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Author Topic: Mach 3 Lathe setting up tools and offsets. hair already gone...teeth next...  (Read 23983 times)

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I have a few good quality switches that I can install on my machine. I should do that.

When I turn on the machine, I could home x and z and then the machine will know exactly where the cutting points of the tools are correct?

The tools would just have to be recorded in the tool offset table as the distance each one is from X0, Z0 (the homed position) does this sound correct?

Example.

Home-
Table moves to X0 about 5 inches out from centerline of spindle.
Saddle moves to Z0 about 18 inches away from spindle face. 
Both positions recorded as Z0, X0.

Then, I could move the master tool over to a workpiece and touch in Z and record the travel distance as the master tool Z offset. I would then take a skim cut, measure and move the tool in in X until it was at 50% of the X number I got from the skim cut. This would put the master tool tip exactly at X0. I could then enter the X distance travelled from the X home position to the master tool tip at X0 location, into the master tool X offset box.

Then I could measure the distances from the other tools in the gang from the master tool tip's Z and X offsets and add the measurements to the master tools offset numbers and then put the total intoi each tools offset table.

This all seems to make sense to me. Is it correct? and is this doable in Mach3?

   




if the above method would work, would it make sense then that when I draw lathe parts in CAD/CAM, that I draw them at a Z(negative) position that has the part face at the distance from the Z home position that it needs to be, when it is set out from the spindle face enough for the turning ops and cutoff.

Example-

Program part in CAD/CAM with a 1.5 inch long part held out .5 for clearance from spindle face. Total material stickout would be 2" and this 2" face location from the spindle would actually be -16" from the Z home position(knowing that my spindle face is -18" from the Z home position(Z0)) .

To do this, I would draw my part with its face at Z-16" in CAD/CAM.

This making sense?

Offline Hood

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If you dont have home switches then you could do as described but it just means each time you start Mach you will have to take a cut with your master tool and type the dia into the X Dro, all other tools would still be correct once that was done.
Fitting switches would likely be a better option however as it would solve the problem of having to set the X every time you start Mach. When I start my lathe, home then call any tool and tell it to go to a Dia it does. For Z, that changes from job to job so the home switch is not quite so important on that although it does come in handy if ffor example you are running the same job the next day.
Hood
Great, so what I propose should work if I have home/limit switches installed?

Additionally, does drawing the parts in cad at the -Z location as I described make sense?

I think I might be getting a bit closer to understanding this...
I have a few good quality switches that I can install on my machine. I should do that.

When I turn on the machine, I could home x and z and then the machine will know exactly where the cutting points of the tools are correct?
Definite yes IMO on the switch issue although I'd go with optos instead of mechanical at least on the X.  I went through 3 (what I thought were) "good quality" mechanical switches before getting one that was reasonably consistent.

Yes on statement 2 except the machine will know exactly where your SWITCHES are but won't know where the tool tips are until you set them up.  That's where my knowledge ends as of this time.  I'm still trying to get my head around the tool table and offsets.  I have established where the spindle center is via cutting a piece of stock, measuring the dia. and using that to MDI to the center and then zeroing the X DRO.  Works great for that tool but will have to set up the table for other tools before it becomes really useful.

edit: oops, Hood posted before I could type this so dunno if this helps or not.

I'm slow but I'm old so I have somewhat of an excuse.;)
Milton from Tennessee ya'll.

Offline Hood

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Personally I wouldnt have Z the same on all parts but if all your parts will be of similar length then it may be ok. However to my mind it is just as easy to move close to the end of the stock and then take a facing cut and setting that as Z zero. Doesnt matter which tool you use if they are all set in the tool table as calling another tool will offset the Z for it.
Hood
Yeah, i was just talking about how I would draw that one particular part in CAD/CAM. It would have to be diff for each different part. Same principal though...

Offline Hood

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I will try and explain how I work. Z Zero is always the end of the stock and any material being removed in Z is towards the chuck, so negative. I put the stock in the chuck maybe leaving 10mm extra longer than the part, so say I was making a part that was 200mm long I would have 210mm sticking out the chuck. I would then call the tool I use for facing and move it to the end of the stock and enter 0.2mm into the Z  DRO, then my first cut in the code would be a facing cut, it will move to Z Zero and face off, it will remove approx 0.2mm from my stock.

Now if the next part is 30mm long I will place that in the chuck with maybe 40mm sticking out and do the same, move Z to face of stock, enter 0.2mm into the Z DRO and again when I start the code it will face off the part.

Its kind of hard to explain, would be simple if I could take a vid of tool setup and how I work, maybe when I get the wee lathe up and running fully I can, big lathe is just too big to be able to set up a camera for that.


Hood
...maybe when I get the wee lathe up and running fully I can, big lathe is just too big to be able to set up a camera for that.
Yes please...show us how you set up and use your tool table too!:)  You make it sound so easy and I'm sure it is once one gets "over the hump."
Milton from Tennessee ya'll.

Offline mc

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I never could figure out why my G52 offsets ended up being ~1.9 inches away from each other per tool, when the tool block is on 1" centers. Never made any sense....

I use G52s with my gang tool holder, but then mine is set up for drills only, so the X offset never changes, and I just manually edit the G-code if the drill lengths change (I have a whiteboard with a corner dedicated to the drill offsets).

As to your offset being off, now you mention it, I think there is actually a bug in the tool change macro.
I noticed that if after doing a tool change where the X offset changed alot with minimal Z movement, the X axis would loose lots of steps/stall. It's like Mach was ignoring the X axis maximum speed, and setting speeds via the Z axis settings.
For example, if the X-axis had to move 80mm and the Y only 10mm, it would move the Y at rapid speed, and X would stall as it was expected to move at speeds far higher than it should.
I worked around it by adding extra lines to the G-code that move the carriage into the approximate place that is needed after the tool change.

I suspect the issue is something in the tool change macro, however I've never had a chance to look into it in any more detail, and given how cold it is outside, I'm taking the "if it's working, it doesn't need fixed" approach!