How to avoid heat marks of substrate edge after laser cutting?

C02 laser cutting is essentially finely burning through a material and engraving is delicately burning into it. Markings are an inevitable part of the process but they can be minimised. 
Fumes and debris are emitted when cutting / engraving. These fumes are extracted from the rear or base of the machines. The fumes are dragged over the material surface causing marks. Marks also appear from hot debris which glazes or scorches the exhaust-facing edges of the cut line. (most noticeable on thick materials and more combustible materials.)  
Burn marks are an inherent part of the laser cutting process - we are cutting things with a highly focused beam of fire after all. There are some tricks to minimizing this issue for different materials. 
Ways in which we minimize burn / heat marks
All our material settings are optimised to maintain the cleanest cutting and engraving conditions and to keep these burn and heat marks to a minimum. Methods used vary from material from material but generally involve the combination of the appropriate cutting bed selection, protective backing and compressed air.
Large format protective paper backing
Large format protective backing is a sticky back masking tape that can be applied to a material surface prior to any cutting or engraving is carried out. It comes in rolls up to 1220mm wide. Applying the tape helps to limit surface burn marks particularly on the reverse surface. All the markings will transfer onto the protective tape and not the material. You will then need to peel off the backing to reveal the clean material surface. Plastic materials such as acrylic usually have the a thin plastic film applied as standard to help prevent scratches. Protective backing can be used on most materials but not all. Paper, card and some leathers / fabrics pose the biggest problems because the surface can get damaged / ripped when peeling off.
Compressed air
Compressed air (up to 4 bar / 58.02 psi) is used in most laser cutting applications to remove heat and combustible gases from the top material surface. By directing a constant stream of compressed air at the point where the laser meets the material, flaming, scorching and charring is reduced on materials such as wood, acrylic and rubber. It also helps to limit smoke deposits on the material reverse. Smaller Kerf widths are also maintained with compressed air by minimizing the heat of the laser at point of contact with the material surface.

More info:
Company Name: Fei Yue Digital Technology Co.,LTD
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Address: Central Road 323, Nanjing, Jiangsu, China