# 3D printed bldc motor is not working



## Lordcx (Aug 28, 2021)

Hi every one.
I've made a small size 3D printed outrunner brushless DC motor but it is not working. It has 9 stator slots with ABCABCABC winding pattern and delta connection with 14 turns, 0.6mm wire per slots, also 6 magnet sets attached to rotor with NSNSNS pattern (blue color print). Also I printed the same size motor with 12N 14P with the same wire and turns (white color print), as attached photos. The magnet sizes also are 15*3*2mm for white one and 15*7*2mm for blue one.
When I connect it to the 40A, 12v ESC, it is drawing 2A from my DC power supply unit and start to vibrating and turning a bit with continuous noise which you can hear in the attached video. 
I also connected it to more powerful PSU and it starts to draw about 5A with the same symptoms but stronger.
I checked the winding directions and points of delta connection, and also polarity of the magnets many time but no luck.
If you need I can also share you the SolidWorks drawings.

Recodred Videos:









Any Idea?

Thank you in advance.


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## electro wrks (Mar 5, 2012)

In order to focus (I'm not sure if that is the right term) the magnetic flux in motor it needs or helps to have iron cores in the coils and for sure back iron to redirect the flux between the magnets: https://www.celeramotion.com/applim...at-does-a-back-iron-do-and-when-is-it-needed/


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## electro wrks (Mar 5, 2012)

If you have access to a CNC laser cutter, you could cut out thin steel laminations with the same cross section of your stator. These could be stacked-up to make a proper stator. Magnets glued inside a section of steel tube is the simple, classic way of making an out runner rotor. You could use the 3D printer to make the bearing(s) and rotor support piece as in your original design.


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## brian_ (Feb 7, 2017)

With concentrated three-phase winnings in nine slots, you have built a stator for a three-pole motor, which makes no sense to me. The "14P" motor presumably means "14 pole"... which makes no sense either. How did you pick these configurations, and what are you using as a reference guide to motor design that would lead you to pick those?


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## Lordcx (Aug 28, 2021)

electro wrks said:


> If you have access to a CNC laser cutter, you could cut out thin steel laminations with the same cross section of your stator. These could be stacked-up to make a proper stator. Magnets glued inside a section of steel tube is the simple, classic way of making an out runner rotor. You could use the 3D printer to make the bearing(s) and rotor support piece as in your original design.


Thank you for your reply, unfortunately do not access to the CNC. But , if the iron core is the case, I wonder how many 3d printed motors work as shown in youtube!!


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## Lordcx (Aug 28, 2021)

brian_ said:


> With concentrated three-phase winnings in nine slots, you have built a stator for a three-pole motor, which makes no sense to me. The "14P" motor presumably means "14 pole"... which makes no sense either. How did you pick these configurations, and what are you using as a reference guide to motor design that would lead you to pick those?


Thank you for your reply, as I know 14 pole means 14 pieces magnet. Also the combinations of the slots and magnets are chosen based on the following table. Please correct me if I am wrong


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## brian_ (Feb 7, 2017)

Lordcx said:


> Thank you for your reply, as I know 14 pole means 14 pieces magnet. Also the combinations of the slots and magnets are chosen based on the following table. Please correct me if I am wrong


It looks like you intended to attach a table, but it's just a link to imgur that doesn't show any relevant image. Where did you get the table? Is there a website with instructions for building motors that you are following?


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## Lordcx (Aug 28, 2021)

brian_ said:


> It looks like you intended to attach a table, but it's just a link to imgur that doesn't show any relevant image. Where did you get the table? Is there a website with instructions for building motors that you are following?


I attached a table in jpg format. The source is the following webpage:
www.bavaria-direct.co.za


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## brian_ (Feb 7, 2017)

Lordcx said:


> But , if the iron core is the case, I wonder how many 3d printed motors work as shown in youtube!!


Motors certainly can work without iron cores, but except in the case of specific designs to work that way, they will generally work poorly. I suspect that most stuff (of any kind, motors or otherwise) shown working in YouTube is either barely working or simply fake, as the maker is more interested in YouTube views than the technology.

Decades ago in a high school shop class we built working brushed DC motors, back before "3D printing" existed (before most people had any kind of computer at home)... and even it that design had an iron strap for a field (stator) core and a bundle of nails for an armature (rotor) core.


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## electro wrks (Mar 5, 2012)

Lordcx said:


> But , if the iron core is the case, I wonder how many 3d printed motors work as shown in youtube!!


You're right, there are working 3D printed motors on YouTube. These motors are made with no typical iron cores in the coils or back iron next to the magnets, but the trade off is much less power for the amount of expensive copper and magnetic material used. Also, these motors are much more prone to overheating with even small overloads. So, these motors generally come under the classification of novelties and fun, but not very useful toys. Is this what you were intending to make? Or, did this just look like a great application for plastic based 3D printing? In design work we call this a solution looking for a problem to solve. 
It's funny, I am knee deep in researching motors for an application right now. I saw this post and went right into researching 3D printed motors. I was taken in by one slick YouTube video on a 3D printed 600W motor. Until I realized a comparably sized motor, with the about the same amount of copper and magnets but with proper iron in the coils and back iron, would put out at least 3-5kW of power! In my opinion, this is a step backwards in motor design. But, it almost had me fooled!

Lorcx, this is of course unrelated to your questions. As brian relayed, I think you need to recheck your winding layout.


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## brian_ (Feb 7, 2017)

brian_ said:


> With concentrated three-phase winnings in nine slots, you have built a stator for a three-pole motor, which makes no sense to me.
> ...
> How did you pick these configurations, and what are you using as a reference guide to motor design that would lead you to pick those?





Lordcx said:


> The source is the following webpage:
> www.bavaria-direct.co.za


Okay, I see what they're doing. Rather than using windings for each phase is pairs mirrored across the motor, they have only a single winding per motor pole pair per phase. The magnetic field paths are terrible, but I don't think anyone building these is concerned with designing an effective motor anyway... they're not the sort of thing you would find in an EV.

The blue motor (9 slots in stator, 6 magnets in rotor) is a 6-pole motor - it has three times as many magnets in the rotor and three times as many winding sections in the stator the simplest 2-pole motor. A normal 3-phase 2-pole motor has six windings:








(ignore the voltages in this example, and note that this example is delta-wired; also note that this is an inner-rotor motor, but the principle is the same as an outer-rotor)
... so a 6-pole motor would have 18 windings (in 18 slots if using a concentrated winding scheme like this).

The motor built according to this more crude design has only three windings for 2 poles








... and so only 9 windings (in 9 slots) for the 6-pole version.
(this one is shown with wye wiring, but it works the same with delta)

So now I understand that the 9-slot 6-magnet motor should work, if driven correctly, although with no iron it will be ineffective and inefficient.

This page gives a decent description of how the three phases must be driven to work, and why it works:
Controlling BLDC Motors
It even uses the minimal winding pattern (without mirrored pairs of windings). Note that it uses the normal 3-phase notation of UVW instead of ABC, but they mean the same thing.
The key to making this work may be that the phases are not just "turned on" in a suitable sequence - they are connected to positive or negative as appropriate to make the current flow the correct direction through the winding for the stage in the energizing pattern - it goes in six steps, not just three - and I don't know if your controller is doing that:








(the green arrows show the current flow and the pink arrow shows the resulting magnetic field)


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## remy_martian (Feb 4, 2019)

My OCD is getting triggered - can you add a couple of skateboard bearings to the rotor shaft?


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## Lordcx (Aug 28, 2021)

electro wrks said:


> You're right, there are working 3D printed motors on YouTube.


You are totally right, I just wanted to make one for curiosity. The lack of iron is not logical to me too, but I did not think that much!


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## Lordcx (Aug 28, 2021)

brian_ said:


> Okay, I see what they're doing. Rather than using windings for each phase is pairs mirrored across the motor, they have only a single winding per motor pole pair per phase.


Thank you for sharing great info. Actually I made this motor based on one of my outrunner motors which has the same slots and magnet pole, but I am not sure about the slot's wire turn numbers since I have not dismantled it, and it is working with the same controller but mine not.


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## Lordcx (Aug 28, 2021)

remy_martian said:


> My OCD is getting triggered - can you add a couple of skateboard bearings to the rotor shaft?


Can you please explain more what OCD is?


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## remy_martian (Feb 4, 2019)

When a minor detail irks you


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## brian_ (Feb 7, 2017)

Lordcx said:


> Can you please explain more what OCD is?


Obsessive Compulsive Disorder


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