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deanq
12-06-2010, 11:03 AM
I'm building a 4th axis. I'm converting an 8" rotary table directly coupled to a stepper motor.

Is a 500 oz-in one large enough or should I go larger?
I have a 900 oz-in, but it seems rather large/heavy and it's a NEMA 34 size. A NEMA 23 size would work out dimensionally better, but 500 oz-in is about max for that size.
Dean

PaulT
12-06-2010, 01:34 PM
Take a look at the 8" table sold by www.tormach.com .

I think in their specs they say what size motor they are using, if not you can probably figure it out from the size and current requirements.

Paul T.
www.power-t.com

ldbent
12-06-2010, 01:51 PM
Tormach web site shows nema 23 for 6 inch and nema 34 for 8 inch.

Larry

philbur
12-06-2010, 02:02 PM
I have fitted an 8" Vertex RT with a direct drive 650 oz-in motor, as per the Tormach table. It will drive the table at full speed (5 rpm) with the table locks on without a hicup, so my guess is that 500 oz-in would be OK.

http://i186.photobucket.com/albums/x36/philbur/rt3lr.jpg

Phil:)

PaulT
12-06-2010, 04:09 PM
Phil, I'd like to add an 8" fourth axis to my machine but I'm tight on dough so I'll have to do it the home brew way you did.

Did you select the Vertex table for any particular reason?

Was there anything unexpected in fabbing up the bracket and coupling and getting it to work?

Thanks,

Paul T.
www.power-t.com

gary350
12-06-2010, 04:23 PM
A few years ago I sold a 10" rotary table for scrap metal. It was rotated 60 degrees at a time by putting air to the cylinder. Every time the air was inergized it rotated 60 degrees and locked in place. Someone gave it to me I saved it 16 years never used it so I trashed it 5 years ago because I could never find a project for it. Wish I had been on this forum 5 years ago I bet someone here would like to have it.

squirrel
12-06-2010, 07:30 PM
A few years ago I sold a 10" rotary table for scrap metal. It was rotated 60 degrees at a time by putting air to the cylinder. Every time the air was inergized it rotated 60 degrees and locked in place. Someone gave it to me I saved it 16 years never used it so I trashed it 5 years ago because I could never find a project for it. Wish I had been on this forum 5 years ago I bet someone here would like to have it.
Was that the Erickson Flash indexer or something like that? If memory is correct the scrap pile was an appropriate spot because it could not be converted over to a motor.

deanq
12-06-2010, 07:36 PM
Thanks guys,
I have looked at the commercially converted tables and they are using anywhere from Tormach's 650 oz-in to Industrial Hobbies 1250 oz-in.
If I were to use a belt/pulley drive I could gear any way I needed, but the Vertex type table doesn't have enough space to add what I consider a needed roller bearing without major parts re-design to accommodate the side loading.

Philbur,
Thanks for the picture. It appears my design is similar to yours. I am very impressed with my Taiwanese made table. The only fault I have is it needs another thrust bearing on the fore end of the drive shaft, the aft end has one in place already.It's very well made.
I'll take some pictures to document any problems.
This should be very simple :rolleyes:
Dean

John Stevenson
12-06-2010, 07:53 PM
An 8" vertex needs a minimum of 420 oz in up to 650 oz in, anything over this is overkill as you need to take the 90:1 gear reduction into account.

What is more important is the supply voltage going to the stepper,
If you can use the high power drives and run at 70 - 72 volts then you will get far greater performance than running at 30 odd volts.

The 8" vertex can be converted to double ball thrusts but there is no room for bearings on the worm shaft.

philbur
12-06-2010, 08:06 PM
I use the Vertex because that's what I already had.

Have a look here:

http://www.franksworkshop.com.au/Workshop/RotaryTable/RotaryTable.htm

Phil:)


Phil, I'd like to add an 8" fourth axis to my machine but I'm tight on dough so I'll have to do it the home brew way you did.

Did you select the Vertex table for any particular reason?

Was there anything unexpected in fabbing up the bracket and coupling and getting it to work?

Thanks,

Paul T.
www.power-t.com

philbur
12-06-2010, 08:12 PM
I machined some off the outside end of the eccentric and added a second thrust bearing. Seemed to work well enough.

Phil:)


The only fault I have is it needs another thrust bearing on the fore end of the drive shaft, the aft end has one in place already.It's very well made.
I'll take some pictures to document any problems.
This should be very simple :rolleyes:
Dean