Re: [Emc-users] LinuxCNC 2.7 manual typo

[Luka Kavčič]

Another one

page 199
5.2.2.4 Number
at the end of the section
"A decimal number which is supposed (*to*) be close to an integer
is considered close enough if it is within 0.0001 of an integer."


Luka

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Re: [Emc-users] bash & . ./scripts/rip-environment

[Dewey Garrett]

In  theman 
whosoldtheworld  writes:

>I try to run this simple script:
>#!/bin/sh

/bin/sh is typically NOT the bash shell:

$ which bash
/bin/bash

so, try using:
#!/bin/bash


Aside: use of the dot (.) notation for sourcing a file is sometimes
confusing to new users.  The following are equivalent in the
bash shell:

.  path_to_some_file
source path_to_some_file

Ref: man bash

-- 
Dewey Garrett



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Re: [Emc-users] Fwd: More on bed wear fix

[Chris Albertson]

OK the dots really ARE multiple beams.   Perhaps you have a very poor
quality laser and the lens has facets like a cut diamond?  If it really is
"speckle" then it will change when you change anything and look like your
other laser.

But even if the beam has 40 spots, it will still work just fine this
purpose and maybe even better than a perfect laser would.  A complex signal
is helpful. As long as the dots don't have a pattern.

What you care about is the displacement (shift) from one image to the next
as you take images.  So you shift one image until it lines up perfectly
with the previous image and you remember how much shifting was required and
figure that must be caused by the bent/worn/warped bed.

With a complex image made of many random dots you not only can measure the
X and Y offset but a rotational component too, if one exists.   Yes, there
just might be a rotation on the lathe bad.

If you multiply two images together you get a huge spike when the alignment
is perfect The Wiki describe the 1D case but 2D is just the same.
https://en.wikipedia.org/wiki/Autocorrelation



On Wed, Sep 26, 2018 at 9:31 PM Gene Heskett  wrote:

> On Wednesday 26 September 2018 21:45:42 Chris Albertson wrote:
>
> > I think what you are seeing is a "speckle pattern"  The laser is not
> > making 40 small beams.  it is making one nice uniform beam but
> > remember the light is all in phase.  After a reflection from a
> > textured surface the light hitting the back your eye adds in phase and
> > the spots you are are where the light adds in phase and the other
> > places the wave self-cancels
> >
> > see the second paragraph on this page:
> > https://en.m.wikipedia.org/wiki/Speckle_pattern.
> >
> If I am interpreting that correctly, and with the spindle stopped, I
> should see this "interference" pattern change rapidly as the carriage to
> target distance changes by a single microstep of the screws driving
> motor. I don't see that effect, the individual dots remain stationary.
>
> Not discused is the diffraction effect of passing this coherent bean thru
> a pinhole other than a passing statement that this speckle effect will
> cause the spots to be larger if viewed thru a pinhole. One naturally
> assumes the pinhole is in front of the eye, not the lasers exit aperture
> from a statement like that.
>
> Also, all the patterns shown are circular.  The patterns thrown on the
> wall by a laser pointer I've had for years, a laser level, and both of
> these devices are bars 3 or 4x longer than wide. The dot patterns I am
> seeing rotate with the device, remaining stationary when the reference
> is the rotation. IOW go put a magic marker dot on the paper for each dot
> on a distant target many feet away, then turn the device on its axis by
> some arbitrary number of degrees. The dots will rotate, and the dots can
> be re-registered by rotating the target by the same number of degrees.
>
> One side of most alu wrapping foil has a frosted finish, so internal
> reflection of that that light that does not pass thru the pinhole on its
> first pass but bounces around should result in a larger more diffuse
> pattern, The other side, being more highly polished should result in a
> more easily seen circular diffraction, and it will be interesting to see
> if in the real world, a difference can be seen. And the pinhole material
> s/b thin. A 1/32" thick piece of brass will have far larger diffraction
> than a .0005" piece of alu foil for a same sized hole.
>
> Interesting series of experiments ahead when the stuff gets here.  And
> someone mentioned using a lappy to view the results, but I'm not sure my
> old hp with a 1.4ghz turion cpu is enough "iron" to get the job done.  I
> have 640x480 cameras that can focus down to 2 or 3" in order to focus on
> the target, so it will be tried, and results reported in due time.
>
> > If the pattern of the dots stay the same as you move the laser around
> > then the "speckling" is happening on the lens and some parts of the
> > beam are flying in a shorter or longer path length. and add the all
> > add in phase.
> >
> > Even if the laser were making 40 spots and the beam as not on-axis,
> > don't bother to fix it.  You don't need to.  A 1 depress misprinted
> > beam will give only tiny error for your purpose.  Down in the 2% error
> > range. and I bet you can aim the beam by eyeball to 1/2 a degree.
> > That is good enough.
> >
> > Even if there are 40 beam hitting your target, so what?  Be happy not
> > you can take 4 measurements at once and drastically reduce the signal
> > to noise ratio.   If you are using software you are like tough an
> > autocorrelation between images and the is a peak when yu have found a
> > match.  having a complex parter makes the peak of the function more
> > steam and you have better and more accurate results.  40 points is a
> > Good Thing, as long as they don't change.
> >
> > Again, you beam is fine, it is just that most people forget the laser
> > is 'coherent" lig

Re: [Emc-users] More on bed wear fix

[Gene Heskett]

On Wednesday 26 September 2018 14:06:36 Gene Heskett wrote:

[...[

> After this mornings work, the major remaining error is the nearly 4
> thou the z screw moves endways because of a poorly fitted thrust
> bearing. Thats too much backlash to correct with lcnc. And 3x the x
> backlash. Its a bear to get off to fix the preload which does not now
> exist. But it will be a good project while I wait for the stuff I
> ordered last night. I'll have a week to entertain myself before that
> stuff arrives, by which time I'll have had a couple near beers to
> celebrate my 84th. :)

I did that today inserting short bits of 10 thou shim between the outer 
races of the twin AC ball bearings in the thrust bearing, which was 
about 5 thou too much, but the clamp nut driving the inner races has an 
excellent locking facility, so I took it up to to zero lash, and another 
5 degrees for preload. Z backlash is now about 2.0 thou.

But in double checking x, I found it up to about 4 thou, quite dependent 
on the location of the x table.  I dialed the pulley the motor drives, 
zero end play there. That leaves the screws in the end of the nut cage, 
driving a plate with a tapered bore at a 45 degree angle, compressing a 
felt ring into the screws threads to serve both as a swarf wiper, oiler 
AND the endplay adjuster in the shop made nut cage. The felts outer edge 
has a finite thickness, and the felt seems to be doing a final collapse. 
Pulling that out to get to those screws is a bigger project than I 
wanted to tackle yet today, so thats tomorrows chore. I /think/ they are 
on the back face of the nut cage, so uncovering the rear face of the 
well covered tunnel that screw turns in, might let me get to them w/o a 
full disassembly of the carriage.

I was attacked on the phone by a phisher today, so stopped the card and 
got a new one. I'll see if between the fuzz and the banks security they 
can stop him before he hurts somebody. If I find him first, the fuzz 
won't have to worry. Like Marion Morrison (aka John Wayne) once said, 
stupid should hurt. But not for long...

-- 
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] bash & . ./scripts/rip-environment, moved directory?

[Nicklas Karlsson]

On Thu, 27 Sep 2018 19:00:00 +0200
theman whosoldtheworld  wrote:

> I try to run this simple script:
> 
> #!/bin/sh
> 
> cd '/home/bmeccoffice/linuxcnc-dev'
> 
> . ./scripts/rip-environment
> 
> linuxcnc
> but in terminal I get an error about . ./ obviusly in a bash script is not
> accept these command (. space .)  there are other way to write it?

No but if files are moved to other directory I think it does not work.


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Re: [Emc-users] bash & . ./scripts/rip-environment

[Mark Wendt]

Backing up just a bit here are you running an executable or just sourcing
anot environment file? If the latter you should have something like this:

'source /path/to/file/file_name'

Mark

On Thu, Sep 27, 2018, 13:02 theman whosoldtheworld 
wrote:

> I try to run this simple script:
>
> #!/bin/sh
>
> cd '/home/bmeccoffice/linuxcnc-dev'
>
> . ./scripts/rip-environment
>
> linuxcnc
> but in terminal I get an error about . ./ obviusly in a bash script is not
> accept these command (. space .)  there are other way to write it?
>
> regards
> bkt
>
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Re: [Emc-users] bash & . ./scripts/rip-environment

[Mark Wendt]

Easiest way is to type the entire path to the executable. Since the script
is being run in a non-interactive mode that's probably the best solution.

Mark

On Thu, Sep 27, 2018, 13:02 theman whosoldtheworld 
wrote:

> I try to run this simple script:
>
> #!/bin/sh
>
> cd '/home/bmeccoffice/linuxcnc-dev'
>
> . ./scripts/rip-environment
>
> linuxcnc
> but in terminal I get an error about . ./ obviusly in a bash script is not
> accept these command (. space .)  there are other way to write it?
>
> regards
> bkt
>
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[Emc-users] bash & . ./scripts/rip-environment

[theman whosoldtheworld]

I try to run this simple script:

#!/bin/sh

cd '/home/bmeccoffice/linuxcnc-dev'

. ./scripts/rip-environment

linuxcnc
but in terminal I get an error about . ./ obviusly in a bash script is not
accept these command (. space .)  there are other way to write it?

regards
bkt

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Re: [Emc-users] LinuxCNC 2.7 manual typo

[andy pugh]

On Thu, 27 Sep 2018 at 14:38, Luka Kavčič  wrote:

> "The location at which the home switch trips or releases *reletive*"

Fixed

-- 
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] LinuxCNC 2.7 manual typo

[Luka Kavčič]

 Greetings!

There is a typo in LinuxCNC V2.7.14-36-g5674832, 2018-09-22 on page 40.
Specifically at the home switch location point

"The location at which the home switch trips or releases *reletive*"



With regards,

Luka

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