Indexer with a larger than 6" diameter?

[drodda]

I am very interested in the indexer. The main thing that is holding me up at setting one up is the 6" diameter limitation. Does anyone have a setup that allows them to turn 14" or larger on their shopbot? Will the alpha motors allow this to be done? Can they handle the larger load spinning and keep up? I am looking at turning rope pedestals and they need to be 12" to 16" in diameter. They are also about 36" long. Any help with this would be greatly appreciated.

I have been toying with building these in two halves and then glueing them together to make a complete pedestal.

[hespj]

Dave, one of the reasons I bought a ShopBot with 12" Z was to accomodate the indexer. The indexer centre is about 5" high, so it fits in quite well with a 12 " Z.

Much to my shame I havn't used the indexer much since getting it in April - I'm still grappling with 3D stuff before I tackle the 4th axis.

But already I have somebody asking if I could use it to make a round plinth, maybe 2' or more diameter, with carving on the curved face. I don't know till I try it, but in theory the indexer could be mounted below table level to allow this. (Now I wish I hadn't cleverly built under table storage).

If you mounted an indexer 4" below table level your 12" dia would be 2" above table level, and your 16" dia 4" above table level. Mount the indexers' axis parallel to the Y axis and your 36" length + indexer headstock + indexer tailstock might just fit in.

What I havn't found out yet is how heavy a lump of wood the indexer can cope with. I guess that depends on the 4th axis speed to some extent.

Hopefully somebody with more expeience will be along shortly.

John

[dvanr]

I have no more experience than you guys ( probably a whole lot less) but, have you thought about using the Y-axis as a Z axis?

Build the indexer outside and parallel to the X axis.

I have often thought that an indexer that could be wheeled upto and locked onto the X-axis might be a way to over come the 6 inch limitation on my bot.

Just not sure if this would work.

A couple of things to consider.

The Y-axis will need to have all its V wheels installed and adjusted. (TIGHT)

Z driver needs to be connected to the Y motor.

An additional router mount needs to be fastened to the Y car topdeck, the location of the bit would determine how high you built the center of the indexer.

Some kind of dust protect for the X rail pinion gears

and probably a few other gotchas as well.

[gene_marshall]

We have set ours up for the 12" dia
There are pix here http://marshallsmillwork.com/shop.htm
We would be glad to offer advice or tips as we have been turning for about 5-6 yrs.

732-899-4458
Gene

[hespj]

Gene, how heavy can the indexer cope with? I've been wondering about dust collection, it looks like you collect it on the table?

John

[drodda]

Gene,
Very impressive turning on the bot. What software do you use to make a 3d light house?
Are you using the setup that shopbot offers or have you made your own? Is your setup an Alpha? How large of a peice do you think the motor could handle and not burn out the motor?

Thanks for the information,

Dave

[drodda]

Will an older PRT setup indexer work on the alpha shopbot? What would be involved with getting this to work on your setup?

Thanks,
Dave

[drodda]

I already found the answer to the last post but the answer has lead me to another question. Shopbot states that the alpha 10:1 motor will handle 79 pound /inches. Can someone put this in plain english? What does that equate to? How large a piece can this handle? Although I work for an engineering company I am getting a headache just trying to figure that one out?

Maybe I will call Morris Dovey?

Thanks for the help,

Dave

[dirk]

The figure they’re giving you for the motor basically means if you were to attach a lever to the shaft and hung a 79 pound weight to it one inch from the center of shaft, then that is what the motor will pull. This amount sounds rather low to me if it is the same motor used on the other axis geared down 10 to 1. I believe the standard motors are 550 oz inch. Reducing 10 to 1 should give you 5550 ounce inch, converting it to pounds (/16) = 343.75 inch pounds.

[gene_marshall]

Dave, The lighthouse was designed by a friend of ours on autocad, the toolpaths were artcam. We routinely cut oak columns 12" dia x 107" in length.
Raster cut at a stepover of .005
However we have a 25:1 motor.
The 10: 1 motor should do this but may need a smaller step.
The PRT Indexer would need to be modified... Call Grant or Gordon.
John, the peices are VERY heavy, remember the slower it turns the more force it transfers.
The dust collector now works much better, Thanks again to steve and the PC blast diverter. (if you dont have one, GET one)

Dave and Dirk, Those numbers might as well be in a foreign language... the vast majority of woodworkers use sound and feel for determining the stress on the router during machining.
Any indexer should turn any blank, BUT, how aggressively can it be cut.
Basswood is soft and Oak is hard. Each project should be tweaked to where you feel confident.

A Good Tip...
turn off the control box and unplug the indexer before mounting the blank.
If you happen to turn that head chuck while it is connected, you will be shipping a control board to durham NC before you can say OH $#!T.
Gene

[drodda]

Gene,
Thanks for the information. I am trying to figure out how to get a cutting file out of a 3d terrain map in autocad but thats another story. I am still trying to push the PW to the max before investing in more software. Artcam is about 4 deep on my want list right now so I am trying to make things work for now. I appreciate the information and if it was not a 1250 mile trip I would stop out and check out what you are doing.

Thanks,
Dave

[gene_marshall]

Dave, I can make justabout any file you need( for a fee of course)BTW, thats how we started out too.
However, I am glad to help answer some questions and get you going. Really, ask away!
Hope I am helpful,
Gene

[dirk]

Dave
To put the figure I stated above into perspective, cutting with the 11.75 pounds of cutting force is about 1/5 of the cutting force available to the other Axis. This is probably not to much of a problem because most of the cutting is in 3d and a small bit is used. The roughing passes may take a hit and you may have to take light cuts. Another factor is the resolution will also be reduced. If this size blank is going to be the norm I would increase the gear ratio to get closer to the other axis, more like gene has setup at 25 to 1.
Dirk

[hespj]

Gene said - "We routinely cut oak columns 12" dia x 107" in length." - which I guess is over 200lbs? That's really exiting, I want to do it.

A piece of wood like that isn't going in the chuck, how do you fix it? Fit a faceplate of some sort? What about the tailstock fixing?

Thanks for sharing your experience.

[gene_marshall]

Yes John,
We make a 3/4 plywood plate that has notches in it for the jaw teeth
This is basically a 6" circle withe 3 places for the teeth on our 3 jaw chuck.
The center is also drilled for aligning to a center on the wood blank.
on the tailstock the same kind of plate is used but with a washer recessed into the center that the point of the tailstock will ride on.
As far as the gearing goes... We upgraded our motor thru shopbot. i would suggest that to anyone who has intentions of this sort. the unit values need to be tweaked as well which they helped us with. The last columns were around 150-160 lbs (rough guess) and turned quite nicely. be sure to ease into the part with smaller Z steps and a slower speed. I try to listen to the router and watch the peice, so making on the fly adjustments is based on router load.

Cheers
Gene

[marshawk]

You can see the columns here:
http://marshallsmillwork.com/columns.htm

Cheers!

Chip

[jeff_guinn]

Chip/Gene,
I can't find a 25:1 geared stepper on Oriental's site. Can you provide a motor# & do you part off the waste on the indexer? You fellas really do some great work!
Thanks,
Jeff

[mikejohn]

Great stuff.
Incidently, which one is Chip, the good looking one or the other one?
.............Mike

[gerald_d]

The John's are known for their off-center tastes in men's looks.

[marshawk]

Gene is the dorky looking one standing between the two posts.
I am not pictured because Gene can only pick up a camera and complain that it doesn't work.

[marshawk]

Jeff,
Contact Gordon at ShopBot. He *may* be able to help you out.

[gene_marshall]

I have no problem with MEn thinking I am not good looking...
It's the women's opinions that matter
( the truth is this kind of banter takes place in our office and is harder to type than to yell accross the shop)
( more truth- When I am behind the camera and chip is in the pic... THE CAMERA BREAKS. { the old face for radio thing })

Back on topic, the motor was a leftover from an experiment that Ted was up to.
Gordon has the info and we have told them how well it is working so maybe they will know what you are looking for when you call.
This one was a 3/4 arbor that was ground down.

[Brady Watson]

Gene,
You're MUCH better looking than Chip...

5285
Luv,
B.K.

[marshawk]

For once I find myself feeling better about being insulted...