im getting fed up now

[stk2008]

hi all AGAIN hehe i now haveing probs with the Z axis stalling when going up from time to time not every time but does and it aint resonance like i use to gets if it will do it it will straight away as it trys to move.

so i striped it down and could see nothing wrong i then thought well lets see if i can stall it by using my weight well yes i can even on all the other axis which im very sure i couldent do befor.

so what i am lost with is whats changed? im very sure i could hang of these things but now i cant dont get me wrong i have to put a little effort into it but not loads allso this is on rapids feeds i have not checked a cut feed yet.

please help im getting so gutted now with this machine its like one prob after another so far

update

ok did a cut feed and couldent seem to stop it for crap so thats one good thing.

what im still lost on is im sure maybe im wrong it never use to do this befor and the Z axis defonatly dident stall when coming back up on rapid feed.

update 2

ok ive looked in the motors tuning and changed a few things it seems a little better now maybe i was on the verge of em stalling befor plus its alot colder today in here so may have made the rails,trapzoidel spindles shrink a little.

my settings where

10161 100 30 1 5

my settings are now

10161 75 25 1 5

it will stall on rapids if i realy realy hang on em but cut feeds at 25 30 i have no chance of stalling em.

please if u have any suggestions let me know

thanks so much for putting up with me

[vger]

Temperature can cause problems, anything below about 40 deg F and mine will stall intermitantly. I know the problem I have is in the leadscrew nuts made of delrin. I intentionally tapped them to very tight tolerance to try to keep away from backlash. The delrin shrinks more with temperature change than does the steel screw. Your problem almost sounds like your stepper motor power supply may have a problem, might check that. Try turning the screws by hand with the steppers removed, that may give you a clue if it's not the power supply.

Not sure what the numbers in your settings are, I assume the second is max rate, and the third maybe jog rate?

What kind of screws do you have? Nuts? Ballscrew? What power supply? Motors? Are we talking Router? Milling machine? ???

I run my stepper motor router with an acceleration rate of 10,000 steps/s/s, max step rate of 2000 steps/s, start rate of 25 steps/s, fast jog of 2000 steps/s, and slow jog at 20 steps/s. I run in full step mode and get 60 IPM rapids (150 cm/min), much faster than that and I start running into resonance issues.

Anyway, don't get frustrated, get motivated! There is a solution. A bit more info might help with diagnosis.

Steve

[ger21]

Cold will definitely make things tighter. Do you have lubrication on the screws? You might want to increase the step pulse to at least 2 or 3, maybe even 5. Might make a difference.

As Steve said, check the power supply voltage, and also check that the drive current is set correctly.

[stk2008]

hi thanks for the info i am using trapezoidel nuts and screws

http://www.worldofcnc.com/products.asp?recnumber=61

http://www.worldofcnc.com/products.asp?recnumber=47

and power supplys as part of kit number 4 i think it was

http://www.motioncontrolproducts.com...plies_v2.0.pdf

ive got x2 of the ps407,

seems odd that it started with the cold weather because im sure it dident stall this easy in the summer.

i will check the out put of the power supplys both lights on them show good tho.

cheers for the help.

p.s i used it today and it seems ok but i have droped the speed to 75 and the acc to 25 the other two numbers are pulse width and PUL signal as per instructions

http://www.motioncontrolproducts.com...ing-driver.pdf

cheers again

[stk2008]

hi again all i think the problem has been fixed but i am unable to test due to bad back but i dont just want to believe me dropping the vol and acc are the answer as i say i never had this problem before.

only other reason is the cold weather i have posted links to what i use above so would the nuts close up that much in this cold weather.

but it only does/did it going back up (not any more tho after adjusting vol and acc) never down like the problem i use to have before but that was resonance i have fixed that with rubber o rings etc.

i dont want to have to run this machine slower when i knew i never use to.

what kinda of settings would u expect from this machine i know its hard to tell as u dont know the full picture but as a guess?.

cheers all

[vger]

As far as thermal issues are concerned, the coefficient of linear thermal expansion differs for various metals. Aluminum changes almost twice as much as steel, and bronze is about midway between, with values of about 13, 7, and 10 respectivly. A value of 10 is in microinches/inch/degree F. Suppose you have 2 rods, one aluminum and one steel, that were one meter long at 22 degrees C. At 5 degrees C, the aluminum rod would measure about 0.4 mm shorter and the steel would measure about 0.2 mm shorter, providing of course that your measurement device did not change length with the temperature change.

In my work I have to take thermal expansion into account when I am doing shaft alignment. Most often with larger chill water pumps. The pump stays cool due to the water running through it, but the motor warms up when running. When cold, the shafts can be aligned almost perfectly but there will be vibration due to mis-alignment when the motor warms up. So I set the motor just a touch lower when cold.

Back to your Z problem. I had a similar issue to yours with my Z in the up direction. My nuts are delrin blocks with threads tapped into them using a tap that I made out of the same acme threaded rod as my lead screw. There was a minor out of alignment issue with the block/screw that would crop up when it was cold. With the motor off of the Z, I could turn the screw by hand and found it would bind up a bit. If I loosened the upper 2 screws that held the delrin nut to the slide, the binding went away, so I stuck a piece of shim stock under the upper edge and tightened them back down.

Best of luck
Steve