[Coco] Gene Hesket, drop me an e-mail!

[gene heskett]

On 9/2/22 19:52, Francis Swygert via Coco wrote:
> Nothing to do with a CoCo, but I know you're running a CNC machine on Linux. My nephew just got a CNC plasma cutter table and is having some issues with software, and I remembered you have a Linux CNC... lathe? router? His table is made by EZ Router.
>
> Frank Swygert
>   Fix-It-Frank Handyman Service
>   803-604-6548
He could probably drive it with linuxcnc, but he'll have to get pretty 
familiar with the hardware to electrical interface to pull that off. 
What sort of feedback does this router use? Could it be adapted to look 
like what
linuxcnc can work with?

Two common ways to do the control, the easiest is to use stepper motors 
stout
enough the turn the house around, then you do the math in terms of how 
many steps have been issued,
adding to the total if you turn the moor one way, subtracting if you 
turn it the other way, the total steps
times the scale gives you where the tool is. All my stuff with one 
exception works on that principle and
works well. The one exception is a clone of a Brown & Sharp indexing 
head that I control with an estate
gate motor that has a quadrature encoder in the motor. Those tell 
linuxcnc how fast and how far including direction.  It was way too much 
geardown, so its slow, takes around a minute to do a full turn. but I can
tell it to go to a certain angle and it will go there to a very small 
fraction of a degree.

One of the recent developments in motor/drivers is a 3 phase version of 
a stepper that only turns 1.2
degrees for a full step. And the motor has an encoder in it that only 
feeds to the driver. The driver
compares where the motor is to where it should be, and turns the driving 
current up with the error.
So if no load, very little error, very little current to the motor=cold 
motor. Most stepper setups run the motors hard enough they'll burn your 
hand. Only cutting the current in half if it hasn't moved for a couple 
seconds.

Only if the driver has hit max current and still can't get there, does 
it signal linuxcnc of the error, which stops linuxcnc as fast as it can 
get things stopped. You will lose the "home" of that axis because the 
driver shuts
down & needs a power cycle to re-enable. I have that machine rigged to 
turn off all power in that case, So its
pull the tool off the tool-post to get it out of harms way, restore the 
motor power by toggling the F2 key
back on,  rehome the machine, fix whatever got in the way and restart 
the job after putting the tool back on the post. I write my own gcode, 
so most errors are typo's.

What name and model is this router? Maybe its already running linuxcnc 
under the covers. Windows does
NOT have a realtime kernel, required to run one of those, linuxcnc has 
had that variation for 20+ years.

Take care & stay well Frank.

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, 1940)
If we desire respect for the law, we must first make the law respectable.
  - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>