[Dongle]

I've got myself a bit confused here, and as I now need to speak to someone with reasonably intelligent I just want to clear this up before I make a complete fool of myself (other than while hiding behind the keyboard!!!)

Is there a definitive answer to which is the x, and which is the y, carriage?!

I've been doing shed loads of research into my CNC machine, but every so often I come across someone labelling axis differently! Obviously this could have a rather disasterous effect on cutting if I get my orientations muddled

[bdillard]

Well, Dongle, one thing I have learned (if responses to my questions on this forum and others are any indication) is that really basic questions do not always have really basic answers. :-)

Cartesian coordinate systems can be either "left" or "right-handed." I have yet to see a system set up in left-handed fashion.

http://en.wikipedia.org/wiki/Cartesi...rdinate_system

I'm currently building my first router table. I have a friend who wants to exchange his x and y axes, but he wasn't able to verbalize his rationale, and he hasn't tried it yet. I advised against it because logically it makes no sense to me, but hey, I'm new to this.
But the more I think about it the more confused I become.

[joecnc2006]

depends on how material is placed on your machine and which way you are facing your machine either from the front or the side... I treat mine fron the side in which i see many do.

Y= north/south
X= east/west

hope that helps somewhat.

[Dongle]

Thanks guys - I thought as much!

So... seeing as I'll be mostly seeing mine from the front (being the shorter length) then my x axis will be the east/west (shorter axis) and my y axis will be the north/south axis (longest)

No wonder people find this hobby a challenge to start with!!! I was assuming something like the longer (if any) would be the x, or something like that.

Cheers for the help, I can carry on designing my trucks now without worrying about these minor points

Anyone got an asprin?!!!!

[Al_The_Man]

About 400 years ago, a guy called René Descartes laid it out. And most CNC machines conform to this Cartesian coordinate system.
The confusion sometimes comes when viewing the Z axis as in a mill, because movement is defined as spindle movement, but sometimes the spindle is moved and othertimes is not capable of moving in the XY in this instance the table moves in order to achieve the same effective + and - directions. So the table moves in the opposite direction to what the Z would if it was free to move to achieve this.
Any one that has used a 'scope extensively knows that when facing the screen (work)
the Y+ is up, Y- is down, X- is left X+ is right Z is positive towards the viewer and Z- is away from the viewed direction.
So if this is premise is carried over to a mill, the axis would be viewed looking down onto the table from the front of the mill.
Now the confusion sometimes occurs on Gantry machines, as although the Z remains the same. You can operate the table from the long 'side" or the 'short' side, so this on occasion these axis can be either labled X or Y.
Al.

[Dongle]

yeah that makes sense -I'm pretty sure I'm reading it right anyway. For some reason I'm suddenly glad I decided to go 3 axis to get me started rather than 5...

[HuFlungDung]

Perhaps one criteria to keep in mind, is that you would like your machine to follow convention so far as arc directions are concerned. This would mean X+Y+ is in the upper right quadrant. I think pretty well all CAD programs follow this same convention.

It would be up to you to determine the baseline orientation of your machine. X+ is towards table right, Y+ is towards table away from you, and Z+ is from the table up.

It may seem confusing, but the tool is reckoned to do the moving, and on a gantry style machine this may be the actual case. On a bed mill, the table moves instead, but because the tool is the frame of reference, the table actually moves to the left when an X+ movement is commanded.

Most of those things can all be set up later, simply by reversing some parameters, or the motors. But you do want to keep the positive direction of all 3 axis in conventional relationship with each other.

Edit: sorry for the redundancy

[ger21]

On a router, the X axis is usually the longest axis. And on a moving gantry machine, the gantry would always move along the X axis, even if the Y axis (gantry) is wider. Reason being that on a lot of gantry machines, you can route workpieces much longer than the machine along the X axis by indexing the workpiece. cut as much as you can, move the piece, keep on cutting....

I read a good explanation explaning the theory of why the X is longest somewhere online once, but don't really remember it.

[Dongle]

If the gantry always moves on the X axis, then going on earlier comments I have my x and y crossed, but as that's such a simple rule to follow I'll go with that - X is the one the gantry travels along! Will definitely go by the x+ y+ as well, want to have a common reference for you guys when it doesn't work and I start screaming for help!!

Many thanks for again for all your replies, much appreciated.

[WhiteTiger]

I read a good explanation explaning the theory of why the X is longest somewhere online once, but don't really remember it.

Harks back to Descarte's Cartesian coordinates. East/west goes all the way around the planet, while north/south goes halfway (both stop at the poles). So X is the long one following that convention.


Tiger

[ger21]

Harks back to Descarte's Cartesian coordinates. East/west goes all the way around the planet, while north/south goes halfway (both stop at the poles). So X is the long one following that convention.


Tiger

That wasn't it, but it'll work

[swarfmacdaddy]

Does anyone remember the right hand rule from high school machine shop?

[spalm]

IMHO:

In the world of printing (like a laser jet, not offset) the X and Y can flip depending on the situation. In one case you call it Portrait; in the other you call it Landscape. The X is always horizontal.

It really doesn’t matter, but it is nice to have a convention so that we all talk the same language. In my CNC world, I like to think of the X as being the lowest set of rails (which is usually the longest). This way the rails stack-up alphabetically.

Steve

[ViperTX]

Yeah, I remember the right hand rule....z is the finger pointing up.....x is the finger towards your face and y is the thumb....

[Geof]

Harks back to Descarte's Cartesian coordinates. East/west goes all the way around the planet, while north/south goes halfway (both stop at the poles). So X is the long one following that convention.


Tiger

Actually the Cartesian coordinates X and Y define a plane that touches the Earth's surface at a single, invisibly small, point and extends to infinity in both X and Y. The Z coordinate is a radial line that passes through the point and the center of the Earth.

[WhiteTiger]

Not as applied to world mapping, unless that has been redefined. The z is on the polar axis, all three are used. Two to define the section plane on which the point lies and the third to fix the plane's position.

Cartesian is cubic last I heard. Get radial, it's not classic cartesian I believe.


Tiger

[Geof]

I thought the topic was machine tool coordinate definitions not world mapping. I was always under the impression that the conventional coordinate designation, at least for vertical machining centers used for metworking, arose naturally out of the choice of quadrant III in the classical cartesian system. To me this choice seems logical because when a VMC is sent to machine zero the table is toward the operator and the tool is raised to its maximum extent. I think it would be difficult to find a commercially made metal working machine with a vertical spindle that does not follow this convention.

[WhiteTiger]

It didn't refer to machine tools 400 years ago


Tiger

[ger21]

I thought the topic was machine tool coordinate definitions not world mapping. I was always under the impression that the conventional coordinate designation, at least for vertical machining centers used for metworking, arose naturally out of the choice of quadrant III in the classical cartesian system. To me this choice seems logical because when a VMC is sent to machine zero the table is toward the operator and the tool is raised to its maximum extent. I think it would be difficult to find a commercially made metal working machine with a vertical spindle that does not follow this convention.

I think the topic was actually gantry wood routers.

[Geof]

It didn't refer to machine tools 400 years ago


Tiger

It also did not refer to wordl mapping; at least not on a global scale.