Smoothieboard to control plasma cutter

[Mark Rehorst]

I've been talking with an orthopedic surgeon who makes surgical screws for several hospitals in Africa about making plates to splint fractured bones.  He was looking at using a plasma cutter to cut plates from a larger plate of stainless steel, then doing some post processing to finish them up.  We were talking about how to make a small (maybe 400 x 700 mm) CNC plasma cutter to allow changing the design of the splints to be cut from 1'x2' #10 gauge SS plates, and I figured the coreXY platform that I used in my printer would provide more than the required speed, accuracy, and precision.  What software/file format is used in a machine like that and would it work with Smoothie?  The requirements seem to be a cross between a 3D printer and a CNC mill in that there's minimal resistance to the motion, only one tool, and and it's either full on or full off (please correct me if I'm wrong).

Any suggestions on where to start?  Would I need to do any special shielding of the cables, etc. to prevent electrical noise from screwing up the controller?  Is there some dwell time required to melt through the steel before you start moving, and how is that implemented?  Thanks!

[Marius Liebenberg]

Plasma is not that simple and requires a component called THC (Torch Height Control) This feature is required due to the fact that metal will warp when heated during the cutting process. This means that the Z axis reference that the CNC controller started off with on every move will no longer be correct. In order to counter act this problem, the Z axis has to be controlled outside of the Gcode interpreter in order to correct the torch distance on the fly. At every new pierce the Z axis reference is set again only to be fudged again while cutting.
This kind of feature is not a Gcode feature as it has to happen in the actual controller code and it has to be realtime. You have to employ some hardware that will measure the torch height above the metal while cutting. This is done by measuring the flame voltage and then, by using a window comparison, provide the controller a signal or two to tell it to lift or drop the Z axis. Almost like a PID on the Z axis. The controller must also be told if the flame has arced and is still live.
The THC hardware is available from several sources but the Smoothie firmware will need some serious adaptation. I dont have the time at the moment otherwise I might have looked at such a solution.

A cheap solution that works will involve Mach3 and some hardware that suits. Smooth Stepper comes to mind but I am not sure if they implemented THC yet. I am also waiting to see a THC release from Pokeys.

My last word on Plasma systems. STAY AWAY FROM USB with plasma systems. The USB controller will shut down when spurious voltage levels are detected on the USB lines. This means that connection is dropped until it has been recycled by means of unplugging and reinserting.
The plasma arc earth lead is really positive and the arc is at -100 to -400 volts. The signal is very noisy and lastly, most THC systems will prfer the Hypertherm products as the Chinese low cost systems are not suite d for THC. ( I have in many years of building machines never got a Chinese plasma to work with THC systems).

[Mark Rehorst]

Good info!  Thanks!  We're looking at other methods now.

[Arthur Wolf]

We have several people using Smoothie as-is with plasma cutters, you just need a THC system to keep the torch at the right distance, and wire the "torch out" signal to Smoothie's pause or halt subsystem.

On Tue, Dec 19, 2017 at 9:44 PM, Mark Rehorst <mark.r...@gmail.com> wrote:

I've been talking with an orthopedic surgeon who makes surgical screws for several hospitals in Africa about making plates to splint fractured bones.  He was looking at using a plasma cutter to cut plates from a larger plate of stainless steel, then doing some post processing to finish them up.  We were talking about how to make a small (maybe 400 x 700 mm) CNC plasma cutter to allow changing the design of the splints to be cut from 1'x2' #10 gauge SS plates, and I figured the coreXY platform that I used in my printer would provide more than the required speed, accuracy, and precision.  What software/file format is used in a machine like that and would it work with Smoothie?  The requirements seem to be a cross between a 3D printer and a CNC mill in that there's minimal resistance to the motion, only one tool, and and it's either full on or full off (please correct me if I'm wrong).

Any suggestions on where to start?  Would I need to do any special shielding of the cables, etc. to prevent electrical noise from screwing up the controller?  Is there some dwell time required to melt through the steel before you start moving, and how is that implemented?  Thanks!

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[Michael Vowles]

Hi Arthur,

Do you know of any resources for integrating THC with the smoothieboard? 

[Arthur Wolf]

Well THC is supposed to be automatic so pretty much it changes nothing from Smoothieboard's perspective. What exactly do you want to integrate ?

Hi Arthur,

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[Magnus Pernemark]

I'm sticking out my neck here.. not fully up to speed with the discussion.

But my interpretation is:

Users with a plasma cutter and a THC want to connect the THC to the smoothieboard. When THC say "z-up" or "z-down" smoothie should change the Z, while still moving x and y.

Much like the bed leveling for a 3D printer. The bed leveling algoritm adjusts Z-axis according to a pre-calculated offset in the XY-plane.
The differance, the THC is not pre-calculated, it is like having a constant z-probe feeding the system with data and controller needs to adjust z-height accordingly.

8 hours ago I didn't know what THC was, so I might be wrong... I have a smoothieboard and a plasma cutter that I want to hook up, so I am reading up on the subject.

/Magnus

On Sunday, July 8, 2018 at 12:42:22 PM UTC+2, Arthur Wolf wrote:

Well THC is supposed to be automatic so pretty much it changes nothing from Smoothieboard's perspective. What exactly do you want to integrate ?

On Sun, Jul 8, 2018 at 12:34 PM Michael Vowles <michaelv...@gmail.com> wrote:

Hi Arthur,

Do you know of any resources for integrating THC with the smoothieboard? 

On Monday, 5 February 2018 00:15:58 UTC+10, Arthur Wolf wrote:

We have several people using Smoothie as-is with plasma cutters, you just need a THC system to keep the torch at the right distance, and wire the "torch out" signal to Smoothie's pause or halt subsystem.

On Tue, Dec 19, 2017 at 9:44 PM, Mark Rehorst <mark.r...@gmail.com> wrote:

I've been talking with an orthopedic surgeon who makes surgical screws for several hospitals in Africa about making plates to splint fractured bones.  He was looking at using a plasma cutter to cut plates from a larger plate of stainless steel, then doing some post processing to finish them up.  We were talking about how to make a small (maybe 400 x 700 mm) CNC plasma cutter to allow changing the design of the splints to be cut from 1'x2' #10 gauge SS plates, and I figured the coreXY platform that I used in my printer would provide more than the required speed, accuracy, and precision.  What software/file format is used in a machine like that and would it work with Smoothie?  The requirements seem to be a cross between a 3D printer and a CNC mill in that there's minimal resistance to the motion, only one tool, and and it's either full on or full off (please correct me if I'm wrong).

Any suggestions on where to start?  Would I need to do any special shielding of the cables, etc. to prevent electrical noise from screwing up the controller?  Is there some dwell time required to melt through the steel before you start moving, and how is that implemented?  Thanks!

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[Arthur Wolf]

All THCs I've seen either control the motor themselves, or have an output for a stepper driver that will control the motor. So there is no need and no reason for Smoothie to even know the Z axis even exists in this case.

On Wed, Sep 5, 2018 at 12:02 PM Magnus Pernemark <magnus.p...@gmail.com> wrote:

I'm sticking out my neck here.. not fully up to speed with the discussion.

But my interpretation is:

Users with a plasma cutter and a THC want to connect the THC to the smoothieboard. When THC say "z-up" or "z-down" smoothie should change the Z, while still moving x and y.

Much like the bed leveling for a 3D printer. The bed leveling algoritm adjusts Z-axis according to a pre-calculated offset in the XY-plane.
The differance, the THC is not pre-calculated, it is like having a constant z-probe feeding the system with data and controller needs to adjust z-height accordingly.

8 hours ago I didn't know what THC was, so I might be wrong... I have a smoothieboard and a plasma cutter that I want to hook up, so I am reading up on the subject.

/Magnus

On Sunday, July 8, 2018 at 12:42:22 PM UTC+2, Arthur Wolf wrote:

Well THC is supposed to be automatic so pretty much it changes nothing from Smoothieboard's perspective. What exactly do you want to integrate ?

On Sun, Jul 8, 2018 at 12:34 PM Michael Vowles <michaelv...@gmail.com> wrote:

Hi Arthur,

Do you know of any resources for integrating THC with the smoothieboard? 

On Monday, 5 February 2018 00:15:58 UTC+10, Arthur Wolf wrote:

We have several people using Smoothie as-is with plasma cutters, you just need a THC system to keep the torch at the right distance, and wire the "torch out" signal to Smoothie's pause or halt subsystem.

On Tue, Dec 19, 2017 at 9:44 PM, Mark Rehorst <mark.r...@gmail.com> wrote:

I've been talking with an orthopedic surgeon who makes surgical screws for several hospitals in Africa about making plates to splint fractured bones.  He was looking at using a plasma cutter to cut plates from a larger plate of stainless steel, then doing some post processing to finish them up.  We were talking about how to make a small (maybe 400 x 700 mm) CNC plasma cutter to allow changing the design of the splints to be cut from 1'x2' #10 gauge SS plates, and I figured the coreXY platform that I used in my printer would provide more than the required speed, accuracy, and precision.  What software/file format is used in a machine like that and would it work with Smoothie?  The requirements seem to be a cross between a 3D printer and a CNC mill in that there's minimal resistance to the motion, only one tool, and and it's either full on or full off (please correct me if I'm wrong).

Any suggestions on where to start?  Would I need to do any special shielding of the cables, etc. to prevent electrical noise from screwing up the controller?  Is there some dwell time required to melt through the steel before you start moving, and how is that implemented?  Thanks!

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[Magnus Pernemark]

Maybe so.. the 300 USD versions... but not the DIY arduino THCs for the price of a beer or two. They send a signal, and what I understand,this signal is feed into the control software, like linuxcnc or mach3 and the existing hardware changes the z.
That would make switching tools easier too. Same hardware to controll the steppers, just different extentions to control the external environment

/Magnus

On Wednesday, September 5, 2018 at 12:03:28 PM UTC+2, Arthur Wolf wrote:

All THCs I've seen either control the motor themselves, or have an output for a stepper driver that will control the motor. So there is no need and no reason for Smoothie to even know the Z axis even exists in this case.

On Wed, Sep 5, 2018 at 12:02 PM Magnus Pernemark <magnus.p...@gmail.com> wrote:

I'm sticking out my neck here.. not fully up to speed with the discussion.

But my interpretation is:

Users with a plasma cutter and a THC want to connect the THC to the smoothieboard. When THC say "z-up" or "z-down" smoothie should change the Z, while still moving x and y.

Much like the bed leveling for a 3D printer. The bed leveling algoritm adjusts Z-axis according to a pre-calculated offset in the XY-plane.
The differance, the THC is not pre-calculated, it is like having a constant z-probe feeding the system with data and controller needs to adjust z-height accordingly.

8 hours ago I didn't know what THC was, so I might be wrong... I have a smoothieboard and a plasma cutter that I want to hook up, so I am reading up on the subject.

/Magnus

On Sunday, July 8, 2018 at 12:42:22 PM UTC+2, Arthur Wolf wrote:

Well THC is supposed to be automatic so pretty much it changes nothing from Smoothieboard's perspective. What exactly do you want to integrate ?

On Sun, Jul 8, 2018 at 12:34 PM Michael Vowles <michaelv...@gmail.com> wrote:

Hi Arthur,

Do you know of any resources for integrating THC with the smoothieboard? 

On Monday, 5 February 2018 00:15:58 UTC+10, Arthur Wolf wrote:

We have several people using Smoothie as-is with plasma cutters, you just need a THC system to keep the torch at the right distance, and wire the "torch out" signal to Smoothie's pause or halt subsystem.

On Tue, Dec 19, 2017 at 9:44 PM, Mark Rehorst <mark.r...@gmail.com> wrote:

I've been talking with an orthopedic surgeon who makes surgical screws for several hospitals in Africa about making plates to splint fractured bones.  He was looking at using a plasma cutter to cut plates from a larger plate of stainless steel, then doing some post processing to finish them up.  We were talking about how to make a small (maybe 400 x 700 mm) CNC plasma cutter to allow changing the design of the splints to be cut from 1'x2' #10 gauge SS plates, and I figured the coreXY platform that I used in my printer would provide more than the required speed, accuracy, and precision.  What software/file format is used in a machine like that and would it work with Smoothie?  The requirements seem to be a cross between a 3D printer and a CNC mill in that there's minimal resistance to the motion, only one tool, and and it's either full on or full off (please correct me if I'm wrong).

Any suggestions on where to start?  Would I need to do any special shielding of the cables, etc. to prevent electrical noise from screwing up the controller?  Is there some dwell time required to melt through the steel before you start moving, and how is that implemented?  Thanks!

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[Arthur Wolf]

My understanding is the arduino-based ones too send signals intended for stepper motor drivers ( if they sent signals intended for the controller it'd pretty much be the exact same signal anyway, there's no added work/complexity here ). If you can find documentation to the contrary I'd be super surprised by it.

Hi Arthur,

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[Magnus Pernemark]

Well again maybe so. My though is just that if an external source can tell smoothie to z up/down. That external source would not need to have any stepper drivers, it could be as simple as just an arduino, or even as simple as a push button. Push for up, push for down (a very manual tourch control).
Or call it a manual jogg function.
It would be compatible with the expencive thc and even the cheapest home made thcs

[Arthur Wolf]

On Wed, Sep 5, 2018 at 12:26 PM Magnus Pernemark <magnus.p...@gmail.com> wrote:

Well again maybe so. My though is just that if an external source can tell smoothie to z up/down. That external source would not need to have any stepper drivers,

Well something needs to talk to the stepper drivers. It makes no much difference if it's Smoothie or the THC. Even assuming you want to use the on-board drivers on the smoothieboard, you can still have the THC control those directly.

Everything you mention is possible with a Smoothieboard and a THC, just not with Smoothie interfering with the process, which isn't a useful step to have. You can do all of it without Smoothie being aware of it.
 

it could be as simple as just an arduino, or even as simple as a push button. Push for up, push for down (a very manual tourch control).
Or call it a manual jogg function.
It would be compatible with the expencive thc and even the cheapest home made thcs

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[Magnus Pernemark]

Hi,

I Have now spent most of my free time trying to mount my plasma om my CNC and make it work with smoothie.... I do need a THC to make it all good. And in my search for a THC I have found that the majority of the THCs out there output three signals
Arc OK
Z up

Z down

and they send this signal to the controller. In most cases the THC is used by Mach3 users. Even the ArduinoTHC outputs these signals. So, you saying most THC take control over the Z axis is not correct.
Anyhow, I have now ordered a Proma THC SD (300 USD) hoping it will work. It lets Z axis signals pass-through from Smoothie, and if needed it intercepts and sends its own Z axis moves. There is a 10 usd solution with a voltage comparator that in an analog way determines if Z needs to go up or down. That works with Mack3, since it will listen to up/down signals and alter the Z axis accordingly, but that would not work with Smoothie. Too bad.

No I have to figure out how to handle the "init sequence" for the cutting procedure. You cannot move until ArcOK is true, you must stop if ArcOK is false, you have to zero Y, move to pierce, wait, move down, then move.
If anyone have used smoothie for this, please reply how you ddi!

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[Arthur Wolf]

On Sat, Sep 8, 2018 at 11:39 PM Magnus Pernemark <magnus.p...@gmail.com> wrote:

Hi,

I Have now spent most of my free time trying to mount my plasma om my CNC and make it work with smoothie.... I do need a THC to make it all good. And in my search for a THC I have found that the majority of the THCs out there output three signals
Arc OK
Z up

Z down

and they send this signal to the controller. In most cases the THC is used by Mach3 users. Even the ArduinoTHC outputs these signals. So, you saying most THC take control over the Z axis is not correct.

Well ... the 4 I've seen on actual machines work the way I described, and when I looked around ( which was a few years back, probably on ebay or aliexpress ) it was that way too on the models I looked at.

For ArduinoTHC I didn't actually look at the spec, I was just presuming it worked that way, so thanks for correcting.
 

Anyhow, I have now ordered a Proma THC SD (300 USD) hoping it will work. It lets Z axis signals pass-through from Smoothie, and if needed it intercepts and sends its own Z axis moves. There is a 10 usd solution with a voltage comparator that in an analog way determines if Z needs to go up or down. That works with Mack3, since it will listen to up/down signals and alter the Z axis accordingly, but that would not work with Smoothie. Too bad.

Actually you can just use the switch module to route pins to specific Gcodes, that would allow you to route signals to up and down movement, so this could work depending on exactly what the signals are.

No I have to figure out how to handle the "init sequence" for the cutting procedure. You cannot move until ArcOK is true, you must stop if ArcOK is false, you have to zero Y, move to pierce, wait, move down, then move.
If anyone have used smoothie for this, please reply how you ddi!

On Wednesday, September 5, 2018 at 12:29:43 PM UTC+2, Arthur Wolf wrote:

On Wed, Sep 5, 2018 at 12:26 PM Magnus Pernemark <magnus.p...@gmail.com> wrote:

Well again maybe so. My though is just that if an external source can tell smoothie to z up/down. That external source would not need to have any stepper drivers,

Well something needs to talk to the stepper drivers. It makes no much difference if it's Smoothie or the THC. Even assuming you want to use the on-board drivers on the smoothieboard, you can still have the THC control those directly.

Everything you mention is possible with a Smoothieboard and a THC, just not with Smoothie interfering with the process, which isn't a useful step to have. You can do all of it without Smoothie being aware of it.
 

it could be as simple as just an arduino, or even as simple as a push button. Push for up, push for down (a very manual tourch control).
Or call it a manual jogg function.
It would be compatible with the expencive thc and even the cheapest home made thcs

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