This post is collected information from the Light Object Laser Lab Facebook page.

BASIC TECHNIQUE OF RUNNING A LASER MACHINE

1. Focus lens: 38.1mm, 50.8mm, 63.5mm, 75mm, 100mm, 150mm.
   1. How do we choose a focus lens? For a mid-size laser machine (600×400, 900×600, 1300×900), it comes with 50.8mm in general. With 50.8mm, quality engraving, and up to 1/4″ plywood cutting is expected.
   2. If you need to engrave fine text 2mm in size, you may want to go for 38.1mm. But it is a little difficult to fine-tune focus precisely. Plus, the beveling effect is more obvious when cutting thicker materials. So, why not use a long-focus lens. Well, you gained something, but you will lose something simultaneously. The cut edge will be more straight (less curve). If you want to cut 1/2″ acrylic, I suggest the 63.5mm focus lens.
2. How to cut acrylic with glassy quality? I offer you three tricks: low air, low speed, low power. Some people said they must upgrade their 80W laser to 130W or higher if they wanted to cut ¾” thick. Well, there is no right or wrong. It depends on your goal; speed or quality. If you wish to fast cut, yes, you need a bigger gun. But if you want a quality cut, then it is not necessary at all. Why? For most belt-driven laser machine, the best speed to cut acrylic with glassy quality is to run it at 4mm/s or slower. With slower speed, it avoids vertical lines from the gantry vibration. We need lower air because the surface shows blurry or smoky if you have too much air blowing. While the machine is running at low speed, you don’t want to use 100% power, but 20~30% depends on your laser tube. The excess power (heat) will cause the surface not flatted. CAUTION: When cutting acrylic with low air, the smoke generated from the cut will catch fire very quickly. Make sure that you have a strong exhausted fan installed. When you see fire built-up under the acrylic, pause the job until the fire goes away. And, NEVER walk away when the machine is operating. I need to call it ‘Very Loud’!
3. How to engrave acrylic with icy look? Again, low power and low air. Speed, I used to use 550mm/s. Plus, you need to raise the laser head up by 1mm to 1.5mm over the focus point intentionally to ‘out-focused’. That way, the engraved area would be more ‘soft’ and ‘evenly’, more like an icy look.
4. How do we cut ¼”, ½”, ¾” plywood or MDF? Yes, a bigger gun is preferable. Generally speaking, it is easy to do cutting without much Technique needed. Set the focus and hit Go, right? Yes, but with my little advice, it will cut a bit better and fast. A) move the laser head down 1mm to 1.5mm from the fine focus point, depending on the plywood’s thickness. For ¼”, drop 1mm, while1.5mm for ½”. B) use higher air pressure. 40~50psi will result in a brown cut instead of charring. In some cases, it speeds up the cutting by 30%~40%.
5. How to engrave more efficiently? If you’re engraving an array of graphics, make sure to engrave it in a group instead of one by one. It is because the XY gantry takes time to accelerate and to decelerate.