Re: Dedicated CNC Controller - THC help

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1

Hello Jat,Good job, we produce Capacitive Height Controller fo Plasma and oxy fuel cutter. Our Cap04V model has 0-10V input for height controlling from operators panel or pendant.
Please let me know, if your output can be use for this purpose, Mach3 has some drawback for this issue.
I can also discuss with you about voltage control based THC.


Best regards,
Argun Gucdemir
Capacitive Sensor

Capacitive Sensor FOR THC APPLICATIONS CAP04 New Product Cap04 has 5 warning LED’s and 4 outputs: Down, In-position, Up, Touch or Collision of cutting plate and Cable Fa…



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2

Argun thank you so much for your message.

Surely the 0-10v output can be used and we can reprogram that as per need. For your reference its a pure 10bit 0 to 10 volts through DAC and not a PWM type as used on Mach3 and this resolves coupling and inductive issues in the 0 to 10VDC signal.




Regarding the THC signals I would like to understand the basic concept so that we can program the unit accordingly. So to my understanding from the GCODE the controller will switch on the plasma for example at M3 and at this point what should be the reaction of Z axis?


We can control the Z axis separately from the GCODE and for example if we get a UP/DOWN signal from your THC then should the controller move the torch up or down as required by the your THC?


I have a lot of questions in this regards such as what should be the initial position of the torch before starting a cut, what should be the position of the torch at end of cut, what should the controller do when it gets a IN POSITION signal. Basically trying to understand how the sequence of things work for automatic THC.


Thanks again,
Jat


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Posted by: jatinder.grewal9@yahoo.com

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3

Here is pretty much an ideal sequence of events

At the start of the cut you need to find the top of the work. The usual way is to mount the torch on a small auxiliary slide with a limit switch. You move the torch down until it hits the work and trips the switch.

Next you lift to the commanded pierce height, pierce and start cutting. After a short delay to allow the arc to stabilize you turn THC on. If the actual speed drops below the commanded speed by a certain percentage (i.e on sharp corners) turn off THC. If the THC stays on when the machine slows down the torch will dive into the work.

At the end of the cut turn off THC and lift to rapid height.

Ideally it should also be possible to turn THC on and off via code. The machine should keep moving smoothly when this happens. It should not hesitate. Motion through corners and arcs should be as smooth as possible. Any hesitation will leave marks.

You can use SheetCam’s cutting rules to generate THC on and off commands on corners if your controller cannot do this automatically based on the feed rate.

I believe most THC controllers have simple up and down outputs. When the up output fires, move the torch up at a fixed rate and vice versa. Alternatively you could sense the voltage directly through your ADC the do all of the THC logic inside your controller. Keep in mind the torch voltage is around 200VDC with possibly a few kV of high frequency AC superimposed so the voltage divider/filtering needs to be very robust. Opto isolation is also a good idea.

Les


On 18/02/2015 16:02, jatinder.grewal9@yahoo.com (jatinder.grewal9@yahoo.com) [sheetcam] wrote:

Argun thank you so much for your message.

Surely the 0-10v output can be used and we can reprogram that as per need. For your reference its a pure 10bit  0 to 10 volts through DAC and not a PWM type as used on Mach3 and this resolves coupling and inductive issues in the 0 to 10VDC signal.




Regarding the THC signals I would like to understand the basic concept so that we can program the unit accordingly. So to my understanding from the GCODE the controller will switch on the plasma for example at M3 and at this point what should be the reaction of Z axis?


We can control the Z axis separately from the GCODE and for example if we get a UP/DOWN signal from your THC then should the controller move the torch up or down as required by the your THC?


I have a lot of questions in this regards such as what should be the initial position of the torch before starting a cut, what should be the position of the torch at end of cut, what should the controller do when it gets a IN POSITION signal. Basically trying to understand how the sequence of things work for automatic THC.


Thanks again,
Jat


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Posted by: Les Newell <les.newell@fastmail.co.uk>

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4

Thanks Les,

So that means that there two different types of THC’s that are mainly used.


First Type - Arc voltage is not used and only the distance between the work piece and the torch is used. The torch up and down command is given to the controller based on the gap and this will have issues while turning at slow speeds?


Second Type - With this the torch up and down command is given to the controller based on the arc voltage and this will work on different feedrates?


So in all from our controller point of view we only need to adjust the torch height as per the feedback from the torch height or arc voltage units.


Also curious if the user needs to add any further parameters such as sheet thickness on our controller itself. The reason for asking this question is that we have left room on the controller’s UI and if required we can put some options that will help the user change some parameters on the machine itself, maybe the required arc voltage or job gap. A lot of people mention that hyperherm controllers have extra options, just wondering what they might be?


Regards,
Jat


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Posted by: jatinder.grewal9@yahoo.com

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5

Hi Argun,

I think I have a better picture now but still would like to go through a designing specification phase for myself so that I can make sure that I understand everything right.

Regarding business opportunity, I will be happy to do that. I also see a great opportunity here using your THC’s with our controller and some custom features.




You can directly email me on jatinder.grewal@hindtechnology.com and we can start our conversation from there or over the phone.




Best Regards,
Jat



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Posted by: jatinder.grewal9@yahoo.com

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6

Hi Jatinder,

**First Type **> - Arc voltage is not used and only the distance between the work piece and the torch is used. The torch up and down command is given to the controller based on the gap and this will have issues while turning at slow speeds?

No. The machine controller directly measures arc voltage and regulates the height to maintain the set voltage.

Second Type - > With this the torch up and down command is given to the controller based on the arc voltage and this will work on different feedrates?

In this case you have an external THC controller. The external controller measures the voltage and outputs up/down commands for the machine controller. Basically it just takes some of the work load off the machine controller. If I was building a system from scratch I would have the machine controller regulating the voltage. That way you can do things like set the arc voltage from g-code.

All voltage sensing THC systems suffer from the corner dive (slow feed rate) issue. There are some other systems that don’t suffer from corner dive such as capacitive sensing but they are much more complicated and don’t always play nicely with noisy plasma cutters.


So in all from our controller point of view we only need to adjust the torch height as per the feedback from the torch height or arc voltage units.


Also curious if the user needs to add any further parameters such as sheet thickness on our controller itself. The reason for asking this question is that we have left room on the controller’s UI and if required we can put some options that will help the user change some parameters on the machine itself, maybe the required arc voltage or job gap. A lot of people mention that hyperherm controllers have extra options, just wondering what they might be?

Arc voltage is a combination of material type, material thickness, arc current and feed rate. Most operators end up building up a table of settings that work well on their systems for different materials. In SheetCam this is done by defining different tools. It is not difficult to add an arc voltage parameter to the tool definition so all settings could be kept in SheetCam. It would be nice if your system can read the arc voltage from g-code, maybe with an option in the GUI to adjust the voltage.

Les





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Posted by: Les Newell <les.newell@fastmail.co.uk>

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