First cuts on the Bantam!!

Steady on!
My lathe conversion is now 99% functional, albeit laid out on the bench for now. The next step will be to rip it apart and install it for real in the cabinet I've just bought. Before doing so, I'd like to convince myself I have a functional system by machining a test piece. This would be a major milestone to tick off at least.
I see that the lathe_pawn.ngc example file that comes with LinuxCNC installations is missing a lot of info you'd actually need to run a real machine. I guess this is enough for running a sim but I'll have to create a proper version myself. For instance, there are no tool numbers or offsets specified and it is missing some of the initialisation lines you'd want to see at the start and end of the file. 

So I recreated my own CNC porn in Fusion:

Tool library:

I need to set up a tool(s) in the Fusion tool library before I can create any toolpaths. I got a couple of these Chinesium holders from APT Tools (right and left handed) and the matching VCGT16 inserts:

Then set the RH version up in the Fusion tool library:

 

CAM setup: 

The stock and machine setup could be fraught with opportunities to crash the tool / work / chuck etc. There's a bit of an insight into how this works in the latest (Dec 2019) lathe update from Autodesk.

Roughing settings:

Finishing pass:

Post processing:

There's a LinuxCNC lathe post processor in the Fusion post library that seems to work. At least this code specifies the correct tool (T4 in this case). That feels like a good start.

%
(1002)
(LATHE PAWN)
N10 G7
N11 G18
N12 G90
N13 G21
N14 G28 U0.
N15 G28 W0.
(PROFILE ROUGHING1)
N16 T4 M6
N18 G54
N19 M8
N20 G97 S1402 M3
N21 G95
N22 G90 G0 X45.4 Z3.
N23 G96 D2000 S200 M3
N24 G0 Z0.75
...etc

However, when I try to run it, I get a couple of errors:

• I have a couple of lines at the start specifying U and W coordinates
• I get a message saying it can't find the specified tool 4 in the tool library

This would be my first ever lathe program, so perhaps the U and W coordinates are fairly normal but I can't see anything in the Peter Smidt books about them. I can delete them, which gets rid of the error message but presumably the LCNC post produces them for a good reason?

As for the tool library message, this may be another symptom of the immaturity of the PB Lathe GUI. When I edit the library, the lathe.tbl file gets updated correctly, so T4 seems to exist and can be found / edited by other parts of the GUI. Is there any obvious reason I'd get this message?

The only way I can find to frig the system is to change the program tool number to zero(!). I guess I could do this solely for the purposes of running my one-off test piece although I don't know if the part zeroing macros would work with this method.

I'll see what state the PB Lathe GUI is in when I finally have the system installed in the cabinet and working again. That should buy me some time, otherwise I may have look into one of the other lathe GUIs. I'd certainly like to be able to use Andy Pugh's macros and obviously the tool library is a bit of an essential function that needs to be in place.

Bollocks. Let's get 'er done, then I can move on with the cabinet installation.

Just do it, fatty!

Homing the machine, then positioning the tool at where I imagine the part origin to be and zeroing the WCS should do the trick, you'd think. Sure enough it seems to get us most of the way there. A bit of air cutting with a bit of wire to mimic the tool nose suggested it was reasonably sensible, so off we went:

For some reason, it seemed that the program stopped between the roughing section and the finishing pass. 

So I deleted out the roughing section and reran it so get the finishing pass out of it. This seemed to almost do the business, although it didn't completely finish off the vee groove feature for some reason.

Manually parting off:

So, I seem to have a pawn on my hands:

That wasn't a complete disaster, although I could make some comments:

• The surface finish isn't exactly spectacular. I can't see any "smoothing" settings in Fusion. Perhaps there is something in LinuxCNC. Or perhaps it doesn't exist in lathe in quite the same way it does in milling? Something to look at.
• The part is 0.5mm undersize on diameter. I guess this happened when I eyed up the tool nose, not being bothered to figure out exactly where to position it.
• The first (facing off) move seemed a bit aggressive and resulted in "some degree of chatter". Once past this, everything else was OK. 
• The 0.1mm stock to leave may have been a bit light. Not sure if this is partly why the finishing pass didn't always remove any stock.

That'll do for now. So now let's focus on the cabinet installation....