Hot motor

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
NewGuy
Posts: 39
Joined: Wed Sep 21, 2016 4:01 pm
Location: Krakow, Poland

Hot motor

Postby NewGuy » Wed Aug 09, 2017 8:31 pm

Something has been going on for a while now. I have a bondtech extruder and when printing from the right side, the motor heats up to the point where I can melt a strand of filament by keeping it on the motor for a few seconds. The extreme heat melts the filament inside and makes it impossible to push through, leading to air prints. Any solutions? Some sort of mod like a heat sink?

Vref is at 0.6 (first thing I checked), printing raise3d red PLA at 215 with top cover off.

Jetguy
Posts: 1790
Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Wed Aug 09, 2017 10:41 pm

You are not the first person to report this and at this point, I think maybe it's something specific to the motor you got? That's the only answer that really makes sense because I did extensive testing on my original prototype and did thermal measurements. Please contact Martin. support@bondtech.se
He is very fast to answer and likely will include me as well.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Wed Aug 09, 2017 10:46 pm

Wait, wait, you have the new BMG or you have the original Mini style that reuses your stock motor? If so, then you likely have the stock black motor right? Since that motor came from Raise 3D, they handle the "support" and likely are not going to help specific to the mod but it goes back to what I said about those new motors. You might have to lower Vref by 0.2V more than the recommended setting to get the temp down and that reduces the torque. So, if running a mini style that reuses the motor and has overheating- that overheating was partially present before the change to the bondtech, and because the bondtech is a plastic nylon body instead of aluminum, it cannot cool the motor. So you have the double situation of a motor that got hot (when it shouldn't) and then the mod even though you reduced the current, you also reduced the heat sinking capabilities and so it might be better to roll with a different motor.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Wed Aug 09, 2017 10:50 pm

Either way, more details are likely required.
Which exact upgrade?
What motors exact model?
You say right extruder, so again, the right extruder driver is also adjusted correctly?

Again, definitely glad to help- but at this point, I think there is a chance if the current is correct, then the motor is out of winding spec. That the only reason it would get that hot. Again, it's generally one or the other (current setting not matching the motor or motor not matching the current spec).

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Wed Aug 09, 2017 11:34 pm

The other reason I want to know the exact motor model number, I just ordered a pair of single (not raise 3D specific) Bondtech BMG extruders from SMW3D (really nice shop in Texas) and they are supplying a pancake motor for the BMG with 1.2 A rating that in theory runs very cool. Have not tried yet. That pancake motor Brand is MOTECH MT-1701HS140A.

NewGuy
Posts: 39
Joined: Wed Sep 21, 2016 4:01 pm
Location: Krakow, Poland

Re: Hot motor

Postby NewGuy » Mon Aug 14, 2017 1:36 pm

Hey Jetguy,

Unfortunately this printer, along with its mods, were all done by someone else. I had bought this printer for cheap off of a friend due to her company having nonstop trouble with it. I had tinkered with it but still come across issues like this. I will try to contact her to see what was done, but I know she worked with other printers, not raise printers. Thanks for the help.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Mon Aug 14, 2017 1:51 pm

It's stamped right on the motor. A picture goes a long way here.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Tue Aug 15, 2017 12:49 pm

Sorry, just checking in on this but would love to help you get to the bottom of the problem and be happy printing.
This might be as simple as an adjustment.

NewGuy
Posts: 39
Joined: Wed Sep 21, 2016 4:01 pm
Location: Krakow, Poland

Re: Hot motor

Postby NewGuy » Wed Aug 16, 2017 2:12 pm

Sorry Jetguy, have had a busy couple of days and haven't had a chance to touch the printer.

Is this what you need?
Attachments
20170816_083517.jpg

Jetguy
Posts: 1790
Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Wed Aug 16, 2017 2:36 pm

So, you have the BOHONG motor, the exact one listed in the thread. This is a double issue on a Bondtech upgrade and no real fault of the Bondtech since this is the factory motor that came with your Raise 3D printer. Again, Raise 3D changed motor suppliers and insists there is no change but we have MORE than few threads going on this that real world results say otherwise.

Per this thread, you either need to adjust the stepper driver to a LOWER current per my guidance OR replace that motor and then adjust the stepper current to match the new motor.
Let me state this again. The 0.6V VREF is ONLY valid for the original Minbea 17PM-K342BN08CN motors that were shipped with Kickstarter units.
If you have the BOHONG- you must further lower the Vref.
viewtopic.php?f=4&t=1887&p=15764&hilit=glue#p15517
Key points:
As such, I feel a modified recommendation should be:
If you have the BOHONG stepper motor model 42HBF09AB for your extruders, the vref I came to experimentally:
For stock aluminum body extruder mount-0.7V Vref, a reduction of 0.2V from the old PDF instructions.
For a Bondtech or any other plastic body feeder upgrade (the E3D Titan could be an example), then reduce further to 0.5V Vref.
Attachments
Adjust voltage of A4988.docx
(1.98 MiB) Downloaded 29 times

Jetguy
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Re: Hot motor

Postby Jetguy » Wed Aug 16, 2017 2:40 pm

Vref is at 0.6 (first thing I checked), printing raise3d red PLA at 215 with top cover off.

If you have the BOHONG stepper motor model 42HBF09AB for your extruders...................
For a Bondtech or any other plastic body feeder upgrade (the E3D Titan could be an example), then reduce further to 0.5V Vref.

NewGuy
Posts: 39
Joined: Wed Sep 21, 2016 4:01 pm
Location: Krakow, Poland

Re: Hot motor

Postby NewGuy » Wed Aug 16, 2017 2:52 pm

I'll make the change and test it out when I get the chance. I appreciate the help.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Wed Aug 16, 2017 3:02 pm

Note, you may have to go to 0.45 or even 0.4V depending on your specific setup. Start with 0.5V, test, print a test cube, see how hot it gets.
Lower to 0.45V if the test was still too hot.
Note that the lower you go, the less force the motor has so at some point, this becomes a tradeoff of motor strong enough to not skip steps but cool enough to not overheat. You might decide a different motor is better suited and given motors are about $15, given the total cost of the printer, that $15 might make your whole experience a lot better. Here is a fine example of a 1.3A rated motor that would give you the same connector, same size, and much better rating of 1.3 A coils, so running way cooler https://www.amazon.com/LEORX-Phase-4-Wi ... B015SS3Y7O

artlab
Posts: 3
Joined: Sat Jun 04, 2016 11:02 am

Re: Hot motor

Postby artlab » Sun Oct 15, 2017 4:28 am

Jetguy, got the motors in that you linked but am getting a weird issue.

I installed the new motor, swapped the wires and then the motor refused to move at all. I then swapped back to the old motors and they now also lock up. The old motors do get current as there's an audible back and forth sound but do not turn. The new motors however don't move at all. This motion is similar to when you don't assign the wires in the correct order on the connector.

Interestingly enough, I repeated this on another machine (thinking I damaged the wire) and got the exact some results. Do I have to change the wiring configuration? Or am I looking over something?

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Sun Oct 15, 2017 2:44 pm

You have to change the wire configuration to match the motor. Rocking back and forth is an indication you have crossed the 2 pairs.
Some motors intentionally have the pairs crossed, other motors may not.

Since I do not control the supply of the motors- the best answer is always use a multimeter and check before wiring the motor.
Again, many motors have 6 terminals, but we use only 4. @ may not be connected to anything inside the motor and are just physically there.
Most are:
A space A B space B
Some are A space B A space B
But there are other potential combos.

The point is, at the mainboard there are ONLY 4pins and they are arranged AABB
At the motor side, you simply need to figure out what combo of wire order matches your motor.
CAUTION- NEVER unplug a motor connector while powered. This can blow a stepper driver as the wires make and break contact during the unplugging process.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Sun Oct 15, 2017 2:59 pm

Even though the motor is a 6 wire connector, it is unlikely to be unipolar.
Thus, you have to find the pair contacts in the connector and move the pairs as required.
http://42bots.com/tutorials/stepper-mot ... ng-how-to/
Or
http://reprap.org/wiki/Stepper_wiring
Or
https://learn.adafruit.com/all-about-st ... f-steppers

Again, let's go through your sequence:
installed the new motor, swapped the wires and then the motor refused to move at all.

Simple answer- you did not somehow get the wiring change correct.
I then swapped back to the old motors and they now also lock up

If, just like the order of steps here implies- you simply plugged in the old motor but with the wiring order still modified- yep- not going to work as you now crossed pairs and the motor will not rotate but will rock back and forth.
The new motors however don't move at all

This means that again, more likely than not you have completely failed to move the wires in the correct order specific to that motor and as such, are not even passing current through the coils. As I said, many of these motors have 2 pins in the 6 pin connector to "nowhere" and if the order of wires you chose doesn't match the actual internal motor wiring, it won't spin (rock back and forth only) or if somehow you chose the 2 pins to "nowhere" you didn't even complete the circuit.

Lastly, if you corrected the wiring back to original and the original motor does not work- there is a small chance you damaged the stepper driver in the process of connecting and disconnecting. The extruder stepper drivers are extremely cheap to replace. https://www.raise3d.com/collections/acc ... per-driver

Before you ask
Stepper motor wiring standards.jpg

Jetguy
Posts: 1790
Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Sun Oct 15, 2017 3:27 pm

In general, you won't damage the stepper driver by miswiring to a motor. The problem comes when plugging or unplugging while the stepper driver is energized. The stepper motor is just a coil of wire but a coil of wire is an inductor. If the driver is powering the coil at the time of plugging or unplugging a connector, this causes the inductive properties of the motor coil to generate a massive voltage spike several times the original source voltage. This spikes the driver output FETs and they having a maximum voltage limit being exceeded fail.

So connecting the stepper motor incorrectly- unless you dead shorted the stepper driver (beyond highly unlikely given the connector system), that in and of itself should not damage the driver. Crossing the coils and open circuit are perfectly fine- just the motor does not spin as expected.

Jetguy
Posts: 1790
Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Sun Oct 15, 2017 4:18 pm

Also, if this is the motor you are trying https://www.amazon.com/LEORX-Phase-4-Wi ... B015SS3Y7O
Then it came with a stepper cable that should be wired for that motor and is a clue to the pin placement.
Stepper motor wiring.jpg

As you can see, the center pair is definitely crossed.
Look at the 4 pin black dupont style side.
Left to right, black, green, blue, red
The 6 pin connector
Red, space, black, blue, space, green
Black and green is one pair, blue and red the other pair- keep in mind a reversed pair just reverses motor direction. What is most important first is matching the basic pairs. Then we can worry about motor direction.

Another way to test would be to unplug at the mainboard, plug this supplied cable over the socket pins of the white connector at the mainboard connected to this new motor for testing. Obviously ensure this is connnected and secure before powering and be careful for it not to slip off during testing.

Jetguy
Posts: 1790
Joined: Tue Mar 22, 2016 1:40 am

Re: Hot motor

Postby Jetguy » Sun Oct 15, 2017 5:17 pm

Also, just a note about the stock stepper drivers and that alternate motor linked. The math is that the A4988 based extruder stepper drivers as supplied by Raise 3D follow the basic formula of 0.8V vref= 1.0A of stepper current. Stepper motor current is often rated by the manufacturer of the stepper motor either through calculations or testing to achieve a set maximum temperature rise in the motor. The problem is- that rating and point has a lot of unknowns. For example does it assume the motor is bolted with sufficient contact to a large heatsink or thermal mass? What is ambient around that motor and airflow? What is the duty cycle of the motor?

So based on these unknowns, we de-rate the value typically somewhere by 80-90% and yes, some of this is completely armchair talk- but having seen the unique applications of 3D printing and literally thousands upon thousands of users and motors- these are good rules to live by. Basically, by the new linked motor rated at 1.3A, it has lower resistance meaning less energy is converted to heat and hopefully more is converted to force. What I would consider to be valid vref for that motor is based on some easy baseline values. If 0.8V vref =1A, then 1.2V (0.8 +0.4) is 1.5A, then 1.2A is 0.8+0.2(1/2 of 1/2), so somewhere between 0.8V-1.0V would be a recommended starting point. You might start with 0.9V ref first, and when go up if the motor is cool or down if the motor still gets noticeably hot.

artlab
Posts: 3
Joined: Sat Jun 04, 2016 11:02 am

Re: Hot motor

Postby artlab » Mon Oct 16, 2017 4:03 pm

Thanks for the thorough response Jetguy! I had run into this once before but didn't take into account that the standards would be different on your original amazon link. Just a brain fart I guess but you've provided a lot of knowledge I didn't look enough into yet. Appreciate it!


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