RapidTurn Z axis referencing

[David TaylorParticipant @davidtaylor63402]

Hi,

I put my RapidTurn back on the PCNC 1100 today and when I went to reference the Z axis (what is usually the mill's X axis), the table went left, and just kept going.

When in milling mode, referencing the X axis makes the table move to the right.

Have I forgotten that this is how the RapidTurn mode works? The table did not look like it was going to stop so I hit the stop button myself.

I can get it to hit the limit switch going to the right.

Regards, David.

[David TaylorParticipant @davidtaylor63402]

[NealebParticipant @nealeb]

CNC control software includes a set of machine-dependent parameters that define things like "steps per mm" for the different axes, max speeds and acceleration, etc. One parameter is direction to move on homing. Don't know which generation of Tormach control software you are using or whether these parameters are easily accessible or locked away in some hidden area but that's where I would be looking. I presume that you load a different set of parameters for milling or lathe modes?

[David TaylorParticipant @davidtaylor63402]

I've set PathPilot to RapidTurn mode and it all looks as I remember. I just can't remember it moving the table this way when referencing the Z axis.

I guess there's limit switches on both sides of the travel so perhaps I'm stopping it right before it hits the switch but it's pretty scary how far over it is and I don't want to damage the ball screw.

[NealebParticipant @nealeb]

Is it possible to look at the machine parameters to check? Maybe compare mill and turn mode settings?

Quite plausible that there are limit switches at both ends of travel, though, or even one switch with two triggers. My own mill only has switches at one end for homing and I rely on soft limits at the other end.

[John HaineParticipant @johnhaine32865]

Leaving aside whether the drives are properly configured, do you mean referencing or homing? The only axis I "home" on my lathe is the "real" X axis (i.e. radial) so I can use tool offsets. I always "reference" the Z axis off the end of the workpiece (cf the surface when milling), as there could be various chucks and variable "stickout" depending on what I'm doing. I have a tool contact sensor to do this.  So, to be clear, program coordinate Z = 0 is the end of the material. 

Edited By John Haine on 31/07/2023 17:10:26

[David TaylorParticipant @davidtaylor63402]

PathPilot requires you reference all axes before it will do anything else. So it wants to hit a limit switch on each axis so it knows where the table and head are.

Even the Y axis, which is not used in RapidTurn mode, must be referenced. Tormach leave the Y axis usable for checking the lathe head is perpendicular to the Z axis and centring the lathe head in that direction. Once you've done that, you leave it alone until next time you install the lathe head.

With the aid of a torch I had a look under the front splash guard on the table and found the limit switch is in the middle of the bed casting, with lugs at either end of the table. I had about another 10mm to go before the right lug tripped the switch, which exposed about 10mm of the dovetails and had the table a LONG way over to the left.

But it's finally happy so now I can go onto trying to remember how to set up the toolpost!

[Ady1Participant @ady1]

When a machine fires into life it sometimes has pretty goofy settings so zero your xyz

Also zero your xyz at the start and end of any gcode routines as a housekeeping habit (unless its impractical)

[John HaineParticipant @johnhaine32865]

Actually though I always re-home the X axis on the lathe on startup it's usually within a fraction of a mm, which I put down to the non-integer whole step being lost when the drivers power down. I only re-home to make sure my tool offsets give the right diameter.

Likewise on the mill, I generally find that on power up the actual position of the spindle closely corresponds to the DROs, though I generally re-reference to the new workpiece. When I was doing a lot of rotary axis stuff doing CNC knurling where the Y axis is referenced to zero along the rotary axis, I found that the Y axis setting was preserved when powering down and up again. I very rarely "home all" as apart from giving a reference for soft limits it has no useful function. I do all my work by referencing to the workpiece.

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