HAL component for tangential knife

Having looked at this a few times, I think that the best place to do it is actually in a G-code filter. ie calculate the heading from the G-code and insert / append C axis moves as appropriate.

andypugh wrote:

Having looked at this a few times, I think that the best place to do it is actually in a G-code filter. ie calculate the heading from the G-code and insert / append C axis moves as appropriate.

One way I guess, but how does the gcode continually update the heading on a G2 or G3 as it traverses the arc? I found this had to  be done in motion. This will work, I just got taken over by other priorities which are now subsiding.

dear sir i spent the last days trying to improve my understanding to linuxcnc system and structure , i hope to give hand and i suggest this proposal " what if we do the tangent calculation in parallel interpreter and syncronize the data somehow whith index ", i am not sure if it is the best practice but i am tring

andypugh wrote:

Having looked at this a few times, I think that the best place to do it is actually in a G-code filter. ie calculate the heading from the G-code and insert / append C axis moves as appropriate.

Actually, there is a use case that needs motion pins. A plasma cutter cutting bevels. An additional joint is needed to tilt the torch and there are complicated tilting torch holders that keep the torch tip axial to the Z axis (single axis bevel head). I was just chatting to a user with one who uses the post processor approach.

But picture a simpler torch holder design where the torch tip position moves when tilted. A component could take the bevel angle and calculate the offset x,y,z positions of the tilted torch tip and then apply external offsets to locate the torch on the cut path in real time. This way, the machine could consume simple 2D x,y gcode (which is the norm for plasma cutters) and enter plasma cutting nirvana with bevelled holes.

This appeares to be working now
checkout  the state-tags-arc from my repo to test
github.com/rodw-au/linuxcnc/tree/state-tags-arcs

There is some house keeping to sort out. I need to work out how to use equate G_1,G_2  etc in motion (control.c) I remember the devs last time I tried, they did not like this  but I have not got a solution yet. Its just housekeeping and will only be an issue ig the equates for gcodes are ever changed.

"Great work, Rod! This looks like a monumental step forward for LinuxCNC.

I believe this branch is the perfect strategy for implementation. It elegantly solves the real-time synchronization issues that have hindered advanced tangential control in the past.

For my part, I have an assignment to study this implementation . You have indeed laid a cornerstone for the system, and I am very excited to leverage your work for this project.

If I may add my opinion: I fully support your point of view regarding the modifications of G_1, G_2, G_3 equates in control.c. I understand the devs' concerns about real-time sanctity, but your approach to code readability (housekeeping) is crucial for the long-term maintainability of such complex code. Finding that balance is the key.

Thank you again for your incredible contribution."