Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Gene Heskett
On Thursday 10 August 2017 00:01:38 Kirk Wallace wrote:

> On 08/09/2017 11:33 AM, Dan Bloomquist wrote:
>
> ... snip
>
> > You made me look. :) My wheels have no markings so taped a piece of
> > paper and made pencil mark. I mounted a .0001" dial indicator. I
> > can't see any backlash, just my wheel is sloppy. The wheel is 6 1/2"
> > in diameter and to get a .001" move, the outer rim moves ~.075".
> > This is an integrating solution to an accurate setup.
>
> ... snip
>
> I'll try to remember to take pictures of my dial setup and post them.
> Each dial is housed in the box where the motor to screw coupler is.
> There is a window on the box for viewing the dial. One problem I have
> is that the stepper drivers are setup for quarter stepping so I have
> 0.00025" jumps. I can see this on the dials well enough, but the DRO
> display increments between these steps and I feel compelled to work
> out the DRO value at the time the last step trips, which wastes a bit
> of time. I replaced the x axis driver with an MA860H which has
> micro-stepping. The MA860H doesn't sing like the old drives and it can
> use twice the voltage. I'd like to change out the other axes when I
> can get around to it.

The MA860H I have has a rather poor step vs current mapping, I cannot 
reliably feel the 8th step in a /8 setup.  Adjusting the current up or 
down one notch should effect it if its iron saturation, but that has no 
detectable effect.  I've an auto tech drive of the same voltage rating 
and a hair more current I've been intending to swap it out for, but I'll 
likely put a 960 oz motor in at the same time as that one is the 1600 oz 
that was originally on the mills heavy Z.  I took it off because the 
missing step caused stalls at anything over 26 ipm on the mill.  Its 
geared down some on the lathe, but the lack of dead weight lets it move 
the z almost 90 ipm. The 960 will probably do 150+ ipm.  Overkill IMO 
when x is stuck at less than 40.

Cheers, Gene Heskett
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Kirk Wallace

On 08/09/2017 11:33 AM, Dan Bloomquist wrote:

... snip


You made me look. :) My wheels have no markings so taped a piece of
paper and made pencil mark. I mounted a .0001" dial indicator. I can't
see any backlash, just my wheel is sloppy. The wheel is 6 1/2" in
diameter and to get a .001" move, the outer rim moves ~.075". This is an
integrating solution to an accurate setup.


... snip

I'll try to remember to take pictures of my dial setup and post them. 
Each dial is housed in the box where the motor to screw coupler is. 
There is a window on the box for viewing the dial. One problem I have is 
that the stepper drivers are setup for quarter stepping so I have 
0.00025" jumps. I can see this on the dials well enough, but the DRO 
display increments between these steps and I feel compelled to work out 
the DRO value at the time the last step trips, which wastes a bit of 
time. I replaced the x axis driver with an MA860H which has 
micro-stepping. The MA860H doesn't sing like the old drives and it can 
use twice the voltage. I'd like to change out the other axes when I can 
get around to it.



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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Gene Heskett
On Wednesday 09 August 2017 21:26:33 Jon Elson wrote:

> On 08/09/2017 10:38 AM, Dan Bloomquist wrote:
> > I know how accurate this thing is. The idea is that I can
> > start up without hunting switches.
>
> Why is that such a big deal?  LinuxCNC now can do all axes
> with the press of ONE button!
> I really don't see the need for exotic and possibly finicky
> sensors when a VERY simple switch will actually do the job
> BETTER!  A lot of people who don't have encoder index to
> refine the accuracy report simple microswitches have a
> repeatability of about 0.003"
>
> Jon
>
I think I am beating that with dollar a copy on ebay microswitches, Jon.  
A thou or so.  Which is about what I can measure is absolute terms. Z 
repeatability is better than the backlash on the Sheldon.

Cheers, Gene Heskett
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Jon Elson

On 08/09/2017 12:53 PM, Dan Bloomquist wrote:
Ok, so maybe I'm over thinking this. So I should just 
mount switches in the centers, make sure I'm jogged close 
to a known side on start up, and just home on them.
Yup, that's how it is set up on my Bridgeport.  The X trip 
bar is in the center, and the Z is near full up.  The Y is 
at one end, but the Y travel is pretty short, anyway.



So now I'll have to work out switches that are repeatable 
to 5 microns. I'd think focused optical if you could keep 
it clean would be the way to go, I don't know.


Do you have encoders on this machine, or is it step-driven?  
No sense in making the home switches any more accurate than 
an encoder count or distance of a step pulse.  If your 
encoders have an index pulse, then you can have it refine 
the home position to the encoder index pulse after finding 
the home switch.  That is how my machine works.


5 um repeatable switches might be tricky, but 5 um encoder 
counts are simple.


Jon

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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Jon Elson

On 08/09/2017 10:38 AM, Dan Bloomquist wrote:


I know how accurate this thing is. The idea is that I can 
start up without hunting switches.
Why is that such a big deal?  LinuxCNC now can do all axes 
with the press of ONE button!
I really don't see the need for exotic and possibly finicky 
sensors when a VERY simple switch will actually do the job
BETTER!  A lot of people who don't have encoder index to 
refine the accuracy report simple microswitches have a 
repeatability of about 0.003"


Jon

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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Stuart Stevenson
Hi,
What is your mill?
Does it have stepper motors or servo motors?
What position feedback (ie. encoder, scale...), if any, do you have?

thanks
Stuart


On Wed, Aug 9, 2017 at 1:41 PM, Dan Bloomquist  wrote:

> andy pugh wrote:
>
>> On 9 August 2017 at 18:40, Kirk Wallace 
>> wrote:
>>
>> For an absolute position sensor, I'm thinking that a section of tape from
>>> a
>>> tape measure glued to the slide would work well in conjunction with a
>>> screw
>>> dial or pointer.
>>>
>> Maybe something like I found on eBay.
>> http://www.ebay.co.uk/itm/Renshaw-Reader-Head-/332301624409
>>
>
>  -with-rgs-linear-scale--6443>
>  .3 um error, that is impressive.
>
> Best, Dan.
>
>
>
> 
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Dan Bloomquist

andy pugh wrote:

On 9 August 2017 at 18:40, Kirk Wallace  wrote:


For an absolute position sensor, I'm thinking that a section of tape from a
tape measure glued to the slide would work well in conjunction with a screw
dial or pointer.

Maybe something like I found on eBay.
http://www.ebay.co.uk/itm/Renshaw-Reader-Head-/332301624409



 .3 um error, that is impressive.

Best, Dan.


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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Dan Bloomquist

Kirk Wallace wrote:

On 08/09/2017 10:07 AM, Chris Albertson wrote:

One use I can think of for a low precision sensor is that you should be
able to home faster.   The motor can run at full speed until it gets 
close
then slow just before it hits a mechanical switch.   For this use 
case 10%

error is good enough.


My Shizuoka mill doesn't have home switches, but does have dials on 
the ball screws. I put a pieces of tape on each axis slide which I use 
to jog to get close to home. I then fine jog to zero the dial. I try 
to jog from the same direction every time so that backlash is not an 
issue. I can home within 0.0005" without much effort.


For an absolute position sensor, I'm thinking that a section of tape 
from a tape measure glued to the slide would work well in conjunction 
with a screw dial or pointer.




Hi Kirk,
You made me look. :) My wheels have no markings so taped a piece of 
paper and made pencil mark. I mounted a .0001" dial indicator. I can't 
see any backlash, just my wheel is sloppy. The wheel is 6 1/2" in 
diameter and to get a .001" move, the outer rim moves ~.075". This is an 
integrating solution to an accurate setup.


Thanks, Dan.


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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread andy pugh
On 9 August 2017 at 18:40, Kirk Wallace  wrote:

> For an absolute position sensor, I'm thinking that a section of tape from a
> tape measure glued to the slide would work well in conjunction with a screw
> dial or pointer.

Maybe something like I found on eBay.
http://www.ebay.co.uk/itm/Renshaw-Reader-Head-/332301624409

I don't have the tape, but that's the cheap part.
I have noticed that "Renshaw" parts are much cheaper than the
equivalent "Renishaw" on eBay :-)

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designed for the especial use of mechanical geniuses, daredevils and
lunatics."
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Dan Bloomquist
Ok, so maybe I'm over thinking this. So I should just mount switches in 
the centers, make sure I'm jogged close to a known side on start up, and 
just home on them. I don't want to have to bounce off the limits, my X 
is almost a half a meter away from the center. (35" between limits). And 
I keep my vise usually bolted on the left side... The quill, yea, as 
putting a switch in there would be a challenge and I've set the 'home' 
at -1" from the limit. And because I'll most often change tools in a 
collet touching off the Z will happen. I'm slowly buying NBTB 30 tool 
holders, I have an Erickson quick change.


So now I'll have to work out switches that are repeatable to 5 microns. 
I'd think focused optical if you could keep it clean would be the way to 
go, I don't know.


Thanks, Dan.


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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Kirk Wallace

On 08/09/2017 10:07 AM, Chris Albertson wrote:

One use I can think of for a low precision sensor is that you should be
able to home faster.   The motor can run at full speed until it gets close
then slow just before it hits a mechanical switch.   For this use case 10%
error is good enough.


My Shizuoka mill doesn't have home switches, but does have dials on the 
ball screws. I put a pieces of tape on each axis slide which I use to 
jog to get close to home. I then fine jog to zero the dial. I try to jog 
from the same direction every time so that backlash is not an issue. I 
can home within 0.0005" without much effort.


For an absolute position sensor, I'm thinking that a section of tape 
from a tape measure glued to the slide would work well in conjunction 
with a screw dial or pointer.



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http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/

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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Todd Zuercher
Most of the machines I configure, I normally set them up to park close to the 
home switch, so that search times are relatively short.  And on the occasion 
that it isn't, it is usually no big deal to manually jog the machine close 
before beginning the homing sequence.  It is also why the homing sequence has 
two speeds.  With the right switch configuration, the machine should be able to 
search out the home switch at it's fastest speed, then use the latch velocity 
to precisely locate the home position (either using the switch or the index 
pulse of the encoder.) 

- Original Message -
From: "Chris Albertson" <albertson.ch...@gmail.com>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Sent: Wednesday, August 9, 2017 1:07:43 PM
Subject: Re: [Emc-users] Using laser time of flight sensor to home mill

One use I can think of for a low precision sensor is that you should be
able to home faster.   The motor can run at full speed until it gets close
then slow just before it hits a mechanical switch.   For this use case 10%
error is good enough.

On Wed, Aug 9, 2017 at 9:40 AM, Stuart Stevenson <stus...@gmail.com> wrote:

> Hi,
>
> Positioning the laser with magnets seems like an invitation to disaster.
> The laser WILL get bumped or jiggled out of position. Hopefully, the out of
> position would result in the machine not moving instead of moving to the
> wrong position.
>
> Using the laser to establish rough position (therefore eliminating  the
> need for a limit switch) to allow homing from the startup position seems
> "reasonable" if you can determine the laser position is repeatable enough
> to catch the encoder index mark on the correct rotation.
>
> To me, if you plan to home the machine, this sounds like a solution in
> search of a problem although I don't know the complexity of installing
> limit switches.
>
> thanks
> Stuart
> 
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Chris Albertson
One use I can think of for a low precision sensor is that you should be
able to home faster.   The motor can run at full speed until it gets close
then slow just before it hits a mechanical switch.   For this use case 10%
error is good enough.

On Wed, Aug 9, 2017 at 9:40 AM, Stuart Stevenson  wrote:

> Hi,
>
> Positioning the laser with magnets seems like an invitation to disaster.
> The laser WILL get bumped or jiggled out of position. Hopefully, the out of
> position would result in the machine not moving instead of moving to the
> wrong position.
>
> Using the laser to establish rough position (therefore eliminating  the
> need for a limit switch) to allow homing from the startup position seems
> "reasonable" if you can determine the laser position is repeatable enough
> to catch the encoder index mark on the correct rotation.
>
> To me, if you plan to home the machine, this sounds like a solution in
> search of a problem although I don't know the complexity of installing
> limit switches.
>
> thanks
> Stuart
> 
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Stuart Stevenson
Hi,

Positioning the laser with magnets seems like an invitation to disaster.
The laser WILL get bumped or jiggled out of position. Hopefully, the out of
position would result in the machine not moving instead of moving to the
wrong position.

Using the laser to establish rough position (therefore eliminating  the
need for a limit switch) to allow homing from the startup position seems
"reasonable" if you can determine the laser position is repeatable enough
to catch the encoder index mark on the correct rotation.

To me, if you plan to home the machine, this sounds like a solution in
search of a problem although I don't know the complexity of installing
limit switches.

thanks
Stuart
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Todd Zuercher
Homing to a switch (it is an automatic probing routine.) is generally a lot 
faster and more accurate, than trying to manually touch off on a work piece.  
Granted sometimes manually touching off on a work piece is nessisary.  But when 
it isn't or when you have a power loss, or other mishap that could cause 
Linuxcnc loose position, having the ability to restart accurately is well worth 
the small effort it takes to add a few switches.

- Original Message -
From: "Dan Bloomquist" <z...@lakeweb.net>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Sent: Wednesday, August 9, 2017 11:38:28 AM
Subject: Re: [Emc-users] Using laser time of flight sensor to home mill

Dan Bloomquist wrote:
>
> So it occurred to me to us a laser range finder. Then lcnc would know 
> where the table is without having to move on boot. It does not have to 
> be accurate like to mm as I probably never have to mill to the limit 
> switches, and even then
>
> <http://www.ebay.com/itm/VL53L0X-Time-of-Flight-Distance-Sensor-Breakout-GY-VL53L0XV2-Module-for-Arduino-/201718280643>
>  
>
>

Hi All,
I know how accurate this thing is. The idea is that I can start up 
without hunting switches. Then when it is time to work I would touch off 
if I needed to. I just milled my first real thing and learned a lot 
about machining. I'm very new at machining, CAD, CAM, CNC. This is what 
I made...

<http://a360.co/2u8KhSq>

What I ran into was, "..movement will exceed" errors if I did not make 
sure I started up with the machine in the right place. If I started up, 
moved to the right places and g92 my work, the software limits could get 
hit even if the mill was fine.

The sensors could get me inside the soft limits close enough that I 
still would not hit the hard limit switches. That is my goal.

Best, Dan.


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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Dan Bloomquist

Dan Bloomquist wrote:


So it occurred to me to us a laser range finder. Then lcnc would know 
where the table is without having to move on boot. It does not have to 
be accurate like to mm as I probably never have to mill to the limit 
switches, and even then


 





Hi All,
I know how accurate this thing is. The idea is that I can start up 
without hunting switches. Then when it is time to work I would touch off 
if I needed to. I just milled my first real thing and learned a lot 
about machining. I'm very new at machining, CAD, CAM, CNC. This is what 
I made...




What I ran into was, "..movement will exceed" errors if I did not make 
sure I started up with the machine in the right place. If I started up, 
moved to the right places and g92 my work, the software limits could get 
hit even if the mill was fine.


The sensors could get me inside the soft limits close enough that I 
still would not hit the hard limit switches. That is my goal.


Best, Dan.


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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread Mark

On 08/08/2017 09:42 PM, Dan Bloomquist wrote:
I have not set homing up on my mill yet, I've been mulling it over. A 
switch is not satisfying unless there is a way to keep from hunting 
for it, can't imagine...


So it occurred to me to us a laser range finder. Then lcnc would know 
where the table is without having to move on boot. It does not have to 
be accurate like to mm as I probably never have to mill to the limit 
switches, and even then


So I started to look around out there, this is amazing for the price:
 



I would not have to drill or bond the hardware, it is so light that a 
microwave magnet to hold it would be overkill. Has any one done this 
yet? Or am I missing something fundamental that makes it a bad idea?


Thanks, Dan.


Can you live with 1 mm resolution at 2 meters?  And that's plus or minus 
10%.


Mark

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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-09 Thread andy pugh
On 9 August 2017 at 02:42, Dan Bloomquist  wrote:

> am I missing something fundamental that makes it a bad idea?

If you never need to re-start a job after the machine has shut down
then I think that it could be made to work.

The development branch of LinuxCNC has support for absolute encoders for homing.
What interface hardware are you using? There is a bit-banged SPI HAL
component for temperature that could be easily made to work with these
sensors.
https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/components/max31855.comp

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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-08 Thread Chris Albertson
The sensors are about as accurate as cloth tape measure.   So if you don't
mind a home switch that gets you to within about 1/8 inch of where you need
to be use it.

They work really well for some kinds of automation and measuring the level
of liquid in a tank.

Light moves at about one foot per nanosecond  So if you want to measure
distance by time of flight and you want an uncertainty of distance measured
to be about 0.1 inch you need to measure time to about 10 pico seconds.
THAT is about the best you can do outside of a large institutional lab.

The sensors are very useful.  I want one or more of them to place on a
robot "hand" so it can measure distance to an object it is trying to grasp.
  The sensor is ideal for this but NOT for machine shop accuracy.

On Tue, Aug 8, 2017 at 6:42 PM, Dan Bloomquist  wrote:

> I have not set homing up on my mill yet, I've been mulling it over. A
> switch is not satisfying unless there is a way to keep from hunting for it,
> can't imagine...
>
> So it occurred to me to us a laser range finder. Then lcnc would know
> where the table is without having to move on boot. It does not have to be
> accurate like to mm as I probably never have to mill to the limit switches,
> and even then
>
> So I started to look around out there, this is amazing for the price:
>  Sensor-Breakout-GY-VL53L0XV2-Module-for-Arduino-/201718280643>
>
> I would not have to drill or bond the hardware, it is so light that a
> microwave magnet to hold it would be overkill. Has any one done this yet?
> Or am I missing something fundamental that makes it a bad idea?
>
> Thanks, Dan.
>
> 
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-08 Thread Przemek Klosowski
On Tue, Aug 8, 2017 at 9:42 PM, Dan Bloomquist  wrote:

> I have not set homing up on my mill yet, I've been mulling it over. A
> switch is not satisfying unless there is a way to keep from hunting for it,
> can't imagine...
>
> So it occurred to me to us a laser range finder. Then lcnc would know
> where the table is without having to move on boot. It does not have to be
> accurate like to mm as I probably never have to mill to the limit switches,
> and even then
>
> So I started to look around out there, this is amazing for the price:
>  Sensor-Breakout-GY-VL53L0XV2-Module-for-Arduino-/201718280643>


THey claim 1mm accuracy in measuring light time of flight. I doubt that: it
would require measuring time with a 3 picosecond accuracy, in other words
requiring ticks of a 300 GHz clock. I am sure they do some sort of phase
measurement, which is by definition sloppy, which is why they apparently
claim 10% accuracy.
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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-08 Thread Gene Heskett
On Tuesday 08 August 2017 21:52:35 Jon Elson wrote:

> On 08/08/2017 08:42 PM, Dan Bloomquist wrote:
> > I have not set homing up on my mill yet, I've been mulling
> > it over. A switch is not satisfying unless there is a way
> > to keep from hunting for it, can't imagine...
>
> If you have encoders with index, that can set the home
> position to an exact encoder count, there's no sense
> in resolving finer than that.  This allows you to align the
> work coordinates one day, shut down and then come back the
> next day and home the machine, and have as accurate an
> alignment to the part or fixture as the previous day.
>
> > So it occurred to me to us a laser range finder. Then lcnc
> > would know where the table is without having to move on
> > boot. It does not have to be accurate like to mm as I
> > probably never have to mill to the limit switches, and
> > even then
> >
> > So I started to look around out there, this is amazing for
> > the price:
> >  >kout-GY-VL53L0XV2-Module-for-Arduino-/201718280643>
>
> 10% of range guaranteed?  Hmmm, I am NOT impressed by the
> specs. So, from a foot away, they guarantee you can resolve
> an inch!  The mirror would eventually get dirty and result
> in reduced accuracy, too.
>
> Jon
>
10%? Not at all usefull.  That sort of accuracy will cost one broken 
tooling at >$20 a copy. I'm using  ebay sourced microswitches at about a 
buck a copy. Doesn't sound like much, but on a dry circuit, which the 
homeing circuits are, milliamp or so, I seem to be able to get .001" 
repeatable accuracy. Some might not think thats good, but its certainly 
close enough for the stuff I do.  And in 3 years, I have had no 
failures.  Zero.

Cheers, Gene Heskett
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Genes Web page 

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Re: [Emc-users] Using laser time of flight sensor to home mill

2017-08-08 Thread Jon Elson

On 08/08/2017 08:42 PM, Dan Bloomquist wrote:
I have not set homing up on my mill yet, I've been mulling 
it over. A switch is not satisfying unless there is a way 
to keep from hunting for it, can't imagine...


If you have encoders with index, that can set the home 
position to an exact encoder count, there's no sense
in resolving finer than that.  This allows you to align the 
work coordinates one day, shut down and then come back the 
next day and home the machine, and have as accurate an 
alignment to the part or fixture as the previous day.
So it occurred to me to us a laser range finder. Then lcnc 
would know where the table is without having to move on 
boot. It does not have to be accurate like to mm as I 
probably never have to mill to the limit switches, and 
even then


So I started to look around out there, this is amazing for 
the price:
 



10% of range guaranteed?  Hmmm, I am NOT impressed by the 
specs. So, from a foot away, they guarantee you can resolve 
an inch!  The mirror would eventually get dirty and result 
in reduced accuracy, too.


Jon

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