it is really pretty simple, I used to work in an engraving shop back when we used manual pantographs. Gorton Machines. Where you set type or pattern on the copy table and then used a stylus to trace the images, while flipping a lever to raise and lower the spindle.
I use my CNC Plasma Table, I make a Fixture for the part, secure the part to that fixture, then Zero the "Z" off the part without changing the X/Y position...
I am using Onsrud Carbide Tooling, 60 degree Zero Tip... that means that the TIP of the tool has no diameter it is SHARP the width of the tool path will increase by a factor of 1.5, so if you say you want .008 depth of cut the tool will make a .012 width cut, that is the factor of a 60 degree tool. You can get tools with larger diameter tips too.
In MACH I use the standard Plasma screen it is really no different than the "Router" screen.
I go into ports and pins and change my spindle to "2" 1 is Torch, 2 is "A", 3 is "B"
I then plug my router into output "A" of the CandCNC Ethercut box.
In Sheetcam I build a tool for engraving you want a "V" groove tool.
You will be pocketing and Contouring with this setup Pocketing for the fixture and Contouring for the engraving.
If you are filling your letters then you need to shoot for about a .012 DEPTH for enamel fill.
I use an aluminum blackener Birchwood Casey Aluminum Black. it is a conversion coating similar to cold blue for steel. I do engrave steel on occasion but I do a paint fill on that. Again need to have about .012" depth for proper fill....
I start by using a Milling operation to pocket out the fixture into some MDF or HDPE or Plywood.
This will create a Level Surface to hold the part, vacuum out the pocket when complete, I make it a bit deeper than the thickness of the material, you zero off the top of the material, I use a piece of paper as a feeler gage while I lower the spindle until I can just not move the paper.
Zero "Z" turn on the spindle (fire torch) lower zee to create a divot.... if anything happens I can return to this point and re-zero x and y if need be.
I then secure the plate to the fixture (perhaps just a sheetrock screw driven into one of the round pegs of the fixture in this case it will expand the wood or plastic to hold the part. Or you could use some flat washers to secure the part as long as the cutter will not strike them.
You COULD make Delrin Buttons that will hold it down without marring the material. I have done all of that and more.
Then change your cutter to the Vee Cutter and Apply an Operation to the Text or Branding in this case the Branding will have to be NO OFFSET in this instance because the tool won't fit any other way, the TEXT can be inside or outside depending on whether you want a LARGE letter or a SMALL letter, or can be no offset if you just want a narrow outline... Again I have done all of these at various times. You will need to zero off the plate, same method with a piece of paper... then check Top/bottom/left and right and select the average Zero point, you may be a few tenths (ten thousandths in Machinist parlance) different... put the Z where it would be in the MIDDLE of that so you have an average width not a lot of thick and thin spots... like if the Zero is at .001 in the middle, -.0005 on the left and + .0008 on the right... set the Z zero at .001 and call it good, or if there is a broader difference get somewhere in the middle like in this instance set it at .0002 positive and go for it! should be good all the way around.
You will want to slow your feed speed down a bit to make nice straight letters since we are working with tiny turns here.
I cut them then wash them with dish soap and a small brush to get the chips flushed clean away without scratching my Powder coat, Then I rinse them clean and blot them dry and apply the blackener. Followed by another clear water rinse (the Blackener is acidic) if you are doing an enamel fill then flow it in with a brush you will probably want to thin it some, then use a wood block with a no nap cloth wrapped tightly around it and some naptha to clean the surface after the fill flashes off.
I have also used an Air Brush to fill letters then cleaned the surface the same way.
Screen Shots below
