Command CNC torch height jumps UP

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Nuke Utter
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Re: Command CNC torch height jumps UP

Post by Nuke Utter »

For me, A Axis is my 2 sensors on the torch mount for if your tip Fuses to the plate or hit something. One of them was tripping randomly, so I backed it off a bit and it helped.
I will try those other cad programs and see if it helps out. I think it's just some settings i messed up when I tried to troubleshoot my initial problem though.
tcaudle
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Re: Command CNC torch height jumps UP

Post by tcaudle »

The "Configurator" program where you make changes to things like motor tuning and THC settings has a feature that lets you create a COPY of a running Config and then you can run that and make chnges without going down the rabbit hole. Its advised to mess with a copy and leave the main alone . If you find the new one works better you can delete the older one. You can have as many CONFIGS as you want

You might also check in that same menu if there is a "template " from when the table was new . A template cannot be edited it can only be Coped to a new config
Awesome
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Re: Command CNC torch height jumps UP

Post by Awesome »

tcaudle wrote: Thu Oct 17, 2024 12:36 pm Now I need to go figure out what a crash sensor is......
Pretty sure he means the Z tip-switches. I call them crash switches too.

I'm currently having the same issue the second guy was talking about - on long, straight cuts the torch is diving into the material and tripping the crash switches. Ruined a couple of parts so far. I did learn to turn the DHTC off when cutting out small objects, but on these long cuts I need it on. Maybe I just need to adjust the voltage settings a little better.
tcaudle
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Re: Command CNC torch height jumps UP

Post by tcaudle »

In the DTHC manual about page 85 is a 4 step test taht will poin tout any issues

Basically you set up some long straight futs on a falt piece of material and run the touch-off; move to pierce height ; move to cut height and then do a cut wuth the DTHC in MANUAL and Off and watch the Torch VOLTS. Torches dive under THC beasue they see a volage increase. That can happen nataurally as the motion slows to make a turn or corner . The VAD is designed to sense that slowdown in real time and stop the torch dive by momentarily disabling the torch. If you run the test and you dont see voltage anolilies more tha 4 - 4 volts than:

Make sure your VAD is enabled in the cut file
make sure that you are running CommandCNC 1.3 or higher release.. Older releaseshad problmes in VAD if you u used FRO (feed rate override)
Make sure the VAD % in the THC Settings in CommandCNC is at 85 - 90%
Retune you your XY motors and lower the acceleration to 20 IPS/sec (makes VAD work better)
Make sure you use the EOC path rule in SheetCAM but NO OTHER RULES.
Use the Min cut lenght of DTHC setting in the Operations (make it the total length of the largest object you want to turn off the DTHC on. A 1" ciricle is 3.2" PLUS lead-in)
Watch your cuts on detailed objects and you can see the DTHC ON LED on the screen and on the box go on and off

If ANY of the test fail then stop and report and we can fix that.


So the two forms of anti dive are VAD which is during motion and EOC PAth rule that turn the DTHC off a distance before the end . Since the motion does not slow down in a straight cut until it too late and you are very close or past the lead-in you get voltage spikes. NOTE: That distance has to be greater than the point about 1/2| to 5/8 before the end of the cut . If you use lead outs that distance has to be tacked onto the length. I suggest little or no lead out

In the end something is happening with the Torch volts and the DTHC dutifully dives to compensate

Anther factor is that the DTHC settings for thin (10ga and under) are different than thicker stuff. In prior posts I suggest you build separate configs for different kinds of cutting . You can have as many as you want and making a new one and copying the existing CONFIG to get the motor tuning ans inputs is easy.

On thick material you can slow the DTHC response way down (it has separate max velocity and acceleration) and you can slow down the Z .

So understanding what causes a voltage spike and how the system detects and compensates for it are critical. The reason we say not to use other Path rules is because SheetCAM and COmmandCNC have built inrules and they can conflict with the PATH rules and cause just the opposite action you want.
tcaudle
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Re: Command CNC torch height jumps UP

Post by tcaudle »

A true collision switch will not only trip on UP motion from the torch holder but also from any side or front to back hits. On our SUperZ II comes witha Breakaway sensor on the torch mount. On some others they have sensors on a "Halo" torch holder and those are used (some even as mechanical backup for touch off with Feather Touch) So it senses a crash in any direction and stops the motion.

A simple Z limit on a floating head only stops if the torch gets shoved UP by an object .
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