Introduction: Exact Scale Images for Laser Engraving
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. It has an engraving area of A5 format and it can be supplied with a different range of laser power, starting from 300mW to 5500mW. Mine is a 2000mW (2W)
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 a previous instructable I'll show how to make and use a customized grid plane to help you positioning the object and scale images to be engraved on it. In this one I'll show you how to produce an image already scaled to the correct size and ready to be engraved only positioning the objet with the upper left corner in the home position of the laser engraver.
Software I installed on the engraver is the suggested Benbox, while to obtain a correctly scaled drawing I'll use Inkscape.
Step 1: Setting Object's Dimensions
First you have to measure the exact overall dimensions of the object to be engraved, then you have to set the inkscape document properties to reproduce the the object’s size.
To do this select from Menus - File > Document Properties, or press (shif+ctrl+D) ... the Document Properties window appears.
On the Page Tab in the custom size box, select the Down Arrow and choose as units : mm (or whatelse you prefer) and fill in Width and Height the dimension that you have measured. (in the example 61 mm)
Another important things about exporting images for Benbox is related to the color and transparency of the background that is must set to white, with no transparencies. This because Benbox sometimes have trouble with transparent png showing the area in black.
When done, close the Document Properties window and the page dimensions will change following the exact dimensions and proportions of the object that you filled in the dialog box.
Step 2: Importing Images
Once the area of the object is available, you can draw something using the drawing capability of inkscape, or import a readymade graphic (vector or bitmap).
Obviously is preferred to use a B&W or grey shading image.
To import the graphics file of your choice from Menus - File > Import, (or press ctrl+I) … open an explorer window where you can choose the graphics file format.
If you choose a raster image you will be asked to embed the image or link to the file. Is your choice, ebbedding results a bigger svg file size.
Once you have made your choice, the raster image appear in the workspace selected with handles. You have to resize and center it in the page (you can use the centering tools of inkscape to help you in this operation).
When the graphics is centered correctly save the image and, from the file menu, choose export bitmap (or use the shortcut ..shift+ctrl+E). In the pop up window you have to select the "PAGE" button, choose the file name and click on the "Export" button
Inkscape export only png file format. Benbox sometimes have problem with transparencies of png files so, after, it could be better convert the exported into a jpg file, but if you choose the white background you do not need to.
Step 3: Engraving
Once exported the graphics, the only thing you have to do is open the generated file with the open file from Benbox menu and you obtain the exact scaled drawing anchored to the left corner of the engraving area.
If you have the beam aligned to referenced home position place in position the object to be engraved and starting the engraver it will fill exactly the area you need
Step 4: Engraving 2
If you are not sure where the home position of the beam is located, and you do not have a reference board, you can adopt the following simple trick to obtain a perfect alignment of the object :
put on the board a thin piece of cardboard or paper (better of a dark color, if you do not want to adjust the focus) and increase the engraving speed enough to a value that leave only a sign on the surface.
Make the laser to engrave boundaries of the object using the dedicated button on the menu. The laser will engrave the whole boundary of the graphics file, so you have a reference of the exact position of your object.
Put your object in the area marked and make the laser run.
In attachment I made available files I used for this Instructables