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Author Topic: Mach3 Ignores Feedrates In G Code  (Read 4996 times)

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Re: Mach3 Ignores Feedrates In G Code
« Reply #10 on: February 07, 2012, 05:17:19 PM »
 :) OK Hood, you tha man.
Russ
Re: Mach3 Ignores Feedrates In G Code
« Reply #11 on: February 07, 2012, 05:20:47 PM »
ahhh....Hood beat me to it. :D
Perhaps the clip from the manual will help you to better understand.
Cheers,
Russ
 :)

Offline RS

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Re: Mach3 Ignores Feedrates In G Code
« Reply #12 on: February 07, 2012, 06:56:14 PM »
That is why then, G95 is feed per rev mode so if you do not have any spindle speed Mach can not really feed per rev. What are your feedrates? In other words are your meant to be feeding per rev or per min? Lathes usually work in g95 but really you need spindle speed feedback for that to work correctly.
Hood

Ah, now I see what you mean.  If I am in G95, I need to add a spindle speed to the code, but if I am in G94, I don't.  I have been working in G95 because that is how it was set when I started.  I am very new at this.  I have only had the lathe for a couple weeks.  Should I stick to G95 just for the sake that it is more commonly used on cnc lathes?

Offline Hood

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Re: Mach3 Ignores Feedrates In G Code
« Reply #13 on: February 07, 2012, 07:02:44 PM »
Personally I would rig up spindle  feedback to Mach and work in G95. You can still work in G95 without but it will just assume the spindle is doing the commanded speed and feed at the requested rate which may not be good if you have manually set a lower spindle speed than the code requests. If using G95 remember to set the F word accordingly as by the sounds of it you are maybe using a feedrate equal to feed per min. Reason I say that is you said it went at the correct feed when you set spindle to 1, so 1 rev per min and a feedrate of 10IPM and it would do so where if you had say a fpr programmed it would move very slowly.
Hood
Re: Mach3 Ignores Feedrates In G Code
« Reply #14 on: February 07, 2012, 09:01:42 PM »
 :)
Here is another clip from the manual, to bolster Hood's previous explanation.
Russ
 :)

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Re: Mach3 Ignores Feedrates In G Code
« Reply #15 on: February 07, 2012, 10:02:56 PM »
I was wondering about that.  When I changed the g95 with the S1 to a g94, the speed was still the same.  That didn't seem right.  The Feed titles changes from MM's/Rev to MM's/Min so I know Mach3 understands the code but there must be something overriding it.  Or would it do that if I had the spindle turned off in Mach?  Maybe that is why it doesn't change the speed.  So MM's/Rev is spindle speed times feedrate?

Offline Hood

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Re: Mach3 Ignores Feedrates In G Code
« Reply #16 on: February 08, 2012, 03:22:31 AM »
Putting the S1 in did not change Mach to G94 (Feed per min) but rather because the feedrate you had in your code  it made it look like it did.
By putting the spindle speed DRO to 1 you are telling Mach the spindle is doing 1 rpm so if your feedrate is F10 then Mach is thinking you are wanting 10mm per rev. As the spindle is doing (or Mach thinks it is) 1 revolution per minute the axis will travel 10mm per rev which is the same as 10mm/min in this case. If you had the G95 feedrate programmed correctly the F word would be somewhere in the region of maybe 0.1 to 0.3mm/rev. Now if your feedrate was that, say F0.1 and your spindle was seen by Mach as 1 RPM the  axis would only travel 0.1mm in one minute.

And to answer your last question, G95 units/rev (mm in your case) means exactly that, the axis will travel the feedrate distance for every revolution of the spindle.

Hood