# Where is Home XYZ000 Supposed to be located on a Mill?



## countryguy (May 9, 2014)

Gang,  I'm sitting w/ my Son and we're banging away hour after hour trying to setup Mach3 and our Mill.  Sorry in advance for all the Q's but we are trying hard here.   It's purchased used (yeah, I know I know).  But I am OK w/ sweat equity and solving others mistakes.   And there have been some doozies.  

Where is a Mill tables Machine Home (000) supposed to be?    I'm trying to load and tell Mach the home based on the switches as follows:

FROM THE FRONT OF THE MACHINE . Standing facing it. 
X is to the far Right.   (run length of 14.2")
Y has the table coming back at you to hit the limit switch (run length of 11.5") 


Thanks


----------



## Ray C (May 9, 2014)

countryguy said:


> Gang,  I'm sitting w/ my Son and we're banging away hour after hour trying to setup Mach3 and our Mill.  Sorry in advance for all the Q's but we are trying hard here.   It's purchased used (yeah, I know I know).  But I am OK w/ sweat equity and solving others mistakes.   And there have been some doozies.
> 
> Where is a Mill tables Machine Home (000) supposed to be?    I'm trying to load and tell Mach the home based on the switches as follows:
> 
> ...



Try downloading the instruction sheet I created for the PM45 mill.  It shows how to do it for that machine.  See Post 24.  http://www.hobby-machinist.com/showthread.php?t=21179

Also, there is no "standard" location for home.  It's all relative to what you want.


Ray


----------



## countryguy (May 9, 2014)

Thanks Ray.... Ever go by RayRay? LOL ;-) I found this as well on the Net. (everything there is true right) . I've seen Hood around and he's big into Mach3 and Home/Limit q's. 

WE'll I have something wrong since Mach3 indicates the wrong layout so if I can use anything I wish, then I need to appropriatly setup the softmin max..   . Moving now and resetting. 

*Hood*:
Table fully right means tool fully left in relation to work and that is X0 (Machine Coords)
Table fully towards column means tool fully towards you in relation to work piece so that is Y0
Head fully up is tool fully up and that is Z Zero.









Ray C said:


> Try downloading the instruction sheet I created for the PM45 mill. It shows how to do it for that machine. See Post 24. http://www.hobby-machinist.com/showthread.php?t=21179
> 
> Also, there is no "standard" location for home. It's all relative to what you want.
> 
> ...


----------



## JimDawson (May 9, 2014)

The way I normally set things up is to set X & Y 0 at an extreme corner of the work and Z 0 at the work top surface.  I typically use the upper right corner as you are standing in front of the machine so that all of the moves into the work are in the negative direction.  -X, the table moves right, -Y, the table moves toward the column, -Z, the quill moves down.  It keeps me from getting confused, and also allows setting to the stationary vice jaw if you are using a vice to hold the work.  When I create the G-code in the cam program, I move the part into the lower left quadrant.  There a few cases that I use the work center for 000, but not often.

As Ray stated, there is no standard location.  You just need to make sure that any move will not exceed the machine travel limits.


----------



## DMS (May 9, 2014)

As others have said, there is no "standard" location. I have mine set to roughly the middle of travel for X and Y (9x42 BPT clone), and at the top of the Z. 

Keep in mind I don't have much experience with Mach, I have only used LinuxCNC, but as far as home/limit switches, I think the following behavior is pretty common. 

On my machine, I place the home switch wherever I want, and then I tell the machine that home represents some value. I have called all of mine "0", but I could just have easily said they were 5.334". With LinuxCNC you can also tell it to go to a certain position after hitting home, so on my Z, I drop down by 0.5" after hitting the Z home because I am sharing a home and limit switch on Z.

One thing that you may not have learned yet (and the reason why the exact location doesn't matter) is that there a number of different "zero" points. What you are talking about is called the "machine zero". I never, ever (well, mostly never) use the machine zero for anything. Before machining a part I will set a relative zero on the stock by touching off. The machine will remember this point (it's relative to machine zero) even after you power down. So don't sweat the location of the home switches too much, just make sure they work reliably and everything else works out in the software.


----------



## John Hasler (May 9, 2014)

Is there a standard handedness?  Sounds like countryguy is describing a left-handed coordinate system while JimDawson is describing a right-handed one.


----------



## Ray C (May 9, 2014)

Most of the tutorials I've seen describe it as though you're looking at a map and use N, S, E, W to describe the origin of the table and/or piece coordinate system.

Most of the Mach 3 tutorials put the origin at the S-W corner of the table from the perspective of you standing in front and looking down at it.

----------------------
!-------------------                                                ! 
!--------------------!
x------------------- !

The "x" would be the table origin of a S-W coordinate system and this is how I generally do things.  In terms of the part, I tend to put the part origin on the S-W corner of a square item and use the center of a cylindrical item.  -Just my preferences but, it really makes no difference.

I have two vises on the table right now and have G55 and G56 setup at each vise and when I put a part in there, I set a local origin for the part itself.  G54 is the table home (i.e. "x") position.  Just remember when you have multiple vises to make sure that each home (wherever it may be defined) has a safe Z level to not crash into anything.

Ray


----------



## countryguy (May 9, 2014)

*COORDINATE Systems and Onward Ho' Was:  Where is Home XYZ000 Supposed to be located on a Mill?*

Thank guys!! I really appreciate this forum as the "Friendly place"     Much happier here than some others I experienced!  TIA!!!!  

That said;  
I found several options and methods.   Most work if you can get the machine and your brain to sync!  I did figure out my issues in Mach3 and am aligning just fine now on what is Table Work 000(XZ) -vs- Machine HOME and relevant offset to 000 with the Home switches!    Simply click ZERO XYZ and REGEN when I've positioned myself.     What I need are two more switches!  X++ and a Y++  I'll put Home in the middle and use this coordinate system.   the best tip of my day today was that you think in terms of TOOL MOTION.  Not table.  Kewl! 

This is a really nice website Ya'll (yes I put in Ya'll ;-)   I am from Michigan but work w/ a lot of folk from OH and KY  Anyway,  I digress! 
The Site: http://www.hsmworks.com/docs/cncbook/en/#Ch04_VMCMachineMotion

The statement: 
when working with a CNC, always think, work, and write CNC programs in terms of *tool motion*, not table motion.
For example, increasing +X coordinate values move the tool right in relation to the table (though the table actually moves left).
Likewise, increasing +Y coordinate values move the tool towards the back of the machine (the table moves towards the operator).
Increasing +Z commands move the tool up (away from the table).






Thank a Ton RC.  
So that X in this Drawing is the ToolBit location right?   This is what I have setup now.  (man I hope anyway).    I'm unsure how to really emulate the "soft limits" for X++ and Y++ now.  I have Home and zero points and a frame of reference.   I'm so close!!!   I'll read about "softl limits and what "emulation does later.  I did input G55 and a fixture loc too.  Very nice!     MAn I want a PM-45 CNC setup     I may just need to get this running smooth and sell it for one.    Those Pics and your Setup doc are awesome!    Love what your doing guys. 
JJ




Ray C said:


> Most of the tutorials I've seen describe it as though you're looking at a map and use N, S, E, W to describe the origin of the table and/or piece coordinate system.
> 
> Most of the Mach 3 tutorials put the origin at the S-W corner of the table from the perspective of you standing in front and looking down at it.
> 
> ...


----------



## Ray C (May 9, 2014)

*Re: COORDINATE Systems and Onward Ho' Was:  Where is Home XYZ000 Supposed to be located on a Mill?*



countryguy said:


> Thank guys!! I really appreciate this forum as the "Friendly place"     Much happier here than some others I experienced!  TIA!!!!
> 
> That said;
> I found several options and methods.   Most work if you can get the machine and your brain to sync!  I did figure out my issues in Mach3 and am aligning just fine now on what is Table Work 000(XZ) -vs- Machine HOME and relevant offset to 000 with the Home switches!    Simply click ZERO XYZ and REGEN when I've positioned myself.     What I need are two more switches!  X++ and a Y++  I'll put Home in the middle and use this coordinate system.   the best tip of my day today was that you think in terms of TOOL MOTION.  Not table.  Kewl!
> ...




Thanks for the kind words...

Yes the 'X' is the home location for the table.  This is usually called "Machine Home".  It moves to the S-W corner and the spindle moves to the highest location as defined by the home switches.

If you read that instruction sheet on homing, it should describe how to set soft limits.  The values you enter will need to be commensurate with your table dimensions.  Does your machine have limit switches as well as home switches?  If you don't have limit switches, you need to rely on properly defined soft limits.  FWIW,  I use soft limits that are defined about 1/8" short of my physical limit switches as, when you physically trigger a limit switch, it throws a reset and Mach stops all operations.  When hitting a soft limit, Mach stops but, does not need to get fully reset to start-up again.


Ray


----------



## JimDawson (May 9, 2014)

*Re: COORDINATE Systems and Onward Ho' Was:  Where is Home XYZ000 Supposed to be located on a Mill?*



countryguy said:


> The statement:
> when working with a CNC, always think, work, and write CNC programs in terms of *tool motion*, not table motion.
> For example, increasing +X coordinate values move the tool right in relation to the table (though the table actually moves left).
> Likewise, increasing +Y coordinate values move the tool towards the back of the machine (the table moves towards the operator).
> Increasing +Z commands move the tool up (away from the table).



Looks like I have been doing it backwards all this time, but I guess I'm not going to change now.:thinking:  I might have to if I ever decide to start selling my controller software.


----------



## John Hasler (May 9, 2014)

*Re: COORDINATE Systems and Onward Ho' Was:  Where is Home XYZ000 Supposed to be located on a Mill?*



JimDawson said:


> Looks like I have been doing it backwards all this time, but I guess I'm not going to change now.:thinking:  I might have to if I ever decide to start selling my controller software.



I don't know CNC but I don't see how you've got it backwards.  "-X table moves right" equals "+X tool moves right".  "-Y table moves toward column" equals "+Y tool moves toward column".  "-Z tool moves down" equals "+Z tool moves up".  It's a right-handed coordinate system with +Z up into the spindle and X along the length of the table.  From my admittedly brief and incomplete research that is as near as it gets to an industry standard.


----------



## JimDawson (May 9, 2014)

*Re: COORDINATE Systems and Onward Ho' Was:  Where is Home XYZ000 Supposed to be located on a Mill?*



John Hasler said:


> I don't know CNC but I don't see how you've got it backwards.  "-X table moves right" equals "+X tool moves right".  "-Y table moves toward column" equals "+Y tool moves toward column".  "-Z tool moves down" equals "+Z tool moves up".  It's a right-handed coordinate system with +Z up into the spindle and X along the length of the table.  From my admittedly brief and incomplete research that is as near as it gets to an industry standard.



I guess you're right John,  I was looking at the picture as the table movement rather than the tool.  Glad you pointed that out.


----------



## Ray C (May 9, 2014)

*Re: COORDINATE Systems and Onward Ho' Was:  Where is Home XYZ000 Supposed to be located on a Mill?*



John Hasler said:


> I don't know CNC but I don't see how you've got it backwards.  "-X table moves right" equals "+X tool moves right".  "-Y table moves toward column" equals "+Y tool moves toward column".  "-Z tool moves down" equals "+Z tool moves up".  It's a right-handed coordinate system with +Z up into the spindle and X along the length of the table.  From my admittedly brief and incomplete research that is as near as it gets to an industry standard.



This is correct.  BTW:  The conventions of X+, Y+, Z+ etc are indeed standard and not just so in CNC but in all milling.   There is no standard convention for home positions though and Machine Home can be set anywhere you want it.  There might be some brands of equipment that come preconfigured in a specific location -but it doesn't have to.  And just to really make things crazy, I'm now getting ready to start doing some 4th dimension (rotary) cutting and things can get confusing.  Some machines (like the Hurco I'm looking at) have built-in trunnion tables (5 dimensions) with finite ranges of motion.  In those cases, the directions of movement have static definitions.  My machine has a 4th axis that can be located in different places and I find myself triple-checking my strategies as I proceed. 

Similar confusion takes place when folks learn to thread both LH and RH threads and furthermore, need to make ID and OD threads and/or do so with a conventional bit position or opposite-cut position.  This can lead to confusion at first but, after a while, you'll find it comes second-nature. 


Ray


----------



## DMS (May 10, 2014)

Something to point out, the tool vs table movement issue is something that takes a bit of getting used to (took me a couple months to be honest). It especially tricky while jogging with the jog rate turned way up. Keep the jog speed low while you are learning, otherwise, it is very easy to go the wrong way, and snap a small cutter before you can stop or reverse direction.


----------



## Craig_J (May 11, 2014)

One of the posts asks why the predominant convention is used (zero at the lower left corner of the part).  I believe that this is because this is a drafting standard.  The convention is to create a datum from which all other dimensions are measured.  Most commonly this is the lower left corner of the part for a 2D drawing.    So when putting the part on the mill, the convention was carried over.  It doesn't have to be that way.

For most of us with milling vises with the back jaw fixed and the  moveable jaw in front, this can be awkward, because you have to touch off the zero point every time you reinsert a new part.    One way to avoid that is to index off the back, fixed jaw.  But if you index off the back left edge, the dimensions are not to the drawing's datum.  So you can make a case for indexing off the back right edge and reversing the sign of all X and y movement.  Or maybe we should all go out and buy a new $600 milling vise with the fixed jaw in front...

Re the drafting convention, interesting bit of history:  when I was in college, I signed up for a work-study program at the local bomb factory.  Now I was an aspiring electrical engineer, but had to wait  almost 3 months for the security clearance, sitting in an office outside the secured area (where all the interesting work was being done).  For make work, they gave me a programmed instruction course on True Position Dimensioning.  In TP dimensioning,  all features are given a location and tolerance w.r.t. the datum.  The text explained that this was to eliminate build-up of tolerances when features were dimension in a chain, like a series of holes.  Cadcam has rendered much of this less important.  Re getting the security clearance:  the FBI finally interviewed me (a bearded kid from Berkeley ca. 1965) and asked me a lot of mindless questions, like "What magazines did your reference (my godfather) read when he was in college...(15 years before I was born!)  This was back in the day of J Edgar  Hoover and all of the FBI types had crew cuts and wore black suits with narrow black ties.  It dragged on and on, no clearance, until by happenstance I was invited to a faculty party and introduced to the Dean of Engineering, who asked what I was studying.  When he heard about my situation, he said he would contact the Atomic Energy Commission rep on campus...lo and behold, 2 days later my clearance was granted! I eventually did get to do EE work at the  bomb factory, which was interesting and educational.

Craig


----------



## John Hasler (May 11, 2014)

What convention is used for horizontal mills?  Is +Z still into the spindle?


----------



## bloomingtonmike (May 11, 2014)

John Hasler said:


> What convention is used for horizontal mills?  Is +Z still into the spindle?



Yes, Up.

Z+ - Tool moves up/into spindle.
X+ - table moves left/west
Y+ - Table moves away from you/North


----------



## John Hasler (May 11, 2014)

bloomingtonmike said:


> Yes, Up.
> 
> Z+ - Tool moves up/into spindle.



On a horizontal mill up is perpendicular to the spindle.



> X+ - table moves left/west



Moving the tool right.  Ok.



> Y+ - Table moves away from you/North




Moving the tool toward me and making your coordinate system left-handed.


----------



## papermaker (May 11, 2014)

One thing to remember when setting up Mach 3The computer looks at the machine just opposite of how we see it.  Picture it like your standing behind the Mill. It helps you to make a drawing of X +/-, Y +/- and Z +/-. Homing is nice to have but Once you get it set it's not really anything you need to mess with. Once you do get the axis homed you never need to touch it again.
There is a video on Youtube that explains how to set X, Y  and Z to home. I seems complicated but it's not!


----------

