COMPUTER CONTROLLED CUTTING
ASSIGNMENT
Design, make and document a parametric press-fit construction kit and cut something on the vinylcutter.
TESTING THE KERF
Kerf is the amount of material removed by the laser cutter as it burns through it. The kerf depends on the properties of the material, focal length, thickness and how the air is pushed out in the machine.
The lab's laser cutter is the Epilog Laser FUsion M2.
In order to find the kerf, a simple set of enclosed rectangles is used.
The design is completed in draftsight. The square tool is used to draw two rectangles as shown below.
Draftsight's pattern tool is then used to create 9 equally spaced rectangles.
The pattern tool results in the following image.
Then, dimensions are added and an outer rectangle too.
Another design is also used to test the kerf; freecad is used to draw the piece.
The sketcher toolbox is used to trace the outlines of the piece in 2d.
Constrains are added easily using the dimensional limits.
KERF TESTS
My draftsight design was imported into Rhino, as it is the supported software for the laser cutter in our fablab.
The dimensions are double-checked and the order of cutting is colour-coded.
The green colour, in this case, will be the first to be laser cut; followed by red and blue.
Then, I proceeded to print the design. In this step it is necessary to Set the window, in the 'view and output scale' options.
Then, the printer settings are configured by clicking the properties button. This will launch the Epilog engraver settings window.
In this window, the order of laser cutting is set in the color mapping options.
Screenshot below shows the settings used for the cutting.
As the material to be tested is the MDF 5mm piece, the settings are:
Green, Red, Blue in descending order. Speed: 3% Power: 100% Frequency: 20 Vector: Yes
The final cut-out clearly shows the kerf, it is calculated as the empty distance divided by 10 in this case.
The kerf on a cut made on a 5mm MDF is approximately 0.21mm.
DESIGN OF PRESS-FIT KIT
FreeCAD is used to design a modular press-fit construction kit.
First, the sketcher workbench is selected, it provides a set of tools for 2D parametric design on one of the planes.
We proceed to draw a simple outline of the design and then trim the undesired edges.
Constraints are set for using the 'equal' constraint button in the tool-panel. It is useful as it sets equality of sides.
The necessary sides are dimensioned accordingly.
Before laser cutting, it is necessary to export the design file in the correct format.
FreeCAD has the option to export the design as .SVG format.
After taking into account the kerf and modifying the dimensions accordingly, the final design is exported.
Within Inkscape, it is easy to duplicate the original image. The result is as follows:
LASER CUTTING OF PRESS-FIT
The printer in the Fab Lab Kamp-Lintfort is the Epilog Laser Fusion M2.
In order to print from Inkscape, it is necessary to send the job as 'win32 vector print'.
The following laser cutter printer settings were used for a 3mm MDF:
DPI: 600 POWER: 100% SPEED: 3% FREQ: 20 PIECE SIZE: (1000x600)mm JOB TYPE: VECTOR
The result of the printout did not come as expected. The inkscape exporter send the job to the printer as half the size as intended.
In order to solve the issue, the inkscape file was exported to dwg format and printed from there.
The printing procedure was similar to that of the kerf-test file. As 3mm MDF is to be used, the settings are the same.
The laser cutted pieces came out as follows:
VINYL CUTTING
A Silhouette device is used to cut a vinyl design. The design is drawn on Inkscape.
A star with 5 corners is drawn using the polygon tool.
In the same way, several super-imposed stars are drawn.
The union operator is selected to create a unique design.
The star is rotated, eyes and an outer square is also drawn to finalize the design.
SIlhouette has an easy to use proprietary windows compatible software. Import the design.
Next, check the dimensions are right by enabling the grid. Go to send to silhouette panel by pressing on the 'printer' icon at the far right of the top panel.
Note that if the printer is not connected, a warning will appear. Proceed by connecting the printer to an available USB port.
Next, check with the software that the tip of the cutting tool is set at the right setting. The machine has a slot where to place it to change.
Place the vinyl paper on the grid (if necessary, attach it with a double sided tape).
Next, use sticky paper to attach the non-sticky part of the design.
Finally, put the design on the surface of choice. My case, on a powerbank!.
LESSONS LEARNED
- Learned to use draftsight and improved my skills in Inkscape.
- Learned to use the laser cutter.
- Experimented with parametric design on FreeCAD.
