[Nelson_2008]

I'm thinking about making an "electronic indexer" for my 6" Vertex rotary table, but up front I'm wondering: How are people attaching stepper motors to tables like this?

From a few examples that I've seen on the internet, it looks like the motor is ultimately turning against...set screws?

IOW, there is a collar that slides over the "eccentric housing", and that collar has two radial set screws - which fix it to the eccentric housing - and it has a radial lever attached to it, and that lever is used to rotate the eccentric housing (through which the "worm shaft" passes) to engage or disengage the worm gear.

For some reason, that collar also has three M5 threaded holes in it (and I've been wondering what was the purpose of those three holes), and it looks like people are using those three holes in the collar to mount the stepper motor.

If this is the case, then the stepper motor is anchored by the set screws. Is this how it's generally being done? If so, that doesn't seem like a very desirable method to me.

Has anyone done it a different way?

[lsces]

But that is only clamping the eccentric sleeve in the hole, the rotary pressure is not excessive if the table is set up properly. The motor stalls long before you could twist the plate

[hoss2006]

J Fettig has free plans for mounting to a 4 inch phase 2 which may help.
JFettig Machines
This guy did a very nice conversion of a phase 2.
[ame=http://www.youtube.com/watch?v=2JLnW3-JX2w&list=FLjoRKEpk7uE5Wzf4b-IFTFg&index=67&feature=plpp_video]DIY 4th axis CNC rotary table conversion - YouTube[/ame]
Hoss

[mhackney]

+1 pm Fettig's mount. I did the same on my Phase 2 and it was easy and works great.

cheers,
Michael

[Nelson_2008]

Hello lsces,

Thanks for your reply. If I understand correctly, you're saying that: yes, the motor does work against set screws (actually two sets of radially "nested" set screws, right?), but in practice that's not an issue.

So basically there's no machining operation you could do with the table, e.g., cutting a groove in a flange for a gasket or something, where you could cause the motor to rotate against the set screws, because the motor doesn't have enough torque?

[lsces]

Hello lsces,

Thanks for your reply. If I understand correctly, you're saying that: yes, the motor does work against set screws (actually two sets of radially "nested" set screws, right?), but in practice that's not an issue.

So basically there's no machining operation you could do with the table, e.g., cutting a groove in a flange for a gasket or something, where you could cause the motor to rotate against the set screws, because the motor doesn't have enough torque?

I've not done a lot of work with the 6" table, and it only has a 180Ncm motor, but I've never had a problem. I have yet to try with the DMSuper into 300Ncm motor, but I would not expect the set screw to be a problem, since their points dig into the eccentric body anyway ...

[Nelson_2008]

Hello Hoss thanks for the info.

I was thinking about just using a few standoffs and a plate to mount the motor, to keep the assembly as light weight and simple as possible, and then I went to Jfettigs web site and saw exactly what I had in mind.

J Fettig has free plans for mounting to a 4 inch phase 2 which may help.
JFettig Machines
This guy did a very nice conversion of a phase 2.
DIY 4th axis CNC rotary table conversion - YouTube
Hoss

[hoss2006]

Hello Hoss thanks for the info.

I was thinking about just using a few standoffs and a plate to mount the motor, to keep the assembly as light weight and simple as possible, and then I went to Jfettigs web site and saw exactly what I had in mind.

Yeah a backing plate with standoffs is basically how I've converted my rotary tables over the years.
Trunnion Table - CNC - The Hossmachine Forum
Projects2
Hoss

[Nelson_2008]

Lsces, what do you think of this idea:

On my Vertex 6" rotary table, there's a flange that bolts to the body of the table with 4 M3 socket head cap screws. The flange holds the eccentric housing in place. Suppose you made up your own specialized threaded-stud/standoffs that had a male 3mm thread at one end - to replace the cap screws - and a female thread at the other end (or a male thread for that matter) so that a motor mounting plate could be bolted to the studs. And of course you could put some wrench flats on the standoffs somewhere so you could snug them down.

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Edit: I just realized the obvious problem with that idea: How would you hold the eccentric housing in the engaged position? Actually you could still lock it down it would just be somewhat inconvenient to get at it I suppose.

Edit#2: I don't have any experience with "oldham" couplings, but they're probably too big to fit into the area between the studs, right? If so that would kill the idea.

I've not done a lot of work with the 6" table, and it only has a 180Ncm motor, but I've never had a problem. I have yet to try with the DMSuper into 300Ncm motor, but I would not expect the set screw to be a problem, since their points dig into the eccentric body anyway ...

[lsces]

Edit#2: I don't have any experience with "oldham" couplings, but they're probably too big to fit into the area between the studs, right? If so that would kill the idea.

The think to bare in mind is that the coupling needs to stay in line with the shaft. If you mount of the body of the table, then the eccentric action may be in the wrong plane? My adapter simply bolts to the same set of holes used for the division plates and there has never been any problem. I supply a 25mm coupling, but sometimes the stepper motor shaft needs cutting back a little to fit it.