Painted Plywood

Method

1. Material used was 1/2 inch spruce plywood
2. Cut to desired length. I did 48×48 inch, to be cut to 4×4 inch once painted
3. Patch the holes, cracks, and imperfection with dry wall repair paste
4. Sand down to a smooth finish
5. Paint base coat once (the color that will show up when lased). I used Flat Black, painted with a brush.
6. Let dry and apply a second base coat
7. Let dry and apply the top coat. I used a white primer, painted with a brush.
8. If required, apply a second very light coat. I had to due to missing spot and brush strokes (I used a very thin coat at first)
9. Once all dried, cut to final pieces. 4x4s and 6x6s in my case.
10. Use a router on the edge to give a nice finish.

29 Sep 2019 – Power Grid

This test was to determine the best power/speed ratio to burn the top layer to reveal the base layer. A power grid was used, ranging over multiple power and speed. The resolution was set to 127 dpi. The board was blown with air to remove the ash particles, but was not wash. The result were as depicted below. The top layer started to be burned at 50%/1000 mm per minute, but did not fully burn until 90%/1000. This was significantly higher than expected, whereas people achieved a good burn at 30%/1200. Multiple factor should be looked into, including cleaning the lens and refocusing. Recommend spending more time to achieve a pin-point focus.

06 Oct 2019 – Jarvis Dither

The photo was 40mm x 40mm, and was burned at different settings. It was initially not washed, then washed with water. Prior to being washed, the greyscale has good details, but after being washed, many parts did not burn deep enough to reveal the base layer. The greyscale seems to only be the white paint being burnt. If the base layer was another color (i.e. blue) it would still show up as black, since it never revealed the base layer. After being washed, the black has burnt too deep, while the light grey has not burned deep enough. This indicated that the laser beam bleeds over and overburn when too close apart, while not being strong enough when burning single dots (more spread apart). Each imperfection in the wood is also revealed, where more white paint is present, and thus more burning is required. The surface needs to be as uniform as possible.

08 Oct 2019 – Greyscale Gradient

The greyscale gradient was used to optimize the laser setting for painted plywood. Using a greyscale had the advantage of having larger areas having exactly the same color, and thus should be burnt the same. At 50% power, it was very faded, while 70% was overburnt. The bottom line, which is supposed to be black throughout was not uniform, indicating that the paint was likely at fault.