Author Topic: MT and TCP TP questions  (Read 4571 times)

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Offline Calum

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MT and TCP TP questions
« on: August 09, 2010, 05:03:45 AM »
Thanks Dave, That the 0.70 Probing lib fixed the positioning issue and I can now run the "Set TCP TP MCz “ function every time.

I'm not sure that I'm using this correctly because the MCz set point doesn't look right and the relative tool lengths of other tools seem to be too long and don't go to the top of the work ie short by the extra length as measured.

I use the end of my spindle without its nut or collect as my master tool and to set the machine ref at start-up.  This makes the TP Z0 and my MT has a 0 length which is verified with a Measure TLO.  When I enable MTM and go to the "Set TCP TP MCz “ function the spindle moves to the touch plate then retracts and stops with a message that the Z0 has been found, when I accept the setting the spindle return to the TCP and I get a setting of +12.4869, this looks to be about the distance of the retract, I was expecting 0.  Am I doing something wrong?

I also notice that if I have a value in the Probe Slow FR on the WC Offset > Probing tab the spindle will touch the TP and stop there, no Step off and slow probe as I was expecting.

Calum

Offline DaveCVI

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Re: MT and TCP TP questions
« Reply #1 on: August 09, 2010, 05:41:19 PM »
Calum,

It would be rather unusual to use the spindle w/o a tool as the master.
Perfectly possible from a math and MSM standpoint, but generally not preferred. The reason is that this will make ALL tools longer than the master.  Most people want the master to be the longest tool.
This is so that if you turn on TLO when you didn't mean to, the tools shorter than the master all move away from the work piece.
With the master as the shortest tool, they will all plunge into the workpiece - not as nice as the other way around.
This is covered in the MSM manual.

When you refer to Z0, you'll need to qualify - MC or WC?
Generally, MCZ0 is at the top, farthest away form the table and the TCP TP.
You measure the MT PTL offline (a positive number as it is a physical length that the dialog wants , not a TLO), and you have to use that value when finding the TCP TP MCz location. You did not mention that in your description - so I'm not sure exactly what you are trying.

The TCP TP MCz coordinate location will not be a positive number - it will be negative as it is below the MCZ0.

Please give the chapter on advanced tool handling another read before playing with MTM more.
I say that for two reasons - 1) it has lots of info that I can't repeat in a posting, and 2) if it is not communicating the concepts well, I would like to know why not, so I can improve the manual contents.

Dave


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Offline Calum

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Re: MT and TCP TP questions
« Reply #2 on: August 10, 2010, 01:24:38 AM »
Hi Dave,

I think I may need to revise my Z strategies.  I have chosen the spindle as this is the best RH I have, I do understand the risk of having all tools longer that the MT.  I also have chosen to make the table MC zero as I have not fitted a home switch at the top of the Z travel.  I think this is not standard practice either but it has been working for me so far.  This is a home made gantry router and I have learned all I know form the forums and just doing it.  These plenty to learn, thanks for your help.

I'll go over the advanced tool handling again to see if I can't get a better understanding of it.

Cheers
Calum

Offline DaveCVI

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Re: MT and TCP TP questions
« Reply #3 on: August 10, 2010, 02:24:30 AM »
Calum,
Ah, interesting.... MCZ0 at the table should work too - the math doesn't care (or shouldn't unless I messed up a formula somewhere).  I'm guess I'm just so used to thinking of Z0 as away from the table that I didn't consider that set up when reading what you posted.

Think through the examples in advanced tooling chapter carefully - they all use examples of a typical mill with MCZ0 at the top.
Some signs will swap with Z at the "bottom".

The deal with the tools being shorter than the master is that when you set WCZ0 with the master, and all tools are shorter, then tools tend to move away from the work. With MCZ0 at the table, all tools will be longer than the master, but with Z essentially reversed that may end up giving the equivalent results.... I'd need to work thru some examples to be sure.

Soome random thoughts:
1) When you touch the spindle nose to the TCP TP, you are telling the dialog that the MT PTL is 0 - correct?
2) Normally there is a tool tip touching the TCP TP, so slight non-perpendicularity of the tool to the TP doesn't matter to much. With the spindle touching instead there is no "point" so the spindle has to be parallel to the plate to be accurate - Some part of that surface has to touch "first". Also this seems it may exacerbate the need for the TP to be "flat". I'm not sure how you would check this, but I can see wanting check what part of the spindle nose touches the plate first.... if the spindle surface is not a flat parallel plane to the TP plane, this might introduce errors?

Dave
« Last Edit: August 10, 2010, 02:27:46 AM by DaveCVI »
Author of the MachStdMill Extensions for Mach3
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Offline Calum

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Re: MT and TCP TP questions
« Reply #4 on: August 10, 2010, 03:11:02 AM »
Thanks Dave.

Beta 4 seems to have got MTM working the way I was expect it to.

Yes I'm setting the MT PTL to 0 and the MCz is giving me a 0 not the 12.something I was getting.

I'll now work my way through this again, I'm sure I do have a risk of crashing if tool length comp is off.  My spindle shaft is hollow so there is nothing to stop my longest tools at a consistent position, I have an ER20 col let chuck.  I not in the manual, section 8.1.4.2.1, you mention Measuring the MT PTL with TCP TP, would this work if I cant guarantee the MT is not inserted to the same length each time I setup the machine?

Calum

Offline DaveCVI

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Re: MT and TCP TP questions
« Reply #5 on: August 10, 2010, 11:19:19 AM »
Calum,
Once the TCP TP is accurately located (and had not moved), it can be used to measure a tools PTL.
However, with MTM, it is important to remember that **each and every time*** the MT length changes, you have to remeasure all the other tools.
Since in MTM, all TLOS are **relative** to the MT length, if the MT length changes, then all the other TLO values are now wrong.

Dave
Author of the MachStdMill Extensions for Mach3
www.CalypsoVentures.com