Re: [Emc-users] G38.2 probing in machine coord system?

[Andrew]

2016-08-26 22:02 GMT+03:00 Andrew:

> G11 L11 P#<_current_tool> Z0
>

Sorry it's

G10 L11

I prefer using tool lenght offset and G54 offset. Even though I use manual
toolchange.

Andrew
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Re: [Emc-users] G38.2 probing in machine coord system?

[Andrew]

2016-08-26 7:27 GMT+03:00 :

> I'm trying the G38.2 z-probe in an ngc call.  I keep getting an error
> "Probe move on line 6 would exceed joint 2's negative limit".
>
> Problem seems to be that G38.2 uses the current coord system.  I've got
> the Z-home working now, and machine coords knows the furthest it can go,
> whereas the active coord system Z-value is meaningless for a max probe
> target.
>
> I tried to prefix the G38.2 with G53 (machine coord operation), but I get
> an error that G53 only works on G0/G1.
>
> Am I looking at the problem right?  How can I make this "probe to a fixed
> machine coord point"?
>
>
This is how I probe tool lenght offset:

G53 G0 Z0 (max Z)
G91
F600
G38.2 Z-100 (Z stroke)
G1 Z2
F60
G38.2 Z-5
G11 L11 P#<_current_tool> Z0
G90
G53 G0 Z0
G43

It requires a toolchange before probing.

So you can probe to a fixed machine coord using incremental mode after G53

Andrew
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Re: [Emc-users] G38.2 probing in machine coord system?

[andy pugh]

On 26 August 2016 at 18:35,   wrote:
> So #[5203 + [10 * #5220] is how you get the work offset of the current coord 
> system?


There may be other ways.

>  That's a strangely convoluted way to access the single most straightforward 
> parameter there is, used by almost all moves.

But you almost never need it inside G-code.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] G38.2 probing in machine coord system?

[dannym]

Yeah like I say, to zero out the Zwork coords at present location would be 
confusing, and doesn't actually resolve much.

I'm not familiar with the internally defined parameters.  So #[5203 + [10 * 
#5220] is how you get the work offset of the current coord system?  Wacky... 
there's no "offset of present coord system"?  That's a strangely convoluted way 
to access the single most straightforward parameter there is, used by almost 
all moves.

Danny


 andy pugh  wrote: 
> On 26 August 2016 at 05:27,   wrote:

> I tried to prefix the G38.2 with G53 (machine coord operation), but I get an 
> error that G53 only works on G0/G1.
> Am I looking at the problem right?  How can I make this "probe to a fixed 
> machine coord point"?

That's annoying :-) (and G53 was going to be my first suggestion).

One way that comes to mind (and it is very likely that someone else
has a better idea) would be to zero out the Z offset, do the probe,
then put it back.

; Get the current Z offset,  it's lucky that #params can be computed
#1 = #[5203 + [10 * #5220]
G10 L2 P0 Z0
G38.2 F10 Z-200
G38.3 F10 Z0
G10 L2 P0 Z#1

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] G38.2 probing in machine coord system?

[dannym]

Yeah the probe input definitely works.  I did get the G38.2 probe to work in 
some controlled circumstances.

Say that machine Zhome=0 is 7" above the bed, and ZMin= -7.0".  In most cases 
this probe will be near the Z min (thin materials).  Z min is not set absurdly 
low (or no limit) to at least guarantee people don't rub the NUT against the 
bed.  The nut stops like 1/2" above the bed.  

The G38.2 is in work coords.  The Z-target must be given, but that's in work 
coords, and it will fail to enter the .ngc call if the Z-target is outside 
machine limits.

So, if you have no work offset, Zmachine and Zwork are the same, and G38.2 
Z-6.5 works.  

But if the user already zeroed on one material, there might be a -5" work 
offset.  Zwork=0 is Zmachine=-5.  It won't matter where your z-axis currently 
is located, the G38.2 Z-6.5 becomes a command to move to machine coord Z= -11.5 
which, as the error says, exceeds joint 2's negative limit.

Someone's example I found online that I was copying started by declaring the 
current Z to be work Z=0.  That's undesirable because if you abort or fail the 
probe cycle, your prior Z offset is still gone.  In any case it won't actually 
do much to fix the z-limit problem.  If you're at Zmachine = -5 and make that 
Zwork =0, your routine can only probe to z=-2 max in that case, but there's no 
way to know what that distance is when coding the .ngc.  It could be -1" or -7".

I guess that does mean that if you have one probe cycle fail to make contact 
with a -1" drop, you would just repeat until it does because the new cycle will 
reset Zwork=0 and G38.2 Z-1 down again.  But that's a bit confusing.  

Danny


 Gene Heskett  wrote: 
> On Friday 26 August 2016 00:27:00 dan...@austin.rr.com wrote:
> 
> > I'm trying the G38.2 z-probe in an ngc call.  I keep getting an error
> > "Probe move on line 6 would exceed joint 2's negative limit".
> >
> > Problem seems to be that G38.2 uses the current coord system.  I've
> > got the Z-home working now, and machine coords knows the furthest it
> > can go, whereas the active coord system Z-value is meaningless for a
> > max probe target.
> >
> > I tried to prefix the G38.2 with G53 (machine coord operation), but I
> > get an error that G53 only works on G0/G1.
> >
> > Am I looking at the problem right?  How can I make this "probe to a
> > fixed machine coord point"?
> >
> > Danny
> >
> Generally, give it a probe distance that would not exceed that limit.  It 
> moves in the current co-ordinate system.  So if your limit is set 1mm 
> above the table, the z-value you give it, shouldn't be lower than 
> 1.001mm at the end of the probe move from where its at at the start.  If 
> the probe contact is not made by then, you get a different error.
> 
> I assume you have verified with a halmeter, watching motion.probe-input, 
> that the probe circuit is working?
> > --
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> 
> 
> Cheers, Gene Heskett
> -- 
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page 
> 
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Re: [Emc-users] G38.2 probing in machine coord system?

[John Thornton]

You might look at the probing routines here
http://www.mesaus.com/info/probe-subroutines.zip

JT

On 8/25/2016 11:27 PM, dan...@austin.rr.com wrote:
> I'm trying the G38.2 z-probe in an ngc call.  I keep getting an error "Probe 
> move on line 6 would exceed joint 2's negative limit".
>
> Problem seems to be that G38.2 uses the current coord system.  I've got the 
> Z-home working now, and machine coords knows the furthest it can go, whereas 
> the active coord system Z-value is meaningless for a max probe target.
>
> I tried to prefix the G38.2 with G53 (machine coord operation), but I get an 
> error that G53 only works on G0/G1.
>
> Am I looking at the problem right?  How can I make this "probe to a fixed 
> machine coord point"?
>
> Danny
>
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Re: [Emc-users] G38.2 probing in machine coord system?

[Gene Heskett]

On Friday 26 August 2016 00:27:00 dan...@austin.rr.com wrote:

> I'm trying the G38.2 z-probe in an ngc call.  I keep getting an error
> "Probe move on line 6 would exceed joint 2's negative limit".
>
> Problem seems to be that G38.2 uses the current coord system.  I've
> got the Z-home working now, and machine coords knows the furthest it
> can go, whereas the active coord system Z-value is meaningless for a
> max probe target.
>
> I tried to prefix the G38.2 with G53 (machine coord operation), but I
> get an error that G53 only works on G0/G1.
>
> Am I looking at the problem right?  How can I make this "probe to a
> fixed machine coord point"?
>
> Danny
>
Generally, give it a probe distance that would not exceed that limit.  It 
moves in the current co-ordinate system.  So if your limit is set 1mm 
above the table, the z-value you give it, shouldn't be lower than 
1.001mm at the end of the probe move from where its at at the start.  If 
the probe contact is not made by then, you get a different error.

I assume you have verified with a halmeter, watching motion.probe-input, 
that the probe circuit is working?
> --
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] G38.2 probing in machine coord system?

[andy pugh]

On 26 August 2016 at 05:27,   wrote:

> I tried to prefix the G38.2 with G53 (machine coord operation), but I get an 
> error that G53 only works on G0/G1.
> Am I looking at the problem right?  How can I make this "probe to a fixed 
> machine coord point"?

That's annoying :-) (and G53 was going to be my first suggestion).

One way that comes to mind (and it is very likely that someone else
has a better idea) would be to zero out the Z offset, do the probe,
then put it back.

; Get the current Z offset,  it's lucky that #params can be computed
#1 = #[5203 + [10 * #5220]
G10 L2 P0 Z0
G38.2 F10 Z-200
G38.3 F10 Z0
G10 L2 P0 Z#1

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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[Emc-users] G38.2 probing in machine coord system?

[dannym]

I'm trying the G38.2 z-probe in an ngc call.  I keep getting an error "Probe 
move on line 6 would exceed joint 2's negative limit".

Problem seems to be that G38.2 uses the current coord system.  I've got the 
Z-home working now, and machine coords knows the furthest it can go, whereas 
the active coord system Z-value is meaningless for a max probe target.

I tried to prefix the G38.2 with G53 (machine coord operation), but I get an 
error that G53 only works on G0/G1.

Am I looking at the problem right?  How can I make this "probe to a fixed 
machine coord point"?

Danny

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