Fusion 360 post for Centroid lathe and rear toolpost, spindle rotation, tool "hand" etc

I'm preparing to do some initial trials finally. For this, I'd use the pawn test piece I made for the Bantam trials, as it includes a variety of surfaces - radial, axial and curved. Here it is:

I bet this isn't simple. No indeed, there is the matter of working out which settings need to be changed, some of which are in the tool library and others in the post processor. 

Note the cryptic comment in the Centroid lathe post processor description "Generic turning post for Centroid. Use Turret 0 for Positional Turret, Turret 101 for QCTP on X- Post, Turret 102 for QCTP on X+ Post, Turret 103 for Gang Tooling on X- Post, Turret 104 for Gang Tooling on X+ Tool Post." 

Whaaaat? As ever, it sort of makes sense once you know what it means(!). In our case, we want X coordinates to be defined as +ve when moving away from the central axis and we also want the "QCTP" option. Not so sure that part of the description makes a great deal of sense for a turret toolchanger which is an ATC, not a QCTP but hey.

So in fact, that means we need to select "Turret 102" for this application. But WTF do you do with this info? Luckily I've been down this confusing path before. The answer is that you need to enter it into the "post processor" section of each tool in the tool library. I wonder how many people have torn their hair out over this!!

The final piece of the puzzle is selecting the correct direction of rotation for the spindle. For an internal tool, this will be CCW and for an external tool, it will be CW.

Setting up external tools for the Tree:

In some ways, changing the tool library and post processor settings should be fairly straightforward, as I simply(?) need to specify LH tools and ensure the spindle is rotating in a CW direction (most conventional lathes rotate CCW, looking at the spindle). This is evident when you consider that the turret presents the tool in a mirror image of the way a conventional machine would, with the insert 3/4" (19mm) from the base of the turret. I can't simply fit the tool "upside down" and use an CCW spindle rotation.

Here are the settings for the tool library. Note the toolholder has to be a Left Hand version - this isn't something I have a lot of choice over with this setup:

...and the mysterious "Turret 102 for X+ post" setting:

Here's the resulting toolpath

This a section of the resulting g-code, giving +ve values for the X coordinates:

N10 G98 G90
N11 G21
N12 G50 S6000
N13 G28 U0.
N14 G28 W0.
;PROFILE ROUGHING2
N15 M0 ;CHANGE TO T1 ON REAR TOOL POST
N16 T0100
N17 G54
N18 M8
N19 G99
N20 G97 S641 M4
N21 G0 X45.4 Z3.
N22 G50 S5000
N23 G96 S91 M4
N24 G4 P1.
N25 G0 Z1.
N26 X23.4
N27 G1 Z-36.674 F0.127
N28 G2 X24.2 Z-36.743 I0.99 K4.594
N29 G1 Z-40.8
N30 X25.4
N31 X27.4 Z-39.8
N32 G0 Z1.
N33 X21.4

... etc

Note the M4 spindle direction (ideally CW) and the +ve X coordinates.

What about internal tools?

For an internal (boring or threading) tool, I need to avoid the need for a LH tool, as LH boring bars are a bit of a minority sport. They don't really make any sense unless you are thinking of a dual spindle machine which sounds expensive. Instead, I need to turn the spindle in an CCW direction(like a normal lathe) and present the tool "upside down" (so that the swarf falls down, rather than coming off the "top" of the tool). The other reality that forces this behaviour is the fact that the Tree cross slide will only just reach the centre line with the boring bar / drill holders, so any internal operations will need to occur "behind" the centre line.

And finally, I need to make sure the lathe recognises movement of the cross slide away from the axis as being in a +ve direction. I've got a feeling that I've set it up so that cross slide movement towards the front of the machine (ie towards the operator) is considered to be +ve. If so, I'll need to use the wizard to redefine the X axis, doubtless including the soft limits and homing direction.

Note that the required post option for the internal tools is "Turret 102 for X+ post" again. 

NB: Note however, the tool needs to be defined as "RH", unlike the external tool which has to be "LH". Once that is taken care of, the post processor figures out the rest.

This results in the following posted g-code:

N10 G98 G90
N11 G21
N12 G50 S6000
N13 G28 U0.
N14 G28 W0.
;THREAD2
N15 M0 ;CHANGE TO T6 ON REAR TOOL POST
N16 T0600
;LH THREADING MF18X1.5
N17 G54
N18 G99
N19 G97 S250 M3
N20 G4 P1.
N21 G0 X15.093 Z6.125 T0606
N22 G0 Z-31.092
N23 X16.96
N24 G32 Z2.474 F1.5
N25 X16.093 Z2.908 F1.5
N26 G0 X15.593

..... etc

Note the M3 spindle direction (ideally CCW) and the +ve values of the X coordinates.

Whew. Now I just(!) need to frig about with the Acorn setup to get the X axis direction and limits correctly configured.

Swapping axis directions / coordinates in Centroid Acorn wizard:

Luckily it's fairly quick and simple:

• Axis > Configuration > Direction reversal
• Axis > Homing and travel > Automatic homing direction
• Axis > Homing and travel > Software travel limits (change from 0...+230 to -230...0 etc)
• Save and restart

Job done. Obvs this displays G53 machine coordinates as zero after homing. You can change the G54 coordinates or set G30P3 / G30P4 moves etc according to what you are trying to achieve.

That will do for now. So hopefully I will soon be in a position to try out my pawn test piece next. But first, I need to shave down some toolholders so that they have a 3/4" height rather than 20mm...