[tommylight]

Here is a config for simple plasma that have the usual UP DOWN ARCOK signals that actually works properly without giving feed errors and moving the Z axes randomly.
It is based on the THC300 config with relaxed timings and properly tested on 2 machines with PROMA THC.
There is a readme and how to file with some explanations for pin and scale and velocity/acceleration setup, so please do let me know if it is understandable.
regards
Tom

[wendtmk]

Tom,

The config doesn't seem to have made it through.

Mark

[tommylight]

Tom,

The config doesn't seem to have made it through.

Mark

Fixed, thank you ma man.

[tommylight]

Added some more info and videos @ linuxcnc forums.

LinuxCNC Support Forum :: Topic: THC config that works. (1/2)

Regards,
Tom

[tommylight]

Here's a detailed HOWTO for this config, also added to the attachment together with modified gcodetools for this config.
Pasted from the README:
May,26, 2014, Peja, Republic of Kosovo Europe
by Toma

This is a fully functional configuration file for Linuxcnc to be used
with any and all of the "simple THC" systems on sale, like:
-Proma Elektronika Compact THC (tested and verified on production machines)
-Cand CNC LCTHC should work with minor editing of files mentioned and explained below
All that output "UP""DOWN""ARCOK" signals even those that normaly use 2 parallel ports
can be made to work with only 1 parallel port if you can manage the changes in wiring
and change the pins in the config files.

This setup is configured with slightly relaxed timings so can be used even on older
systems and systems with lattency problems with a bit of trial and error.
It is based on the "thc_300" config found bundeled with Linuxcnc but it is heavily
modified to my needs and since in it's original form it does not work due to feed errors.

Some more info.
The config works flawlessly so here are some functions that were already implemented and
some added.

0- IT does not need 2 parallel ports, just a single one. Granted you don't use limit
switches.

1- Absolutely noo need for Z axes anything, so remove anything related to Z axis in Gcode
since it will slow down the execution waiting for it, but it will not efect the axes,
the machine WILL function properly even if you have Z values.

2- The floating switch, if it trips while running in auto mode, it will force an E-stop
and halt the machine so try to make the floating switch as sensitive as posible, if the
nozle dives into material it will stop everything.

3- It will remember last position so even on power loss you can continue exactly where it
left. I added this since where i live power outs are very frequent so it is a life
saver (or material and time saver in this case).

4- If the plasma cutter stops for any reason (mine beeing heat due to running full time
doing 11meter cut 3 second pause and again 11 meters and..........10 hours a day) it
will stop movement and try to fire the torch several times and wait for ARCOK. To
continue just press F9 and do a right click and "run from here" over the highlighted
gcode line. The Z axis will again find the metal and move up and fire the torch and
continue as usual.

5- No need for a post processor at all, exept if you need "lead in and lead out",
so NO G38.2 or whatever, nothing. Everything works with M3, finding the metal, moving
to pierce height firing the torch and moving on.
I have added the "gcodetools" for "inkscape" with modications needed for outputing gcode
with only M3 and M5 for every cut.


Some tips on editing attached files :
-Use a text editor like "gedit" or "vi" or "nano" or "notepad" in windows, do not use
word procesors.
-Add a "#" sign (shift+3) without quotes in front of any line you dont need, and remove
the same sign in front of any line you need.
-Always have a copy of all config files set as "read only" for safety if something goes
wrong during editing.

Before you start, be sure to check the "parport addres" and the output pins for motor
drives in the "thc_parport.hal" file, see picture "thc_parport.hal.png".
The "thc_parport.hal" has only the outputs for motor controls ( step and direction pins )
with added lines for reverse direction of any of the axes if it need be. There are
settings for 4 axes although i use 3. Check your output pins and edit this file based on
your setup. The standard pin order should be (yours may vary) :
-pin 2 Xstep
-pin 3 Xdir
-pin 4 Ystep
-pin 5 Ydir
-pin 6 Zstep
-pin 7 Zdir
etc etc

Next change the pins in the "thc.hal" file to match the "UP","DOWN","ARCOK","TORCH ON" signals.
You need to check for positive or negative input signals and change that based on the break
out board you are using. See picture "thc_hal.png". There are already lines for positive AND
negative type inputs, you just need to omit the ones you don't need and remove # in front
of the ones you need.

Also you need to change the "scale" "velocity" and "acceleration" in "Axes Section" in
the "thc_toma.ini" file to mach your setup. See picture "thc_toma.ini.baseperiod.png" and
"thc_toma.ini.velocity.accel.png".

For "scale" i use "40" since i have full step drives connected to 200 step/rev
(1.8 degre/step) motors attached to 5mm/rev ballscrews. This is simple
math: steps per rev/mm per rev, in my case 200/50=40.

For "velocity" use anything between 30 and 100 that your setup can handle without
loosing steps or stalling. The value is mm per second so 30 is 1800mm/minute
and 100 is 6000mm/minute.
FYI do this for each AXIS separatly or just use a value that is below the maximum
your setup can handle to be on the safe side. For actual cutting on a plasma the
maximum usable speed is about 4200mm/minute for cutting a 1mm thick mild steel plate,
in this case that would be a value of 70 for "velocity".

For "acceleration", again depending on your setup, put 300 to 800, that is mm/s squared,
but for geting sharp corners you need at least 500 if cutting under 3mm thick
plates, 300 for 4 to 6mm thick plates and 100 if cutting anything over 10mm. But if
your setup can handle 300 and above just leave it there, do not change this.

This config also remembers last machine position so if the machine is not moved while
powered off, you can continue from where it left. This is done since where i live
power outs are a normal occurence.

Regards,
Tom

[urbnsr]

Thanks Tom. I have yet to test your setup as I got one of the examples that come with LinuxCNC working, but wondered if your setup has editable settings for returning Z Axis from correction. By that, I mean when done cutting, all of the setups I have used before try to return the THC modified Z axis setting to it's original location (prior to THC adjusted location) at a rate so high that it loose steps if the THC moved Z far enough. This apparently is not the same as the speed that corrections are made while cutting .

Thanks again...
Paul

[tommylight]

I had no such problem with this config, it has been working for several days all day long churning parts (just today 80 parts of 8.4 meter cuts each).
I have also made most of the configs bundled with LinuxCNC and some others found on the net, but all of them had stuff not needed for this THC or just plain did not work properly and almost all had feed error problems, especialy with Z axis running wild.
Give it a try and let me know how it goes.
Tom

[planescott]

I got a proma thc last week, do I need a relay to trigger the torch switch? also I have mach3 so im guessing your settings wont work for me?
thks scott

[urbnsr]

I use a 5 volt relay to trigger the torch. Almost any SPST will do depending on the current draw and power supply. I think there is a script to convert Mach 3 config to LinuxCNC, but I haven't heard of a script to do the reverse - I also haven't been looking for one, either.

PK

[tommylight]

Yes you do need a relay to switch the torch on and if you do not have it on a break-out-board, you will also need a resistor of 100 ohm and a NPN darlington transistor.
As far as Mach3 goes, man i realy do not envy you, i did a setup last year on a big plasma cutter with THC, i had to test about ( exactly, exactly ) 11 computers just to get 1 that works on that setup. Now before some wise a@@ starts telling me i should have done this and that and used ant milk and snake oil, I AM an expert in electronic and computer hardware, i worked for 2 of the biggest organisations in the world as an COMMS/IT tehnician and network administrator, so save it. I have a purpose built parallel port checker with LED on all outputs -> i checked with it aaaaaaaand some outputs work and some do not under windows and MACH3, BUTTTTTT everything, let me repeat, EVRYTHING worked under LinuxCNC on ALL 11 computers. The owner i built the machine for insisted on using MACH3 and he is still using it, and by some miracle it still works without a hitch for over a year now beeing used all day every day.

[sme101]

HI all I don't like to bother people but I need a little help. First my name is William. I have a home made cnc plasma cutter and running MACH3 with a Proma THC every thing works ok but I am having a problem with the input pins on my breakout board going bad and its only the ones with the proma hooked to. The bob has a 102 resistor before the terminal that I believe is going bad. I am on my forth board and scared to buy another I also want to say that I am using a cheap board. Board says MACH# Interface Loard BL-MACH-V1.1 0302 any help would be great and info on a good board may help too

[planescott]

thks tommylight, I do have a bobcampbell breakout board and a relay board from him so far(7yrs) all works fine. never had any problems yet with my machine but will see when I add the plasma to it !

sme101 u might want to get a better breakout board like bobcampbelldesigns.com they are more plug n play with many more safety features to ur computer and such he also has a setup file for it ,which sets most pins up for you(in mach3) again a simpler deal . I run digital drivers with mine works great ! scott

[wendtmk]

HI all I don't like to bother people but I need a little help. First my name is William. I have a home made cnc plasma cutter and running MACH3 with a Proma THC every thing works ok but I am having a problem with the input pins on my breakout board going bad and its only the ones with the proma hooked to. The bob has a 102 resistor before the terminal that I believe is going bad. I am on my forth board and scared to buy another I also want to say that I am using a cheap board. Board says MACH# Interface Loard BL-MACH-V1.1 0302 any help would be great and info on a good board may help too

This is the LinuxCNC forum. You need to ask your question on the Mach Forum.

[tommylight]

HI all I don't like to bother people but I need a little help. First my name is William. I have a home made cnc plasma cutter and running MACH3 with a Proma THC every thing works ok but I am having a problem with the input pins on my breakout board going bad and its only the ones with the proma hooked to. The bob has a 102 resistor before the terminal that I believe is going bad. I am on my forth board and scared to buy another I also want to say that I am using a cheap board. Board says MACH# Interface Loard BL-MACH-V1.1 0302 any help would be great and info on a good board may help too

Most probably you have the cables going from proma thc to your break out board unshielded or passing very close to the torch or clamp wires, or going paralel with torch and clamp wires. You need to get them as far apart as posible and use a shielded cable and if they have to be close try not to have them running parallel, crosing over each other is ok most of the time. The magnetic field and consequently the inducted current when the torch fires and while running can easily damage a lot of electronic components.
As for a BOB i am using one from Lam Technologies, a chinese one and on 2 machines running daily i have no BOB at all, directly wired to parallel port since all the drives i use have optocouplers on inputs and use a relay to fire the torch so everytbing is properly isolated.
regards
Tom

[whateg01]

Sorry for bringing up this old thread again. I'm wanting to add THC to my plasma table, so I've been doing a lot of reading lately. Seems to be a lot out there, some confusing, some contradictory, some probably just wrong. Anyway, I ran across this thread and now I have some more questions.

A lot of what I read says that cheap THC is to be avoided at all costs because it can't prevent dive. So, I've been thinking about that, and where the THC controller is just sending up/down and arcok to the NC software, in this case LinuxCNC, where does the decision making take place to prevent dive when going around a corner or crossing a kerf? Is that done in the THC? Or does the NC software have to be able to identify those situations and ignore the THC input at those times?

Or does it vary by THC manufacturer, where some do it on the NC side and others have an algorithm in the THC side?

Dave

[tommylight]

A lot of what I read says that cheap THC is to be avoided at all costs because it can't prevent dive. So, I've been thinking about that, and where the THC controller is just sending up/down and arcok to the NC software, in this case LinuxCNC, where does the decision making take place to prevent dive when going around a corner or crossing a kerf? Is that done in the THC? Or does the NC software have to be able to identify those situations and ignore the THC input at those times?

Dave

Hi Dave,
Dive can be prevented in many ways, and most probably you can find situations that even the expensive THC setups will dive, but that is a subject for another discussion.
Back on the subject of cheap THC, they do work and they do a decent job once you know the limitations and prevent them, you can be happily cutting all day every day without a hitch.
I have used and still use PROMA THC (4 of them) and 2 of my own designs with a lot of complicated math going on inside them, but on the outside they are still simple UP/DOWN/ARCOK THC systems. Most of them are in use all day every day (all but one of mine).
Dive can be easily prevented by setting the lower limit on the Z axis to not go under the table ribs. Having a floating head that can be easily moved up to trigger the float switch when in contact with the material helps a lot ( from my experience that is very important and a must since it will save the torch always without breaking). Also a magnetic torch holder is a nice feature to have.
All of the above will help prevent dive and a lot of mess ups.
On the software side, Linuxcnc has a corner height lock that actually works and is adjustable from 0 to 100 % of the feed speed.
Anyway, go for it and learn as you go, it helps to know where you want to go.
Regards
Tom

[mancavedweller]

As far as Mach3 goes, man i realy do not envy you, i did a setup last year on a big plasma cutter with THC, i had to test about ( exactly, exactly ) 11 computers just to get 1 that works on that setup. Now before some wise a@@ starts telling me i should have done this and that and used ant milk and snake oil, I AM an expert in electronic and computer hardware, i worked for 2 of the biggest organisations in the world as an COMMS/IT tehnician and network administrator, so save it. I have a purpose built parallel port checker with LED on all outputs -> i checked with it aaaaaaaand some outputs work and some do not under windows and MACH3, BUTTTTTT everything, let me repeat, EVRYTHING worked under LinuxCNC on ALL 11 computers. The owner i built the machine for insisted on using MACH3 and he is still using it, and by some miracle it still works without a hitch for over a year now beeing used all day every day.

Hi Tommy,

Just joined the forum after finding your thread on Google.

I've been using Mach3 for plasma but a specific version and works great once you find a compatible PC. Mach3 has so many versions and sometimes the earlier versions work better with things than newer versions. You can get a powerful PC that works crap with Mach3 and a not so powerful one that works great, seems kind of pot luck finding the right one. Yep I keep hearing about the stability of Linuxcnc. I've actually just started printing the Linuxcnc manuals to begin the long process of learning. I've also been designing my own THC, and writing scripts and screensets for my own custom plasma cutting system, but Mach3 won't be for sale in a year or so, and Mach4 looks crap at the moment, poor documentation, etc.
So, am I in for a tough time if I want to create my Linuxcnc screenset, and customise it with macro programming. For instance the script I wrote will save a bunch of DROs to a file (Cut Profile), then I can later display a list of these files on screen, and select one, then all the DRO values are automatically entered. The DRO values will then be continuously sent to the THC over a serial connection, as well as recieving values from the THC for displaying on the screen. While the plasma is cutting I can adjust these DRO values and the THC gets updated.

Will that sort of thing by a pig for me to learn with Linuxcnc.

Cheers,

Keith.

[whateg01]

Tom,

Thanks for that explanation. I guess it's like anything - there are those who believe it can only be done one way and anybody doing it differently isn't worth listening to. That is very reassuring to know that the less expensive THC setups do work.

I just downloaded the THC config you uploaded. I have't had a chance to look at it yet, but I hope to this weekend. Since I don't have a THC yet, I will have to set up a couple of momentary switches to simulate up/down commands, but I do want to try it out.

I have some "why" questions, but I'm not sure they belong in this thread.

Dave

[tommylight]

@mancavedweller :

I do not know and i did not use serial ports in the last 15 years, so i can not help you there, i simply try to avoid them, wasted way to much of my life fiddling with rs232 in my youth and have gathered quite an array of bad memories with the win3.1/win95/win98/rs232 combo, and when w2k came, it was utterly useless.
I know it can be used and it works most of the time, so give it a go.
As for "screensets" they do not exist in Linuxcnc, but it has multiple GUI's and some of them can be modified to your hearts desire, or you can create your own GUI from scratch, there are some nice tutorials on the net, so i do believe you can get to what you want quickly.
If by DRO you mean changing the voltage and subsequently the cut height of the torch and the feed speed, there are already configs that can display and adjust all those and more.
Best way to learn it is by doing it, so install it or boot it from a usb drive and spend some quality time with it.

@whateg01
You will need one more on/off switch for arcok signal, since if you keep that on, Linuxcnc will not move anything. It works and responds to it only after issuing an M3 command.
Regards,
Tom

[whateg01]

@whateg01
You will need one more on/off switch for arcok signal, since if you keep that on, Linuxcnc will not move anything. It works and responds to it only after issuing an M3 command.
Regards,
Tom

Thanks. I have that ported out the machine now, so I just have to connect it to the BOB. I need to look at the config and see which pins it's configured for, or decide which pins I'll use and configure for that. Or, I could just connect a switch for testing.

Dave