhering, resulting in a smoother finish. (Don't use too much water, otherwise the wood will warp, especially the plywood.)

Common Issues and Solutions

1. Why Do Edges Still Blacken After Using Masking Tape?
Masking tape only shields the surface; edges are exposed during cutting. To minimize edge darkening, focus on air assist and optimized settings, or consider post-processing like sanding after the cutting.

2. What If Burn Marks Persist Despite Adjustments?
Double-check your machine's focus and cleanliness. A dirty lens can intensify heat. Also, ensure proper ventilation in your workspace to avoid fume recirculation.

3. Can These Methods Be Used for All Laser Machines?
Yes, these tips are generally applicable, but consult your machine's manual for specific features like air assist compatibility.