Just to follow up: machinekit with BBB and thc works on my setup - here is 
video of machine in action.
https://youtu.be/2oMeL6kEZrk


Dne sreda, 23. december 2015 12.58.00 UTC+1 je oseba Klemen Zhivko napisala:
>
> OK I understand.
> My first goal is to finish machine, than I will try CRAMPS setup for 5 
> axis with THC enabled.
> I received CRAMPS board in the meantime. 
> If @Charles author of CRAMPS can assign analog pin that can be used for 
> THC it would be great.
> If there is some shortcut to working INI and HAL files for CRAMPS that 
> support THC control it would be great - I would appreciate for any example 
> I can use so I don't need to begin from scratch..   
>
> On Saturday, December 19, 2015 at 8:18:09 PM UTC+1, Viesturs Lācis wrote:
>>
>> Then I do not understand, what is not clear to you. Yes, rotating the 
>> tube will require the torch to go up or down, but there are other reasons 
>> as well that can require to adjust torch height (material surface being 
>> curved, material not laying totally horizontal etc), that is why the plasma 
>> tip voltage is measured and the torch position is adjusted according to 
>> that (if the torch is too close, the voltage is lower, if it is too high, 
>> the voltage increases; it might be ~140-160V for 3-4 mm distance, but that 
>> will vary for particular plasma torch and plasma source). In this case it 
>> is _not important_, what are the causes. You do not need to tackle 
>> kinematics, simply implement standard THC functionality. One way to do that 
>> is the task sequence I provided.
>>
>> On Friday, December 18, 2015 at 9:27:26 PM UTC+2, Klemen Zhivko wrote:
>>>
>>> Viestrus,
>>> maybe I was misunderstood - yes option 1 is the right one.
>>>
>>>
>>> On Fri, Dec 18, 2015 at 6:08 PM, Viesturs Lācis <[email protected]> 
>>> wrote:
>>>
>>>>
>>>>
>>>> On Friday, December 18, 2015 at 5:40:41 PM UTC+2, Klemen Zhivko wrote:
>>>>>
>>>>>
>>>>>> Second of all, I understand that you want basic THC functionality 
>>>>>> (not adding offset moves for X and Z to keep the torch tip at the same 
>>>>>> spot 
>>>>>> on tube's surface, when the rotary head is moved) and since you are 
>>>>>> using 
>>>>>> CRAMPS, I understand that you are using stepper motors. 
>>>>>>
>>>>> Ugh, as I understand if - if THC is operating, rotating pipe (moving B 
>>>>> axis) should have effect on Z axis. Standoff of torch to pipe surface 
>>>>> (acording to my sketch) is measured in Z direction.
>>>>>
>>>>
>>>> THC description clearly says that it adjust torch height according to 
>>>> plasma tip voltage - either you did not read it or I do not understand, 
>>>> what exactly do you want. Which one of these 2 options?
>>>> 1) adjust Z position, based on plasma tip voltage, aka standard THC;
>>>> 2) adjust Z (and X as well) position to keep plasma torch tip on the 
>>>> same spot on the square (rectangle to be more precise) tube surface as 
>>>> rotary head is turning;
>>>>
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>>>
>>>

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