Centroid Community CNC Support Forum

I would fix the lathe, sounds like lot of mechanical issues.

I run Acorn only on a cheap benchtop lathe with 5" chuck, but TT works from Alu to stainless steel.

Negative rake tooling is only good with very rigid lathes.

Uwe

Can I ask again - has anyone actually used touchoff on a boring tool and got sensible looking offsets, as demonstrated by the tool positioning correctly to the required X position after a tool change? I have no problem with external tools but for internal tools, you need to touch off on the other side of the probe.

I have the parameters set up correctly, using the wizard and double checked against the CNC12 manual. And yes, my machine is pretty rigid. It weighs several tonnes.

You should try it with the current v4.82 "release candidate".

If that version still does not measure ID tools correctly against the back side of the tool setter, then it will be helpful for you to let Centroid know that before it is formally released, rather than after.

Acorn 4.80 and later measures ID tools perfectly on the opposite side of the TT if the TT is in the centerline with the spindle.

It also works if you have gang tooling with approach from both sides.



Uwe

cncsnw wrote: ↑Thu Dec 08, 2022 9:51 pm You should try it with the current v4.82 "release candidate".

If that version still does not measure ID tools correctly against the back side of the tool setter, then it will be helpful for you to let Centroid know that before it is formally released, rather than after.

I will do a fresh trial today, now that I am back home for the weekend. The best result would be some sort of idiot mistake on my part but if so, it's not revealed itself yet.

Part of the complication is that both internal and external tools can only be used on the same side of the axis on my machine (in my case, "behind" it). X+ is a move away from the operator. The spindle also changes direction for internal tools. And my default tools are actually sold as "left hand", for turning towards the headstock. It's a bit of a logical nightmare - ideal if your brain is being mushed by a virus.

suntravel wrote: ↑Fri Dec 09, 2022 12:09 am Acorn 4.80 and later measures ID tools perfectly on the opposite side of the TT if the TT is in the centerline with the spindle.

It also works if you have gang tooling with approach from both sides.

You are actually using your boring bar as an external tool on the opposite side of the spindle axis to normal - it's essentially a "left hand boring bar" - where did you manage to buy that - I've never seen one of those before and it's hard to imagine where you'd use one apart from a repetition lathe that turns in reverse although I've often used a normal boring bar with the spindle in reverse.

Mine is an internal, right handed (normal?) tool on the same side as the external tools. It's mounted upside down and the spindle rotates clockwise when it's being used.

That was only a example, works with RH Boring bars for ID also.

To make it work you have to set the approach direction accordingly in the ToolLib.

Uwe

Been a busy weekend with minimal workshop time but I've just repeated some tool touchoff action using my DIYO probe. This is actually 2 mirror image toolholders (left and and right hand external, with VNMG inserts), so they touch off on different sides of the probe in the Z direction, whereas in the X direction, they both advance from the same (+ve X) direction and have similar (but different) offsets.

Here's the touch off process:


Next, I set a DTI up with X0Z0 at the zero reading on the dial with tool #1. When I index the turret to the other tool (#5), a Z offset is applied but it's not correct, with the result that the Z position is out by exactly 10.00mm. The X positions read within a few microns.



It seems to be the application of the offset that is the issue here. It only happens to tools where the touchoff is away from the headstock for these external tools. All the "normal" or "right hand" tools (that cut towards the headstock) have their Z offsets correct.

Similarly, when an internal "right hand" tool is touched off in X and then positioned against an external "right hand" tool in X, its X offset is also wrong (error 2.50mm). It's a bit more complex to play with boring bars in this fashion, as the DTI likes to be moved in the same direction in X, which I why I've chosen to focus mainly on the Z axis offsets. It's also a bit more scary playing in X with probes, DTIs, powered turrets and tools all at once.

Pretty convinced there is something not right with the controls, as I seem unable to get a sensible result. When touching off on opposite sides of the probe, the 2 parameters that come into play are #281 and #'282 - in my case they are both set to 3/8" (9.5mm), not 10.00mm or 2.50mm.

Report attached

Thinking about this the next day, these inserts have a 0.2mm nose radius, so the Z offsets will end up being a total of 0.4mm different than would be measured by a ball nosed DTI probing the X axis end of the insert tip. So I guess this makes the Z offset problem closer to 9.60mm rather than 10.00mm, which sounds like the width of the probe tip (3/8"), as I previously suggested as a root cause. This effect wouldn't apply to X axis offsets though.

@Uwe - any chance you could attempt a touch-off in Z with a left hand tool, ie touching off away from the headstock and see how it compares with a (more normal) right hand tool in terms of G54 Z position? On my machine, this seems to result in an error of (probe width + insert tip diameter) in the resulting G54 position in Z.

I am unable to resolve this issue from my end, as the problem seems to be very repeatable and consistent.

Many thanks!