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Author Topic: Feedrate overide for each axis independently  (Read 3146 times)

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Feedrate overide for each axis independently
« on: November 20, 2013, 04:38:04 PM »
Hello,

i would like to know if there's a way to add sliders to control the overide of the feedrate  for EACH axis.
At that time the overide function acts on every axis.

I would like  to be able at least to control the common overide for  X/Y feedrate and besides  this  be able to
alter the Z feedrate independently.

Do you think it is something achievable by creating sliders and macros?
I don't have any clue which instruction(s)  can modify the feedrate...

Any help would be appreciated.

Thanks

Offline Hood

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Re: Feedrate overide for each axis independently
« Reply #1 on: November 20, 2013, 04:47:07 PM »
You can not do that as far as I can see as it would screw Mach up. What I mean is you command a move to  a position at a feedrate and Mach gets the axis there at that feedrate. So if you said G1X10Y20f100 and you wanted independent overrides Mach could not possibly move the axes as it would have to slow one down to make sure they both got there at the same time and thus only the slowest override would be adhered to.

Hood
Re: Feedrate overide for each axis independently
« Reply #2 on: November 21, 2013, 12:00:34 PM »
hi Hood,

thank you for your reply.

Maybe a mid solution can be found:
1 slider for overriding X/Y together
1 slider for overriding Z alone.

I don't understand why it wouldn't be possible as i guess the overriding command
"changes  artificially " the feed rate in the G-Code, and the feed rate can be different  for  the X/Y translation
and the Z translation.
It's a proof that they're can exist 2 feedrate values, no?

Offline Hood

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Re: Feedrate overide for each axis independently
« Reply #3 on: November 21, 2013, 01:18:37 PM »
When you command a multiple axis move Mach calculates the path so that both axes reach the end point in unison. If you could override one axis and not the other then the path would not be adhered to and that would potentially be disastrous.

Quote
I don't understand why it wouldn't be possible as i guess the overriding command
"changes  artificially " the feed rate in the G-Code, and the feed rate can be different  for  the X/Y translation
and the Z translation.
It's a proof that they're can exist 2 feedrate values, no?

When you do a feed override it is acting upon all axes so the path that Mach calculated is still the same, just you have changed the time frame for it to happen, the feedrates of the axes in that move are still linked together by the % you increase or decrease with the override and are not independent.
Hood
Re: Feedrate overide for each axis independently
« Reply #4 on: November 21, 2013, 05:15:43 PM »
OK !
I understand your statement  for X and Y as they should be in "unison".

But concerning Z, in the G-code , i'm used to always specify a low  F value for the plunge action, to avoid breaking small mills.
And i can clearly see Mach waiting for the mill to "slowly" go down to the requested depth before going on.
So X and Y are "waiting" and are not in "unison" with Z, aren't they?

Anyway,  i don't want to bother you,  Hood.If Mach can't do it, it can't do it , that's all !

THX
Re: Feedrate overide for each axis independently
« Reply #5 on: November 21, 2013, 05:40:08 PM »
Put X, Y, and Z gcodes all on separate lines, and you can set each for a different feed rate.  Code may (will) run "choppy" if you do, however.
John Champlain

Offline Hood

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Re: Feedrate overide for each axis independently
« Reply #6 on: November 22, 2013, 03:31:04 AM »
The thing is Mach will synch ALL 6 axis if they are called so that is why you only have one feed override. You may only ever call the Z axis to move on its own but you can not set the feed override to affect it only.,
 You could possibly use a brain or macropump to look at the axis moving and set the feed override to what you want if it is but I do not see the point in that as it would be just as easy  to do what is normal, ie call a feed rate in the code.
Hood
Re: Feedrate overide for each axis independently
« Reply #7 on: November 22, 2013, 04:11:53 AM »
Hello,

thanks for your answers.
The reason for asking such a question is that i'm doing some tests with very small mills.

I'm doing engraving and cutting jobs on thin solid silver.

At that moment i'm working with a carbide  0.2mm conical (15°) bit two cutting edges .My spindle speed is 45.000rpm , X/Y feedrate: 350 mm/mn and Z feedrate 20mm/mn
each cut : 0.05mm

I think i can go higher but i't's pretty hard to know precisly the best feedrate i can achieve either  in X/Y and either in Z.
The documentation on such  small mills is pretty hard to find.

And having the opportunity to alter the feedrate on Z independently is convenient to find the highest feedrate
for X/Y and Z (with good work quality and no mills breaks !).This way i would'nt have to rewrite the G-Code for each value
of the feedrates i want to try.
« Last Edit: November 22, 2013, 04:14:39 AM by kilooli »

Offline Hood

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Re: Feedrate overide for each axis independently
« Reply #8 on: November 22, 2013, 04:28:45 AM »
It is easy to replace feedrates in G Code, you can use the Edit button and that will open the code in Notepad, you then from Edit menu choose Replace, then enter the F rate you are wanting to change and then below type the new F rate and then press Replace All and you are done.
Hood