A probing/tool setter dilemma in Probe as MT

[tmostad]

I want to use my probe as the master tool for doing tool changes but my tool setter has some give and the probe has some give such that I don't know how to accurately measure the probe. When I use it as the master tool, all tools measure too short and so end up closer than one inch after doing a Z1. I would suspect it is a consistent amount since the probe and the setter are of good quality. The problem is that I need to use both in the process, the setter to measure tools and the probe to setup the material.

I am thinking that I should instead put some drill rod in a collet and use that as my MT since it will never change length then the possibility of having to recalibrate everything in case of an MT change is eliminated. Is there another solution?

[DaveCVI]

I want to use my probe as the master tool for doing tool changes but my tool setter has some give and the probe has some give such that I don't know how to accurately measure the probe. When I use it as the master tool, all tools measure too short and so end up closer than one inch after doing a Z1. I would suspect it is a consistent amount since the probe and the setter are of good quality. The problem is that I need to use both in the process, the setter to measure tools and the probe to setup the material.

Uh, Could I convince you to stop using the moving tool setter...?
Here is some more information to help give a deeper understanding of the issues involved:

1) When using a tool setter with a spring to measure a probe you have indeed set up a situation where you have two springs opposing each other. We'll let Fp be the force of the probe spring, and Fs be the force of the tool setter spring. The trigger event will happen when Fp = -Fs and the magnitude of the force is enough to trigger the probe.

2) The trigger point is the probe force trigger point, because MSM knows that the probe tool is mounted and pay attention to the probe input event over the touch plate input event.

3) Now then, at what displacement will the tool setter and the probe be at when the probe triggers?
For the probe we don't really care because we are really wanting to measure the (compressed) length of the probe at the moment when it triggers. Note that this will not be the same as the uncompressed, non-triggered probe length.
In theory the probe force will be F=-kX but we don't know the spring constant K so we can't really calc the amount of compression at the trigger event. Fortunately MSM does not care, it simply wants the trigger point to re repeatable - as long as the trigger point is at the same compression each time it all comes out in the wash.

4) I suspect the Z error you are seeing is from the tool setter spring. It is compressing when a tool touches it... That effectively changes the "height" of the touch plate (tool setter) in MC z and that has to be accounted for when you calibrate the MSM TCP TP. If you calibrated the TP Z uncompressed, then everything you measure with the tool setter will be off by the difference - I suspect that is close to the amount of error you are seeing?

5) Now you can calibrate the TP easily with a rigid tool - that removes one of the variables and if the tool setter is repeatable re trigger point vs tool setter travel, you are OK.
But that does not work for the probe - as the introduction of the probe spring means the tool may or may not trigger (MSM does not care as there is special code to look at the Probe event and not the TP event in this situation). So now the Tool setter is effectively moving some unknown distance when opposing the probe force....

Using a nice simple touch plate removes one spring from the complication and makes this all work nicely.

I would suggest that you get things working with a simple plate and then try to reintroduce the setter if you really want to. The usual reason for using a moving setter is so that "it does not chip a cutter" - uh, all I can say is that I've been using MSM to measure tools with a simple plate for years and have never had that occur.

I suppose that IF I had a huge mass, super fast machine, it might not stop fast enough after plate trigger and could damage a cutter, but I've not had the reported in 5 years so it does not seem to be a huge worry to me and my main machine is a reasonable size (Bridgeport travel range bed mill).

I am thinking that I should instead put some drill rod in a collet and use that as my MT since it will never change length then the possibility of having to recalibrate everything in case of an MT change is eliminated. Is there another solution?

That will be fine as a MT - but that will NOT allow you to use the Probe as the MT. The nice thing about having PT# = MT# is that a simple corner find button click sets all the WC zeros and you are done - all tools are ready to go (assuming they are all in Repeatable height holders). What will trip you up is that you have to use the MT to set WC Z0 when in MT mode. - so if the MT is a rod, it's a bit hard to probe with a rod to set WC Z0.

Dave

[tmostad]

How about if I measure the probe off the mill at its triggered length then subtract the toolsetter trigger distance and manually enter that in the (PTL? or TLO?) and indicate it is in an RHH (which it is) and set it to be the MT? MSM then should not measure it and as long as I have the mill properly referenced to the tool setter then all tools should have their lengths properly set, no? Of course in doing two different measurements some very small amount of accuracy may be lost but if I repeat the measurements several times I should be able to get very close I think. I can tweak the probe's setting by probing for Z0 then doing a tool change and doing a Z1 then checking with a gauge block. Not ideal I know but I paid for the (very expensive) tool setter and by golly I am going to use it (if possible).

I appreciate your help Dave!

[DaveCVI]

Hi,
Ok, for this post I'm going to be talking about MTM mode only (so readers will not get confused).
I'm also doing this off the top of my head; I've not run thru the steps I'm writing here - so please think this thru independently of me (Hey, it's April and I'm about due for my first mistake of the year )

How about if I measure the probe off the mill at its triggered length then subtract the toolsetter trigger distance and manually enter that in the (PTL? or TLO?)

To manually set the tool table information for the master tool (and only the master tool) you need to do this:
a) measure the Probe physical length offline. You want the length at the moment it triggers.
b) enter the measure length as the Probe tool PTL in the table.
c) make sure the tool table has the correct value for diameter - MSM knows the tip on a probe is a sphere an uses the diameter for Z as well as X and Y.
This is where my memory is fuzzy (and I don't have the code in front of me as I write this) - I don't remember if the PTL value should be with or without a radius amount... it things end up off by a radius amount adjust accordingly (or bug me again and I'll goo look at the code - I'm just in a hurry this morning as I've got to run off right after I post this).
d) set the TLO value = 0.
In MT mode TLOs are always the difference between the master tool PTL and the measured tool's PTL. Since these values are the same for the MT, the TLO will always = 0 for the Master tool (X-X=0).

and indicate it is in an RHH (which it is) and set it to be the MT? MSM then should not measure it

Remember that as well as being in a RHH holder, you will also need to turn on the "Skip RH Tools" button on the tooling page.

Now for a sanity check:
Set up a drill or something in a holder. Manually set the PTL for this to be exactly the same as the measured PTL for the Probe. We now have a rigid MT tool to play with. Ask MSM to mount & measure this known length tool - the measured PTL value should come out to be the known value. ALso in MTM mode the TLO should come out to be 0 (or very close since the MT PTL will = fake MT PTL). If not, the tool setter is either not calibrated correctly re MCZ or it's trigger point is varying etc.

Now that we know that the TCP gives the correct PTL for the "rigid fake probe" it should also give the correct values for other tools.

as long as I have the mill properly referenced to the tool setter then all tools should have their lengths properly set, no?

That is the plan! - i think this should work out ok - but there is nothing like actually doing it to find out.

Not ideal I know but I paid for the (very expensive) tool setter and by golly I am going to use it (if possible).

I understand that motivation.

I appreciate your help Dave!

No problem.

Honestly, I think the real way to do this would be for me to teach MSM about a moving tool setter. I could then handle the special cases inside of MSM and reduce the user set up to
a) do you have a moving tool setter yes/no?
b) Movement amount at trigger for rigid tool?
c) movement amount at trigger for the probe?
I dislike this so far because it makes the TCP TP calibration dependent on a single probe and it's spring. What if a guy has two or three probes?
Those details are the kinds of things I'd need to figured out before I could add such a feature and there are
very few MSM users with a moving tool setter so I've not had much demand for this.

I suppose I could be bribed - anyone want to give me a nice moving tool setter? I'd probably then some flashes of inspiration...

Dave