Parameterized Mask Generation
The manufacturing technology (Epilog Laser Cutter shown above) requires vector (e.g. pdf) not raster (e.g. jpg) images, so two types of NPR cells were parameterized and generated as pdf "mask" files by a python program. - v20101210 (thanks to Bill Paseman for help on the python programming and assistance in running the Epilog machine). This program makes use of reportlab's open source libraries to generate the pdf files once the geometry is known.
Rectangular cells (each filled with one "bowtie" made of two opposed overlapping triangles) were parameterized by- the triangle height and width
- the height and width of the rectangular cell containing the triangle
- the "strut width", which is the width of material separating the triangles bases.
- the length of center to center hexagonal cell spacing
- a "scale factor" which determined the relative size of the triangular design in the hexagonal cell
- two co-ordinate points which specified the intermediate "Bezier points" used to create a Bezier curve from a unit line segment.
Manufacturing
The pdfs generated by the python file were cut on an Epilog Helix 60 watts CO2 Laser Laser Cutter at the techshop. The cutter has a resolution of 600 dpi.Mask Generation procedure
- Edit parameters in python file and run it to generate pdf file(s).
- Open pdf in Adobe Illustrator and save as svg
- In CorelDRAW X5, create new page
- change size to 8.5 x 11.0
- import svg
- Select all and ungroup
- Select triangles and select hairline from outline pen tool (Hairline is the code recognized by the cutter to activate the laser)
Printing (Cutting) Procedure
You now have a mask. Running CorelDRAW's print command downloads these to the Epilog cutter, which interprests the pdf's "moveTo" and "curveTo" instructions as "moveTo" and "cutTo" instructions..
Epilog Helix 60 watts CO2 Laser "printing" parameters
Horozontal: 8.5
Vertical: 11.0
Vector only
| paper | gum rubber | |
| Speed: | 80% | 20% |
| Power: | 20% | 90% |
| Freq: | 500 | 100 |