(Solved) PlasmaC new config Z going up when probing

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31 Jul 2020 22:42 #176705 by snowgoer540

I’m with Phill, what did you mean by P10?


Ok I have had a few sherbets so please excuse me.

P10 is the pid loop whatever in the ini file and the machine in question that I had to help set up was 40 miles away so done with phone and Dropbox. we had to increase the P10 TO 2O to get it to work.


Good to know, a friend of mine had to increase his to 50 to have it keep up. PID tuning for everyone :laugh:

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01 Aug 2020 00:19 #176715 by phillc54

I have bumped this: As the above questions seem to have fallen through the net. Although the machine is working.

I "think" mine is negative but I am not 100% sure. I will check my machine tomorrow.
I also "think" I have the jumpers set as per Peters suggestion. Again, I will check tomorrow.

I have a 7i96 with:
W2 right
W3 left
W5 right
At zero volts hm2_7i96.0.encoder.00.velocity reads around positive 3790
When voltage is applied, velocity counts in the positive direction
The following user(s) said Thank You: Clive S

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01 Aug 2020 08:54 #176762 by Clive S

I have bumped this: As the above questions seem to have fallen through the net. Although the machine is working.

I "think" mine is negative but I am not 100% sure. I will check my machine tomorrow.
I also "think" I have the jumpers set as per Peters suggestion. Again, I will check tomorrow.

I have a 7i96 with:
W2 right
W3 left
W5 right
At zero volts hm2_7i96.0.encoder.00.velocity reads around positive 3790
When voltage is applied, velocity counts in the positive direction


Thanks. That helps. Mine is the same including the switches so I would like to find out why the other machine is the opposite and had to change the setp hm2_7i96.0.encoder.00.scale to 1.

But if it ain't broke don't fix it :)

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16 Aug 2020 21:21 #178430 by snowgoer540

Yes its strange the machine above would not work with P10 and delay 1.5 just changing these two things made the machine fly we have just cutout a big control panel using Hypertherms cut parameters in 3mm alli at 7.5M/min without any issues.

If there are no pictures or video, it did not happen ! :) I was told this same thing by a member here not long ago.

Ok I will put them both together. Doubting Thomas.


I'm curious how to get my THC dialed in there. It seems that no matter what I do, it's not fast enough.

Video:


I had the P in the PID all the way up to 50, that didnt seem to help (in fact probably made it worse). I also changed the setup speed to 150ipm (though I dont think this affects the THC speed), and that didnt help either. In the video, the P value is 25. Am I expecting too much of the THC? I see videos of people cutting congregated metal with theirs, and there is probably no way that could happen here (not that I need to at the moment, just trying to tune the table in). That cut speed was 150ipm. Perhaps that's too demanding of the THC?

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16 Aug 2020 23:03 #178433 by PCW
Something limiting the Z axis velocity or acceleration could cause this
Also something wrong with the plasma voltage reading could cause this issue (too much filtering for example)

What does the plasma voltage do during the cut?

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17 Aug 2020 00:15 #178436 by rodw
That almost looks like the THC is not enabled when it hits the material. Can you check the THC light is coming on in Plasmac?
Can you tell us the THC delay you have set?

It does work and this was with default settings and probably a bit more onerous than your test.



The Z axis velocity and acceleration is what limits cutting corrugated iron because the torch must follow the sinusoidal profile of the iron.
I have a spreadsheet calculator somewhere. I think for my machine it was limited to about 4 m/sec cut speed (oops there we go again)

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17 Aug 2020 00:54 - 17 Aug 2020 00:57 #178438 by snowgoer540

Something limiting the Z axis velocity or acceleration could cause this
Also something wrong with the plasma voltage reading could cause this issue (too much filtering for example)

What does the plasma voltage do during the cut?


@PCW
I recall when you were helping me with my Joint 3 following error via email that you said something similar about something constraining the Z axis. At that time, you had me double the acceleration for the stepgen. I also should remind you that I had latency that's pretty high for a PCI machine (over 100k ns) I attached the ini file, but here is the Z axis snippet:
#******************************************
[AXIS_Z]
# set to double the value in the corresponding joint
MAX_VELOCITY = 10.000
# set to double the value in the corresponding joint
MAX_ACCELERATION = 100.00
# shares the above two equally between the joint and the offset
OFFSET_AV_RATIO = 0.5
MIN_LIMIT = -3.875
MAX_LIMIT = 0.001

[JOINT_3]
TYPE = LINEAR
HOME = 0.0
FERROR = 0.5
MIN_FERROR = 0.05
MAX_VELOCITY = 5.000
MAX_ACCELERATION = 50.00
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 6.250
STEPGEN_MAXACCEL = 100.00
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
# these are in nanoseconds
DIRSETUP   = 10000
DIRHOLD    = 10000
STEPLEN    = 5000
STEPSPACE  = 5000
STEP_SCALE = 5080
MIN_LIMIT = -3.875
MAX_LIMIT = 0.001
HOME_OFFSET = 0.050000
HOME_SEARCH_VEL = 0.416667
HOME_LATCH_VEL = 0.083333
HOME_FINAL_VEL = 0.083333
HOME_USE_INDEX = NO
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = -1
#******************************************

Also, I have the lowpass frequency set to 0 (by default) in my connections.hal file (setp plasmac.lowpass-frequency 0).

The voltage seems to read correctly, and the THC seems to try to keep it at the prescribed voltage, just not fast enough. Here is a video:

Attachments:
Last edit: 17 Aug 2020 00:57 by snowgoer540.

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17 Aug 2020 00:56 - 17 Aug 2020 00:57 #178439 by snowgoer540

That almost looks like the THC is not enabled when it hits the material. Can you check the THC light is coming on in Plasmac?
Can you tell us the THC delay you have set?

It does work and this was with default settings and probably a bit more onerous than your test.

The Z axis velocity and acceleration is what limits cutting corrugated iron because the torch must follow the sinusoidal profile of the iron.
I have a spreadsheet calculator somewhere. I think for my machine it was limited to about 4 m/sec cut speed (oops there we go again)


I thought the same, so I played around with the delay. I had it as low as .3 seconds, but after I was done I put it back to 1s.

I'm fairly confident I couldnt do what you did on my table :(. I went back and watched Clive's video after he tuned his, you can see his crash into the material in the beginning as well, but his limit switch must not be as sensitive as mine.

At any rate, a video, and my ini settings are attached above.
Last edit: 17 Aug 2020 00:57 by snowgoer540.

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17 Aug 2020 01:07 #178441 by phillc54
That seems to show the down led on just before the crash.

It would be interesting to see a plot with the arc voltage and the up and down leds

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17 Aug 2020 01:11 - 17 Aug 2020 01:36 #178443 by PCW
Looking at the cut, I think it runs into the material before the THC is enabled
(0.3 seconds from the start of motion would do this even if there was no velocity lockout)


The other issue is how much distance is needed to get to the THC enable velocity threshold
with you current acceleration from a static start?

My guess is that the basic issue is that the THC is assumed to operate at constant XY velocity
so when you have a case where it needs it to work instantly and during acceleration, it fails
Last edit: 17 Aug 2020 01:36 by PCW.

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