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Messages - ozzie34231

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1
VB and the development of wizards / Re: Internal taper wizard
« on: November 11, 2006, 09:31:06 AM »
Cool. When you get to it.
By the way that same problem exists with many of the wizards, i.e. they do not take into account that many machines have backlash (some might say all machines) and cut in such a way that the tool can easily be pushed away from the workpiece.

Jerry

2
VB and the development of wizards / Internal taper wizard
« on: November 09, 2006, 06:43:48 PM »
In a world where all of us  have zero backlash machines this wizard would be fine, but a few of us do not.
The cuts should be made from the inside out, so that the x feed is feeding into the metal, at least that should be the case with shallow number angles. The pressures on the Z axis are minimal.

What think Brian?

Jerry

3
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 25, 2006, 01:22:59 PM »
Okay, Final Wrap,
Put the shield wire in the Gecko "encoder minus" terminal, partially rebundled, changed indicator to .0001 unit.

Repeatability .00015 and that's probably in the indicator stand. the indicator is so sensitive it moves in a big wind. :-) :-) :-)

It appears that the ground connection had deteriorated over time!???

Jerry

4
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 25, 2006, 12:35:06 PM »
Brian,
The signal shield, Yes?
What about shielding the motor power leads? Think that'll help?
Jerry

5
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 25, 2006, 12:18:22 PM »
Brian,
Yes thanks about the grounding, the shields are grounded at the control box only.


I have some 16/2 shielded wire, do you think changing the twisted pair would enable me to re-bundle signal and power lines? I run the servos at 70 V and seldom pull more than 2 amps.

Thanks,
Jerry

6
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 25, 2006, 12:11:18 PM »
Friday Morn:

I was wrong about the grounding yesterday. The signal shield is grounded and the motor power is not shielded, but a twisted pair.
I wrote a short program to enable me to quickly reproduce the problem; half dozen rapids and feeds. Good test, saw huge gains in one direction.
Tested the par port by switching leads, no change.
Re-checked grounding of signal shield, small wire but definitely grounded.
Decided to change Geckos still another time, and just on a whim I unbundled the wires and physically separated them by several inches. I powered up and ran the test.

GREAT BALLS OF FIRE! It returned to zero dead on! Accident? Ran it ten more times and didn't get any error I could read on the indicator. I might try it now with a .0001" indicator just to wallow in my happiness.

So it's definitely noise, but I don't know why the shield is ineffective. I'll work on that at my liesure.

Again, many thanks to Brian and Chip,
Jerry

7
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 24, 2006, 04:24:35 PM »
I just spent a couple hours "dorking" with it.

 Chip, I first changed the Gecko before I decided that I had mechanical problems.
I don't think The gain is too high because I've tried it at zero gain and very low settings. At some settings it goes smoothly in one direction and rattles in the other until it faults.

Brian, I did notice that I did not re-connect the shield to ground, maybe that's it.

Pin 5 is not connected to power, permanently.

After working with it for a while and trying to "turn" with it the problem has gotten much worse and is in one direction.
I started with a .625" rod, using wizard, tried to take it to .575 in .01 cuts. Ended at a measured .545!!!
Adjusted axis tried to go to .525, ended at .480, adjusted again, etc
Final try was when the diameter was down to .380 and this time it wiped out the stock in two cuts!
Between successive tries I made changes in the Gecko gain but other than getting a fault when too high, I didn't see much difference.

So, either I'm gaining steps going in, or losing them coming out.

As I sit here writing this and thinking about what you have written, I'm thinking it is noise.
The signal and motor power are both shielded but the shields are not grounded, and they are bundled.
Tomorrow I'll fix that and if it doesn't help I'll change the encoder. (Grrrrrr)

Thanks so much for all the pointers,
Jerry

8
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 24, 2006, 11:23:21 AM »
PS:

Does anyone know if it's possible for the gain on the Gecko to be set so low that it misses steps sometimes?

9
General Mach Discussion / Re: erratic behavior on servo machine
« on: August 24, 2006, 11:18:58 AM »
The steps per inch are correct. This same basic setup has been operating for a few years. The Gecko is however new and I find adjusting it much different from the original; it seems much more sensitive. The directions for adjustment that come with the Gecko are very difficult for me to understand. I don't have a pulse generator or oscilloscope.

Using a long stroke indicator, and setting step jog to .100" I can jog back and forth or go one direction several times. Using this method, I can adjust the backlash fairly close, but not exactly. I get erratic readings to the extent of a couple thou. If I keep playing with it I suddenly get a jump in one direction or the other of about 8 to 10 thou. and then that seems to be the spot that the dial oscillates about for further tests. It acts as if the indicator has moved but I'm pretty sure it hasn't.
I tried another indicator on another base and I get the same results. Other than the indicator moving I'm thinking something else erratic in the communication between the Gecko and encoder is happening.

I think I'll try some actual machining and see what's up.
If it won't cut right I guess I'll start changing components, a long slow process, and pain in the butt.

Jerry

10
General Mach Discussion / erratic behavior on servo machine
« on: August 23, 2006, 11:01:58 AM »
After rebuilding my X axis, I am getting wierd test results when trying to get a proper backlash number. I'm not new to cnc and realize most problems like this are machanical, but I have been meticulous in putting the axis back together. I have had this axis down to .001" backlash but now it's in the area of .010 and not consistant! I even seem to gain steps sometimes!

Before I take it all apart again, I'd like to ask:
Is it possible there is something wrong in any of the following areas:
Gecko or Gecko tuning
encoder or wiring connections
Servo motor

In other words is it possible that anything other than mechanical problems, (screws, nuts, ways, bearings, pulleys, belts,) can be causing the problem.

Thanks,
Jerry


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