Command CNC torch height jumps UP

[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]

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]

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]

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]

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 .

[Awesome]

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

I ran the tests (again) and didn't come up with any issues. I went ahead and set the acceleration velocity to 20ipm like you said. Cyrious had it set at 35 and it seemed pretty aggressive. Seemed to run smoother at 20ipm. I also changed the THC response rate to Medium (was at Slow). Cut out several parts and had zero issues that weren't caused by me.



I may have forgotten to turn the air compressor on and got confused when the machine started cutting worse and worse. I was able to save the part though.

[tcaudle]

NO! DO NOT CHANGE the the response. I just made the DTC a lot more aggressive . It should only be set to med for really thin material or corrugated.
The only thing that saved you was tuning the Z acceleration down . The response is an adjustment ot he PID loop of the DTHC.

[Awesome]

NO! DO NOT CHANGE the the response. I just made the DTC a lot more aggressive . It should only be set to med for really thin material or corrugated.
The only thing that saved you was tuning the Z acceleration down . The response is an adjustment ot he PID loop of the DTHC.

Retune you your XY motors and lower the acceleration to 20 IPS/sec (makes VAD work better)

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 I'm not sure what your last post (the first quote) is referring to, as I was going off of your other post (the second one I quoted).

I turned the XY motor acceleration down to 20ipm and then increased the THC response to Medium since I'm cutting 10/11ga material. Not really all that thick but also not super thin. It does warp some when running long cuts. I didn't mess with the Z.

I did notice that when I'm recutting parts that didn't cut properly, the THC flips out and dives the torch or sometimes throws a motion hold. That may have been what was causing my issues to begin with. On virgin cuts, the THC doesn't seem to have any problems.

[tcaudle]

Increasing response a whole level should only be done on really thin material. Slow (probably misnamed) will handle down to 16ga (even thinner with fine cut) You risk having head oscillation on thicker material . The DTHC 4/5 is capable of extremely fast response and I have cut thin corrugated at full speed with it (takes a Z that can handle over 300 IPM) but that setting on flat material will make the loop unstable.

The response is a lot like the GAIN of a servo loop and too much causes it to be unstable and over react. Slowing the accel down is kinda the Dampening element in the servo loop but consider what 20 IPS/Sec is: its 1200 IPM . 0 to 1200 at the rate you Z can move. so 0 to 200 IPM if that is you max Z speed would happen in 1/6 second.

The XY setting causes the acceleration and deceleration to calm down a little and the motion starts slowing down sooner as it approaches a direction change. With a conventional THC that can spell diving but with VAD it makes it work better. Another side effect is it can smooth out some of the motion.

Another setting in the POST that controls the Tool path tracking will also smooth out a ragged tool path and allow the motion to round out the harsh moves on a ragged piece of artwork with lots of nodes. A lot of the canned art is auto traced and not very smooth .

[tcaudle]

Precutting parts presents a whole different set of issues. Cutting into or over a void is a guaranteed torch dive. There is not speed change (usually) so VAD detects nothing and the DTHC responds at full speed to ANY voltage variation. Cutting close to a prior cut starves the torch for metal and that forces it to raise the voltage to maintain the preset current. Unfortunately nothing can detect that issue (like cutting too close to the edge or too close to a piece that has already fallen out. It may be best if the piece is flat to disable the DTHC with the screen button until it gets to a "virgin" area.

[Awesome]

Increasing response a whole level should only be done on really thin material. Slow (probably misnamed) will handle down to 16ga (even thinner with fine cut) You risk having head oscillation on thicker material . The DTHC 4/5 is capable of extremely fast response and I have cut thin corrugated at full speed with it (takes a Z that can handle over 300 IPM) but that setting on flat material will make the loop unstable.

The response is a lot like the GAIN of a servo loop and too much causes it to be unstable and over react. Slowing the accel down is kinda the Dampening element in the servo loop but consider what 20 IPS/Sec is: its 1200 IPM . 0 to 1200 at the rate you Z can move. so 0 to 200 IPM if that is you max Z speed would happen in 1/6 second.

The XY setting causes the acceleration and deceleration to calm down a little and the motion starts slowing down sooner as it approaches a direction change. With a conventional THC that can spell diving but with VAD it makes it work better. Another side effect is it can smooth out some of the motion.

Another setting in the POST that controls the Tool path tracking will also smooth out a ragged tool path and allow the motion to round out the harsh moves on a ragged piece of artwork with lots of nodes. A lot of the canned art is auto traced and not very smooth .

Ok, thank you for explaining. I'll set it back to Slow.

It may be best if the piece is flat to disable the DTHC with the screen button until it gets to a "virgin" area.

That's what I ended up doing and it worked great.

[Deezl Smoke]

Wow. Just wow. Learned way too much for one sitting reading this. Gunna have to re-read it several times.