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Author Topic: Intermittant problem with Z stepper loosing steps on rapids (used to be fine)  (Read 4848 times)

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Offline bowber

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Long title, says it all basically so I was after a bit of advise.

My mill is a Denford Easymill with 3.5 amp steppers on all axis, this weekend while machining some parts the Z started to loose steps while retracting on rapid moves in fact it just stopped moving sometimes, just like it was getting stuck or something.

Anyway I tried the axis by hand and it felt OK and moved smoothly, I then lowered the rapids down from 1m/min to 500mm/min.
The same happened but I noticed that the stepper seems to go through a funny patch like it's vibrating or something, could this be harmonics?, it's when it's making this noise that it stops being able to drive the axis.

X and Y have no problems with the same 2:1 ratio and 5mm pitch ball screws but they are dealing with the weight of the whole table however they weren't doing anywere like the same amount of work as the Z axis.
The workshop was really hot this weekend so I wondered if the driver was overheating and not being able to output enough power to the stepper so when I get chance I'm going to try it one evening when it's cooler. (unfortunately that looks like tomorrow)

I'm using Routout CNC 10amp drivers and a 37V 20amp power supply but no cooling fan in the case.

So if anyones got any ideas please let me know.

Thanks
Steve

Offline RICH

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Steve,
Were the stepper motors getting hot? They will start to act funny sometimes when they get hot. Say over over 140 deg  where you can't keep your hand on them.
RCIH

Offline bowber

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Hi Rich

No the steppers were relatively cool, just above workshop ambient, which was hot I was dripping stood still doing nothing.
It's a lot cooler today as it rained last night and the air temp is down a lot.

Listen to me! makes it sound like the south of France or something not Cumbria! The dark green box profile roof doesn't help, when the sun shines on it it's like a radiator.

Steve

Offline bowber

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I've tried the Z axis when it was cooler and while it didn't drop any steps it sounded rough on occasion so I took the head apart and cleaned everything and reassembled and while slightly better it still goes through patches of roughness, mainly near the top of the stroke.

I think I'll fit a spring of strut to help with the weight of the quill.

Steve

Offline Hood

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Make sure you have enhanced pulsing enabled, its to the right hand side on the General Config page.
Hood

Offline bowber

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Thanks Hood, I'll check that as I had a power out a few weeks ago and it may have altered a few settings (I just remembered ::))

Steve

Offline bowber

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Hi

Just a quick update on this problem.

I checked the enhanced pulsing was selected and it was so after letting the weather take it's course i ran the mill again when the weather had cooled down a lot last week and there was no problem, the stepper sounded like it should and I couldn't get it to lose steps no mater how I tried until i upped the accelaration so it's defenatly heat related.

so when it warmed up again this week I've checked a few mechanical things and the most obvious is the oil lubricating the quill is running out of the bottom and seems to be leaving the quill drier than it normally is, so this has led me to the conclusion that the oil I'm using isn't upto running in hot environments.

Steve