Indexer - builing you own?

[paco]

I'm seriously considering an indexer.

I've noticed that some user have built their own and what I"d like to know is if it's worth to go this way considering the current price at SB.

Even if I built my own, I still have to get a motor (geared), cable and driver (from SB?)... can I really save?

[paco]

Bill,

your Internet provider is way too serious about SPAM, I cant reach you... but to answer you; YES.

[paco]

Humm... COMCAST really doesn't like me. I sent an inquiry about this issue...

I cant reach fellow Botter WHO JUST MAILED ME AT 18:32...

Thanks for the links. I'm not sure about about the motor part though...

[waynelocke]

Paco,

I used a Harbor Freight Lathe for About $169.00 and had a sleeve made to mount a stepper motor onto the back of the headstock. I also had a lathe extension made to extend the lathe to over 8'. I bought the stepper and the stepper mounting bracket from Shopbot. I did this to have the option of running the lathe with the original motor for sanding or other uses and still have the indexer.

I know little about steppers or drivers and am really not very interested in them which is why I bought them from Shopbot. I'm sure you could save some money if you knew something.

Wayne

[paco]

Do I need that much torque to turn a 6" blank (let say up to 72")?

Do I really need a geared motor?

Just how much torque or power do I need to turn a 6" diameter blank and to hold it still while I machine one of it's side?

[stevem]

Paco, you will probably need some kind of gear reduction unless the stepper has a great deal of torque. You will also want reasonable resolution.

I would suggest using an inexpensive geared belt system that will allow you to extend stock through the lathe spindle, in case you want to machine small diameter round stock.

This project is on my to-do list for the near future..

[richards]

Paco, a geared motor from Oriental Motors (PK296A1A-SGx.x) will cost $257. A Gecko G202 will cost $134. A toroid transformer, capacitor, bridge rectifier will cost $100-$200. A logic board to invert the signals from the Shopbot controller board to interface to the Gecko will cost $15 (for components). Fuses, switches, wiring, misc. will cost $50-$100. (All prices exclude shipping and are in U.S. dollars.)

Depending on your comfort level with electronics, build time might be a few hours or an eternity. If time is money, I would consider buying as much as possible from Shopbot.

The indexers that I've read about all have at least a 1:9 gearbox. A single-stage geared belt system would probably have a maximum ratio of 1:3.6 (using a 20-tooth gear on the motor's shaft to drive a 72-tooth gear). Using XL pulleys and belts, the 20-tooth gear is the smallest gear that can be bored out to 1/2-inch (manufacturer's recommendation) and the 72-tooth gear is the largest available.

[paco]

Steve,

Canadian source for the gearing?... or which US?

I'm looking for Canadian motor source too...

Keep me post on your development.

[paco]

Thanks for the reference Mike!

260$ is a few bucks more than for another non-geared motor I was having my mind on... much bigger though.

That sound quite interesting; I'm looking at the 18:1 and I wonder if it could be fast enough. To still have enough torque, it look like it could make a full rotation in about 6 seconds... I wont be in a hurry but still!?

[richards]

Paco,
If I were building an indexer, I would choose the gear ratio that worked best with the kind of work that I wanted to do. If I truly used it as an indexer, meaning that most of the cuts would be along the long axis (flutes on posts, for example), a high gear ratio would be best (greater accuracy and higher torque to hold the piece in position). On the other hand, if I wanted to use the indexer more as a traditional lathe (turning pens, for example), I would choose a low ratio gear box.

Since the Gecko requires 2,000 pulses to turn the motor's shaft one revolution, an 18:1 gearbox would require 36,000 pulses to turn the work one revolution. Frankly, I don't know how fast the Shopbot can produce pulses. I'll guess that you could expect 25,000 to 30,000 pulses per second, but that's just a guess. Even at 18,000 pps, it would only take 2 seconds to rotate the work one full turn with an 18:1 gearbox.

It probably wouldn't hurt to contact Shopbot and ask them about the pulse rate.