MPCNC: Diamond Drag Engraving Speed Tests

The MPCNC isn’t the most stable of CNC machine tools, given its large masses and 3D printed structure. My early plotting pen tests suggested speeds around 250 mm/min were appropriate:

Diamond drag engraving produces a thinner line and makes the wobbulations more obvious:

Another test showed similar results:

Slowing down definitely reduces the shakes:

Producing the best results takes quite a while:

Similar results on another test:

Those “mm/s” labels are typos; they should read “mm/min”. Plotting at -1.0 mm on scrap CDs and DVDs produces a downforce around 200 g.

Eyeballometrically, 100 mm/min seems fine, but 50 mm/min (I’d likely use 60 for a nice round 1 mm/s) eliminates all the shakes.

Smooth curves, like Guillloché patterns, can run much faster, because they don’t have abrupt direction changes. This 3-½ inch hard drive platter has text engraved at 100 mm/min and the pattern at 600 mm/min, both at -3.0 mm for 300 g of downforce:

A closer look at the text:

And some digits:

When I want to brand an engraved CD, this will suffice:

All in all, the MPCNC engraves much better than I expected!