Is it possible to use MSM without home switches?

[chrisattebery]

Hello,

I'm just getting my mill up and running and have not installed home/limit switches yet. Is it possible to manually home the machine and then use MSM to handle touch plate offset probing and TLO?

Thanks,


Chris

[DaveCVI]

Hi,
Well, yes and no... it's possible, but I think you'd find it painful enough that you'd just want to go ahead and add the home switches.

There are some operations which MSM will refuse to do unless Mach's axes are referenced. For example: going to the Tool change position (TCP) as part of a tool change sequence. The TCP location is specified (and saved) in machine coordinates. If the machine is not referenced, the code would not really know where is it physically trying to send the spindle - so MSM aborts the operation (that's much better than crashing an axis).

Now, it's possible to get mach into a referenced state without actually homing the machine... and MSM can only tell if mach is in the referenced state or not- it can't tell how mach got to that state. But if MCZ0 is not really where MC zero is physically supposed to be.... well, bad things may happen. If one lies to the software about having set MCZ0, well GIGO (Garbage in, garbage out...) applies.

Re using the MSM's auto TLO feature to measure tools (without home switches) - I'd not recommend doing that. Here's why: The TCP Touch plate (TCP TP) location is physically calibrated and the location stored (in machine coordinates) by MSM. The TCP TP location is then used with the MC Z location when the TCP TP is triggered to calculate the tool length and then the tool length offset.

BUT - that all depends on the stored location of the TCP TP being accurate and not changing between each use of the TCP TP. This is why the manual says that if you move the TCP, you have to recalibrate it. If you don't have accurate home switches, you won't have an accurate MCZ0 - so effectively the TCP TP location will be different (wrong) each time it's used - the result will be a bad TLO measurement.

This could be avoided if you were to recalibrate the TCP TP location after each and every time you set MCZ0 to some new spot - but that would be such a hassle that I don't see one gaining anything from doing that.

My best advice would be to add the home switches - you are much better off that way.

In general most of MSM works fine w/o the machine being referenced, but anything that depends on the use of (previously stored) machine coordinates, will refuse to execute if the machine is not referenced.

Dave

[chrisattebery]

Alright Dave, I broke down and installed home switches over the weekend. I'll get my touch plates wired up this week and start playing with ATLO.

Thanks,


Chris

[gdmarsh]

Chris, you're going to love ATLO .. It's made using my machine so much easier & so much less worrisome ..

Enjoy,
Gary