What glasses would you recommend
You are looking for certified glasses designed for the 445-450nm wavelength making them orange in color. The glasses I got with my laser module were uncertified and red. I purchased this pair from Amazon, but I cannot claim they are better than the many other pairs I found on Amazon that meet the above criteria.
In regards to turning the laser on and off is this all set in the gcode software
When setting up your machine in LightBurn, select “inline” as the method. Other software may not have this option, so M3 / M5 will be the choice. The g-code will handle the commands to turn the laser on and off.
Also, how is the laser run manually to figure out the power setting and travel speed
You will want to do test patterns to determine travel speed and power. LightBurn has the ability to vary the power output by shape. This makes it much faster to setup a test pattern. See this video. You can turn the laser on manually. If you are using a display with your Rambo board, note that the menu item for turning the laser on manually is confusing…at least for the version of Marlin I’m running. In the laser sub-menu turning the laser “off” puts it in manual mode. That means when you set it to “off” it will immediately come on at whatever power you’ve set. Turning it “on” means it will be controlled by g-code.
Note that LightBurn can be used as a g-code sender like Repetier-Host. There are some benefits (and probably come complexity) running it in this mode. Personally I have LightBurn generate the g-code and run my machine from the SD card. Also I have LightBurn setup so that it mimics the g-code from my other apps in that cutting is relative to the stock and there is no auto homing. This is not the default setting in LightBurn.
Edit: I’ve not made anything with 3mm plywood, but I did run some quick cut tests on some material that was billed as 3mm Baltic Birch. My spreadsheet indicates a single pass at 3.5mm/s at 100% power and two passes at 6.5mm/s and 100% power. These numbers indicate the outer edge of successful cutting where faster or less power failed to cut. In my cut library (part of LightBurn) I have two passes at 4.5mm/s and 90% power for 3mm plywood. Based on a couple of things I’ve read, I avoid running my laser at full power if the duration of the job is over 30 minutes. These values should give you a place to start to figure out your power and speed for your plywood.