Homing to sides of workpiece with real tool How? Lathe

Deleted .see next...

Re re reading that lathe text...

Major point of confusion:
The touch off there works off the tip of a tool. ie machined workpiece diameter.

Assume Round tool orientation 9.

The described method is actually ignoring cutter compensation.
It results in the outer tool radius being the tool reference instead of the tool centre.

And that is my problen.

Any further machining with cutter comp on now results in the tool running incorrectly.


Documentation. Section 4. Z axis point 6 states:
"Select Touch Off and pick Tool Table and set the position to 0.0."
What is meant here and which window? I cannot figure it out.

Below point 7 then:
"If you have a 0.125" wide parting tool and you touch the left side off but want the right to be Z0, then enter 0.125" in the touch off window"

Which window exactly? And the at what point is this offset active?

Documentation. Section 4. Z axis point 6 states:
"Select Touch Off and pick Tool Table and set the position to 0.0."
What is meant here and which window? I cannot figure it out.

Below point 7 then:
"If you have a 0.125" wide parting tool and you touch the left side off but want the right to be Z0, then enter 0.125" in the touch off window"

The touch off button is next to the home button. For the selected axis you can enter a value that gets stored in the tool table.
This is where you can enter your 1.5mm difference.

OT-CNC wrote:

The touch off button is next to the home button. For the selected axis you can enter a value that gets stored in the tool table.
This is where you can enter your 1.5mm difference.

But there are 2 buttons there.
In theory this all makes sense but I just can't seem to duplicate it in practice.


There are 2 buttons there. "Touch off" and "Tool touch off" but no "Tool table touch off" as described.

None of them seems to set the values entered into the tool table.
The values in the tool table do SOMETIMES(!) change when I fiddle with the both touch off buttons but not necessarily to the values entered.
Example:
At some stage I entered 1.5 into touch off (not tool touch off) and there was not change in the tool table values.
Later I did the same in "Tool touch off" but then suddenly the value in the tool table was -2.53.

thinking I understand this, I manually entered -1.5 into the tool table as well.
However, it still never gave me the expected result in that 0,0 still ends up 1.5 away from the workpiece and the machining is off when I turn cutter com on..

Could someone perhaps please try this and send me a screen shot of how it is supposed to look and where the tool will sit when going to 0,0

Maybe something is not working as expected?
I sure can't seem to get it right.

Regards
Bernt

I'm going by memory here...the tool touch off sets the tool table and touch off sets the material location relative to the machine origin.
You can find the tool table under file menu - edit tool table. I think you may need to re load the tool table to have it take effect.
Also, are you going into MDI and doing the tool change followed with G43 before touching off?

Ok, but please tell me WHICH one I am supposed to use?

The tool touch off or the touch off ?

you have to use both, but tool touch off can just be 0 most of the time.

touch off move the work coordinates so that 0,0,0 is in a distance from 0,0,0 in machine space(set by your home switch) this is g54, there are other ones but lets keep it simple. this lets you work in a "local space" and you dont have to program in machine space. you can use g00 X1 Y0 instead what ever the distances from your home switch. On a production CNC you would have a probe that you use to set this, also a well defined setup process that you run though to change program/part

OK now tool touch off is used to loads info into your tool table(think default is length only. this is X on lathe?) this info is call by the cutter comp line. you will use a cutter comp g-code like

G43 (Tool height offset compensation negative) then give it some values like H1 would be for tool 1 in you tool table. this all happens after set up, if you set up with tool 1 then then H1 should equal 0, then the different between H1 and all your other tools would be what you load in to your table. if you do not use cutter comp the tool table does nothing and you would need to program based on the tip of each tool. also if you move you tool post(like a non fixed style) then you would have to check your zero and reset your work space (coordinates).

im learning this stuff myself teaching others help me learn so if you dont agree let me know so we can improve our understanding. also check your local collage for a into to CNC i found on and it helped a ton

Ok thnanks,

So let us follow my original example.I need my machine to go
Say round tool 3mm diameter (half round in real life but same for this purpose)

No cutter compensation.
T1 M6
G54
G00 X0 Z0

To go and align the tool centre with the front right corner of the workpiece.
In other words, I needs it to crash there.since this position is impossible to get to due to 1.5mm tool metal in the way.

So I try to set touch off (not tool touch off) to 1.5mm.

I try again. Now I see cross hair G43 on the screen but now everything have moved with it, including the 0,0 point and when I do the
G00 X0 Z0
The tool goes to 1.5mm from the cross hair G54 zero and the tool centre shows yet again OUTSIDE the shown 0,0 and all the machine path have moved too so I have nothing really achieved.

Either I still do not understand this or it is not working as expected?

I try again. Now I see cross hair G43 on the screen but now everything have moved with it, including the 0,0 point and when I do the
G00 X0 Z0
The tool goes to 1.5mm from the cross hair G54 zero and the tool centre shows yet again OUTSIDE the shown 0,0 and all the machine path have moved too so I have nothing really achieved.

Either I still do not understand this or it is not working as expected?

I think you are getting close.

One way to think about it is that the tool touch off button allows you to establish tool offsets if you are using multiple lathe tools based on a reference. That reference could be a dowel pin in the chuck, stock in the chuck or a some point away from the chuck such as a tool setter arm. It established the relationship between each tool. It does not define the G54 etc location.

Touch off established the G54 location.

What's important is that you issue the G43 during the tool change so the proper offset gets loaded when you then position the tool to the G54 position.
Jog your selected tool to the material in the chuck and touch off to the face for Z0,(in your case enter 1.5mm for the Z) then touch off the diameter, measure it and add that number to the entry box. (diameter/2 +1.5mm) note the X axis has to be selected or you'll override the previous Z value.

To test it, jog away from the part and go to MDI and enter G01, Z10 X0 F200. Tool center should come to a stop 10mm from the face and in center line of the rotational axis.

it maybe a tool orientation problem here is the manual link that may help.
linuxcnc.org/docs/html/lathe/lathe-user.html