Home is where the part is?

(just a bit of feedback for Lee, when someone wants to create a new thread...wouldn't it be a bit more logical to have the button placed at the top? - I had to have a hunt about for it)

I'll probably be importing my next machine from Redsail....and cos I'm lazy, I'll ask then to prefit home switches.

Now I realise a machines's home location can be anywhere you want it to be, but is their a common approach? Here's what I'd like....

http://hostmypicture.com/images/cncmachine.jpg

My thinking here, is I normally mount the stock at the front of the table (as there it's just better to get a view of things, get access to things etc), therefore I don't really want homing to take ages (shuttling all the way to other axis extremity) & since the spindle is already gonna be doing its thing somewhere near the front of the table during its cutting cycle, homing will be quickest where my arrow is)

So would it be a reasonable request to ask the factory to fit homing switches to make the home point where my arrow is?

Comments?

If the factory fit homing switches to machines for customers them they will probably already be set up to mount them where you would like them for the American market.
My Gerber's homing switches are in that location & I was told by them that it was usual for American machines. My x & y axis are also different from the way it is usually done over here as well.

Actually, there are "several" homes! The home switches will give the Machine Origin coordinates (G53) and as you have shown, is one of the common locations. Next, you will want an offset to your working part (usually G54). For instance, on my machine G53 home is as you show and I have a permanently mounted fixture for doing PCB work. It was made and the offsets for G54 (top side of the PCB) and G55 (bottom side) have been saved to a file.
Now when doing a setup, it is a simple matter to home the machine, load the offset file and your ready to go.
But having said this, you can set it up to suit your own personal preferences. If the factory has it in one place, you can make you own offsets and away you go.

Bubba's kinda correct but really there's only 1 true HOME position and that's Machine Zero has designated by fixed switches.
All other positions are WORK offsets G54 G55 etc which have there own Zero point coordinate which is a 100% Known distance from Machine coordinate Zero.
Think of the complete machine work envelope(G53) has Machine coordinates area which has a fixed unmovable start point this can then be broke down into many individual work areas each having there own Zero start point using work offsets G54 etc.
This applies whether using offsets or not and Often G54 is the only offset used and it's zero position is the same has G53 machine zero coordinate for this reason G54 is used has default offset if no other offset is specified, so in this case G53 and G54 have the same Zero point.

On top of this there can be another Zero position known has a Local coordinate called using G52 which is a set distance from the current Work offset Zero position but won't go there has it's not often used unless using multiple fixture jigs in the same work offset.

So all this said then I'd have the HOME switches positioned to match Cartesian coordinate system relative to how your going to view the machine.
Then don't think of this Home position has WORK zero but absolute Machine zero. Work zero is any were choose on table start the cutting of the job with a known distance from MACHINE Zero.

The real beauty and point to having a 100% unmovable Home position is to use has cast iron reference point for getting back to exact WORK Zero position when job goes tits up.
The work offsets just designate a set point from Absolute(53) Machine coordinate position.

Home switches can and will save you hours of work when things go wrong but don't wreck the work. They allow you to quickly get back into exact position at any point on the work and start job again from that point.

Thanks chaps.

I always cut my part in the top right quadrant of the XY 'quadrant view' (i.e. my part is positioned in such a manner that X & Y coords are all positives)....therefore it just makes sense (to me at least) to have my machine home where I placed the red arrow on the piccie above.