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Author Topic: Strange backlash activity.  (Read 1776 times)

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Offline SScnc

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Strange backlash activity.
« on: April 29, 2012, 12:16:37 PM »
Okay last night I ran into two backlash problems I've not yet seen before while setting up my X axis. First off I replaced my ball nut with larger balls to reduce backlash. After installing the new nut and testing my backlash by moving the table in step mode by .001 increments and then moving the other direction, and watching for indicator movement, I came up with about .004 backlash. This struck me as weird, because I did the same on the Y axis and it has .001 backlash.

So I decided to move .100 via MDI and then back to zero. Same result .004. Now this is where it gets weird. I next decided to move a larger amount like 1in. The table came back to zero perfectly every time. I increased the movement each time until I was at the full travel of my machine, and guess what, perfect every time. I don't get it, anyone have any ideas?

The second issue is backlash comp. When I turn it on and it goes to move in the opposite direction it hesitates for a second and then it moves. I have the backlash comp set at 100% and it enabled, but it seems no matter what I put in the % box it has no effect on the machine. I've used backlash comp before many times and this is the first time this has happened.

Any help is appreciated.

Offline Hood

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Re: Strange backlash activity.
« Reply #1 on: April 29, 2012, 01:16:21 PM »
You have to make sure that when setting the zero on your dial that you are moving in the direction of your initial move. In other words, place the dial against the axis being measured, step in say a positive direction until the needle is zero then also zero the DRO in Mach. Then move your preferred distance still in a positive direction then command back to zero and see if you have backlash. Remember backlash is not always just due to screws, the supporting bearings for the screws can often have more backlash if not correctly adjusted, also flex in bracketry can cause lost motion.
Hood

Offline RICH

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Re: Strange backlash activity.
« Reply #2 on: April 29, 2012, 05:59:24 PM »
Quote
but it seems no matter what I put in the % box it has no effect on the machine

Haven't used backlash in a long time. Now if i can only find my 50-50-50 settings rule ......which goes something like this:

50% - for the % of max speed ( in backlash flyout window)
Shuttel Accel .050 to start ( in general config)
Debounce Interval 50 to start  ( in general config)

The last two settings have an affect on how the backlash is implemented.

RICH