How is this done?

[Scott Alberts]

324936I've etched a few skateboards like this. And cannot figure out how to keep it from going out of focus on the two ends. I have Trotec speedy 300 just like they are using in this pic. Any ideas?

[Clark Pace]

Not sure what lens you have but a longer focal length would help. Like a 2.5 or 3

[Scott Alberts]

I have a 2.5. Wonder if a 4" would do it.

[Keith Winter]

I have a 2.5. Wonder if a 4" would do it.

4" will help or you can color the end areas a different color and set the z to drop for that color on Job control if 4" won't do it

[Scott Alberts]

Good idea.

[Dave Sheldrake]

depth of field

Assume M^2 = 1

Input beam is 6mm in diameter

Depth of field and spot sizes for different lens's as follows.

50mm focal length:

Depth of field = 2mm
Spot size = 0.1mm

100mm focal length:

Depth of field = 7.5mm
Spot size = 0.2mm

200mm focal length:

Depth of field = 30mm
Spot size = 0.4mm

The depth of field is a total distance between Point A and point B where the spot stays within 1.4x the smallest spot diameter and is an equal distance from the smallest spot size in both the Z+ and Z- directions.

Short version, the total height change must be less than the depth of field for any given lens size

[Samuel Espy]

Many skateboards are made via thin laminates which are formed into their curved shapes via a mold (often shaped foam) and a vacuum press. Using this route, one could engrave before forming. See http://www.roarockit.com/