CNC Engraving

Recently I saw a polished wooden sign where a design was burned onto it using a CNC controlled laser. The detail was impressive and I was told that it was produced on a cheap desk top machine. This set my brain racing with the idea that perhaps it could be used for engraving graduation dials and nameplates in the workshop. I have looked at the usual EBay offers and Youtube but without actually seeing the thing working it is hard to judge.

Maybe there is some experience in the group which would help me decide if it is worth buying a cheap ( £200-300) machine and what results could be expected using a 15W laser or a fine rotary cutter

Wood happens to be a rather good thing to laser engrave as it is so cooperative in going black. There are problems with metal in that it is shiny so reflects the laser and has to have an initial coating of an expensive special spray to make it easier to engrave.

For dials do an experiment with your paper printer and see it it is accurate (enough). You can get special paper especially for laser printers that is self adhesive and oil proof to print dials on, also used for front panels on machines.

A machine that would be fine with a laser (provided that had enough power to mark the material) might not be very good at all with an engraving cutter, for which more rigidity would be needed.

For a non-laser (rotary cutter) machine you could look into the relatively inexpensive 3018 engravers (put 3018 engraver into a Google search).

Be aware that the devil is in the details. If the bed is not exactly aligned with the x and y motions, the engraved line width will vary and look like hell. The problem is that most of these machines have no systematic alignment method. It's just fiddle with the adjustment screws and "btw , lots of luck".

It's possible to come up with your own mods to introduce proper alignment methods, although one of the best suggestions I've seen is to mount a sub-plate on the bed, a milling cutter in the spindle and just machine all over.

I had a feeling that some of the advertisements were a bit optimistic. One suggested engraving stainless steel while another on Youtube demonstrated a partial success on a stainless knife using a coat of mustard which I guess burns onto the metal leaving a mark which would wear away after a short time. Some people have constructed their own machines and one demonstrated cutting a sort of gear from a 1/4" alloy plate using a palm router fitted with a HSS bit and making many passes to cut the depth.

I feel disappointed but happy that I contacted this forum so I keep my money until I find out a bit more about the process.

I've done some simple engraving of plastic name tags on my CNC controlled MF70 mill. There was a thread last year where I was asking for advice about cutters, plastic and so on.

For small machine dials I've also had some success using photo etching (by PPD in Scotland) to make a 10 thou thick nickel silver dial which is then rolled and closed up using a simple lap joint. The core of the wheel is made to be a snug fit inside the dial with a groove to make room for jointing splint. In this case I was lazy and arranged the diameter so that the circumference was exactly 100mm. It's only really viable if you need some other stuff etched and have some spare space on the sheet though.

Thanks Andy. Now that opens up a number of real possibilities and renews my interest. Could be I will have a new toy for Christmas.

No probs. Do read the other threads about the MF70 if you are thinking of going down that route though - it is a small machine and will only take small cutters and do small sized work. CNC conversion is a project in itself.

If you want to do nice serifs like Jason then you need to eliminate any uncertainty in the 'Z' direction - that means dealing with backlash, making sure the job is held properly flat and also having smart enough software to drive it. I have not yet aspired to those levels - most of my work can cope with a a tenth or so of a millimetre of uncertainty in 'Z'.

Laser etching of things in the industrial field will soon wear off and become unreadable. Looks great to start with, deep etching or cutting is better, will hold contrasting paint Etc. Noel.