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Offline stirling

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plasma anti dive
« on: October 09, 2010, 06:47:59 AM »
anyone got this to work? According to the manual if actual feedrate drops below whatever anti-dive is set to then torch up/down input signals should be ignored by Mach but this doesn't seem to happen.

Offline BR549

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Re: plasma anti dive
« Reply #1 on: October 09, 2010, 10:17:16 AM »
I thought anti dive was to keep Mach from diving into a hole or span cause by the rise in arc voltage as it crosses the gap.

Could be wrong but that is how it seems to work here.  Otherwise IF you had a long dwell on start the head would try to dive into the hole to chase the arc voltage. Same if you crossed a span or gap in the metal

Just a thought, (;-) TP

Offline stirling

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Re: plasma anti dive
« Reply #2 on: October 09, 2010, 11:47:24 AM »
I thought anti dive was to keep Mach from diving into a hole or span cause by the rise in arc voltage as it crosses the gap.

Could be wrong but that is how it seems to work here.  Otherwise IF you had a long dwell on start the head would try to dive into the hole to chase the arc voltage. Same if you crossed a span or gap in the metal

Just a thought, (;-) TP

What you describe is an anti-dive feature of SOME THCs - generally the more sophisticated ones. When the arc crosses a gap, the electronics "recognize" the voltage spike and suspend THC until the voltage settles again. BUT - what I'm referring to is the more simplistic anti-dive that comes out of the box with Mach - i.e. a software thing rather than hardware. The problem it's meant to prevent is that when you slow down round (say) a sharp corner, this causes the torch volts to rise. This fools the THC into thinking the torch to work distance has increased so the THC sends torch DOWN to Mach. Ouch - Crash.

So to get round this you can set an anti dive speed in Mach (OEM 82) which basically says if you go slower than this then ignore the UP/DOWN signals from the THC. It's enabled/disabled  with OEM 221 or with OEM 222,223.

Unfortunately it doesn't seem to work! Hence my question.

Offline BR549

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Re: plasma anti dive
« Reply #3 on: October 12, 2010, 10:26:25 AM »
HIYA Stirling I see you are not getting any help. If I can help test something  just let me know. I can bang on it until we find an answer or a fix.

What manual ver are you reading about it in?

(;-) TP

Offline stirling

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Re: plasma anti dive
« Reply #4 on: October 13, 2010, 08:17:15 AM »
Hi Terry

I first came accross it on the screenset from soundlogicus when I got one of their THC300's. The only mention I've been able to find is in the mach2 mill manual on the downloads page section 6.2.13.1.

Not a big deal really - just wondered how to use it to see if it had any benefitial effect.

Ian

Offline kf2qd

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Re: plasma anti dive
« Reply #5 on: October 13, 2010, 02:33:31 PM »
Some Plasma Torch Height Controls have the necesary stufff inside to do this function - sudden changed in carc voltage will be ignored, gradual changes will be compensated for. The other function is a Torch Height Control Disable function that is controlled by the CNC. This prevents the torch from dropping onto the plate when the machine slows down coming into a corner, or when cutting small circles where the machine can't run full speed.

Which function are you talking about?

Offline stirling

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Re: plasma anti dive
« Reply #6 on: October 14, 2010, 03:42:56 AM »
Which function are you talking about?

what I'm referring to is the more simplistic anti-dive that comes out of the box with Mach - i.e. a software thing rather than hardware. The problem it's meant to prevent is that when you slow down round (say) a sharp corner, this causes the torch volts to rise. This fools the THC into thinking the torch to work distance has increased so the THC sends torch DOWN to Mach. Ouch - Crash.

So to get round this you can set an anti dive speed in Mach (OEM 82) which basically says if you go slower than this then ignore the UP/DOWN signals from the THC. It's enabled/disabled  with OEM 221 or with OEM 222,223.

in the mach2 mill manual on the downloads page section 6.2.13.1.
« Last Edit: October 14, 2010, 03:45:03 AM by stirling »

Offline BR549

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Re: plasma anti dive
« Reply #7 on: October 14, 2010, 11:09:40 AM »
Stirling I wonder IF that value is a percent rather than a speed???

You know how criptic mach is sometimes(;-). I would think % would make more sense.

I'll dig into it some more.

I wonder WHY that part of the manual was left OUT of the new version?

Just a thought, (;-) TP

Offline BR549

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Re: plasma anti dive
« Reply #8 on: October 14, 2010, 11:31:05 AM »
Stirling If you look on the CandCNC site in TOms LCthc manual it give a description of the "mach" anti dive and how it is used. His unit has built in antidive(tipsaver).

Just a thought, (;-)

Offline stirling

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Re: plasma anti dive
« Reply #9 on: October 14, 2010, 01:43:47 PM »
Terry - you've cracked it - here's the pertinent bit from Tom's manual: This is apparantly another "legacy" function.

"SLOW DOWN ANTI-DIVE. Anti-Dive Button. Turns ON/OFF the software Anti-dive. The trigger point where it locks downward movement is a percentage of the running velocity (XY combined) and is set in the Anti-dive DRO."

To be honest - the accel is good enough on my machine that it doesn't dive for this reason anyway, but the reason I wanted to know about this is I'm designing a new plasma screenset and wanted to know whether I should include this feature.

Really appreciate you taking the time to sort this for me - thanks

Ian