Axis Calibration Issues

[2_many_hobbies]

Hello, I have had my 'kinda' mill setup for about two months and have not really used it as its currently a positioning table with a drillpress on a crude bench but im starting work on my full Z axis and want to get it setup as an accurate positioning table and manual quill so I can start building parts.

I had the table pretty well setup by guessing but I had odd settings in my motor tuning tab, I have a new PC for the mill and the numbers are completely different on it.

On my old PC (Phenom Quad Core w/ 6G Ram):
Settings Screen > Time in Int: 3.0-3.9
Motor Tuning:
X Axis: Steps Per: 105, Velocity: 65, Acceleration: 20
Y Axis: Steps Per: 105, Velocity: 45, Acceleration: 10

On the new PC (Athalon XP w/ 1G Ram)
Settings Screen > Time in Int: 5.0-5.7
Motor Tuning:
X Axis: Steps Per: 2542.383, Velocity: 35, Acceleration: 8
Y Axis: Steps Per: 2543.324, Velocity: 20, Acceleration: 5

The positioning table is driven by parallel bipolar 2.5A 48V nema23 80oz-in motors on some sized differential roller screw. I have no idea how to measure this screw as its appears to be on a 1/4"-32TPI bronze screw and the roller screw has 5 rollers. Table movement is 6" x 4"

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The problem I am having is on the old PC with Steps Per Rev at 105 I had repeatability to around 0.001" through all my travels (tested it with g-code that went min>max>min x 50 on both axis while I had a caliper on the table)

On the new PC I did the Axis Calibration on the settings screen with the caliper clamped to the table and I get 2500 steps per rev and when I do a calibrate > y axis > move 4.000 the table moved 4.0005 but when I goto the MDI and put in G0 Y-4.0000 the table will move greater than 4". I go back to calibrate and did a calibrate > y axis > move -4.000 the table moved perfectly still.

This only happens is the Y axis and only on this new computer. I also notice that I had to drastically reduce my velocity and acceleration or it would stall. I think I need to figure out my roller screw ratio to get a real steps/rev count.

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Well enough talking for me, anyone care to try and explain my problem away?

[ger21]

Steps/unit should not change from PC to PC. You have a serious issue to have to increase it by 25x. Did you use the same version of Mach on both computers?

[2_many_hobbies]

Yes their both the same version downloaded from the artsoft site. I do notice in motor tuning I can put in any value I want into the steps per and then do axis calibration and it will modify (+- 25%) what I put in.

Whats weird is that at 2500/rev why would it be accurate only during calibration. I only used 2500/rev because that's what is appears most ppl are using in videos I have seen.

Im using Keling KL-5040 drivers on 1/2 stepping and bipoler steppers so would this be right?

1.8deg stepper is 200ppr, wired in bipolar parallel half's the resolution (3.6deg) as your driving two coils at a time so now 100ppr. With the controllers 1/2 micro stepping that's back to 200ppr. Now the screw takes 5 1/3 turns per inch of travel, not sure what to do with that bit of info but oh well.

Should I be using 200ppr as the steps per (are they rev or per inch?) as the rest of the screen is per inch I figured 200x5.33=1066 steps per inch.

Either way are people using like 1/10 micro stepping to get these massive numbers? Should I be using 1/8 stepping on my controllers since my screws are only 5.33 TPI? (effectively)

[ger21]

Originally Posted by 2_many_hobbies 1.8deg stepper is 200ppr, wired in bipolar parallel half's the resolution (3.6deg) as your driving two coils at a time so now 100ppr.

No, it's always 200 steps/rev times the microstepping amount, so 400 steps per rev with 1/2 stepping. The resolution never changes.

400*5.333 = 2133.2 steps/unit

You probably should use 1/8 stepping because it will probably run smoother. In that case, make it 200*8*5.333 = 8532.8

[2_many_hobbies]

I changed my controller to 1/8 stepping and put in 8532.8 then did my axis calibration which yields ~10168

And im back to the same problem of during calibration I say move 1.125" and it does perfectly but in the MDI screen a 'M0 X1.125' moves the axis 2.162"

What am I possibly doing wrong to make the Axis Calibration fail? Its not rocket science yet i'm failing...

[ger21]

I've read a lot of posts lately from people having trouble with the calibration. One answer I've seen is to use as long a movement as possible.

[2_many_hobbies]

I think were missing the main problem, the calibration screen works perfectly here is my situation in detail:

-I load up my default profile with my current ~10500 Pulse Per setting.
-Bolt down electronic caliper and check range of motion, I have 3.2" of leeway
-I goto axis calibration and select X Axis and say 3"
-The table moved EXACTLY 3.0000 which is wonderful
-I then go directly to the MDI screen and Issue M0 X-3.0000 which is exactly opposite what the calibration moved. Im expecting my caliper to go back to 0.0000" but the table moved >3" and trips a limit.

I can move the table all over in Axis Calibration accurately but not through gcode. I don't want to fine tune the Steps Per by hand as it will take forever!

Their must be an issue with the math behind the auto calibrate but what do we do to solve it? (I'm running Mach3 R3.042.020)

[ger21]

Do you have axis scaling on by chance?

[2_many_hobbies]

The scaling by the DRO's all say 1.000, ive restarted Mach and windows between calibrations with no effect as well.

[ger21]

I'd back up the .xml file, delete it, and start from scratch with a new one. Sometimes the .xml files can get corrupted and cause weird things to happen. Unless someone else has an answer for you.

[2_many_hobbies]

Thanks for all the help anyways, when i get home from work im gonna wipe the computer clean and reinstall Mach3 and rebuild my profile. Ill post back if it works.