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Author Topic: Many lost steps in CV mode for A + Z movements  (Read 4805 times)

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Many lost steps in CV mode for A + Z movements
« on: October 28, 2008, 02:27:14 PM »
I have a 4-axis cnc portal mill with 3 linear axis X, Y, Z and one rotary table axis A and I use Mach3 R2.63

When I run the following cnc code:

%   
G21 G17 G40 G49 G50 G80 G90 G91.1

S1500
M3 M8   

F2000

G1 X10

A80
Z-22.99
A79
Z-22.98 A50

Z-40

M5 M9
M30

then A axis hangs at "Z-22.98 A50" with many lost steps, I guess the ramps for acceleration are missing.

It seems this is a bug in Mach3 R2.63. This bug is also present in the newest versions of Mach3.

I tested it with Mach3 R1.83 and there this bug does not exist !

This bug appears only in Constant Velocity mode and only with A and Z movements (not with Z and Y moves).

It also exists with B and Z moves.

This bug also depens on how big the differnce between the two Z positions is (here 0.01 mm).

If the difference is greater than about 0.2 mm then the bug disappears.

I have tried many different settigs in Gerneral Config but the bug remained.

Can anybody try out this code ?

Here is the test file and the xml settings file:

http://members.aon.at/joshin/foren/mach3/RotaryTest.tap
http://members.aon.at/joshin/foren/mach3/RotaryMilling.xml

Josef



Offline Hood

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Re: Many lost steps in CV mode for A + Z movements
« Reply #1 on: October 28, 2008, 02:51:18 PM »
Have you tried increasing the pulse width? Have you tried swapping drives from one axis to the A axis? Have you tried detuning the A axis a bit? You say it only happens with Z and A (or B) axis but you also say not Z and Y so I am wondering if you have tried Y and A moves or X and A moves?
Hood
Re: Many lost steps in CV mode for A + Z movements
« Reply #2 on: October 28, 2008, 03:05:34 PM »
Hello Hood,

your suggestions would not help, because I have taken the xml settigs file from Mach3 R2.63 and copied it into the directory for Mach3 R1.83 and started Mach3 R1.83 with this settings and the bug was not there at all, all was totally OK. Therefor it cannot have anything to do with puls width or the A-axis itself or detuning the A axis. I have tried it with A and Y moves and the bug was not there. The same will probably be true with A and X moves, but this is not important.

Josef

Offline Hood

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Re: Many lost steps in CV mode for A + Z movements
« Reply #3 on: October 28, 2008, 04:36:59 PM »
I have a coil winder set up for A and Z axis and dont have problems with it, but I am not using angular rotation, is that what you have?
Hood
Re: Many lost steps in CV mode for A + Z movements
« Reply #4 on: October 28, 2008, 05:05:44 PM »
My roatary A axis looks like this:

Offline Hood

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Re: Many lost steps in CV mode for A + Z movements
« Reply #5 on: October 28, 2008, 05:07:51 PM »
yes but how do you have it set up? is it set in degrees or just as a normal rotaional axis? What I mean is my coil winder is set up in motor tuning so that one rotation is equal to one unit.
Hood
Re: Many lost steps in CV mode for A + Z movements
« Reply #6 on: October 28, 2008, 05:33:23 PM »
My rotary axis is set in degrees as A axis in "Motor Tuning", it uses angular rotation.

311 steps  / degree

max velocity: 3000 degrees / minute

acceleration: 150 degrees / sec * sec

and in "General Config" : "A-Axis is  Angular" is checked, but this check has no influence to the bug.

Please look at the settings file: http://members.aon.at/joshin/foren/mach3/RotaryMilling.xml there you can see all settings.

Is there another set up for a rotary axis than angular rotation ? I only know angular rotation.

Josef

Offline Hood

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Re: Many lost steps in CV mode for A + Z movements
« Reply #7 on: October 28, 2008, 05:38:29 PM »
The normal way would be to set as degrees like you have but my coil winder is set differently as if I command G0A1 it will do a full rotation.
 I have no way of testing your A axis out as I dont have any 4th axis to try with.
Hood

Offline RICH

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Re: Many lost steps in CV mode for A + Z movements
« Reply #9 on: October 28, 2008, 06:02:06 PM »
joshin,

Quote
Is there another set up for a rotary axis than angular rotation ? I only know angular rotation
.

Do a search "settiing up 4th axis" as i think you will find a lot of different posts in there which may be of interest to you.
One is about linear movement based on using diameter of a part. I usualy only use only degrees. Think you'll fiind some good
tips there.

RICH