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Saturday, October 30, 2021

MoBeam: Text Engraving

Engraving Text

Aluminum Techniques

Engraving Painted Aluminum Vigotec VG-L7 20W Laser Engraver

  • Speed: 750 - 1250 mm/min
  • Power: 90-95%
  • 13 dots/mm
  • Pause: 45ms
Post clean with alcohol & cotton ball

From YouTube Video

From the Manual

In the right parameter control area of the software,
  • Select Binary-Line engraving mode.
  • Adjust the size of the engraving picture.
  • Adjust the line engraving speed value to 3000,
  • Laser power value to 90%,
  • Line or point density DPM value to 6

1st Lettering Experiment #1

The first attempt at engraving letters was somewhat successful.
Wood engraved easily and at very low power.
Painted Plastic and Steel are also etched at an expected higher power but there are visible horizontal scan patterns for which I do not know the source. I suspect the dots/inch setting has something to do with this pattern in that the scans are not adequately overlapped.


No horizontal patterns

  • Speed: ?? mm/min
  • Power: 4%
  • 5 dots/mm
  • Pause: 50 ms

Painted Plastic

Horizontal patterns, scan or settings error?

Painted Steel

Horizontal patterns, scan or settings error?

  • Speed: ??? mm/min
  • Power: 80%
  • 5 dots/mm
  • Pause: 50ms

Test #2

I decided to try this same test [on the blackened steel] using the same settings the YouTube video above used. The results were dramatically better. There is a lot more that needs to be understood about how these engraving settings work. 
Note both the settings and USB image overlayed in the screenshot below.

Calculate the resolution @ 5dots/mm:

5 dots/mm x 25.4 mm/inch = 127 dots/inch [very low resolution]
Line spacing = 1/127 = .007 inches

Calculate the resolution @ 13dots/mm:

13 dots/mm x 25.4 mm/inch = 330 dots/inch [more like a laser printers resolution]
Line spacing = 1/330 = .003.

The combination of higher resolution and power resulted in the ablated areas being more "clean". That is, there is more overlap of the beam from scan to scan.

If I guessed the optics characteristics correctly the laser beam is at its smallest 0.0030315 x 0.00511811. This suggests that at the lower resolution 127 dots/in the beam scans do not overlap by .002-.004" which would clearly be visible.


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