CTR Lasers - Article: Back-burn

Stopping Back-Burn on Thin Materials

Do you work with a particularly thin or soft material? Then be prepared to make your work of a higher quality by eradicating the potential of back-burn with your laser machine!

What is “Back-Burn”?

C02 laser machines, through necessity, have a metal bed on which you can place the materials you want to work with. Because of the nature of C02 lasers, the laser will reflect slightly back off the laser machine bed wherever the beam crosses metal. On most materials this is not a problem as the small amount of the beam that is reflected is a small amount. However, on some thinner or softer materials such as some soft woods, card, some fabrics etc, the back-burn can potentially mark the reverse side of the material, or even melt a small amount of the material on the reverse.

How Can I Stop Back-Burn?

It's a simple case of raising the material in question from the laser machine bed to a height that means the reflecting laser beam will not affect the material. In order to do this and keep the material level at the same time, you need to ensure that the material is supported in enough places that it will not buckle or bend. For example, a material such as wood will bend less than fabrics, and this needs to be taken into account when deciding on the most effective way to raise the material.

Suggestions:

Use a "sacrificial" piece of material that you place either on top of or underneath the material being lasered - this is parcitularly effective with materials such as paper, where the top and/or bottom pieces will take the brunt of the back-burn and leave you with a good quality finish on the main piece of material.

Cut circles out of a cheap material such as 3mm acrylic, stack two of these together and use the resulting pillar to prop up the material above the laser machine bed - this is particularly effective with more rigid sheet materials such as acrylic, wood etc. The acrylic pillars can be replaced as the laser cut through them, but you should get more than one use out of them if you are cutting with the optimal laser settings.

Remember to use enough circles to support your material and keep it level so that the laser beam stays focussed.

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