::runs in and slides in wearing socks on wood flooring::
PPI/DPI!! Pixels Per Inch - With your raster images, this is SUUUUUPER important. 600dpi is the MINIMUM I use when engraving, because it’s ridiculously high def. You CAN achieve this by shrinking the render space, but you have to beware that your image editing program doesn’t resample the resolution to fit the size.
In the print world, you never ever want less than 300dpi unless you’re working on billboards, but even then… This is why we graphic designers use vector graphics. They scale up and down and recalculate their DPI on demand.
Lines Per Inch - If your DPI/PPI is 240, setting your LPI won’t magically make your 240ppi image a 600dpi rendering! 
I wish it worked magically like that, but it doesn’t. Just like your colour printer can only print as high quality an image as your provide it, your laser works the same way. Your input has to be as great or greater than your intended output.