A little unfinished business on my model bombard is the Arabic script and floral decoration around the barrel mouth.
This is what I have managed so far….
It is a practice run in scrap wood.
Some of the detail has disappeared because I used a milling cutter with an end width of 0.5mm. Next time I will add another step using a cutter with a sharp point, and a lot more of the fine detail will appear.
That pattern took a total of 80 minutes to CNC mill, with the feed rate set at 500 mm/min.
Unfortunately my CNC mill developed a problem with the Z axis, probably due to a worn out end bearing. I am hoping that it is not the ball screw nut. Now in the process of removing the bearing. A heavy, awkward, dirty job.
When the mill is working again I will mill the actual bombard model and post some pics.
Computer graphics is not my strong point. To get the CNC mill to cut that pattern I did the following..
- Enlarged the photo, outlined the tracery and the script, then traced the outline onto tracing paper. That 550 year old pattern is worn and hard to define in many places. Quite a bit of guess work. Lucky that almost no-one can read ancient Arabic script these days.
- Scanned the tracing and loaded the scan into Corel Draw
- Used Corel Draw to smooth the curves, and make 3 copies in an array of the floral design
- Converted the drawing to bitmap file (bmp)
- Used V Carve Pro to convert the bmp file to vectors
- Used V Carve Pro to generate the CNC G codes
- CNC milled the scrap wood at 16000rpm, using a 3.2mm carbide cutter