5 axis TCP feature

[frie]

Although the program & controller is very nice to work with, the controlling of 5 axis lacks critical features like TCP. Please make this better more like LinuxCNC which has TCP.

[cncdrive]

Could you please explain how this should work?

[cncdrive]

If I'm correct it's about rotating a table or head with the tool and the controller automatically adjusting the Z height to the tool center point being at the proper surface height always?
Is this what you want? Or ... ?

[frie]

Well can't explain how it actually works but here is it in action. It keeps your tool at the exact point relative to the 5 axis table.
youtube search examples
Simplify 3+2 and 5-Axis Machining with DWO/TCPC – Haas Automation Tip of the Day
5axis CNC TCP mode part1
TCP , Simultaneous 5-axis machining FUSION360 CAM with Linuxcnc

But it must be switchable otherwise while drilling you will break it because off retration at an angle like this
youtube search
#5Axis LinuxCNC - Switchable Kinematics
from to minute 6:50 to 7:10

[frie]

university degree math involved i geuss https://linuxcnc.org/docs/html/motion/5 ... atics.html

[cncdrive]

Yes, I know how to do this kind of Matrix transformations, I learnt it in the University.
I remember that one of our exams was to calculate linear interpolation with a robotic arm, that is simple task.
What I did not understand clearly is how should this feature you requested work in the real world, I mean what is the purpose of it?

[frie]

Did you watch the haas tcp video? https://www.youtube.com/watch?v=HxPjH4v5iEg
The primary function of Tool Center Point Control (TCP) (Fanuc-G43.4) is to translate the tool-tip path defined in the part program into the position and orientations for the machine’s linear and rotary axes. Tool center point control solves the problem of local tool gouging. Since the CNC knows the profile of the workpiece surface, it can coordinate all of the axes to keep the tool tip in precise contact with the surface when moving between points. So when the program includes an X-axis move between A and B and a B-axis orientation change from -30° and +30°, the CNC automatically coordinates the Z-axis to keep the tool tip on the surface path.

The most common practice is for the CAM system to output coordinates relative to the part in top plane. If the part turns, the coordinate system turns with it. The control tracks the part as it turns keeping the zero point pinned to where you set it on the part, this mostly moves in smal linear trajectory moves. TCP is mostly used for 5 axis paths but can also be used for 3+2 paths. When a machine is in TCP mode, it will move the tool along a theoretical straight line between points.
Why is an G2/3 code better then programming a circle in small straight lines, yes precision and better result, that is why TCP is there for 5 axis, accurate control/precision. That is why we use CNC control, precision and accuracy.
Can't speak for the rest of us, but I like best results.

[cncdrive]

OK, I understand it now, that basically this feature is simply to keep the Z height on the programmed height measured from the surface speed of the workpiece which surface can be rotated.
For that the CNC controller should know the kinematics of the rotary axis, the rotation points(lines) and then a coordinate transformation could be done by the controller to adjust the Z height.

I think your example is not 100% accurate though, because a circle could be programmed from G0/G1 with the same precision as with G2/G3.
Because if the line segments are shorter or equal than 1 step then the circle will be the same precise.
The only problem with that could be the too many data which could cause issues like data starving when the controller cannot process all the codes in short enough time, so then the motion could become jittery.
With G2/G3 there is no such problem, because then an arc is a single line of code.

[frie]

yes that is correct, you can program a circle (and a CAM will if you instruct it) it into 0,001mm moves but then your feedrate would go down to almost nothing because of data starving because the controller can be/is to slow and have a program that is many times larger. Well understood, that's exactly the point

[Ruslan]

For me main reason to have RTCP is that it is very simple to position part on the table and it is very easy to write 3+2 program from keyboard. I worked more than 5 years on Hermle C42 with Heidenhain 530 control. It is miracle machine. How it easy to write 3+2 programs without using CAM, even simultan movements in all axis, for example milling chamfer with endmill(using side of mill). So it will be very usefull and will bring this controller to another level.