Thread: Homemade CNC Indexer

For a couple of years I have wanted to build a CNC indexer so a few weeks ago I finally got the job done. Right or wrong I used a worm & Worm gear and of course when using gears backlash is always a concern. With backlash in mind I came up with a few ideas to minimize backlash. I used a 30 tooth wormgear and worm purchased on Ebay. I wanted strong gears.

First the worm is mounted in its own block of castiron and inside a pocket. The worm is centered with spacers that I surface ground to minimize endplay. Endplay of the worm is in the area of .0005". Notice the key is about the same length as one of the spacers. I almost made something that could not be assembled.



larger picture

See it run, Careful audio is loud

To address the backlash issue I mounted the worm and worm gear is separate blocks of
castiron. I determined the center to center distance then added .015 for grinding. I surface ground the mating surfaces to reduce backlash (gear clearance) and not have the gears bind. It was done by trial and error by grinding off a couple of thousandths then testing the backlash. I figured if I took off to much making the gears bind I could make shims to find the best clearance. I got lucky and have the backlash to almost "0" and no shims.



I made the indexer with no bearings. The steel worm gear is mounted by its precision ground hub and held in place by the table and the actual worm gear. I'm relying on the castiron to be the bearing. This could be a mistake but time will tell. The 3/4 hole goes through the entire indexer where I can install DA collect chuck so small collets can be used.




Larger view of worm assembly

Surface grinding the gear fit.
Grinding gear fit

More pics of Indexer

I have no specific application for the indexer but it could be used as a toolchanger for my CNC lathe retrofit.

Hope this was of interest.
Jim

Always fascinating to see what you cook up, Jim.
How are you going to control the indexes--via stepper?
Did you make any provision to lock the indexer in position?
Any issues grinding cast iron?

Originally Posted by JimGlass

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Hope this was of interest.
Jim

It was. Thanks for sharing.
How will you lube it?
Looks like the two blocks are just bolted together - how are they registered, or not?

Cheers,
Rich

Jim,

That looks great!!!

I have been wanting to make something like that.

Everything I see is for another full axis ( rotate while machining).

I just want something to index and hold the part in place while machining.

Maybe splines, rotating jig, etc.

Thanks for sharing.

JAckal

Is it an indexer, or a Forth Axis? If the cnc is running the servo motor, I think you could fumble it around, and turn it into a forth axis. It may be a math problem to synchronize it, but what the hey. I was toying with the idea to pick up another servo motor and switch out the Y Axis now and then, to use the Y Axis "Info" for the "Forth Axis" drive. Build it directly on the servo motor, in a similar method to what you have done.

Nice job!

Regards,

Stan-

Originally Posted by Jean Solderov

Always fascinating to see what you cook up, Jim.
How are you going to control the indexes--via stepper?
Did you make any provision to lock the indexer in position?
Any issues grinding cast iron?
How will you lube it?
Looks like the two blocks are just bolted together - how are they registered, or not?
Cheers,

Indexes controlled with a stepper, the motor you see.

No provisions for a lock on the indexer yet. If it is used as a toolchanger for my lathe I may use a shotpin on linear ball bearings to lock it in place.

No issues grinding cast iron other than cleaning out you nose afterward.

Lubrication; Since the indexer will not likely be running continuously I plan on using light oil on the bearing surfaces and some kind of grease on the worm and worm gear. I may install some ball oilers. I'm open to suggesions.

The two blocks could be dowel together if need be but for light work I think the (4) 1/4-20 SHCS will do the job.

Thanks for all the comments and questions.
Jim