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Author Topic: Z Acceleration  (Read 3876 times)

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Offline Davek0974

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Z Acceleration
« on: April 18, 2016, 05:24:42 AM »
Does G28.1 use z acceleration value or not?

I still have an annoying issue with my Z stalling when doing G28.1 but its fine at all other times.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline RICH

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Re: Z Acceleration
« Reply #1 on: April 18, 2016, 06:51:01 AM »
See the Mach Manual section 10.7.11.

RICH

Offline Davek0974

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Re: Z Acceleration
« Reply #2 on: April 18, 2016, 07:36:19 AM »
Thanks, but i have my Z limited to 2500mm/min which it seems to handle easily unless doing a G28.1, surely the G28.1 command obeys the limits of the axis??

So if my last feed rate was 5000 the z would still only go to 2500 when doing G28.1??

If not then it would explain the odd stalling - the machine X/Y can move faster than the Z can take but if it DOES obey the speed limit then I am back to being confused.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline RICH

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Re: Z Acceleration
« Reply #3 on: April 18, 2016, 06:06:02 PM »
Don't uses home switches here as I have found no need for them.  :o

That said, I assumed that axis velocity for G28.1 would be limited by the slowest axis, BUT, as defined
in the manual the G28.1 "move at current federate, as defined by Configuration".
I ASSuME that configuration means the value in motor tuning.

I guess someone with switches will need to reply about the G281.1.
You may want to say what Mach version your using.

RICH



Offline Tweakie.CNC

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Re: Z Acceleration
« Reply #4 on: April 19, 2016, 02:07:57 AM »
One test you could perhaps do is temporarily half your Z axis Velocity and Acceleration in Motor Tuning then see if the same issue persists ?

Tweakie.
KEEP SAFE !

Offline Davek0974

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Re: Z Acceleration
« Reply #5 on: April 19, 2016, 02:15:43 AM »
RICH, not sure where the home switches come into it? Yes its a bit vague but I would like to think nothing could override the settings in motor tuning or they would be pointless.

I am running V067 as its the one thats recommended for CandCNC THC I have.

Tweakie, thats a good point, might try that next run, I suppose I don't even have to cut - just turn the values down and run G28.1 a few times and see if the speed changes of stays at the current F value.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Hood

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Re: Z Acceleration
« Reply #6 on: April 19, 2016, 04:44:04 AM »
RICH, not sure where the home switches come into it?

G28.1 as far as I understand is to reference your machine, ie it will move to the Home switch/switches and back off just as in a normal homing operation. It is not something I use, never had the need but just tested here and it does exactly as supposed to do as far as I can see.

Hood

Offline Davek0974

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Re: Z Acceleration
« Reply #7 on: April 19, 2016, 05:33:11 AM »
Its used in my top-of-material sensing macro and uses the Probe input on the BOB/Mach3

Most of the time it works fine but sometimes the Z will screech during the rapid portion of the down-feed and not move until it thinks it has reached the slow portion where it will start moving at the slow rate until it reaches the material - it still works ok but takes longer and sounds crap.

This is not all the time, so that was what pointed me to it using the current feed rate and not the Z speed limit in motor tuning - my z is limited to 2500 and the machine X/Y is 9000 so the current feed rate can be anywhere, sometimes inside the z limit sometimes outside it.

There is a reason for this behaviour and its not that the z is set too fast or too much acceleration, it only does this on the rapid portion of the G28.1 cycle.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Hood

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Re: Z Acceleration
« Reply #8 on: April 19, 2016, 05:46:31 AM »
Ok well not sure what it actually means by the "current feedrate" as mine seems to be a  rapid for the initial move and then the % of rapid set in Homing and Limits for the final move to the home switches.

What is the command you are using? is it only a Z move you are doing for the G28.1?

Hood

Offline Hood

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Re: Z Acceleration
« Reply #9 on: April 19, 2016, 05:53:18 AM »
Oh and also meant to say if I move the X and Y as far as possible from the intermediate point and the Z only a small distance then they all seem get there at the same time (quite hard to be 100% certain with 20m rapids and fast accel) which suggest the normal behaviour of blending vel and accel is being adhered to.
Hood