Nema 17 Output Shaft

Greetings to this community!

I am about to start another project using an arduino uno and a DRV8825 driver, which involves a Nema-17 Stepper motor. Before I begin I would like to clarify that I am fairly experienced in 3D design, and can 3D model almost any output shaft I would ever need for this project.

Here is the amazon link for the motors I plan on buying:

For this project, I need to use six of these motors, however I have encountered a problem that I am not sure what to do about.

Specifically I am not sure exactly how I would connect a 3d printed shaft to the shaft of the motor. The "extension shaft" would have one end fitting onto the motor, and another end with a different shape which I will use for my project. The motor shaft is almost a full cylindrical shape, of roughly 5mm in diameter, however there is a slightly flattened side of the shaft, which may be useful in making an extension for the shaft.

However, for this project I cannot afford more than 3 degrees of error in my shaft extension, meaning the output shaft has to be a very tight fit. I could always print an extension to the shaft that fits the motor's shaft near perfectly, but then I would need to hammer in the extension to ensure that all the motors are the same distance from the other end of the extension.

I am unsure if this is a safe and recommended method of attaching a custom shaft to the motor, and wanted to know if anyone here has any better ideas or insight as to how I should do this.

Thanks in advance!

SidKadari:
but then I would need to hammer in the extension to ensure that all the motors are the same distance from the other end of the extension.

Do you mean that your 3D print would be so tight that it could not be pushed on by hand?

On the Nema 17 motors that I have the shaft is accessible at the rear. If you support the rear of the shaft on something then the force of fitting your 3D print won't be taken by the motor bearings.

Other thoughts include warming the plastic to make it an easy push fit and making the aperture in the plastic a little looser and fixing it with glue.

...R

The flat on the motor shaft is so the grub screw that fastens what ever is attached to the motor has a place to dig into the shaft without damaging the curved surface of the rest of the shaft. The grub screw is what makes the extension tight to the motor shaft, NOT friction!

What is your plan to firmly mount the motor to your project so it cannot move when the motor is powered up and trying to rotate the shaft? How are you fixing all the moving parts so they stay in alignment with the motor shaft?

Paul

Paul_KD7HB:
The flat on the motor shaft is so the grub screw that fastens what ever is attached to the motor has a place to dig into the shaft without damaging the curved surface of the rest of the shaft. The grub screw is what makes the extension tight to the motor shaft, NOT friction!

Oh I see so I would use something like the a universal mounting hub and some set screws to use as a hub to connect to the mount, and then the extension shaft.
Ok Thanks!

Paul_KD7HB:
The flat on the motor shaft is so the grub screw ....

I had the impression that the OP was planning a 3D printed plastic collar out of which a screw might pull.

I had also assumed that he would be making the 3D printed plastic collar with a flat within it to match the motor shaft.

@SidKadari, a drawing of what you have in mind would avoid any confusion

...R

Robin2:
I had the impression that the OP was planning a 3D printed plastic collar out of which a screw might pull.

I had also assumed that he would be making the 3D printed plastic collar with a flat within it to match the motor shaft.

@SidKadari, a drawing of what you have in mind would avoid any confusion

...R

Yes, I understand. But the OP seems to be wandering around in the woods looking for something that interests him.
Paul

Robin2:
I had also assumed that he would be making the 3D printed plastic collar with a flat within it to match the motor shaft.

Thanks for this I appreciate trying to clarify. Yes that was my initial plan, however thats because I wasn't sure about what would be the better and safer way of doing this, because I also do not want to damage my motor, and I have previously used motors with attachable shafts, and this is my first time working with D shaft motors. I was open to any suggestion that might help, and I now think I will be getting this mounting hub: Pololu Universal Aluminum Mounting Hub for 5mm Shaft, #4-40 Holes (2-Pack) as well as some 4-40 screws to mount my custom shaft to the motor.
Thanks again!

Paul_KD7HB:
Yes, I understand. But the OP seems to be wandering around in the woods looking for something that interests him.
Paul

Yes that is correct thank you Paul. I was looking for any known safe way to do this, and using a universal 5mm mounting hub and some 4-40 screws should work perfectly.
Thanks again!

I 3D print couplers for my steppers. I make them with a hole that fits a 3mm nut and use a 3mm screw as a set screw (grub screw). They work fine, are quick and easy to make and are more secure than a press fit alone.

coupler.jpg

coupler.jpg

SidKadari:
Yes that is correct thank you Paul. I was looking for any known safe way to do this, and using a universal 5mm mounting hub and some 4-40 screws should work perfectly.
Thanks again!

Further education!
There are three types of set screw/grub screws based on the pointed end of the screw. There are screws with a flat end and they are used in situations where they will be tightened and loosened many times over the life of the project. That way the shaft will not be damaged.
Then there are screws with an inverted cone shape on the end. The edges of the cone are very sharp and will dig into the shaft material and lock themselves. They are used where they must be tight, but still need to be removed often. They will reform the previous screw setting location.
Finally, there are the screws with the single sharp point. These screws are used where the screw must go exactly into the hole created when the screw was first tightened.
All depends on what the project requires, or what you have on hand!
Good luck, Paul