Re: Newbie has some questions

[Till Franitza <till.franitza-at-isw.uni-stuttgart.de>]

"Dean L.Hedin" wrote:
> 
> Hello,
> 
> I am approaching completion of my first 3-axis router table
> and I have a few questions regarding the setup for usage
> with EMC.
> 
> Limit/Home Switches:
> 
> The docs that I have read indicate that the limit switches
> are all wired in parallel.   Am I correct in assuming then that
> EMC will only know that a limit has been hit but will not know
> which limit was hit?
> 

Tills answer: This is correct.

> Likewise, the home switches,  if they are all wired in parallel
> then how will EMC know that all three have been closed
> to determine that the home position has been reached?
> 

Tills answer: Each switch that is hit will (must) be released
afterwards. there must be a strategy. A motor that didnt move cannot be
the one that hit the homeswitch. So the homings must proceed in order,
not all at the same time. 

> Does EMC move towards home one axis at a time checking for
> closures and then back off that axis until a switch opens and then
> attempts the the same on another axis (until it reaches home)?
> 

Tills answer: Yes!

> Coordinate System/Motor direction:
> 
> I've seen an earlier post regarding how the coordinate sytem
> is layed out.  Sounds like a standard "right_handed" xyz coordinate
> system is required.  This being the case, are there options in the
> configuration to alter the sense of direction for the stepper motors
> so that I may achieve proper direction for the actual orientation of the
> motors on my machine?
> 

Tills answer: yes, in the .ini-file you can choose an output scale for
each motor. If the scale is negative, the motor moves backward from what
it did before..

> Cutting Speed
> 
> My setup is rather simple, using stardard threaded rod for the lead screws,
> and I want to keep cutting speeds low to avoid loosing steps.  If EMC is
> interperting a g-code file that specifies a given feed speed, will it know to
> "truncate" the feed speed for my setup?

Tills answer: You can define maximum velocity for the trajectory in the
traj-section and maximal velocities for the drives in the axis section.
I am not sure if the speed is clipped or you get an error. Both could
make sense. In any case it affects the max speed that can be set in
manual mode.
> 
> Probing:
> 
> It sounds like the probing feature is kinda new.  What I would like to
> have is some kind of dialog that asks me for a range to probe through
> (X,Y,Z),  a resolution to probe at, and the dimensions of an unworked piece
> that will ultimately be machined.  I let it run, come back and I am left with
> a usable fragment of G-code.
> 
> I suspect this probing feature does not yet do all of this.  This is OK, I am
> a pretty good Linux C & C++ programmer.   I feel confident that I can write
> a piece of code that can do this.  Where do I start?  What does the probing
> feature do at this point in time?
> 

Tills answer: I do not know but suppose you are right.

> I intend to use an led/photo transitor pair for the probe switch.  I will
> stradle these across a small teloscopic pair of brass tubes with proper
> holes to interupt the light.  I will attach a piece of silicon rubber to the
> end of this that is the shape of the bit.  Sound good?
>
Tills answer: Sounds interesting. 
 
> I am sure many of these questions have been asked before.  Any
> help much appreciated.
> 
> Dean

Good luck with it!

Till