First pass at an inside curve in the Z axis on the mill

I've been thinking about trying to make a low profile focusser for my Skywatcher telescope for a while. A few things to learn before I'm ready for the whole thing.

One thing I'd not tried before was a curve in the Z axis on the mill. The back of the focusser needs to mate with the outside curve of the telescope tube (350mm diameter).

The standard focusser has a base plate around 110*110mm square. I cut a piece of aluminium almost that size out of some scrap and set up the code to cut the curve.

The code aspect is pretty simple, I used the G18 (XZ plane) element then worked my way back and forward along the material using G2 and G3 cut's with a radius of 175.

The cutting commands are in two subroutines
(---------------------------------------------------)
(Cut the Arc)
O0001
G01 Z0 F30
G02 X108.5 R175 F25
G90 G00 Z2
M99
(---------------------------------------------------)
(Cut the Arc)
O0002
G01 Z0 F30
G03 X1.5 R175 F25
G90 G00 Z2
M99
(---------------------------------------------------)

and the main body contains a whole lot of sets of move in the Y axis and start a subroutine commands
G00 X1.5 Y0
M98 P1
G01 Y1
M98 P2
~~~~~

G01 Y105
M98 P1
G01 Y106
M98 P2

I used a 3mm cutter on fairly slow feed rates so it took a very long time to cut (and I still need to do a final cut) but the result looks as expected (I'll try and post a photo in the near future).


The surface is composed of a series of small groves due to the shape of the cutter, I don't think that they will cause me any problem.