One of the objects that has always been on top of my wish list was a Laser Cutter/Engraver.
I get mine from GearBest. Here’s the link: http://goo.gl/ishspx
I made some video about, and you can watch them from here my laser playlist on YouTube
It is a great tool and a well built machine, that is immediately capable of producing satisfactory results, but one of the main trouble about using it, is related to correct scaling the image and centering the object to be engraved in the operating area.
In this instructable I'll show how to make and use a customized grid plane to help you scaling and centering images to be engraved on your objects.
Software I installed on the engraver is the suggested Benbox, so this Instructable referes to it.
Customized belt blocks on my Thingiverse
Step 1: Making the Grid
I made this grid using Inkscape then it has been exported in dxf format.
Dimensions are related to the maximum working area I obtained with my engraver making move carriages very close to their limits
Also if it has to be theoretically an A5 format (that is 148 x 210mm) I find my working area only a little bigger than 140 x 170 mm so I decide to maintain this limit using a grid of 10x10 mm
It is better to use a vector format like dxf to obtain a scalable picture without thickness, using an exported bitmap image makes the laser reproduce it's lines thickness with more passages.
I add both grid files in svg and dxf format so you can modify them for any needings
I add also a grid with reference letters
Step 2: Preparing the Board
You need a sheet of cardboard or plywood with dimensions of 210 x 330 mm
(209x329 mm to be sure not having interference)
Make it slide inside the aluminum frame, it will be supported by the junction brackets and centered by the acrylic frames
Connect and switch on the machine
The engraver do not have limit switches that define an home position, so you have to move manually the laser head to the upper / left corner of the operating area just near to the limits of the carriages.
This became the home position and correspond to the red dot in the Benbox software.
Remember that, every time you switch on the engraver or you manually move the carriage, the home position became the actual position of the change.
Now, using the open file icons, you have to load the dxf file format that I attach in the previous step.
If you appplied the correct setup suggested from Eleks Maker ( PPM 320-320 ) the image will be loaded and scaled correctly, ready to be printed.
To be sure to be centered you can made a test pressing the boundary icon. This makes the carriage move around the maximum perimeter of the image.
In the benbox menu deselect laser and select servo, to simulate the overall dimensions without switching ON the laser.
Step 3: Engraving the Grid
Before starting remember to make sure you have the laser correctly
focused on the surface and with the correct engraving parameters.
Carry out test on a spare material with the same thickness and surface.
Click start icon and the grid of working area will be automatically engraved.
First it engraves the perimeter then vertical and horizontal lines
This grid will help you understanding the available working area and aligning better your objects to engrave along X-Y axis
Remember that every time you switch off the engraver it loses the home position. So you have to manually move the laser head near the upper left limit and, helped by the "momentary on" icon, realign by step the laser beam to the home crossing point.
Step 4: Using the Grid With Benbox Software
With a simple trick the grid is helpful to exact scale drawings and place exactly the object to be engraved.
With the open file (blue) icon import the grid in dxf format. It will be imported with the upper left corner corresponding to the home position (red dot) of the Benbox software.
Place in position the object to be engraved using the grid as a reference
Now from the drawing menu click on the imagine (green) icon and import the image you want to transfer on the surface.
This allow you to have this image overlaid on the grid image.
Now, if you select the imported image, you can move or scale it having as a reference the grid below, this help to predetermine exactly where and how big it will be engraved
When is ok you have simply to select and delete the grid image (if not it will be obviously engraved)
Now everything is ready and you can press the start icon.