stepper motor stall?

[mancave newby]

hi ever body,im in the process of converting a wm14 mill to cnc, i have installed 4nm motors to x y and z,everything is up and running,my problem seems to be x and y stalling at points of travel,im running 36 volts to motors through mach 3 with motor settings of 350cm per min and 30 accelaration,can hold the tables by hand to simulate cutting force with no stalling,can anybody shed any light on the problem.

[JAZZCNC]

Pretty sure you will have the motor tuning set wrong. First off the settings are not in cm but mm and motor tuning is set in steps per mm.

To work out your Steps per millimeter take the Micro stepping value set on the drives and divide by the ball screw pitch. If you have any ratio applied you'll need to take this into account. So lets say you have drives set at 800Ms and 4mm pitch screw with 2:1 ratio. The affective pitch will now be 2mm for one revolution of motor. So Steps per MM = 800/2=400

Velocity is set in MM/Min and how you set this will be dependant on several factors. If your just using the parallel port then you could be limited by the Kernal speed depeding on drive settings, pitch etc.
For instance 25Khz kernal speed with drives set at 1600Ms will give maximum motor RPM of 937rpm which with 2mm pitch gives Max velocity of 1875mm/min. Works out like this. 25,000 pulse per sec /1600Ms = 15.625 rev per sec so 15.625 * 60 sec= 937rpm * 2 (mm)=1875mm/min

Now this is the maximum and in real world use you'll be down more towards 1500mm/min for a stable machine.
So if you have actually set velocity to 350cm min which is 3500mm/min then as you can see this would cause stalling motors when speed increases.

If you have set it to 350mm/min and the steps Per setting is correct then you probably have other issues like binding axis etc.?

[john swift]

whats the specifications for the motors and stepper drivers you have ??

using a 36V supply
ideally you should have low inductance motors
( about 1 to 1.5mH ?)

did you buy a kit,
a link to see exactly what you have will be use full

John

[mancave newby]

thanks for the swift reply,i was having a senior moment when i asked the question,everthing is set in mms,have checked my settings and have x 1000.67 steps,vel is at559.98 mm,acc 30,step pulse at0,y is at 1053.35 steps,vel at 349.98, acc 28 step pulse at 0,i have run the beds to their max travel and only have stalling when i put resistance on the hand wheels,however when i run a programe stalls happen between moves,result is lost positioning,so code cuts in wrong places,im useing 4nm motors on direct drive to all axis;s,am still running 2mm pitch lead screws?will change to ball screws when this fault is sorted,the electronics was bought as a kit from cnc4you .home made motor mounts and bearing blocks,will try to post pics when i find how to do it,many regards richard.

[mancave newby]

thanks john for the input,as per the posting,step drivers are set on 3.5amp,10 steps,36 volt power,cnc4you kit,mach 3 licenced,nt sure but i think step drivers will go to 4.2 amp,sorry to be vague about things,but after months of head scatching and retuneing its starting to blow my mind. richard

[john swift]

whats the part number of your stepper motors ?

some thing like this from cnc4you ?

https://cnc4you.co.uk/resources/57HS82-3008B.pdf

with the coils wired in parallel the inductance of 2.5mH
is not too bad


some kits via ebay have motors with an inductance close to 9mH
that will make for a very slow machine with a 36V supply

John

[mancave newby]

hello john,thanks for the response,my motors are 4nm 60byg401-03,wired bipolar paralle,the drivers are set to 4.2 amps,1/10 step,iam using 2mm pitch lead screws at the moment,will change to ball screws when i can get the motors sorted,bought the kit from cnc4you,3 motors,3step drivers and 36 volt power supply,running mach3 licenced version,computer set to 25hz, regards richard

[Doddy]

Mechanical: Decouple the motor from the screw. Can you still stall the motor with the hand-wheel?, if so, then it's not likely the axis binding and I'd move to the electrics. With the system powered (i.e. steppers energised) can you turn the hand-wheels?

Electrical: Your PSU is 36V... have you measured the actual voltage though? Then repeat with the axis stalled.

From everything you've said you've not indicated lost-steps or loss of direction control - so the BoB sounds okay, as does the integrity of the wiring from the stepper driver to the motor.

Can you describe how you've wired the stepper (which colour wires go where).

Can you post the specification of the PSU?

Can you post the type of stepper drivers that you have? (a photo would be useful)

[mancave newby]

motor is direct drive to lead screw lh side of x,hand wheel on rh, yes can stall motors with hand wheels ,cant stall motors by exerting body weight pressure against x or y,can turn hand wheels when motors energised,resistance felt then clicking from motors.psu is set at36 volts ,have checked.wiring to motors is red and blue to a+,yellow and black to a-,white and brown to b+,orange and green to b- motors are 4nm 60bygh401-03 ,drivers are cw5045 supplied cnc4you, bob is a kk01, psu is marked as 36volts 400watt 11amp,sorry cant post pics until i find out how to do it,something else to learn. regards richard.

[john swift]

from your description I don't see any thing wrong

do you have the stepper driver enable inputs connected ??

if you do
try running with the enable disconnected
(the enable is a negative logic input so the drive is enabled with no input !! )

if Mach 3 is a bit slow enabling the drive that could be a cause of you missing steps


what position do you have switch 4 ?

if its off , the motor current will be reduced when the motor is idle

switched on , the current remains at the 4.2A you set the stepper driver to.
and you should feel more resistance when you try to manually turn the hand wheel



John

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[Doddy]

from your description I don't see any thing wrong


I quite agree. Thanks, Richard, for the reply. It does sound as though the steppers are underdriven... but I can't see any cause.Not sure about sw4 - you do say it stalls when operating so half-current setting shouldn't come into play. How warm are the steppers after a protracted period energised?, if not hand-hot then try upping the current setting on the drivers. After that I'm out of ideas.

You've not got any silly-long lengths of cable in the system?, no dodgy fine gauge cables to drop the supply voltage at the stepper driver?

Ah, one point - you still have the trapezoidal lead screws... ah - they will put a larger load on the steppers than a ballscrew... but you do use powerful steppers. Nope, I'm out of ideas.

[Clive S]

Just my 2 cents worth how big are the hand wheels because they will take a lot of inertia to drive them.

[mancave newby]

hello all out there,thought i would try to send some pics of my man cave,hear goes2446724468