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Author Topic: z axis moving up  (Read 9845 times)

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Offline RICH

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Re: z axis moving up
« Reply #20 on: June 06, 2012, 12:03:26 PM »
dray,
Quote
I have it run a 50 cycle test to move up .0625"
So you moved down and then up some distance just to remove any backlash, and then,  you did 50 consecutive movements of .0625"  for a total up movement of 3.125" up?
And the result was that in the total movement you were off by 0.004"? 

RICh

Offline dray

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Re: z axis moving up
« Reply #21 on: June 06, 2012, 02:41:44 PM »
Hi Rich
I'm sorry for the confusion. The test I run is to rotate the stepper back and forth 1 revalution for 50 cycles and stops at 000. But all of the axis wind up having an error of .004" always in what would be the up direction if on the z axis. The DRO reads 000 but pointer is 4 pulses from start position. Vel and accel do not change the error. If I double the length of the test the error doubles. At first I thought it was only on the z axis, but now realize the same happens on all axis. The z error really shows up in 3d cuts because of the frequent direction changes. The x and y axis are driving the machine during the test. Any help will really be appreciated

dray

Offline RICH

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Re: z axis moving up
« Reply #22 on: June 06, 2012, 06:59:42 PM »
dray,
Only one axis running, namely the Z for the testing. Later you can swap the axis by using the X and or Y drive in place of the Z.
The X & Y should not be run while doing the test because of the inadequate power supply you have.  We are trying to isolate the problem from other influences. You don't do a loop back and forth / up and down, but should first see how the number of pulses / indication in one direction is as compared to the number of pulses in the opposite direction.

Pulses .....one pulse sent to the drive is equal to the resolution in terms of linear movement. So 1/25600=.000040" of "possible" linear movement. Each move per pulse can and will vary some from each other  and it can take more than one pulse to change the rotor position, etc. The rotor of the motor requires 200x 8= 2000 pulses to turn it one revolution. So 1/2000 x 360 deg=0.18 degrees =10.8 min which
is the approx equivilant of .0094" of circumferential movement on a 3" disc. So if the scribe line / mark was .005" wide ( a razor blade cut) you
would see the rotor rotate  by one mark.

RICH
Re: z axis moving up
« Reply #23 on: June 06, 2012, 07:09:08 PM »
i have set up a grid on my table to drill holes every 2 inches in  the y and x axis when i run the mach 3 program the x cuts every 2 inches but the y only cuts every 1.5 the table display shows both axis cutting at 2 inches both my y and x axis motors are set the same in the motor tuning in the config page anyone have any ideas

Offline dray

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Re: z axis moving up
« Reply #24 on: June 06, 2012, 07:28:58 PM »
Rich
I only test 1 axis at a time. I am sending the gcodes i am using. Hope this helps explain the tests
dray

Offline BR549

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Re: z axis moving up
« Reply #25 on: June 06, 2012, 07:57:46 PM »
KGB59 it is NOT good form to piggy back YOUR problem into someone else's post.

Please start your own post, (;-) TP

Online Tweakie.CNC

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Re: z axis moving up
« Reply #26 on: June 07, 2012, 02:37:48 AM »
Hi Dray,

Have you tried changing you Step Active state (High or Low) in Ports & Pins : Motor Outputs. ??

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline RICH

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Re: z axis moving up
« Reply #27 on: June 07, 2012, 07:07:44 AM »
 dray,
Quote
I only test 1 axis at a time.
Please disconnect  the cables from the x &y  or diasble the drives when running the test as you only want power going to the Z axis.
You are cycling back and forth, dray. That is not what i want you to do. Only move the axis in one direction and before you do that, you make a move in the z to position the rotor for the direction you are going to move,then zero the Z and have the marks alligned.

 
RICH

Offline dray

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Re: z axis moving up
« Reply #28 on: June 07, 2012, 07:41:37 AM »
Rich
I will try that later today. Not sure what that will prove as what I am doing is the same as the type movements the z axis does in 3d. The error I'm seeing has nothing to do with backlash or straight line movements. The test I run only involves the stepper and it's repeatabily back to 00.
dray

Offline dray

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Re: z axis moving up
« Reply #29 on: June 07, 2012, 05:51:54 PM »
Rich
After I have diabled x and y, moved z in the up direction, set the 00 and aligned the marks ,am I to cycle up and down or just return to 00?  If Icycle up and down I have an error of not being a 00 but the DRO shows 000.

dray