4th axis tangent to path XY

The best, and most reliable, solution will be to do it in the CAM software, I think that SheetCAM can do this.

Alternatively the calculations could be done with a custom HAL component, and this would make it easier to turn the feature on and off. (Just have a HAL pin to enable and disable the component)

Does your head have bevel and rotation axes, or is it done as a combination of A and B tilts parallel to the X and Y axes?

My hardware design has been made so that Rotating the C and B axis doesn't interfere with the TCP.

C is a direct vector to the tip of the torch at cutting height of 3mm.
B is a direct vector to the tip of the torch at a cutting height of 3mm, tilting around 45º so it's similar to some 5 axis boring machines.

SheetCAM is being a very useful tool for trying to come up with a solution for this, just not good enough yet.
Maybe G93 inverse time will be useful for this, but I haven't figured out how to put it to work in SheetCAM, so i'm still trying with regular G94.

XYZ, C and B all home perfectly and position the machine at 0,0,0,0,0 (vertical, straight C)

rotating B axis to -30 or +30 will produce bevels of this angle (with a snippet code, different tool, or other technique it's achievable to insert this)

-> THC off can be done with snippet code.
-> I would like to be able to increase the CutVoltage here by a bit but i can just have it OFF for now.
-> Interfacing with Amps digitally could be done with M67 M68 but not with my plasma.
-> Slowing down feed with the following code on bevels can be done automaticallyM67 E3 Q60 (reduce feed rate to 60%)
G3 I10 (the hole)
M67 E3 Q0 (restore feed rate to 100%)

On a small arc of 1mm, or a straight 90 deg X/Y angle, I can make the torch follow with the C axis being tangential with the knife post processor adaptation.

What I can't do, is make a bevel on an ARC (conic holes, large circle with bevel for weld prep, etc) , because the velocity of moving C will not be in agreement with the velocity of moving X/Y.

santy wrote:

What I can't do, is make a bevel on an ARC (conic holes, large circle with bevel for weld prep, etc) , because the velocity of moving C will not be in agreement with the velocity of moving X/Y.

That should just work. 

If you are doing an arc, and there is a C move during the arc, then the C move should be exactly matched to the distance around the arc, and reach the programmed angle at the end of the arc. 

So, for example. 

G0 X20 Y0 C0 - position at start point
G2 X0 Y20 I-20 C90 - combined arc and C move (might be G3, I have forgotten which is which)

This should pass through the point X = sqrt(20) Y = sgrt(20) C = 45 and all other matching points. 

All moves in a G-code block should run in synch and finish at the same time. 

I didn't know this. I might be doing something wrong then.
Thank you for your reply.

Within 1-2 weeks the build will be complete and I'll be actively posting about it in the forums.

So, with some changes to the post, this was my achieved code for a Circle with Beveling tool.
If someone needs the post proccessor i can upload



;end material setup
M301 (M300=Stop Tangential Movement) -> DISABLE the C axis motor from the start
G0 X88.674 Y14.391
M3 $0 S1 (plasma start)
M67 E3 Q100
G0 C56.2500 #this movement doesn't take effect because the C axis motor is OFF
G1 X88.6735 Y14.3913
G0 A30                #after Leadin, the A axis tilts torch 30deg
M300 (M300=Start Tangential Movement) -> trigger output to turn ON the C axis motor
M67 E3 Q70 (slow speed to 70%)
M(xxx) (disable Torch Height Control)
G0 C56.2500                                                              #First movement while beveling
G1 X91.4514 Y18.5486                                                #Leadin continues
G3 X91.451 Y18.549 I-36.451 J36.451 C-45.0000         #Does an Arc, where it expects to synchronize the speed of the xy to C??!
G0 C33.7500                                                                   #After the arc finishes, orients C axis to leadout tangent direction
G1 X95.6087 Y21.3265                                                    #Leadout
M5 $0 (force plasma end through my snippet code)
G0 A0 C0                                                                           
M301 (M300=Stop Tangential Movement) -> DISABLE the C axis motor after C0 finishes
Mxxx (Enable Torch Height Control)
M5 $0 (plasma end)