DIY CNC mill from mainly salvaged and 3D printed parts

[dbemowsk]

So, turns out the shaft couplers that I got are kind of crappy and seem to come loose every so often. These are the ones that I got which have their set screws on opposite sides from each other:

I am looking to get some replacements, but am wondering which style would be best to get. There is this style which has set screws at 90 degrees to each other:

There is this style which actually clamps around the shaft:

Then there is this style that also is a clamp style which says that it is somewhat flexible. The thing with this style is that I don't know if it separates at the red part:

The shaft on my stepper is a D shaft, so I am wondering how well the clamp style ones will work, at least on the motor side. The lead screw is round, so that should be fine for the one clamp.

Any thoughts?

[NeverDie]

@dbemowsk My kit came with the same blue couplers, and they came loose too. However, loctite fixed the problem.

[dbemowsk]

@neverdie I'm assuming you used loctite blue?

[NeverDie]

@dbemowsk Yes.

[NeverDie]

I believe the flexible couplers are for when the stepper axis isn't co-linear with the threaded rod.

[dbemowsk]

@neverdie I still may buy another set. I think the clamping style would be the best, but as I said, not sure how that would be on the D shaft.

[NeverDie]

@dbemowsk Are these not something you can 3D print? Then you could customize to the D shaft if you like.

[NeverDie]

BTW, I suspect that using longer linear bearings will lead to less slop:
http://a.co/0yWkPgi

[dbemowsk]

@neverdie said in DIY CNC mill from mainly salvaged and 3D printed parts:

@dbemowsk Are these not something you can 3D print? Then you could customize to the D shaft if you like.

I guess I hadn't thought about 3D printing them. I did order a pack of two though.
https://www.amazon.com/uxcell-Encoder-Coupler-Coupling-8mmx5mm/dp/B01E0CTI42/ref=sr_1_14?ie=UTF8&qid=1522050398&sr=8-14&keywords=5mm+8mm+coupler

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@neverdie said in DIY CNC mill from mainly salvaged and 3D printed parts:

BTW, I suspect that using longer linear bearings will lead to less slop:
I would tend to agree. Does your CNC use linear bearings?

[NeverDie]

@dbemowsk said in DIY CNC mill from mainly salvaged and 3D printed parts:

Does your CNC use linear bearings?

Yes.

[dbemowsk]

Just a note to everyone. These style couplers are NOT good for the X axis, or Z axis if the motor is vertical and facing down.

The problem is that the spiral part is actually quite springy. When say the X axis motor spins to pull the X axis to one side, the springy part seems to really stretch. Pushing the X axis works fine. Since my Z axis motor is mounted on top with the weight of the axis being downward, this will cause the coupler to stretch even more. My 3D printer uses these on it's Z axis which works fine because the motors face up with the pressure of the Z axis down on the couplers.

The only thing about the ones that I got that I liked was the way that it clamps to the shaft. I think the clamping action is better because you get more surface area grabbing the shaft.

Something like this may be the best because it is solid and there is no stretching. It also has the clamping action.

[Technovation]

@dbemowsk they should work if used as intended. These couplings are supposed to be stiff in only one direction of freedom: Rotation of the axis (=transfer the torque of the motor to the axis). The other 5 degrees of freedom should be of low stiffness to absorb misalignment between motor and axis. So the correct type of bearings should actually constrain the axis to only rotate in one DoF and not translate into the coupling.

[dbemowsk]

@technovation DIDn't think about that when I bought them. I will save them for spares for my 3D printer.

[NeverDie]

I notice that the kit from CNCrouterParts does appear to use the springy couplers:
https://www.youtube.com/watch?v=EiOOrOfwKvw

So, I guess it can't be bad, because they seem to make very nice kits.