Laser Settings
What settings do I use for my laser marking or laser engraving or laser cutting? 

Specific to a flatbed CO2 laser...
 
In my 20 years in the laser industry, "laser settings" remains, by far, one of the most widely asked questions.  Unfortunately, it is impossible to make such a document.  Every laser is different not only from laser vendor, but can be different from that specific laser manufacturer, especially CO2 lasers.  Some critcial items include, wattage, motion system design, rise and fall time of the laser and beam quality of the laser.  

The best way to to determine settings is to perform a series of tests by engraving boxes using different power and speed tests on a coupon of each material you may use.  Your eye is the best determination of best settings.  A matrix program can also be easily developed as one file will produce a series of engraved or marked boxes as power and speed settings sutomatically adjust from box to box.    


There are 5 variables mainly that can affect engraving results:

 

1.  Focus – Typically is set at focus point per lens used.
     De-focus engraving can cause a darker result on material especially in wood  
     De-focus cutting can hugely improve results when cutting .25" or thicker.  Example - focus approximately 0.1" into .25" material.     
(Be cautious as de-focus can promote flaming) 

2.  DPI – (Dots per inch or more appropriately is lines per inch) - typically 500 DPI is optimal.  At arm's length a result engraved at 500 DPI and 1000 DPI will look very similar.  Using 10X magnification, the letter "O" will have visable steps around the outside, but at 1000 DPI the outside of the character is smooth.  Many times, depending on the material, such as wood because it is soft and forgiving, lower DPI such as 333 can be used to save process time.      

3.  PPI – (pulses per inch) If your laser has this setting - simply match the PPI to DPI you will print – there are times to double PPI to effectively increase average power at the surface.  This can be helpful when deep engraving into wood or using the Cermark and Thermark process on metals.

4.  Speed
– This is the speed of the laser head and is one of the two major variables - power being the other.  For smaller X travels of let's say 4 inches or less, use lower speed.  For X travel over 4 inches, higher speeds are more optimal because it will reduce process time and time is money!  (Higher speeds will not necessarily reduce process time for smaller X travels and actually increase the time because of overshoot.  There are always "However's" and that is considering acceleration.  Depending on laser vendor, higher speeds for lower X travel can also burn out a motor)  With this said, every laser manufacturer's motion system differs greatly and should be considered when selecting a laser vendor.  There are stepper motors which are typcially 50 inches per second or less max speed and there are brushless servo motors that can be up to 140 inches per second.  These motors have an acceleration specification that can be overlooked as people can be fixated to price of the initial machine cost while not considering production time and repair costs. 

5.  Power – this is the biggest variable when creating laser settings.  A laser engrave is a controlled burn as the laser fires each pixel.  The artwork determines the number of pixels.  The darker the color, the more pixels are fired and therefore more burning.  Laser power remains constant through the engrave.  This is similar to the way a newspaper is printed.  More laser power equates to more burning or lets say if you had a cigarette lighter – more power would be similar to adjusting the flame higher.  There is a 3D mode that will actually adjust laser power in the middle of an engrave depending on the artwork's gray shade color.  3D modes can work well on certain materials such as wood and acrylic.        

Coated surfaces -
Anodized aluminum is a coated material and very easy to engrave.  Low power and fast speeds are used.  Typically every laser pulse is seen so photos are usually easiest to engrave on anodzied aluminum without the need of too much adjusting the original artwork.  Using a 30 watt laser almost any power setting over 30% is Ok, but if engraving a photo lower power is used so that the laser light on the anodized surface appears as a light orange color.  Too much power can wash out the photo.