part rotation stepper motor coupling need help

[Jose Silva]

I'm working on 2 different machines for Pnp,

One is a single Head with Samsung nozzle 

For the Samsung nozzle everything is easy because i can use Nema 28 stepper motor with 8 mm shat with can match perfect the sansung nozzle and the rotating joint since everything match the internal M5 of the motor

https://img.alicdn.com/imgextra/i2/1899119018/TB2UvvgmVXXXXbRXpXXXXXXXXXX_!!1899119018.png

and vacuum is connected to motor with this 

http://gd3.alicdn.com/bao/uploaded/i3/T1qnYFFp8bXXXXXXXX_!!0-item_pic.jpg

And the second machine is a 4 head Juki nozzle, where i have a unsolved problem, I'm forced to use nema 8 for this case due to the multi head design,  And Nema 8 is available only with double 5mm shaft with 3mm or 2.5mm internal, I didn't find a way to buy  a rotating joint for this case who will connect to 5mm of thge motor and conetec to 4 ou 6 PU devices, How are you guys connecting the vacuum tubes to rotate on a 5 mm shaft ? I'm looking for something like a rotating joint , but don't find notjing that can connect to a 5mm motor with 3mm internal

[Mark Harris]

For your NEMA8 , most people are 3d printing a top for the hose to go into rather than attaching something to the motor directly.

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[Henrik]

On my machine I made a little adapter out of aluminium that holds two stacked rubber sealed bearings.

Bearing ID fits the motor shaft,and adapter is machined to accept the vacuum hose. Compared to a rotating pneumatic fitting it requires a lot less torque to turn and at the pressure we're talking about here it works fine.

If you don't have access to a lathe you can likely 3D print it and in a pinch I guess you can even use heatshrink tubing with adhesive to"fuse" the bearings with the hose.

/Henrik.

[mojalovaa1]

Jose Silva , where you are buy this stepper :  https://img.alicdn.com/imgextra/i2/1899119018/TB2UvvgmVXXXXbRXpXXXXXXXXXX_!!1899119018.png and adaptor for  air :  http://gd3.alicdn.com/bao/uploaded/i3/T1qnYFFp8bXXXXXXXX_!!0-item_pic.jpg and what type nozzle and nozzle holder you are use , can you add some image for see ?

[SMdude]

I'm in the process of setting up a nema 11 motor with an M5 thread in the end.
Motor:
http://www.robotdigg.com/product/798
Air connector:
http://www.robotdigg.com/product/606

Now a note as to what size air hose to use.... 6mm is way too large!
If using a valve mounted on the head plate, use 4mm or even smaller for the short hose down to the stepper. Also you will probably want to add a bracket and clamp for a strain relief to stop any uneven force on the motor shaft as the nozzle raises and lowers.

[SMdude]

In the picture you can see the 6mm hose, it is too large for that part of the job.
Not much available real estate there, got to fit all those valves on there at some point...

[Henrik]

And here's a closeup of mine:

Motors are NEMA8 with 5mm (OD) hollow shaft, vacuum hose is 4mm (4,3mm) OD. Inside the aluminium adapter are two MR85-2RS bearings stacked ontop of each other, these are very thin bearings, inly 8mm OD, 2.5mm wide with a 5mm bore (obviously). I don't know about the swiveling pneumatic fittings from Robotdig but the ones I'm used to are actually fairly hard to turn, and designed for at least 7-10bar.

/Henrik.

[Daniel Dumitru]

WAs presented several times on this group too a simpler and more effective solution using a 3D printed back cover for motor.

using that it's not needed that fancy coupling.

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[SMdude]

Henrik, are you using nylon or some other softer more flexible hose?

The Robotdigg one, when I turn the hose, it rotates in the fitting before the swivel fitting rotates and easily turns the unpowered stepper. Haven't powered it up yet, so I'm not sure how much force is required to miss steps.

[Henrik Olsson]

No, it’s polyurethane, FESTO PU-3 to be precise.

Its bend radius is small enough and its actually quite flexible yet torsionally stiff so it flexes nicely as the nozzles moves up and down without falling to the sides or twisting or anything.

 

As for the non swivelling adapter “motor back cover type”, that’s a good option too – if you have access to a 3D printer. I don’t so I opted for 10 minutes in front of the lathe and a couple of off the shelf bearings. Simpler and more effective for me J

 

/Henrik.

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[trentonc...@gmail.com]

Henrik,

Thats a great idea.  I wish i had thought to try that before i machined a very similar adapter to what you made out of aluminum and some old 3d printer ball bearings.

[Jose Silva]

https://world.taobao.com/item/529637839370.htm?fromSite=main

https://world.taobao.com/item/529637839370.htm?fromSite=main

[Jose Silva]

That idea is amazing, do you have any STL of this 3d printed back ? to print this, I guess also will need some kind of ruber to put between adapter and motor

[Jason von Nieda]

Here is my design for a Nema 8 https://github.com/openpnp/openpnp-openbuilds/blob/1.0/Mechanical/3D%20Printed/STL/OpenPnP-OpenBuilds-C-Mount-Right.stl

Part of a larger integrated part, but you'll get the idea.

Jason

On Wed, Aug 17, 2016 at 18:20 Jose Silva <jose.do...@gmail.com> wrote:

That idea is amazing, do you have any STL of this 3d printed back ? to print this, I guess also will need some kind of ruber to put between adapter and motor

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[Ravi Ganesh]

I would prefer a vacuum coupling just like this (Peter Betz machine). How do I fix it to the motor body? Glue it with epoxy resin or rip open the screws on the motor and fix it using them?

(This is a fairly old problem, but as a newcomer I am unable to find info on this particular crucial issue)

[evilwulfie]

I made aluminum ones and bought longer screws

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[Ravi Ganesh]

Thank you. It was like the first response I got in this forum. Any advise on coupling 3D printed parts is appreciated (I don't have access to aluminium)

 'R

[evilwulfie]

I dont see why you cannot use 3d printed parts and drill holes and use longer screws.

On 12/27/2020 7:59 AM, Ravi Ganesh wrote:

Thank you. It was like the first response I got in this forum. Any advise on coupling 3D printed parts is appreciated (I don't have access to aluminium)

 'R

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[Ravi Ganesh]

Hi,

I was hesitant to open up the motor. Here is the 3D printed part that I glued with epoxy resin and it is works fine (as as of now ;-)

Ravi.