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Author Topic: Using The Knee For Tool Length Comp....  (Read 6347 times)

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Re: Using The Knee For Tool Length Comp....
« Reply #10 on: December 17, 2009, 10:33:31 AM »
Hi Ray, I must say I am really looking forward to seeing this working.
With the onset of cold weather I have been back in the shop trying to get to the point that I can install the knee drive.
I can really see the value in this as I have a job where I have a 7 inch tool and then a 1 inch tool. Lots of knee cranking!!!!

I may have enough tool holders that I can have a persistent tool table, will that make any difference in how this gets set up.

I wasn't sure I agreed with the negative tool offset but now I  have to agree with it since you explained what happens when you cancel the tool offset.

Even if you have to measure the tool lengths manually, this will be a great addition to any knee mill. I will hopefully be able to do it automatically soon.

Keep on plugging away at it.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.
Re: Using The Knee For Tool Length Comp....
« Reply #11 on: December 17, 2009, 10:36:41 AM »
Hi Ray, I must say I am really looking forward to seeing this working.
With the onset of cold weather I have been back in the shop trying to get to the point that I can install the knee drive.
I can really see the value in this as I have a job where I have a 7 inch tool and then a 1 inch tool. Lots of knee cranking!!!!

I may have enough tool holders that I can have a persistent tool table, will that make any difference in how this gets set up.

I wasn't sure I agreed with the negative tool offset but now I  have to agree with it since you explained what happens when you cancel the tool offset.

Even if you have to measure the tool lengths manually, this will be a great addition to any knee mill. I will hopefully be able to do it automatically soon.

Keep on plugging away at it.

Mike

Mike,

We'll know within hours...  All works fine in simulation, so I don't expect any surprises.

Regards,
Ray L.
Regards,
Ray L.
Re: Using The Knee For Tool Length Comp....
« Reply #12 on: December 17, 2009, 12:55:16 PM »
Well, it really is just that simple.  Just tested the macros, and it all works just as it should  you can actually define the tools any way you like, but for safety sake, it really is best to make an offset of 0.000 correspond to your longest tool, so there's no danger of a crash when you turn comp off.

The macros I'm now running are below.  M843 applies the comp, M849 removes it.  Use these in place of G43 and G49.  With M843 use the P argument to specify the tool table entry whose length offset is to be applied.  You may find the "extra" moves in there confusing - I do this because I have a lot of backlash in the knee - bevel gears and a leadscrew, rather than a ballscrew - so I get most repeatable positioning by moving the knee up to final position.  So, if a down move is required, I move down a little past the target position, then back up to the target position.  This gives me excellent repeatability.

Regards,
Ray L.


Oops!  Posted the wrong M843 macro.  Now fixed.
« Last Edit: December 17, 2009, 01:48:40 PM by HimyKabibble »
Regards,
Ray L.
Re: Using The Knee For Tool Length Comp....
« Reply #13 on: December 17, 2009, 12:58:50 PM »
Looks like I know what my next project is. LOL

Nice work Ray.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

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Re: Using The Knee For Tool Length Comp....
« Reply #14 on: December 17, 2009, 02:24:51 PM »
If  you used the longest tool method then it would be the same but only if you were sure you would never ever have a tool in that was longer than the reference tool. I am not 100% sure but I seem to remember that you can have positive length offsets or negative length offsets but not a mixture of both, could be wrong though and if I am then it wouldnt matter a toss which way things were done.

Hood

Hood,

Mach3 doesn't care whether the tool table offsets are all positive, all negative, or some of each.  And, in this case, circumventing G43 with a macro, it really doesn't matter.  Mach3 v4 will use a completely different setup, and probably will allow G43/G49 to invoke VB macros.

Regards,
Ray L.

Ray,
 good to know, dont know where I got that from, just seemed to be something in the back of my head saying a mix couldnt be used but obviously the grey matter is turning more to grey  concrete :)

Now I have the Beaver NC5 up and running the knee will be getting a servo put on it, hopefully over the holiday period. This shouldnt take me long as there is already an induction motor there for raising/lowering the knee.
 I would certainly prefer to look at having the gauge line as the reference tool but if it has to be done the other way so be it.
Hood
Re: Using The Knee For Tool Length Comp....
« Reply #15 on: December 17, 2009, 02:57:56 PM »
Hood,

No reason you can't use the gauge line as the reference, and my understading it that's the way it is done on VMCs.  You'll just need to modify which way the knee moves when changing tools.  But I don't understand how you know when it's safe to turn off length compensation, and not risk crashing the tool.  But, then, I don't even know enough to know what I don't know.  I only barely know what I'm doing here.  I've never worked on a "real" machine.

Regards,
Ray L.
Regards,
Ray L.

Offline Hood

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Re: Using The Knee For Tool Length Comp....
« Reply #16 on: December 17, 2009, 03:05:27 PM »
You and me both Ray ;D
 I have never used length comp on the mill as on the Bridgeport it just has the quill driven and the range of tools I use (long drills to tiny endmills) I thought it a waste of time setting it up. With the Beaver I am going to do exactly the same as you have done, and eventually hope to make a toolchanger as well, will have to put the thinking cap on.
 Would length comp ever not be used if you were using the tooltable?

Hood
Re: Using The Knee For Tool Length Comp....
« Reply #17 on: December 19, 2009, 06:36:39 PM »
I now have all the macros I need to use probing to initialize the tool table, and apply the offsets when milling.  Hopefuilly, tomorrow I'll have the time to acrually "use them in anger" for the first time!

Regards,
Ray L.
Regards,
Ray L.
Re: Using The Knee For Tool Length Comp....
« Reply #18 on: December 19, 2009, 06:44:40 PM »
Use them with calm thoughts of perfection in mind and all will go well my son.

Sorry I must have been meditating.

Good luck and I await the results.
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.