@dc42 Thanks for your follow-up.
Forgive me, I thought our client was using a Duet3 6HC, but rather was using a Duet3 Mini with the 2209 TMCs.
Two motor have burned so far, and we are trying to find the source of the problem before going further.
The 5V comes from the Duet.
Only the extruder is affected.
The first motor was set to 0.365A RMS, the second motor was set to 0.5A RMS.
The second motor never over-heated like the first one did.
It seems like the problem is still there. We specifically ask to start with a current set to 350mA, use spreadCycle, and check the stepper temperature.
Despite these validation, our clients using the latest Duet with the TMC5160 still burn our motors coils.
So far, I'm out of option for our support, as the behavior only happen with the Duet 3 hardware. Is there anything that can be done to evaluate if the problem comes from the Duet on your side and find a solution?
My current solution is to suggest our client to use an external stepper driver when using the Duet 3.
Many thanks for your help and prompt replies! I've added the provided recommendation to our support section.
@phaedrux said in Overheating motors with Duet 3HC and Duet 3 mini:
Sounds similar to this comment maybe?
https://forum.duet3d.com/topic/23050/voron-0-duet-3-mini/17?_=1624659025074Which motor is it specifically?
Indeed, it sounds very much like this, thanks for pointing that out! I've seen exactly the same workaround, which is to set the current to something around 40%~50% of the rated value.
@dc42 could there be something wrong with the settings or registers sent to the trinamics drivers for low current values? I can't test it myself, but it seems like low current motor receive more current than they should. I'd be curious to check the voltage on a scope to validate the settings behavior.
@dc42 said in Overheating motors with Duet 3HC and Duet 3 mini:
@pcarrier said in Overheating motors with Duet 3HC and Duet 3 mini:
Is there a lower limit, or a loss of accuracy, for low current settings?
On the Duet 3 Mini the quantum for setting motor current is 74mA. The current you request will be rounded to a multiple of this so that it is close to the requested current and no more than 15mA higher.
When the motors are operated in stealthChop mode, the current used may vary widely from the current you set, especially if you did not follow the correct tuning procedure. So you may wish to change the mode to spreadCycle to see if the motors then run cool.
Excellent, I'll update our documentation to start at a much lower current, and also change to spreadCycle. Thanks for your help!
I'm glad to see that so many people are upgrading their printers with the latest Duet 3 mini and HC versions!
However, on our side, it seems like we are seeing more and more cases of motor overheating. I'd like to check with you if we can find the source of this issue.
The motors comes from LDO and is rated at 1A RMS, and we specify users to set the current at 0.9A RMS (1.28A Peak).
100% of our motors are tested for pushing force and maximum rotation speed and a QC report is generated attached with each serial number. The temperatures rise is usually as specified, reaching about 20°C over room temperature under normal use. They are running on a A4988 stepper driver.
We have 3 machines running on Duet Wifi and never had issues with the current configuration.
As specified above, the new boards seems to behave differently. We have some users using settings as low as 450mA and still have motors impossible to touch due to the high temperature.
Is there a lower limit, or a loss of accuracy, for low current settings?
Thanks for your help!
What happens if you try to set a dead time longer than 60 seconds?
When I send:
M307 H2 D60
```Everything looks good, and sending M307 H2 shows that the dead time is set to 60 seconds.
Sending:
M307 H2 D120
Same does for 61\. I believe the max configurable is currently 60, but a higher value could solve our heating problem.
Thanks for your support!Hi!
I'm trying to set-up a 3D printer with a heated chamber. Since it is heating very slowly, it needs quite a bit of time before increasing temperature.
However, with the maximum setting for M307 dead-time (60 secs), I'm not able to make it work, the heater doesn't heat quickly enough.
Check the code below:
; Chamber
M141 H2 ; Assign chamber heater to heater 0
M143 H2 S100 ; Set temperature limit for heater 0 to 120C
M307 H2 A50 D60 B1 ; use bang-bang control for the chamber heater with 60 seconds dead time
M305 P2 T97968 B4630 C9.486166e-8 R4700 ; Set thermistor + ADC parameters for chamber
Is there a way to either increase the dead-time or disable the protection for this heater?
Regards,
Phil
Hi Guys!
I have designed this extruder and I'd like to take some time with you and maybe answer some questions you've asked here!
The main problem with using the beta value for our high temperature is lost of accuracy. The most precise option would be to use a RT table or the Steinhart-Hart coefficients. With the beta value, for example, the hotend will show 280°C but in actual life the exact temperature would be 275°C. However, the resolution and stability will be excellent. The thermistor is very sensitive and will detect a very tiny variation in temperature, less than 0.2°C at this temperature with the Duet 12 bits ADC. It is plenty for any 3D printing application.
The stepper is not a 0.9°. Our direct drive extruder, the DyzeXtruder used this type of motor, but not the DyzeXtruder GT. The motor is a very light motor (26mm thick), low inertia and low inductance. You can retract fast with high acceleration. The extruder works great with retraction speed at 30 mm/s using 16 µsteps.
We decided to used a fixed spring because we wanted to get the most stable and consistent extrusion flow. Being able to adjust it might sound great, but after much testing, we found out that the pressure applied on a filament will directly influence the steps per mm. With more pressure on the filament, the teeth will go deeper and the effective pitch diameter will be reduced. Also, for some application, it will greatly reduce the output torque because the motor will be mostly fighting plastic deformation. Changing spring setting to another, for example when you change filament, you might adjust it differently and ends up with a different flow from the first filament. For people who want to achieve great tolerances and consistency, it can be problematic.
Also, we tested two powerful extruders for comparison with adjustable spring tension and filament lever. We got the least filament slipping with the maximum spring tension. However, both levers have become unusable with this configuration.
This is why we decided to get a fixed spring tension. The filament lever always works, you always get the same flow and you don't need to worry about an other variable when switching filaments.
The extruder is very light, about 275g. Our previous motor, a NEMA17 x 40mm, weighted about 280g alone. Pretty impressive for an extruder that is twice more powerful!
Don't hesitate if you have any other questions I may answer!