Laser Engraver Bed Grid

I recently bought a NEJE DK-8-KZ laser carver. It is a low cost device aimed to novice users, and, as such, it does not use gcode. Instead, it gets a 500x500 image (according to instructions) or maybe 512x512 image (according to carving software) and burns it over the object placed in the engraver bed.

You can zoom your image in and out and see a preview of the carving area over your object, but I wanted some better way to fine-tune the engraving area, in order to carve multiple objects at a time or design an image wich just fits into a tiny object, such a ballpen.

You could measure the engraving area and make a grid in your drawing program, but it seems best to make a physical grid and place it on the laser carver bed. So that's what i made.

It is a thin cardboard piece that "protects" the plastic of the laser bed, receiving missed beams and collecting dust, and, since it becomes easily burn with missed beams, I advice you to make many of these.

You need:

1. A 8x18 cm. or bigger piece of thin cardboard. I used the cardboard from a box of freezed crêpes, wich might be slightly plastified, but I think any thin cardboard will made it.
2. A cutter or x-acto knife, or scissors.
3. A ruler.
4. A felt pen or pencil.
5. A cutting mat. It is desirable to have a metric grid on it, or you'll need a square and triangle to make the square angles.
6. The same laser carver you are making this grid sheet for. This tutorial is intended for a neje dk laser carver, or any other laser carved that users 500x500 pixel images instead of gcode.

Start measuring the laser bed. Neje dk-8-kz laser bed measures around 9 cm wide (x axis) and 8 cm deep (y axis), with notches for rubber bands 1 cm from each edge.

So we will use a ruler and a cutting mat to draw a 9x8 cm rectangle in the cardboard and mark 1cm margins inside it. Then, we will use a cutter or scissors to cut the rectangle. Using the inner margin lines we will cut notches for the rubber bands. You can either cut off corners (removing 1 sq cm. from each corner), try to make triangle notches or simply cut a thin notch.

I made three of these, with different notch configuration. On one of them I cut a cut a thin notch with a saw, but I found cutter or scissors are better.

Then, we need to draw a grid on a 500x500 pixel image. I could draw it by hand or use imagemagick to make it, but I felt more confident on my processing skills, so I made a processing sketch at studio.sketchpad.cc and run it to get a 500x500 grid.

If you want to know the details of the grid generation, read here. If you don't want to tinker with processing code, simply download the grid.png file.

The sketch is in sketchpad.cc. If you have a local processing install, you can download the make_grid_for_neje_sketch.txt file.

The width and height can be changed in the lines "width=500;" and "height=500;" lines. The sketch makes a 10x10 grid; if you want more squares, change the "steps=10;" line. You could try with "width=512; height=512;steps=16". My sketch draws the grid top leftmost corner at (50,50) and the grid bottom rightmost corner at (450,450). If you want to draw a full grid from (0,0) to (500,500), you need to change the "for" lines.

Sketchpad.cc only allows to save images when running on fullscreen mode, so if you want to generate a new grid from the sketch, please make sure you run it fullscreen.

If you are satisfied with my grid, you just need to download the grid.png file.

Put the cardbox piece in the laser carver, making sure the rubber bands fit in the notches.

Then connect the laser carver to your computer.

Open the laser carver application (on my machine it is "Laser_Carver_five_language_V3.5.0"), then drag the grid image to the preview window.

Set power around 30 or 40. We don't wan't to cut the cardboard.

Finally press "start".

The laser carver will start drawing a grid on the cardboard piece.

The first grid cardboard piece I made had very thin horizontal lines and invisible vertical lines. So I changed my sketch file to make thicker lines. That is reflected in the grid.png included in this instructable.

I put an object on the cardboard grid and then I use a copy of the grid.png file to select the area in wich I want to engrave.

As an example, to engrave a Bic Ballpen using the cardboard grid:

1. Put the ballpen on the laser engraver, over the cardboard grid. You'll see the leftmost side is at fourth square (x=200 pixels) and the rightost side is at fitfth square (x=300 pixels).
2. Create a new 500x500 pixel image on my drawing software.
3. Insert the grid.png on background.
4. Create an object spanning over the squares occupied ballpen on the cardboard ((200,0) to (300,500)).
5. Select the new object as drawing area.
6. Draw a logo in this object.
7. Delete the background grid object.
8. Wrap your ballpen with white paper (it will avoid laser passing through transparent plastic without burning).
9. Place your ballpen on the laser engraver grid, on the exact same position it was before.
10. Save your image with a new name and send it to the laser engraver.
11. Press start.