Re: [Emc-users] Plasma Torch Height Control

[Alexander Brock]

On 09/10/2016 01:21 AM, John Thornton wrote:
> What kind of plasma torch do you have?

This one:

http://www.stamos-welding.com/s-plasma-125h

Best Regards,
Alexander



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Re: [Emc-users] touch probe

[Jon Elson]

On 09/03/2016 08:47 PM, Chris Morley wrote:
> motion.feed-inhibit would be the one to use.
>
> only (maybe) homing and synch moves are un fazed by it.
>
>
This appears to be a new feature in 2.8 or so, my older 
version doesn't have this pin, but it does have
motion.feed-hold, so I used that.  So, when the probe is in 
use, a loss of valid signal from the probe causes a feed hold.

Anyway, I got the thing working!  It seems this probe has a 
rather large deflection of about .008" with a 100 mm 
stylus.  I'm going to get a shorter stylus, as the entire 
thing is an awfully long stack, and the whole idea is to be 
able to measure not only X and Y, but length, too, so having 
to move the knee defeats the purpose.

I did find that the chain of logic is pretty slow.  I probed 
at 1, 5 and 10 IPM, and saw a definite shift in the 
measurement as speed went up.  There can't be more than 1 ms 
delay in the FPGA, and the digital inputs are sampled at 1 
ms, so I'm not sure I understand where this is coming from.  
1 IPM is 1/60th inch/second, and I have 20,000 counts/inch 
on X and Y, so that is 333 counts/second.  Given a couple ms 
delay, that is just a couple encoder counts + or -. But, I 
was seeing a change of .011" when I went from 1 IPM to 10 
IPM.  (I got a shift of .003" at 5 IPM.)  With a 
double-touch probing routine, it is not too slow to make the 
final touch at 1 IPM.

I probed both sides of a gauge block to try to determine the 
effective tip diameter.
When I compensated for the .008" deflection to trigger the 
probe, calculations worked out for the effective tip 
diameter.  The tip appears to be smaller than the measured 
diameter due to the deflection that is needed to activate 
the probe.  (The whole reasoning behind Blum's design is to 
make the deflection to trip it the same from all 
directions.  Apparently, the classic 6 balls and 3 rods 
Renishaw probe has a 3-lobed sensitivity pattern with large 
peaks and valleys.  Blum claims they get 1 um variation in 
the distance to trip the probe from any direction in the XY 
plane.)

Once all this settles down, I will make edge finding probe 
routines that set the XY zero for any of the 4 corners of a 
part, and also sets the Z of the top of the part.

I made an adapter from the FPGA board to the CNC control, 
and it has some flaky contacts, so I may remake the whole 
thing (it is just 3 LEDs, 5 resistors and 2 opto-isolators, 
so not much to redo) when I put it all in a box.

Jon

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Re: [Emc-users] Plasma Torch Height Control

[Marius Liebenberg]

You only need to monitor the cutting voltage of the arc.

-- Original Message --
From: "Alexander Brock" 
To: emc-users@lists.sourceforge.net
Sent: 2016-09-10 00:59:32
Subject: Re: [Emc-users] Plasma Torch Height Control


On 09/09/2016 10:58 PM, John Thornton wrote:

 Most LinuxCNC users use this one as do I.
 
http://mesaus.com/index.php?route=product/product=65_id=64

 or
 
http://mesaus.com/index.php?route=product/product=65_id=65

 depending on your plasma torch.


Thank you for your answer

I have a HF arc start with pilot arc functionality, there are 3 cables:
- thick cable for +, connected to torch
- thinn cable for pilot arc ignition, also connected to torch
- thick cable for -, connected to clamp which I attach to the material 
I

want to cut.

Do I need 2 of the AD converters to monitor cutting arc and pilot arc?
What would be an appropriate resistor to protect the THCAD?

Best Regards,
Alexander
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Re: [Emc-users] Plasma Torch Height Control

[Marius Liebenberg]

The cncprofi work very well and with no fuss. I used it many times.


-- Original Message --
From: "Alexander Brock" 
To: "Enhanced Machine Controller (EMC)" 

Sent: 2016-09-09 20:57:50
Subject: [Emc-users] Plasma Torch Height Control

>Hi,
>
>I recently bought a Plasma Cutter and built a CNC router and now I want
>to add a Torch Height Control to it.
>
>I found these models, does anyone have experience with them or
>experience with other THC systems?
>
>http://www.ebay.de/itm/172288076009
>http://www.ebay.de/itm/262439946439
>http://www.cncprofi.eu/product_info.php?info=p860_profi-plasmabrenner-hoehe-controller-thc.html
>
>Best Regards,
>Alexander
>
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