Open Source Controller with internal THC

The topic is quite old but the problem remains so ..... I do not understand why I should hurry with Ethercat given that LinuxCNC has such a serious fundamental problem. What is still LinuxCNC is just a software environment for creating a working solution. Super unpopular, due to the fact that the people who can complete it are few in number!
Obviously I am one of these people and on the topic I want to make a reservation - external or internal THC, True Hole and others actually depend on a small detail that is not resolved in LinuxCNC unfortunately - constant velocity. Unfortunately this feature is not yet works normally, not to mention monitored and displayed as information.
My company has developed a THC controller and it works very well and very quickly, but it needs to be stopped and started correctly only when it is needed. I am very annoyed by the terms used by people who do not understand plasma cutting. This "anti" diving "" corner lock "and others.
In fact, the controlling CNC controller, be it LinuxCNC, must be able to turn on one of its outputs when there is or is not a constant velocity at the moment. Then THC will turn on only when we have a constant velocity and will turn off when there is none.
Then, in addition to a normal THC controller, it will work well and we can reach an even higher level and want to make True Hole or good holes at all.
We can use the geometry and the information that the voltage depends in direct proportion to the distance of the burner to the table and to the speed.
This way we will understand that the set speed must be monitored during the execution of the file. we change the speed with software - this can be done at lead in, lead out, in small holes, etc. it must also correct the following voltage !!!

I hope you understand something from my Google English because I don't think it's good.

I am the OP and I agree 100% with Tom. Since I have adopted LinuxCNC with a Mesa THCAD for the THC I have not had any issues with my machine. I use it all day everyday cutting parts for our medium sized fabrication workshop and it just works.

How much does your companies THC cost? How easy is it to set up? If something goes wrong how easily can it be fixed? I have learnt the hard way with all those questions. Proprietary hardware is not fun or cheap to work with.

I spent over $10K AUD on a CandCNC controller. If you look on their website they claim their THC is superior to everything else. I have real world experience that says the opposite. I had a lightning strike at our facility a couple of years ago and it fried a small part of the THC module. With the THCAD that would not of been a issue. To replace the CandCNC card cost me $800AUD.

Hindsight is a hell of a thing.

I personally think we are only getting started with plasma control in linuxcnc. It would be trivial to create a component that turned a pin on when at constant velocity (eg the velocity this servo period is the same as last servo period) but you could just as easily set the corner lock threshold to 99% to achieve the same thing. But really this remains quite crude technology. My interest is in having the motion controller reading the arc radius in real time and adjusting both the feedrate and the torch path to account for the physics of circular motion. For example, we can calculate the minimum arc radius that can be negotiated at a given cut velocity and override both the cut velocity and offset from the cut path to account for the wider kerf. Show me another plasma controller that can do this and quote the cost of it... I think Hypertherm Phoenix has similar features.... but we want to make it gcode independent.

I really think the issue is that people who understand plasma on the planet are few in number, nothing to do with Linuxcnc at all.

rodw wrote:

Hypertherm Phoenix.

I was quoted over $40k AUD and they were hesitant about selling it to me Lol.

Ha-ha, I do not participate in this forum for advertising purposes, you notice !!! I wanted to make a real remark but ... for now you don't understand what I mean. Think realistically about how LinuxCNC will deal with SPLINE on a drawing interpreted, for example, by Sheetcam ? Are you saying that he will perform movement all over SPLINE at a constant velocity? Of course not . What kind of corner lock is it then?

In Hypertherm - Age there is information about the speed of the instrument and it affects the amperage (for small holes, arcs and corners).

Our THC behaves just like the one built into LinuxCNC together with THCCad and a few more extras - it works at a speed of up to 10000 mm / min, switches off when going through a hole and does not need any operating settings after it is installed and adjusted. You may not notice that you have THC control.

But the topic is not our THC but how LinuxCNC can get closer to high-end machines.

Whether or not velocity will slow when following a spline is dependent if the centripetal limits are violated for that given cut velocity.
Linuxcnc always knows the velocity the torch is travelling at and it also always knows the programmed feed rate (in v 2.9). Furthermore, there is a pending enhancement that publishes the arc radius github.com/LinuxCNC/linuxcnc/pull/900. So it will soon be possible to compare the arc radius being traversed with the calculated centripetal limit. Granted these calculations are only currently restricted to arcs and splines are not considered but few post processors know how to use splines.

As I said, it is trivial to enable a pin that is true when velocity is constant. I have attached a component that will give you this pin if you wish to experiment with linuxcnc and your THC.
you may install this using the command halcompile --install constantvel.comp
Then you can add it to your hal file.
I've pasted the code for this component below.
I will be interested to hear your results from using Linuxcnc with your THC now you have the output you require. Note that the component probably should also reference motion.motion-type to ensure that the pin is not enabled when the system is idle.

Ha, interesting and commendable is that for you it is quite simple and you even have the desire not only to do it but also to publish it immediately, BRAVO !!!
But now it remains for us on the nasty task, our specialist, who is not as advanced as you, to be able to include it in our Linux system ...., which is currently a test. Unfortunately, we currently have to rely on CNC of the UCCNC, which is a complete mess in the plasma profile. In addition, it cannot be said that it can be relied on for support.
If we get somewhere I will share.
But since we have already noticed that LinuxCNC (as well as the UCCNC, by the way) is slowing down in places in SPLINE, do you have any observations where it should also be wrong now and the CV trajectory planner fails to maintain a CV. I mean test more possible errors.
And in the next moment is it possible to show the analog output the current speed linearly with PWM (this is probably too much right).

If you are wondering why this is important to me - it is important what the speed is not only for corners and small arcs and small holes, it is important even for large round shapes. Because the distance traveled by the burner and the speed measured in mm / min travel the contour and the distance traveled by the axes and the speed at which they travel is not the same. What do I mean if we cross a line on one of the axes - it travels the same distance as the length of the line. However, if we cross a diagonal, it depends on the figure but the distance traveled is more because the movement of both axes is added. However, if we take a circle then the distance is 27.38% greater than the length of the circuit. For this reason, since the speed of the burner is higher, the THC lifts it up and a bevel is obtained from above.

Sorry someone has already tried here and now I just found it.We will experiment and share the result. linuxcnc.org/docs/devel/html/plasma/plasmac-user-guide.html

I understand maybe the mistake is in our settings. We will try harder and if we succeed I will share it.
Our THC is not yet on the market and is distributed only as a precaution for tests in a limited number and price. We can really send you one for a test.
I'll take your address and send you a test controller. We really don't need favourable reviews, but rather constructive criticism, if there are things that need correction.