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Author Topic: Problem with Backlash...  (Read 10727 times)

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Offline DAlgie

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Re: Problem with Backlash...
« Reply #20 on: January 04, 2011, 05:58:23 PM »
I am having issues with this as well, but didn't have them in version 1.84, which I just upgraded from. Hood sent me to this thread, so I thought I might ask here. My lathe does some funny stuff, but if it involves backlash then I don't know what. I have 0.002" in the X axis, and 0.020" in the Z axis. In the Z axis, it accelerates about 0.200", then slows down to almost a dead stop, then accelerates up again. I had changed nothing mechanically since the upgrade, and the XML transferred over fine. I tried not using "enhanced pulsing" on the general config page, no difference there. I noticed that the backlash setting page shows the backlash as in "units", would that be the same as the actual measured amount or?

Offline Hood

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Re: Problem with Backlash...
« Reply #21 on: January 04, 2011, 06:14:19 PM »
Did you change the shuttle setting on the General Config page? If I remember you had 1 there and according to what Rich has said it should be more in the order of 0.050 to 0.005.
Hood
« Last Edit: January 04, 2011, 06:24:40 PM by Hood »

Offline DAlgie

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Re: Problem with Backlash...
« Reply #22 on: January 04, 2011, 06:16:38 PM »
Shuttle wheel setting you mean? I thought that was for a jog wheel.

Offline Hood

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Re: Problem with Backlash...
« Reply #23 on: January 04, 2011, 06:18:26 PM »
Yes thats it, try setting to 0.05 and see or maybe even going down to 0.005

Hood

Offline DAlgie

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Re: Problem with Backlash...
« Reply #24 on: January 04, 2011, 06:29:13 PM »
I set it at zero and it stopped it, nice. But when I went back and looked again, Mach had changed it to 0.001, so I guess you can't have zero. Wondering why it is labelled "shuttle WHEEL setting", which is what made me think it was for a jog wheel that some had used a few years ago.

Offline Hood

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Re: Problem with Backlash...
« Reply #25 on: January 04, 2011, 06:46:15 PM »
This should explain it :)
Hood

Offline DAlgie

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Re: Problem with Backlash...
« Reply #26 on: January 04, 2011, 06:56:33 PM »
Makes sense, thanks Mr Hood. maybe it should be relabelled as something like "Jog wheel/ jog accel" or something like that to avoid confusion.

Offline Hood

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Re: Problem with Backlash...
« Reply #27 on: January 04, 2011, 07:00:33 PM »
Cant do that, it would mean I wouldnt be able to post pretty pictures as every one whould know ;D
Hood

Offline RICH

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Re: Problem with Backlash...
« Reply #28 on: January 04, 2011, 08:43:29 PM »
It's interesting to have a read of all the different manuals as all of them are similar but may add a few additional words about backlash.
In the lathe manual it states backlash will prevent the effective operation of CV.
In the Mach3 software installation and configuration manual it says"Using it will generally disable the CV features at corners and Mach cannot fully honor
axis acceleration parameters when compensating for backlash and detune the stepper to avoid lost steps.
Then you have the Shuttle Accel comment from Hood posted ( it's not mentioned as such in the Using Mach3 Mill manual).
So each wording gives rise to a little different understanding to the user.

So responses to problems are use exact stop, adjust motor tuning and backlash settings. No exact answers when one considers all the differences in machines.
It falls on the user to find what works for them.

The Shuttle Wheel Accel is in seconds. How exactly is the" time" applied to the backlash "cycle"? Well I don't really know. ??? It's internal to Mach. ;)
By observing the difference in how the motor reacts to different settings you will see that it affects the overall time it takes
for Mach to take up the backlash and at say a value of 5 you will find that over five seconds the handwheel / shaft will turn rather slowly.
At 0.005 sec its almost instantaneous. In the real slow setting, and say you jog a distance of .1"  you will find there seems to be almost 3 distinct
motor responses in the cycle,....... a small rotation then deceleration...... then backlash taken up over a time...and then  accel and move to finish the distance.
So to get of flavor of it you need to start slow, observe, listen to see what is happening over an operating range. Work your way up in settings.

RICH
« Last Edit: January 04, 2011, 08:46:57 PM by RICH »

Offline DAlgie

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Re: Problem with Backlash...
« Reply #29 on: January 05, 2011, 04:44:15 PM »
The jog shuttle thing is much better now, but it started losing steps while threading, but not any other time. I have had to go down about 25% for the Z axis speed and have the accel down too, from where it was with 1.84. This is only at 325 rpm, and a fine pitch thread at 24 TPI. Should I bump the shuttle time setting up, so I can go up again with the rapid speeds?