Machine coordinates and homing.

[X-man]

OK, because its different from Mach3.

Machine coordinates:

Jog machine to extreme left on x axis and y to extreme inward position (nearest to z axis) as you look at machine and z to top of travel. Press machine coordinates and the zero all DRO's (I may need to turn off soft limits to get here I know). Do i need to do anything else at this point except press the machine coordinates button again to leave machine coordinates? I have set write offsets automatically on homing. I can then set my soft limits to these 0's and table travel (or just inside them)? Will these coordinates become persistent without anything else being done?

Home coordinates:
I can then set my tool to the ordinate point where I want to start machining and then zero the DRO's again and then home all my axis to this point? These are then my work offsets? If I have to stop the program for any reason and need to start from the beginning again or I want to repeat the machining I just press go to home and it will revert to the work coordinate position. I need to do this every time I start a new piece.

If I press go to zero this will take me back to the machine coordinates I set and if I press home it will take me back to the work coordinates?

Sorry for the newbie stuff....

Tony

[dezsoe]

No.

Machine coordinates are absolute on your machine. You can only zero them by homing. If you have home switches, then you can set home coordinates automatically. If you don't have them, then jog to the home position you want and press home for that axis (or home all, if all axes are in home position). When homing, the homing offset is written into the machine coordinate.

The work coordinates tell the machine where zero point of the workpiece is. (Also called fixture coordinates.) These coordinates can be zeroed with the zero buttons. On the offset tab you can see the offset of the fixture from the machine coordinates. (E.g. I am homing X to -5, softlimit is set to -4. Z is homed to 50 and it is the topmost position on that axis.)

Softlimits are compared to machine coordinates, because they must be absolute to your machine.

Goto zero traverses to the selected fixture's zero coordinates.

[ger21]

And no, it's not different from Mach3, it's exactly the same.

Goto zero takes you to the work offset zero positions. Home sends the machine to the home switches, to home (reference) the machine.

[X-man]

No.

. If you don't have them, then jog to the home position you want and press home for that axis (or home all, if all axes are in home position). When homing, the homing offset is written into the machine coordinate.

Yes, but surely my machine coordinates must be set to zero when homed. So I jog x to the extreme left and my y to extreme travel towards to pillar of the z axis and z to its high position and then surely I must zero the DRO's from machine coordinates? Then my soft limits start from zero and are always positive (or negative dependent on extreme of axis (left or right for the x axis for instance). Or should I pick a central position for the table i.e. halfway between the extremes of travel for the x and y and top of the z for machine zero? So my soft limits will be say -200 to 200 for my x axis table travel of 400mm and the same for my 145 of travel y axis -72.5 and 72.5?



[quote "dezsoe"]Softlimits are compared to machine coordinates, because they must be absolute to your machine.

Goto zero traverses to the selected fixture's zero coordinates.

Understood if I understand the first bit correctly which I don't as you can see.

[ger21]

You left out the part that you homed the machine first.

So, you turn on your machine and home it. Homing sets the machine coordinates, and they can not be zero'd or changed. Your softlimits are referenced from the machine coordinates which are set when you home the machine.
It doesn't really matter where your home switches are located, as long as you set your softlimits to be relative to the home position.

[X-man]

I guess you really must think I'm a thocko but I still don't get it. I seem to have a severe mental block on this. It goes like this:

I set up the machine with a mach3 xml but it seems to not work with UCCNC as I expect. So I need to set this bit up from scrathc (I have never done it before as the machine came with a mach3 xml set up for it.

So I need to set machine coordinates first (or do I?) so then I can set soft limits because I dont have hard switches.

So I turn on the machine for the first time. I need to set my machine coordinates. To do this I hit axis and jog to where I want to it to be home. I then hit the machine coordinates (which appears to be a random number on the DRO's when I do That). Do I then hit set all to zero and then home all to set the machine coordinates? or what. This is the bit I don't really understand. I know that once I have my machine coordinates set I reference my soft limits from that zero setting ?????

I really don't understand why i am struggling but I am....

thanks for your patience and help

Tony

[ger21]

OK, so you don't have home switches.
Turn on your machine.
Jog to where you want the home position to be.
Click the Home All button. The Home All will zero your machine coordinates at the current location. Your softlimits will then be referenced from this location.

Note, that any time you hit the Home All button in the future, you'll need to change your softlimit settings again, unless you can jog to a repeatable position before clicking Home All.
If you install home switches, then the Home All will send the machine to the switches, giving you a repeatable home position, and your softlimits will always be correct.

[cncdrive]

I think what confused you is that in Mach3 you can set the machine coordinates, which is not allowed in the UCCNC.
In UCCNC you can set your machine coordinates only with homing. This is because we think that setting machine coords manually is:
- a very bad CNC programmer practise.
- an accidental typing in the machine coords DRO can cause serious issues, like collisions when you program G53 machine coords movements.

This does not mean that you absolutely need home switches on the machine. It is the best to have them, but if you do not have home switches then you can set the home pin of the axes to 0 and then if you home the machine then it will set your machine coordinate without motion and it will set the machine coords DRO. You can set the Write offset on homing parameter on the axis setup pages and that will be written in the machine coord of the axis when you homing it.

So, you can move your machine to a known point and home it there and then that point will be the 0,0,0 point or whatever your Write offset on homing values are for the axes, it could be 50,100,23 or anything which you want. This is the same as if you write your machine coords in Mach3, the only difference is that you need to do this via homing.
Doing it via homing will teach you a good practise to set the machine coords only via homing. Eventhough you do not have home switches now, but in case you will later work on any industrial machines you will have this good practise and you will not suffer because you can't set the machine coords manually on those machines because you already got familiar with the process using the UCCNC.

[ger21]

I think what confused you is that in Mach3 you can set the machine coordinates

No, Mach3 is the same as UCCNC, afaik.

[cncdrive]

Gerry, I've just checked it and you are right. Mach3 also does not allow to set the machine coords manually. I remembered incorrectly, I thought Mach3 allows it, but it also does not.
So, you are right the UCCNC coordinate system and how you can set it is the same as Mach3's. I thought about this as a possible difference, but now I see that it works exactly the same.