Our app was written with 2008 Visual Basic and will load and run on a Windows XP & up PC. It's a text editor that does calculations from depths of cuts/laser power level commands in one gcode file and then adds a variable feedrate (Feed Rate Change) to the end of command lines based on a set percentage of the feedrate. It creates and saves a new Gcode file with the PicFRC added to it's name so the original file does not get overwritten in the same folder.
The Feed Rate Change process was developed and invented by John Champlain to expand the shade range when engraving photos using a Laser Diode so shading enhancements are achievable.
We used John's process with this simple Windows App that we call PicFRC. Short for "Picture Feed Rate Change".
PicLaser Lite is a simple, easy to use image to gcode Windows App for engraving photos, but it does not have the added option for the Feed Rate Change to the gcode.
This Windows App was included with every EmBlaser shipped from the Darkly Labs LazerBlade KickStarter Campaign, so we needed a way to add this photo engraving enhancement feature to the gcode so it could be used when engraving photos with our EmBlaser.
The EmBlaser uses a grbl controller with a PWM output to vary the intensity of the 9mm Nichia 2.5W Laser Diode with a range of S0-S255 laser power commands. The EmBlaser does an excellent job engraving 8bit shaded images on different materials.
Generating a Gcode starts by loading a 8-bit grayscale or a 24-bit BMP format picture file into PicLaser Lite. Here is the original Roy Rogers image we used before is was re-sized and edited for the example photo engraving shown. Wikimedia Commons is a very good source for public domain images.
The set feedrate is determined by the amount of burning power the laser diode is capable of, on the material being engraved on. We determined that 110IPM (2794mm/min) is the fastest we can laser engrave a photo at max power with the default amp setting at 1.8a when engraving on Poplar wood with the EmBlaser.
Since our first example is without using the Feed Rate Change feature, we starting out with a lower feedrate of 90IPM (2286mm/min) to get darker overall shading
The Pixel Resolution (step over & step ahead) is based on how small the laser's beam can be focused. With our EmBlaser, we were able to focus it down to .005" (.127mm) which is the Laser Diode's burn line width using a 3 element AR coated glass lens.
We set the Pixel Resolution at .006" (.1524mm) and engraved at a 45 Degree angle. By generating the code this way, the Laser Diodes .005" (.127mm) burn line width will slightly overlap to prevent un-burnt lines showing in the engraving.
The Minimum S Laser Value was set at 10 and the Maximum S Laser Value was set at 255..The picture engraving shows the results we achieved on Poplar with these settings.