question about CNC stepper motors ...

WilleeCue

WilleeCue

The Barefoot Cuemaker
Silver Member
Should a stepper motor on a CNC machine continue to buzz, make noise, and heat up after it has been jogged to a new position and stopped?

I was told that is normal operation for the stepper motors to act that way ... not having a lot of experience with the new generation of equipment I am confused.

Willee
 
Stepper motors are noisy any time they are under power, and as soon as your stepper control system is engaged it will constantly be sending power to the motors - even when they're not moving. Everything you describe is perfectly normal.

TW

 
Will,

Are you using a Gecko G540 controller? If Yes continue on to (1). If No, skip to (2).

(1) The short answer is "yes", but it can be reduced some. Did you install the correct sized resistors across pins 1 and 5 on your motor cables at the motor end? Did you use a very small flat screwdriver or plastic tuning tool to adjust each motor to minimum noise via the adjustment screw on each motor output of the Gecko? It is usual for a stepper motor to stay warm, almost too warm to touch, but it bugs the heck out of me too. Also make sure you have the right acceleration and speed set for each motor in "Motor Tuning" in the Mach3 Config tab. Once, one of my motors somehow got set to 0 and 0 and that thing was noisy until I figured out the error.
Here's a link to the best thing I have found for setting the correct resistor value:
http://www.soigeneris.com/ez_g540___set_of_4-details.aspx
Using an ohmmeter, you dial in the exact resistance that you need to match your motor's amperage.

(2) Beats the heck out of me!

Hope this helps,
Gary
 
Thomas Wayne said:
Stepper motors are noisy any time they are under power, and as soon as your stepper control system is engaged it will constantly be sending power to the motors - even when they're not moving. Everything you describe is perfectly normal.

TW
Click to expand...

Thanks Thomas.
The CNC mill I had before did not do that.
It jogged to position stopped, then the motor was quiet.

On this machine ...
The "A" axis was the worst and the "X" axis did not do it.
If I jogged the "A", "Z", or "Y" axis two or three steps it would stop where it should but it sounded like the motor was still trying to run.

If I jogged it back a step or so it became nice and quiet.

Thanks for the info.
I guess I am making problems where there are none.
However I am taking you advise you offered in another post.
I am going to build my own CNC machine this summer after I have learned enough about the parts needed and hoe they interface.
Then I can only blame myself it it just dont cut it ... LOL!

Willee
 
Last edited:
My stepper motors buzz when moving slow and the noise changes to whine then moving fast. After they stop, they are silent even though they are still powered and held in place by the controller. They never get really hot even after cutting inlays for several hours... They just get very warm.


Kim
 
WilleeCue said:
Thanks Thomas.
The CNC mill I had before did not do that.
It jogged to position stopped, then the motor was quiet.

On this machine ...
The "A" axis was the worst and the "X" axis did not do it.
If I jogged the "A", "Z", or "Y" axis two or three steps it would stop where it should but it sounded like the motor was still trying to run.

If I jogged it back a step or so it became nice and quiet.

Thanks for the info.
I guess I am making problems where there are none.
However I am taking you advise you offered in another post.
I am going to build my own CNC machine this summer after I have learned enough about the parts needed and hoe they interface.
Then I can only blame myself it it just dont cut it ... LOL!

Willee
Click to expand...

What machine do you have?

Kim
 
most stepper drives have idle current reduction which means they will not draw max current when at stand still, thus reducing heat. Some will allow adjustment and some will be preset to something like 70% of max. Also, most of the modern digital stepper drives produce much much less noise than the old choppers but there still annoying as hell.

Another reason for steppers being noisy on cue machines, or other similar type applications is that a lot of the motion in our neighborhood "inches per minute relative to stepper rpm" is in the resonant zone of steppers. I never really understood what resonance was until I held a stepper un-attached to a machine while it ramped up. So sluggish and rough I thought it was broken or something.
 
To clarify ... I am not talking about the noise a stepper motor makes when it is moving.
That is to be expected.
I am talking about the noise it makes at rest after it has moved and stopped at the desired or commanded position.

Lets say you want to rotate the "A" axis.
You turn on the controller and all is quiet.
You command the "A" axis to 90 deg with a G-code command or jog button and the motor runs to that position and stops.
Is it normal for the motor to then make loud buzzing noises or sound like it is still running?

Willee
 
WilleeCue said:
Should a stepper motor on a CNC machine continue to buzz, make noise, and heat up after it has been jogged to a new position and stopped?

I was told that is normal operation for the stepper motors to act that way ... not having a lot of experience with the new generation of equipment I am confused.

Willee
Click to expand...

Mine are quiet when they stop moving.
 
WilleeCue said:
To clarify ... I am not talking about the noise a stepper motor makes when it is moving.
That is to be expected.
I am talking about the noise it makes at rest after it has moved and stopped at the desired or commanded position.

Lets say you want to rotate the "A" axis.
You turn on the controller and all is quiet.
You command the "A" axis to 90 deg with a G-code command or jog button and the motor runs to that position and stops.
Is it normal for the motor to then make loud buzzing noises or sound like it is still running?

Willee
Click to expand...

It sounds like the motors are wired incorrectly or the controller is not working right.

Kim
 
Don't worry willee, as most have pointed out, it's pretty much a normal thing.

Yes, the G540, as well as many other drives, has a current limiting system that will reduce the current to the motor once it's idle for a certain period of time. So, that can reduce or change that sound.

Most likely, the sound you're hearing is really created by the switching type power supply used with most systems today. Basically, a stepper motor is at it's strongest when it's at rest and at full current. That's why they're rated in "holding tourque". Once it starts moving, the amount of "on time" reduces the faster it goes. Most likely, the sound you're hearing is the power supply rapidly "switching" the power on and off to keep the voltage and current where it should be. I have a few systems with a "linear" type power supply, basically a toroid style transformer, and they are much quieter. I've heard the same from others as well.

Also, because the motor uses the most current when it's "holding" or sitting still, that's when it will be the hottest. Steppers can get very hot without any real damage, so don't sweat it. I do like the current limiting systems used though, so if you're drive has the capability, then by all means make use of it.


Have fun!

Royce
 
LGSM3 said:
most stepper drives have idle current reduction which means they will not draw max current when at stand still, thus reducing heat. Some will allow adjustment and some will be preset to something like 70% of max. Also, most of the modern digital stepper drives produce much much less noise than the old choppers but there still annoying as hell.

Another reason for steppers being noisy on cue machines, or other similar type applications is that a lot of the motion in our neighborhood "inches per minute relative to stepper rpm" is in the resonant zone of steppers. I never really understood what resonance was until I held a stepper un-attached to a machine while it ramped up. So sluggish and rough I thought it was broken or something.
Click to expand...



That mid band resonance is crazy isn't it!

You'd be amazed at what adding a heavy round steel weight to the extra shaft on the back of a stepper can do. It acts as a resonance damper. Many systems just can't even get past the mid band without it.


Royce
 
RBC said:
That mid band resonance is crazy isn't it!

You'd be amazed at what adding a heavy round steel weight to the extra shaft on the back of a stepper can do. It acts as a resonance damper. Many systems just can't even get past the mid band without it.


Royce
Click to expand...

rigidity is our friend
its about good vibrations
ive wrapped parts and boring bars in rubber or gasket material with a metal band tightened to it to cut out chatter


sound's cheesy but thats machining for ya
 
RBC said:
That mid band resonance is crazy isn't it!

You'd be amazed at what adding a heavy round steel weight to the extra shaft on the back of a stepper can do. It acts as a resonance damper. Many systems just can't even get past the mid band without it.


Royce
Click to expand...

Royce,
How heavy is "heavy"?
Thanks
Gary
 
GBCues said:
Royce,
How heavy is "heavy"?
Thanks
Gary
Click to expand...

Well, that's the million dollar question.

I've never used them myself as I've been a Gecko drive user for a long time now, but those that I've seen looked to be a steel disk probably 2" in diameter and about 1/2 to 2/4" thick.

That could be a little too heavy, but if you made them that way, you could always turn them down later to reduce some of the weight.

Keep in mind that this also adds quite a bit to the rotational mass so your accelerations will have to be kept down so as not to miss any steps during directional changes at rapid speeds.


Royce
 
Magnetic Technologies

IF you are looking for a great way to "smooth" the issues with stepper motors you might benefit from contacting Magnetic Technologies in Oxford, MA. I have suggested to several makers, using stepper motors, that these people have "the solution" . . . including providing a constant tensioning device that works well for doing Irish linen wraps.

pfd
 
GBCues said:
Royce,
How heavy is "heavy"?
Thanks
Gary
Click to expand...

Gary, I know your running g540. What motors though? I've dealt with the ones that cncrouter parts sells "primo, with almost no resonance when coupled with a g540" and the ones that deepgroove sells "which are doo doo and vibrate crazy bad in the midband" I've not seen the specs on deepgroove motors but im guessing theres a big difference in inductance.
 
pfd studios said:
IF you are looking for a great way to "smooth" the issues with stepper motors you might benefit from contacting Magnetic Technologies in Oxford, MA. I have suggested to several makers, using stepper motors, that these people have "the solution" . . . including providing a constant tensioning device that works well for doing Irish linen wraps.

pfd
Click to expand...

prod_constens_stand.htm

http://www.magnetictech.com/prod_constens_stand.htm
Wow!
Thanks PFD.
 
PRED said:
Would servos be different?
Click to expand...



Of course.

Servo's work pretty much the exact opposite of a stepper.

They don't typically use switching type power supplies. But when they do, the supply is at it's lowest load when the machine is still.

Servo's use the most power under load. The higher the load, the higher the power. Servo's are always feedback, or closed loop (sort of). What this means is that, with servo's there is an encoder position signal fed back to the drive. The drive increases or decreases the power to the motor to keep the position signal where it's supposed to be. Servo's are somewhat self correcting.

Steppers use the most power at stop. They're really a holding instrument first, then a motor. A stepper will rotate a very specific amount with each "step" signal received from the controller. It's position is calculated by the number of "step" pulses that have been sent to it. If it ever gets out of position, the controller has no way of knowing, and it can mess a bunch of stuff!


Royce
 
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