No sanding, but I can give it a shot.
Even after focusing your laser with the instructions that I linked below, the 3.8W may need a larger Pixel Resolution (step-over) setting than .006" so the burn lines do not overlap. The 3.8W laser beamās divergence is larger then the 2.8W.
Experiment by adjusting the Gamma & Sharpen in the PEP5 image editor. I recommend starting out with a higher feedrate and use the Feed Rate Change (20%-25%) to enhance/expand the shades. Trial & Error!
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I tried to etch a blue ID tag today with the same settings as the red one and it didnāt even leave a mark. Ran it twiceā¦nothing.
That makes sense. It would not look blue if it didnāt reflect blue light. In order to burn the surface it has to absorb the light, not reflect it.
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It made perfect sense after I tried 
Iāll try green nextā¦doing the Han Solo again now with different settingsā¦Iāll try when it finishes.
New settings:
pixel resolution - 0.007"
Feed rate change - 25%
I was going to try and cut it out with the laser, but I bumped it after the second pass, so I stopped it.
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@JohnChamplain, @picengravertoo, @JTechPhotonics -
Today I swapped out the lens that came with the 3.8W laser from J-Tech with a 3 Element Glass lens. What is your opinions on this? I find it much easier to focus with the new lens as it truly brings the laser to a point (my eyes are not what they used to be).
I understand the 3 element lens reduces power, but since I am only using it to engrave/etch items and I truly have no reason to try to cut anything with it will it make a difference? I was able to focus much easier and etch another business card holder today and the results were great.
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The 3 element glass lens will give you a smaller focal point for achieving more detail when Raster engraving photos. The engraving angle will not change the burn line width with the 3 element glass lens either, because the focal point is more uniform.
The J-Tech single element glass lens works good when you orient the beamās divergence parallel to the Raster engraving angle. When Vector engraving, the engraved angle is constantly changing, so the burn line width constantly changes slightly too.
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This one was done with our Shapeoko 2, 6W LD and Larryās Multi-Mode grbl 1.0c on 1/8" Birch Ply. It has a 2" focal distance because of the air assist and the lens is a J-Tech single element glass. I only use the air assist for cutting & 3D engraving.
I think I found the same image you used, even though it was not very good quality, the laser engraving came out acceptable. The 6W beam divergence is even larger than the 3.8W.
http://www.tampabay.com/resources/images/blogs-photo/rendered/2015/07/01Web_HanSolo_8col.jpg
The original imageās Pixel Width & Height was small, so I had to resize it larger to 9.25" X 6" for a .007" Pixel Resolution. The jpg compression artifacts got worse if I Sharpened it too much, so I only used a setting of 2. I then cropped it to 6" X 6" and it took a little over 46 minutes to engrave. Other image editing & PEP5 setting details would not be relevant for your 3.8W.
Itās best to start out with higher quality images that are larger in size, so they can be resized smaller before editing and generating the gcode. .
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That turned out very niceā¦I really need to play around with the settings to get better results.
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Here is another design for notebooksā¦did a test etch on chipboardā¦the name and date can be changed easily in v-carve.
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Just wanted to show that if you have your machine dialed in it will cut a bit faster/deeper than some of you might think.
This is the roughing cut of a 3d Carve of an elephant scene. It was roughed at 100 IPM with a depth of cut of 0.2" using a 0.25" 2 flute endmill. The carving is 6" wide x 12" tall and only took 48 minutes.
The deepest portions were about 0.5" deep in total.
I am running the finishing pass now at 100 IPM as well with a 1mm radius tapered ballnose bitā¦
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Hard maple. The finishing pass cleaned it up nicely. I ended up cutting a second one as well. This is the center carving of a 5 panel set. I will finish 2 sets this size and a larger one in cherry that will have the center panel like this only 10" x 20".
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Same as @RobertCanning, none of my motors get hot even when I crank them up.
Iāll have to check when I get home (this damn day job gets in the way sometimes)ā¦also I am using mach 3 not anything grblā¦
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I had a Nema17 on Z before, it got so hot water sizzled with authority when dropped onto its casing 
Motor didnāt fail though but it got too hot for my liking, the bigger Nema23/270oz I currently use doesnāt feel warm at all on same job 
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PhilJohnson4m
With the grass texture in Vcarve, my z gets very warm. Not too hot to touch, but enough that I was thinking about trying to keep it cool.
Not to worry. Most are designed for upwards of 70C.
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