Plasma tables are not designed to be a laser
Neither are CNC routers!
I run a Co2 and fiber laser.
The raster speeds of the Co2 lasers are just that, meant for a machine designed for it… its only moving a very low mass deflection mirror , lenses , and very light weights laser head that also integrates a air assist tube all very very low mass / low weight.
None of which your plasma cutter or CNC ROUTER was designed for.
The use of them in laser marking capacity is possible, yea i see many doing it, but it’s extremely rough on the machines rastering that much mass at those speeds. Co2 lasers will only mark metals with expensive marking inks. And youll need a Co2 Wattage / power supply high enough to apply the amount of heat needed to etch using the marking inks.
Its Applied first and allowed to dry. Fully before lasering. I did discover cheaper marking material through trial and error. That worked pretty 
good .
Buy a dedicated C02 laser or better yet, if your only in the metal side of things get your self a Fiber laser for cutting and marking steel and other metals! FIBER lasers or a MOPA laser can ectch and even cut metal and mark and color permanently without expensive laser marking inks.
I imported an Awesome 50W Fiber laser from JW lasers. In CHINA.
Great Co. … many many users especially knife makers and firearms engravers use them and I couldnt find one negative about JINGWEI Lasers or Lucas Lui the service rep. Lucas is awesome with answering questions, software setup etc…
Lucas from JW lasers is tagged in the comments if you wanna check out his lasers.
Ill be Laser marking my Chef Knifes Im starting production on. And the plaques i cut from stainless on the CrossFire Pro.
Below link is custom .040” brass badges I made for a Great Wood working company that makes Custom slab tables , and all kinds of Hardwood furniture , art, etc… MOOSEWORKS SLAB DESIGNS