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Accuracy in Ref All Home
« on: January 08, 2013, 02:21:14 AM »
Hello,

I have practiced repeatedly some tests with AutoZero macros.

He concluded that:
Ref All home, in relation to the probe gage block,
presents a random error up 0.0150" / 0.381mm (+/-)

This happens when I turn off the step motor
and Ref All Home, before running the macro AutoZero.

My question is:

With limit switch and Ref. all Home,
How I can get maximum accuracy in Z axis?

1. - Some settings?
2. - Some macro / script especially for Ref all home?

Offline Tweakie.CNC

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Re: Accuracy in Ref All Home
« Reply #1 on: January 08, 2013, 05:08:39 AM »
Quote
This happens when I turn off the step motor and Ref All Home, before running the macro AutoZero.

Just as a general statement (there are exceptions);

For stepper motor controllers that operate using 'microsteps' - If you turn off the controller it will not remember the last microstep position and when switched on again it will adopt a full-step position. This will cause inaccuracy of position.

There are 'home switches' and there are 'home switches' with some giving better accuracy and repeatability than others. (To a certain extent you get what you pay for and as an example Baumer manufacture switches which they claim to have a repeatability of better than 2 microns).

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Accuracy in Ref All Home
« Reply #2 on: January 08, 2013, 07:47:34 AM »
I would like to know about your experience with the switch mentioned.

You have used a switch as it says?

What is the accuracy you get with Mach3?

Then, no longer require daily calibration table?

Offline Tweakie.CNC

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Re: Accuracy in Ref All Home
« Reply #3 on: January 08, 2013, 08:20:02 AM »
Hi Riphet,

I am not sure that I fully understand your questions so please excuse me if I am going off on a tangent.

I am currently using my own design probe (which is pretty similar to the Baumer contact switch principle) and have measured a repeat accuracy of 0.0037mm (between on and off) on the Mach3 DRO's. However, microsteps are not that accurate so a figure of perhaps 0.006mm may be a more realistic maximum accuracy for me to expect to achieve for my Z axis positioning.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Accuracy in Ref All Home
« Reply #4 on: January 08, 2013, 04:46:10 PM »
Thanks,

I'm looking for maximum precision Z-axis when Ref all home.

I understand that the ability to switch repeatability is essential,
(this is hardware).

I also wonder about Mach3,
Regardless of the limit switch,
(this is software).

About Mach3 setting,
About procedure (macro / script) in Ref All button home.

Is the 100% accuracy depends absolutely limit switch ?

Additionally,

Now I wonder how is the button Verify program,
the MDI screen wil (Sept. standard screen

Furthermore,

Now I wonder
What numbers eliminates the option of Config autozero, Homing / Limits?
Is the distance traveled by slowdown?

Is there a function similar to the tester:
GetVar (2002) 'get the exact point the probe was hit
But that is about HOME signal switch?

Additionally,

Now I wonder how is the script off button Verify in MDI screen(standard screen set).

My doubts are multiplied exponentially,
I appreciate your time and attention.

Offline BR549

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Re: Accuracy in Ref All Home
« Reply #5 on: January 08, 2013, 05:12:36 PM »
RefHome accuracy is all about HARDWARE accuracy .

The script in RefHome is open for you to change.

G31 and G28.1 work opposite of each other as far as switching action.  G31 switches going INTO the trip point G28.1 switches backing OFF the trip point.

I think it is safe to say that Software wise MACH3 can Refhome more accurately that you can actually measure.

Just a thought, (;-) TP