WELsoft Website Notes
Note 11
Target audience: Users of the Emco F1 mill (NB not upgraded with WELmill) and WELedit
Subject: Can I machine an ellipse on this mill? (query from Paul Fletcher via e-mail)
Yes - but you need to think of an ellipse as a series of blended arcs ranging from large to small radius. There is a snag. As far as we know, the largest radius the F1 mill can handle is 99mm. Bigger than that you get an error message.
You could experiment and try cutting an arc with a radius greater than 99mm just in case there is variation between older and newer F1 mills (and F1 woodworkers). Perhaps someone out there knows?
You need to design ellipses carefully and keep them small. Its very easy to get arcs at the ends of the minor axis greater than 99mm radius. Maybe a geometrical drawing textbook will have helpful guidance.
Example: When AlphaCAM draws an ellipse with a major axis of 85mm and a minor axis of 43mm, the radius at the ends of the minor axis is 85mm while the radius at the ends of the major axis is 11mm. (AlphaCAM was set to 4 arcs per quadrant.)
The cutter is 5mm flat ended and the centre of the cutter will follow the ellipse and cut a groove 2mm deep.
Below is the NC code produced by AlphaCAM. You will notice that, because the ellipse has four quadrants and four arcs per quadrant, there are sixteen G03 commands followed by M99 commands. Each pair of commands defines a partial arc and the arcs blend together to form an approximate ellipse.
'(ELLIPSE
EXAMPLE)
%
N- G- X - Y - Z - F
'(OP 1 FINISH PASS TOOL 2 FLAT - 5MM)
'(EFFECTIVE DIAMETER 5)
000 92- 250- 250 3000
001M06D 250S2000 00T002
002M03
003 00 9373 2831 3000
004 00 9373 2831 200
005 01 9373 2831- 200 100
006 03 9113 3553- 200 150
007M99I 1132J 0K 0
008 03 8125 4338- 200 150
009M99I 2357J1953K 0
010 03 6835 4785- 200 150
011M99I 2361J4721K 0
012 03 5111 4962- 200 150
013M99I 1724J8323K 0
014 03 3387 4785- 200 150
015M99I 0J8500K 0
016 03 2097 4338- 200 150
017M99I 1070J5169K 0
018 03 1109 3553- 200 150
019M99I 1369J2738K 0
020 03 849 2831- 200 150
021M99I 871J 722K 0
022 03 1109 2109- 200 150
023M99I 1132J 0K 0
024 03 2097 1324- 200 150
025M99I 2357J1953K 0
026 03 3387 876- 200 150
027M99I 2361J4721K 0
028 03 5111 700- 200 150
029M99I 1724J8323K 0
030 03 6835 876- 200 150
031M99I 0J8500K 0
032 03 8125 1324- 200 150
033M99I 1070J5169K 0
034 03 9113 2109- 200 150
035M99I 1369J2738K 0
036 03 9373 2831- 200 150
037M99I 871J 722K 0
038 00 9373 2831 600
039M05
040 00 9373 2831 3000
041 00- 250- 250 3000
042 64
043M30
MI
It takes 43 lines of code for one pass round the groove. If you need to go deeper you need to take several cuts: therefore more lines of code. If you want to machine an elliptical pocket, eg the inside of a box, there are even more lines of code. And even more to cut the outside of the box.
Here you run into a limitation of the F1 mill/woodworker. It is mechanically a very good machine but its control system can only take 210 lines of code at a time. You need to break a long code list into sections and ensure the cutter starts the next section in the right place.
Please refer to Note 3 for guidance on verifying NC code once it has been loaded into the mill's native controller.
September 2002