Why You Might Want to Use an Unfocused Laser for Certain Operations

When working with a laser cutter, precision is typically key, but there are times when a slightly unfocused laser can offer better results, particularly for certain materials like acrylic. By adjusting the focus intentionally, you can achieve smoother finishes and softer edges that improve the overall appearance of your project. In this guide, we’ll explore why and when you might want to use an unfocused laser, how to do it correctly, and how this technique can enhance your engraving work.

I. Understanding the Benefits of an Unfocused Laser

While focusing your laser is essential for most cutting and engraving tasks, there are situations where intentionally defocusing the laser can improve the quality of your work. Here’s why an unfocused laser can be advantageous:

1. Smoother Engraving on Acrylic

One of the most common reasons to defocus your laser is when engraving acrylic. A perfectly focused laser often leaves behind visible engraving lines, which can detract from the smoothness of the design. Slightly defocusing the laser can reduce these lines, resulting in a smoother, more polished finish.

2. Softened Edges on Wood Engravings

In certain cases, especially with wood, a slightly unfocused laser can create softer edges. This can give the project a more rustic, vintage, or handcrafted appearance, which may be desirable for home décor, signage, or personalized gifts.

3. Improved Aesthetic for Certain Materials

Using an unfocused laser allows for greater flexibility in design choices, especially if you’re looking to create a more blurred or artistic effect. This technique can give your projects a unique, customized look.

II. How to Intentionally Defocus Your Laser

Defocusing your laser is a simple process that involves adjusting the focus point to be slightly above the material surface. Here’s how you can achieve this effect, especially for materials like acrylic:

1. For Acrylic Projects: The 2mm Rule

Acrylic is a tricky material that often shows visible engraving lines when the laser is in perfect focus. By entering the material thickness in your software as 2mm thicker than it actually is, you can achieve a subtle defocused effect that reduces the visibility of these lines and creates a smoother surface.

• Example: If your acrylic material is 3mm thick, input 5mm as the material thickness in LightBurn or your laser software. This adjustment will raise the laser head slightly, creating the desired defocus effect for smoother engravings.
• Why It Works: Defocusing by 2mm spreads the laser’s energy across a wider area, which softens the lines and eliminates harsh engraving marks without sacrificing too much detail.

2. For Wood Engraving: Adjust the Material Thickness

Similar to acrylic, you can apply the same principle when engraving wood. By adjusting the material thickness to be slightly more than the actual thickness, you’ll achieve softer edges and a more rustic appearance.

• Example: For a 4mm thick piece of wood, input 6mm as the material thickness in your laser software. This will result in softer, more natural-looking edges for your engravings.

III. Applications Where an Unfocused Laser Works Best

1. Acrylic Engraving for Smoother Finishes

Acrylic engraving benefits greatly from a defocused laser, particularly when fill engraving large areas. The slightly defocused beam reduces the visibility of individual engraving lines, making the overall finish much smoother and more visually appealing.

• How We Do It: In our projects, we consistently run our laser with the material thickness set 2mm higher than it actually is. This simple adjustment has dramatically improved the appearance of acrylic engravings, resulting in cleaner, more professional finishes.

2. Wood Engraving for Softer, More Rustic Edges

When engraving wood, a defocused laser can help create a more rustic or vintage look. This is especially useful for items like custom signs, home décor, or any project where you want a softer, handcrafted appearance.

• Real-World Example: When we engraved wood with a slightly defocused laser, the softer edges added a unique, weathered look that made the piece feel more authentic and artistic.

IV. When to Avoid Using an Unfocused Laser

While there are benefits to using an unfocused laser, there are times when it’s best to stick with a perfectly focused beam:

• Precision Cutting: If you’re cutting materials, an unfocused laser will not be as effective. The beam won’t concentrate enough power to cleanly cut through materials, leading to incomplete or uneven cuts.
• Fine Detail Engraving: For projects that require intricate details or sharp lines, defocusing the laser will result in blurred or less precise engravings. Stick to a focused laser for fine text or delicate designs.

V. Final Tips for Defocusing Your Laser

• Start Small: Begin by adjusting the focus slightly (like the 2mm rule for acrylic) and run a few test engravings before moving on to your final project. This allows you to dial in the perfect defocus without overdoing it.
• Monitor Performance: Defocusing spreads the laser’s energy across a wider area, so you may need to adjust your power settings slightly to maintain the quality of the engraving.
• Test with Different Materials: Not all materials react the same way to a defocused laser. Run tests on wood, acrylic, and other materials to find the optimal level of defocus for each one.

Conclusion

Defocusing your laser can be a powerful tool for achieving smoother engravings on acrylic or creating softer, rustic designs on wood. By simply entering the material thickness as 2mm thicker than it really is, you can easily achieve these effects and elevate the quality of your laser engraving projects. The key is knowing when and how to use this technique to your advantage.

For more on how to properly focus your laser for precise operations, check out our article on How to Focus Your Laser and Why It Matters.