Nema8 heat?

[Ray Kholodovsky]

Per an earlier conversation with Anthony, we agreed that the Nema8 stepper heats up A LOT to the point of me, a 3d printer user who regularly handles heated beds at temp (without Harbor Freight gloves :) ) , having to let go of it because of how hot it got.  That easily puts it as exceeding 60-70 degrees.  Even with a4988 current turned way down so that the motor just barely is able to move, it still generates a lot of heat.

Now, using the metal "head" system is more than enough to sink all that heat away.

For anyone using Jason's design where the motor is mounted to a printed part, or another non-metal design, what have the experiences been?  Is the PLA not getting softened/ melted?

Trying to determine if I need to add a metal part/ heatsink, active cooling fan, and so on.

Thanks,

Ray

[Mike Harrison]

On Sun, 20 Mar 2016 12:27:36 -0700 (PDT), you wrote:

>Per an earlier conversation with Anthony, we agreed that the Nema8 stepper
>heats up A LOT to the point of me, a 3d printer user who regularly handles
>heated beds at temp (without Harbor Freight gloves :) ) , having to let go
>of it because of how hot it got. That easily puts it as exceeding 60-70
>degrees. Even with a4988 current turned way down so that the motor just
>barely is able to move, it still generates a lot of heat.
>
>

For the theta axis, where there is no static load, reducing current significantly when not moving
down to a level that just holds the current step would seem like a good idea.

[Ray Kholodovsky]

Mike,

That's certainly one solution we discussed, to disable the motor completely on the "return" trip when it is not carrying a component.  That would result in a 50% duty cycle right off the bat which should help with the heat. 

[Mike Harrison]

On Sun, 20 Mar 2016 12:42:06 -0700 (PDT), you wrote:

>Mike,
>That's certainly one solution we discussed, to disable the motor completely
>on the "return" trip when it is not carrying a component. That would
>result in a 50% duty cycle right off the bat which should help with the
>heat.

That's one solution, and probably the simplest - I'm not familiar enough with stepper drivers to
know if/how easily they suppport automatic current reduction when not moving.

The advantage of reducing current all teh time it;s not rotating rather than disabling when not
carrying is that it could be done automatically at the driver (e.g. a monostable on the step line)
rather than needing to be told when to turn off. Though the vacuum on/off is probably a good enough
indicator to not need a seperate control.

As rotation is always relative between pick and place, there is no need to return to a reference
position between picks.
Assuming you don't have any orientation-sensitive nozzle types - MELF is the only thing I can think
of that might potentially need this.

[SMdude]

I am glad that someone has brought this up!

What sort of hold current is being sent to the motors when they are not moving?

In my mind, if the stepper is stopped on a full step position, you could reduce the holding current to 5%?? Or even have it adjustable in the program.
If you were at a microstep position, you may also need more current to hold that microstep.

We are not milling or doing anything that creates force when the axis are not moving.

Mick

[Rich Obermeyer]

FYI 63 deg/C burns skin before you can release your grip to avoid the burn!  

Thought you should know :-)  I had a legal obligation to find out what it was!

Obviously an average but now you know.

I had a stepper motor heat problem on my 3D printer.  Any motor current changes didn't make much, if any difference.  I made a 3D housing that went over the back of the motor and attached a 50mm fan and now it runs fine.  On heavy prints of 4 hours it only raises temp 10 deg/C.  It doesn't take much cooling to keep the stepper under control.

It should be possible to incorporate Anthony's top vacuum adapter and a fan cooler on the top of the nema8 motor.  I don't currently have a NEMA8 with hollow shaft or I would do the design for you.

The attached design works for a NEMA17 motor but the idea should work with any NEMA stepper.

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[Mike Harrison]

On Sun, 20 Mar 2016 14:02:13 -0700, you wrote:

>FYI 63 deg/C burns skin before you can release your grip to avoid the burn!
>
>Thought you should know :-) I had a legal obligation to find out what it
>was!
>Obviously an average but now you know.
>
>I had a stepper motor heat problem on my 3D printer. Any motor current
>changes didn't make much, if any difference. I made a 3D housing that went
>over the back of the motor and attached a 50mm fan and now it runs fine.
>On heavy prints of 4 hours it only raises temp 10 deg/C. It doesn't take
>much cooling to keep the stepper under control.
>
>It should be possible to incorporate Anthony's top vacuum adapter and a fan
>cooler on the top of the nema8 motor. I don't currently have a NEMA8 with
>hollow shaft or I would do the design for you.
>The attached design works for a NEMA17 motor but the idea should work with
>any NEMA stepper.
>[image: Inline image 1]

Assuming we're still talking about the theta axis, a motor which is just holding position against
no force should not get that hot - there must be something not right with the operating conditions
- voltage and/or current..

As heat dissipation is proportional to the square of the current, it's hard to believe that reducing
it makes little difference.
If all else fails, adding heatsink fins to the motor may be a better solution than a fan, as it is
moving around, so will catch a breeze from the motion.

[Rich Obermeyer]

Mike, You got any heatsinks for a NEMA stepper?

Putting on a 3D printed cooler is cheap, works and it exists.

Since it no longer gets hot, PLA works fine.

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[Mark Harris]

Use heatsinks for computers, VGA coolers for NEMA 23/34.. northbridge/southbridge/ram coolers for smaller - heaps on ebay for a couple of dollars shipped. You can just get one the same size as one of the stepper motor sides and thermal epoxy it right to the motor.

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[Mike Harrison]

On Sun, 20 Mar 2016 18:10:16 -0600, you wrote:

>Use heatsinks for computers, VGA coolers for NEMA 23/34..
>northbridge/southbridge/ram coolers for smaller - heaps on ebay for a
>couple of dollars shipped. You can just get one the same size as one of the
>stepper motor sides and thermal epoxy it right to the motor.

Heatsink was really more of an aside - solving the root problem would seem a better approach than
treating the symptoms with more hardware.

[Ray Kholodovsky]

Good thoughts, I think the off when not in use will be a good start, and if the heat is too much (PLA softens at 60 degrees) I will consider a metal part as a sink, or the heatsink.

To answer an earlier question, the drivers on most boards have the current set by a potentiometer.  Smoothieboard sets the current in the config file, and it's entirely possible that it can be overwritten using a gcode command, but it's not something I would do.

For simplicity it's just on and off.  We don't need absolute rotation here.  

[Jason von Nieda]

I've been using my motors with PLA mounts for about a year now and no problems. They do get hot but not burn my hand hot. I'll take a temperature reading next time I think of it.

For reference, here is my Smoothie config. I am using 0.6A per motor: https://github.com/openpnp/openpnp-openbuilds/blob/1.0/Smoothie/config

Jason

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[Mark Harris]

The problem can be that some cheap drivers makes motors hot no matter what, and some stepper motors just get hot no matter what (internal binding of the rotor, high resistance, poor thermal conductivity etc). So if the option is replace hardware or stick a heatsink on... heatsink is the cheap option :)

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[Jason Parmenter]

No problem here with the PLA printed part.  Similar to Jason's machine, our motors get warm but not super hot.

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[Cri S]

What. Voltage? On Chinese machines this motors are connected to 12v , the others on 24v.

[Jason von Nieda]

I'm using 12v.

On Mon, Mar 21, 2016 at 5:10 AM Cri S <phon...@gmail.com> wrote:

What. Voltage? On Chinese machines this motors are connected to 12v , the others on 24v.

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[Jason Parmenter]

We are using 24V.

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[Cri S]

Technical speaking the cheap driver have fixed on time that can be too mutch for the motor especially if the motor in question have low inductance.
In this case lowering voltage is one possibility in order the driver works correctly.

[Paul Jones]

My motor gets quite hot, but I managed to find a balance between heat and torque. Originally I was using glued heat shrink to attach the vacuum tube, but the motor was too hot for that. The PLA mount seems to be ok though.

 

Paul

 

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[Glen English]

Why are the rotation NEMA8s getting hot at all ?

heatsinks on a nema8 used for component rotation ? 

too much current too much of the time. 

Mine on my setup is running room temperature... No obvious heating at all. 

rotate component at full drive ~ 500mA per phase, ( 1/2 sec) reduce to 20% holding.... about 120mA per phase..... about 100mW per winding.

[Jason von Nieda]

Hi Glen,

I suspect that most people are not using drivers or boards that support reduced holding current, so once enabled the steppers are always seeing full current. That's the case for mine, at least.

Jason

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[Ray Kholodovsky]

Jason, this was not the case in my original test when I started this thread.  At that time I was using an A4988 on RAMPS and turned the current pot way down until the motor was just barely moving, and it still got hot enough such that I could no longer hold it in my hand.  

[Robert Walter]

Ever thought about disabling the Nema8 during non operation (ie, during moves post placement back to your feeder) or if the machine is idle? May not get rid of all heat, but would definitely help. Also, as mentioned previously by Cri S, reduced voltage will likely help too.

[Ray Kholodovsky]

Yes that is the intention.  That immediately creates a 50% duty cycle for the motor.  Also a metal heat sink (read: headset) seems to help. 

[Mark Harris]

If you disable the motor you'll jump to the closest full step, and therefore lose positional accuracy. If you were on 3/8ths of a step for 3-4 moves in a row, you'd be out of position really fast.

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[Jason von Nieda]

This is okay as long as a couple conditions are met:

* You only disable when there is not a part on the nozzle.

* You don't require any absolute positioning on the nozzle between cycles. For instance, nozzle runout calibration would cause this to not work.

In general we don't care where the nozzle is between cycles, only during the time that a part is picked.

Jason

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[rayk...@gmail.com]

And I would also add: re-engage the motor before picking up the next part. 

Ray

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[Paul Kelly]

Or you could just man up!  J

 

The way I tune stepper current on all my cnc machines is to set the axis thrashing back and forth and dial up the current until I just can’t touch the motors. This is usually around 60 deg C and the motors are quite happy at that temp....

 

We’ve been running our two PnP machines most of the day and I just measured the servo motor temps, all of them were > 45degC

 

PK

 

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[Michael Anton]

Yup, steppers are designed to run at around 70C, so too hot to hang on to, but that is normal.

Mike

[Ray Kholodovsky]

I was more concerned with them softening/ melting the PLA part they were connected to than burning myself.  PLA softens at 60C.  The more I think about it, the head has to be metal.  

[Glen English]

Agreed on PLA. 
I'm using a hollow shaft NEMA8, but having a airtight plenum (another Pete Thomson idea) on the other end of the stepper and a fixed air fitting.

And that will be made of ABS for the heating reason....

I like the simplicity of the NEMA11 and the KSX/ KXH rotating air fitting but the NEMA11 is like 120g versus 57g for the nema8... and accelerating the Z at 40 m/s/s the weight matters... we'll see maybe I am just trying to go a bit too fast. But I want to spend less time travelling and more time settling and vaccing. I've done spreadsheets for all of this stuff if anyone interested..

[Jason von Nieda]

Glen,

The "airtight plenum", if I understand what you mean, is how my machine and Anthony Webb's machines work, among others. You can see my version in situ here:

https://raw.githubusercontent.com/openpnp/openpnp-openbuilds/develop/Images/overview_front.jpg

And in 3D here:

https://github.com/openpnp/openpnp-openbuilds/blob/1.0/Mechanical/3D%20Printed/STL/OpenPnP-OpenBuilds-C-Mount.stl

Mine is also how the motor is mounted, while Anthony's is only for the air coupling. Mine is made of PLA and I've never experienced any softening of it. That being said, when I eventually get around to re-printing it I will use ABS just because that is what I use for everything now.

Jason

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[Jason von Nieda]

On other note on this, related to motor friction: In my version linked above there is a small o-ring that forms the seal between the mount and the motor shaft. This o-ring is compressed a bit and so squeezes the shaft a bit, adding some small amount of friction.

Jason

[John Socha-Leialoha]

There is a high-temperature PLA that I've been using:

http://store.makerstoolworks.com/filament/1-75mm/exotic-filaments/3d-fuel-high-temp-advanced-pla-black-1-75mm-1kg/

They say that it softens at about 144C instead of 55C for regular PLA. That should allow you to run the stepper at 70C or more without any issues deforming the PLA.

[Glen English]

Yeah you need a load with some inertia value the texts says, and my experiments confirm

so friction doesnt really do the job.

Having said that, in reality the  thing you are doing by adding weight is reducing the natural frequency of the system.

So it is not a real fix, an improvement though.

The best solution I read is an viscously coupled  inertial damper (like in star trek yes ) .

truly overdamps the system which is what you want.... not just reducing the natural frequency 

Its a 'heavy'  ring floating in some viscous fluid. It appears as a cylindrical inertial load. 

 It's useful for low speed damping where the internal (unfixed) mass is not yet 'spun up' but at high speeds has no drag effect as it is spinning with the casing. almost like a torque converter (without the output shaft).

http://multimechatronics.com/images/uploads/mech_n/Step_Motors.pdf

some very complex ones...
http://bbs.homeshopmachinist.net/threads/24319-Stepper-harmonic-dampers

[Glen English]

Hey I like that high temperature PLA.... 

Now that's nice. I really don't like  printing ABS ...

Reminds me of the old days of making a whole in a box with the end of a soldering iron.

On Saturday, May 7, 2016 at 5:11

[Renato Bugge]

This is an older tread, but I could not find anything around with a solution to the heating "problem".

Anyway, the smoothieboard supports using "M18A" and "M18B" g-code commands to switch off the extruder stepper motors. You can try it yourself in the gcode Console. The stepper motor should rotate freely once you switch them off.

Ufortunately, the "MOVE_TO_COMMAND" has to include rotation, so they get turned on again once a movement is carried out.

A solution may be to add the M18A and M18B commands after the movement has finished. One will loose some accuracy, but if bottom vision is used, it may not be noticeable. E.g. to machine.xml, the "MOVE_TO_COMMAND" should end with:

            <text><![CDATA[M400 ; Wait for moves to complete before returning]]></text>
            <text><![CDATA[M18A ; Rotation stepper off]]></text>
            <text><![CDATA[M18B ; Rotation stepper off]]></text>
            <text><![CDATA[ G4P200 ]]></text>

If you need accuracy, just keep the motors on (and hot).

[Cri S]

The solution is simple , beside lowering the supply voltage, that on
smoothie is not possible.
On Pick command, enable the motor.
On Place command, disable the motor completly.
This gives you accuracy when needed and stops generating heat if no
accuracy is needed
giving time to the motors to dissipate heat.

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[Eagle Media]

Hi,

I just read the thread. Actually there is no such thing like heat problem.
Stepper are running more hot and it's normal.

Regulary You calculate needed Voltage and Current level to the Torque and RPM You need.
Look in the datasheet of the stepper and recalculate your settings.

[Renato Bugge]

This does not work. After place command, motor would be disabled. Then it would be enabled again immediately since the move command actuates rotation and engages the stepper, which leaves the motor enabled.

[Renato Bugge]

Well, we can call it the Nema8 heating feature. I burnt out my first stepper three weeks ago, and it was all due to this feature.

Closely adjusting the current seems to take the temperature below immediate meltdown, but still it is very high. And the temperature varies from stepper to stepper, indicating that some steppers will probably fail.

[Bernd Walter]

This might not help you, since my setup is running NEMA11 and I'm using
a board with StepStick drivers, but maybe it is helpfull to others.
For smooth rotation I'd though it would be a good idea to use TMC2100
drivers for rotation, which I had been laying around and AFAIK do automatic
current reduction.
The NEMA11 stays very cool.
What current are you actually using on the NEMA8?
I've never seen any rating above 0.6A for them.

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[Michael Anton]

If you stay within the current rating of the stepper, it should be fine.  These are designed to run fairly hot.  If you are outside the rated current, all bets are off.

[Cri S]

You have right, it don't work.
To work, inside ReferencePnpJobProcessor.java,
after "// Feed the part"
you need to insert :
try {
HashMap<String, Object> params = new HashMap<>();
params.put("nozzle", nozzle);
params.put("placement", placement);
params.put("feeder", feeder);
params.put("part", part);
Configuration.get().getScripting().on("Job.Placement.Feed", params);
}
catch (Exception e) {
Logger.warn(e);
}

This allows to enable activating of rotation stepper motors.

Now, when you activate motors on pick (for manual control oiutside
automatic run)
and using the new hook for enable motors before there are needed, and
during place gcode,
disable the motor.

This should work. The rotation after placement to 0 is not necessary
for hollow shaft motors.

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[Paul Jones]

I burnt out one of my nema8 steppers as well. No matter what I did I couldn’t get the current low enough to stop it heating up. Eventually it melted itself and caused me to replace it. Problem solved now 😊

 

Paul.

 

From: ope...@googlegroups.com <ope...@googlegroups.com> On Behalf Of Renato Bugge
Sent: Tuesday, 10 April 2018 2:03 PM
To: OpenPnP <ope...@googlegroups.com>
Subject: Re: [OpenPnP] Nema8 heat?

 

Well, we can call it the Nema8 heating feature. I burnt out my first stepper three weeks ago, and it was all due to this feature.

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[SMdude]

Cri S, "This should work. The rotation after placement to 0 is not necessary
for hollow shaft motors."
But it would be good for pick accuracy when the nozzle/holder has runout.
Perhaps for good house-keeping it would be good to always return the nozzle to 0 before disabling.
That being said, my nema 8 motors don't get hot.

[Cri S]

It is better to have a pnp that maybe have problems pick up some
components because of runout problems as one where the motors are used
at heaters and destroy itself.

Every motor driver off/on switch destroys the accuracy of the setup,
this must be clear
to everyone.

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[Mike Menci]

Hello, 

my Nema8 is heating up as well  but only N1-H1   but not N2 -H1 / why if config file is the same for both Nema8?

 

I paste here config with smoothie:

Mike

[Mike Menci]

and I am using a bit longer Nema8 - 20HB4003KB model (more torque for sealing vacuum)

https://it.aliexpress.com/item/M059-20HB4003KB-Hollow-double-shaft-Stepper-motor-NEMA8-20-Hybird-2-phase-4-wire/1335529665.html

Mike