Messages

1811

General Mach Discussion / Re: Z Acceleration

« on: April 19, 2016, 01:53:40 PM »

Thanks Hood, that backs up my tests, same results - it uses the rapids and not the feed rate.

I have also been advised my setting is too high - currently 2500mm/min and 2400mm/s/s on Z axis.

I got there by just whacking it up until it failed then dropped 30% and tried again then 30% and so-on. There is very little mass in the Z and it seemed happy when using manual G00 commands and jogging etc so i left it - the THC and piercing love it

I will wind it back a notch and see how she goes, maybe I'm just pushing too hard and one in ten times it says "no way buddy"...

1812

General Mach Discussion / Re: Z Acceleration

« on: April 19, 2016, 08:16:03 AM »

Thanks, i'll have a quick play tonight and also try throwing an F in there.

The subroutine and macro perform perfectly but I have read stuff on the G92 etc, but as it all does exactly what i want it to I will leave it as-is.

I am hoping it is just as simple as the G28.1 using the machine feed-rate and ignoring the z limit, as that really would explain why it works sometimes and not others, if it really does use the z limit all the time then i am back to square one!

I have tried tweaking micro-step values, also fitted a coarser lead screw but made no difference.

1813

General Mach Discussion / Re: Z Acceleration

« on: April 19, 2016, 07:47:36 AM »

It does seem odd, I have the homing subroutine/macro as a test file on the desktop so i can run it as a program over and over, it works ok, but then I have never set a high F rate and tried it, hopefully have a play tonight, there must be a root cause for this.

1814

General Mach Discussion / Re: Z Acceleration

« on: April 19, 2016, 06:40:42 AM »

Also, on a plasma, isn't referencing the axis the correct procedure anyway as all the measurements are relative to the TOM?

1815

General Mach Discussion / Re: Z Acceleration

« on: April 19, 2016, 06:19:45 AM »

Hmm, ok so what changes do i need to make to my probing routing to switch to G31

I'm fairly certain this is my latest macro..

Code "G91" (switch to incremental mode)
Code "G00 X22.00" (position probe switch)
Code "G90" (switch to absolute mode)

ActivateSignal(OutPut3) (triggers the probe cylinder)
Sleep(400)

Code "G28.1 Z10.000" (probe the surface)
Code "G92 Z#15045" (apply the probe switch offset from settings screen DRO)

DeActivateSignal(OutPut3) (raise the probe)
Sleep(200)

Code "G91" (switch to incremental mode)
Code "G00 X-22.00" (put the axes back to where we came from)
Code "G90" (switch to absolute mode)
Code "G00 Z0.00" (Go to Z Zero)

1816

General Mach Discussion / Re: Z Acceleration

« on: April 19, 2016, 05:59:13 AM »

The code i have is G28.1 Z10 and seems to work "most of the time"

It does slow down to the value set in homing/limits so that is being read ok, its just the odd rapid bit thats baffling

1817

General Mach Discussion / Re: Z Acceleration

« 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.

1818

General Mach Discussion / Re: Z Acceleration

« 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.

1819

General Mach Discussion / Re: Z Acceleration

« 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.

1820

General Mach Discussion / 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.