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:
> > <http://www.ebay.com/itm/VL53L0X-Time-of-Flight-Distance-Sensor-Brea
> >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
-- 
"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 <http://geneslinuxbox.net:6309/gene>

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