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  #1  
Old Tue 01 January 2008, 08:53
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Indexer Tailstock and Headstock Source

When I build my MM, I want to add an indexer. I have looked at the ShopBot Indexer and I like it but I can't buy them and I think they are over priced.

I would like to find a source but I have not had any luck using Google and other sources.

If you have an indexer that you bought or you have a source, would you supply your source. Links would be nice.

I plan to use the same motor to drive the indexer.

Thanks
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  #2  
Old Wed 02 January 2008, 11:52
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
I contacted a user on the ShopBot forum that made an indexer using the Headstock and Tailstock from a Harbor Frieght wood lathe. So I went and looked at the HF one. On sale you can get one for around $200.

I decided to look at the lathes at WoodCraft. The have a mini Delta and Jet that run arount $329 / $250 on sale you can pick up a Jet for $225. They can handle 10" piece of material or swing over bed. I would take the Headstock and Tailstock and attach them to the X or place at the end of Y.

I would still like to hear from anyone that has an indexer.

Thanks
Nils
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  #3  
Old Wed 02 January 2008, 16:16
garyc
Just call me: Garyc
 
Charlotte, North Carolina
United States of America
This is the one that I bought.
http://www.littlemachineshop.com/pro...ory=1034788869

Last edited by garyc; Wed 02 January 2008 at 16:17.. Reason: Typo
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  #4  
Old Thu 03 January 2008, 11:46
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Art is the turning guy on the forum. You could look at his site www.turningaround.org for some pics of his stuff and some ideas.
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  #5  
Old Thu 03 January 2008, 19:36
Robert M
Just call me: Robert
 
Lac-Brome, Qc
Canada
Send a message via Yahoo to Robert M Send a message via Skype™ to Robert M
Nils, I too will be on the making of MM with an integrated indexer, This project of mine is been on ice for +/- 2ys, but although I’ve keep my eye open for such and in my opinion base on what I’ve seen, your way better to make your own if you ever intend to mill stock bigger than what those mini-lathes can give you. Best of all, not only you make it, it also cheaper !!
Art is one heck of an inspirational example of this DIY !!
Robert.
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  #6  
Old Thu 03 January 2008, 23:42
BernardR
Just call me: Bernard
 
Georgetown Texas
United States of America
Nils,

I feel there may be a small communication problem here where guys from two different disciplines are trying to reach an understanding.

Generally in the machinist field I would be thinking on an indexer as a heavy duty precision spindle being turned through something like a 60:1 worm drive, the ultimate rotary position being accurate to minutes of arc from some reference. Generally used to make gear wheels, there are different sets of index plates which are used to get the right angle. Rotary tables are similar but the index plates are not fitted unless that type of exact repetition is required. Again there are various configurations and you can get an idea of what is available here: http://www.use-enco.com/CGI/INPDFF?PMPAGE=415&PMCTLG=00

On machinists gear cutting lathe there are occasions when they require to do accurate division work, in which case they use an indexing jig which engages the lathe's bull gear.

If you can give an idea of what you will be using it for, maybe I could be of more help.
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  #7  
Old Fri 04 January 2008, 17:38
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Barnard,

I will be cutting more wood, MDF and Corian type material before I cut any metal though I might cut Aluminum is small amounts. The indexer with be more like a wood lathe but use the stepper motor to drive the rotations of the Headstock.

I decided I seriously wanted an indexer after seeing a local ShopBot machine with one and seeing the interesting work that was being produced.

The ShopBot prices are way too expensive in my opinion. Even some ShopBot users are buying a Harbour Frieght low end wood lathe and converting it. I like the Mini Jet JML 1014 unit. The headstock is smaller than the HF unit many are buying and the cost is not that much more if you buy a Jet on sale.

The Jet will give me a Max of 10" that I can cut. I think that will work for the things I want to use it for.

I hope that more MM users will talk about their designs for an indexer. I know I can use all the help I can get.

I have looked at Art's machine and what he is doing. He does nice work but his machine is designed for lathe type work to be the primary reason for his machine. My index interest is secondary.

Robert M

I will be intersted in hearing more about what you are going to do.

Mike

I hope that you will chime in because I know you built one for your ShopBot. Mike I am planning to purchase another 203V Gecko and the same motor - PK296A2A-SG7.2. Will this motor be a good fit?

Thanks

Last edited by sailfl; Fri 04 January 2008 at 17:52..
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  #8  
Old Fri 04 January 2008, 20:04
BernardR
Just call me: Bernard
 
Georgetown Texas
United States of America
Nils,

I can see nothing wrong with using either the headstock from an existing lathe or using a separate dividing head. My own inclination would be to go to a separate head which can be tilted through 90 deg, this then gives you the ability to do precision drilling work as well. As tailstocks are readily available for these separate heads it also makes for a much easier installation as regular lathes are specifically designed with V grooves and strange hold down methods to fit between the ways.
The only real objection I see to using a dividing head is what is the maximum turning speed you need. A semi universal dividing head (probably the most suitable device) has a gear ratio of 40:1, recover 4:1 back from the motor to shaft, i.e. an overall gear ratio of 10:1, so you could expect round about 300 RPM out of a reasonable servo.

If you were to convert a lathe you would be removing the V belt and replacing it with some form of toothed pulley. For a dividing head the simplest method is to replace the worm gear handle with a pulley.

My own inclination for this operation would be to go with a servo motor and an appropriate Gecko (320) drive. The reason I suggest this is that the servo can deliver significantly greater power at turning speeds and has the advantage of strong location force to resist cutting effort. Remember, there will be no resistance / clamping force to the bed.

I just had a look at the Shopbot indexer and I would agree that they seem outrageously priced, it is likely that a six inch unit will do everything you want, but there is an intermediate step that Shopbot don't show which is an 8" unit. The only thing you need to be aware of are that these are significant lumps of metal and by the time you have a 3 jaw chuck on the end you are talking reasonable weight. My own precision Hoffman 6" head weights is at around #90!!!

Hopefully this has at least given some food for thought.
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  #9  
Old Sat 05 January 2008, 03:41
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Bernard,

Thanks so much for your input. I am mechanically challenged so I need assistance with the mechanical part of my design. My background is software. I don’t see a need at this time for the head to be able to tilt or to do precision drilling. I thought the V groove was an advantage as it keeps every thing lined up and will not require a process to insure that they are aligned when moved. What would you use? I was not planning to add a toothed pulley but to have a direct connection from the motor to the shaft that connects to the head like ShopBot and others have set up.

I found some better pictures of the ShopBot system which shows the Headstock and Tailstock. (I realize that the price ShopBot charges is not just for the Head and Tail but I am amazed they are asking so much.) I have also included a picture of a Harbor Freight connect which is also direct.

I would like things to be simple. I think I could get some one to cut and weld a headstock like the ShopBot. I like the tailstock from the lathe but I am having trouble finding a new one that is separate.

What motor and Gecko to use is where I need assistance and suggestions. I do realize these are different forces which may require a different motor and Gecko.

A maximum turning of 10” will suite my needs. It looks like some users attach the indexer onto the X axis when they need to use it and other at the end of the table. I am not sure where I will locate mine.

ShopBot Headstock and Tailstock

Last picture Harbor Freight Headstock
Attached Images
File Type: jpg Simple Headstock.jpg (23.0 KB, 603 views)
File Type: jpg Simple Tailstock.jpg (23.6 KB, 604 views)
File Type: jpg HF Headstock.jpg (22.2 KB, 601 views)

Last edited by sailfl; Sat 05 January 2008 at 03:43..
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  #10  
Old Sat 05 January 2008, 04:57
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Bernard,

I have not seen an indexer operate on a CNC machine but I don’t see the force being any greater than that of the X or Y axis. Your comment, “the servo can deliver significantly greater power at turning speeds and has the advantage of strong location force to resist cutting effort” suggest that the indexer will be turning like a lathe head would be turning at high speed, if I understand you correctly.

My sense is that the indexer motor will not be moving any more than any other axis depending upon the design and shape of the material. For this reason the current motor and Gecko should be suitable for an indexer.

Am I think incorrectly? Some one with experience with an indexer needs to comment here please.
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  #11  
Old Sat 05 January 2008, 08:37
BernardR
Just call me: Bernard
 
Georgetown Texas
United States of America
Nils,

Normally on a mill or a router table the work piece is firmly clamped to the body of the machine and the cutting forces all ultimately react to those clamps (and friction). When you mount a workpiece in an elevated holder, such as we are discussing), there are generally only two points of contact, one very small one, the tailstock and the main body. The body by itself is free to turn, or be turned, and when the cutting force of the router is applied will only be restrained by the characteristics of the driving motor. Say for example you example that you directly mount a 800 oz/in stepper to the shaft and you apply a cut against it with a 3HP router, which is going to be boss?

I recommend you read what little literature there is on the Shopbot site, as my understanding is that all the heads are geared, either tapered hob, or planetary in the more expensive unit. Also look at how they are driving them, the more expensive units use a closed loop, gearhead stepper, the standard uses open loop, geared servo. Unfortunatly they give no detailed technical specifications.

As far as tailstocks are concerned, if you look at the link at Use-Enco you will see that there is a large selection, and each company normally supplies or recommends one with each of their heads. Also if you look at the catalog you will see that all these heads and tailstocks are designed to be mounted to some form of slotted base assembly and normally a close tolerance strip is fixed to the base of the tailstock to keep alignment while it is being positioned.

Because you can not see an immediate need for a function, I wouldn't rule it out, especially if it can give you greater funtionality at some future stage.
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  #12  
Old Sat 05 January 2008, 09:08
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Bernard,

Thanks again for you information. Could you give me a link the all the tailstocks you are finding on the use-Enco site because when I do a search on tailstocks, I am only finding a few and they are the machine type.

I agree that I don't want to rule out any capability but I need to see a use for it.

Thanks
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  #13  
Old Sat 05 January 2008, 11:04
BernardR
Just call me: Bernard
 
Georgetown Texas
United States of America
Nils,

At the moment the Useenco site is down, but if you look at the photo in the Shopbot site of the digitizer and indexer, the tailstock shown there is identical to those sold with rotary tables. At the end of the day all these are 'dead centers' as opposed to high speed ball bearing type, and they apply thrust to the piece being held. The only criteria you are looking for is, is it the same height as the head, can you apply pressure and is it easily mounted. The type sold with rotary tables normally have the ability to make small adjustments in height and again looking at the shopbot photograph I believe it has the same ability.
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  #14  
Old Sat 05 January 2008, 22:34
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Nils,
Normally, you wouldn't want to use a 'standard' motor with an indexer. By definition, an indexer, moves, rotates, or indexes a certain number of degrees and then holds the part motionless while the X or Y axis along with the Z-axis makes the cut. When that cut is made, the part is indexed to the next position and the process repeats. Of course, sometimes the rotation takes place while the other two axes move, for instance, to cut a spiral pattern; however, the indexer motor is not expected to 'spin' the part as fast as a regular lathe motor.

So, if we assume that resolution is more important for an indexer than speed, how do we know what resolution to expect? That is determined by the diameter of the part. If we want to cut 12" dinner plates, we would multiply the diameter of the plate, i.e. 12" and multiply that by pi, i.e. 3.14159 and then divide the product by 2,000 steps, which would give us 0.0188" per Gecko G20x stepper driver step. Aproximately two-hundreds of an inch might be too course, so we use a geared motor. A 3.6:1 motor would give us 3.6X better resolution (and 3.6X less speed). Likewise, a 7.2:1 motor would give us 7.2X better resolution and 7.2X less speed. Several people that I've talked to who use indexers like to have at least 10:1 or more. The practical limit, without adding an auxiliary reduction unit is 36:1 if you use Oriental Motor PK296A2A-SGxx motors. A 36:1 geared motor still costs only a few dollars more than a 7.2:1 motor. I haven't looked at Mach 3 to see how it handles angular movement; but, on my Shopbot, I specify how many steps the indexer requires per degree of movement (instead of specifying how many steps per inch of movement). It only took a few minutes to dial in the necessary numbers before I could test a mock-up indexer for speed and for accuracy.

The two shops that I've visited that have operational indexers both used a $200 Harbor Freight lathe for parts (headstock and tailstock). One shop lifted his gantry 2" to allow the lathe parts to fit. The other shop built a drop-down table at the foot of his machine so that the lathe parts would fit. (So far, I've done nothing to my machine, so the lathe parts won't fit, but I have built the electronics and successfully tested the Gecko G203v, the PK296B2A-SG3.6 motor and the power supply with my Shopbot PRT-Alpha controller.)

What I found out, is that the indexer is quite slow compared to normal machine operation; however, Dirk Dunham and Pat Fulghum have both done fantastic things with their indexers.
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  #15  
Old Sat 10 January 2009, 01:19
Nita
Just call me: Nita
 
Raleigh
United States of America
Indexer

Mike,

Will 203V Gecko drive work with PRT Alpha? How?

Thanks...
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  #16  
Old Sat 10 January 2009, 05:29
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
On the Shopbot PRT-Alpha controller board is a header for each motor that accepts a ribbon cable. By "picking off" the step and direction signals from that header, you can use any step/direction stepper driver, including a Gecko G203v. Because the G203v requires Ground as common and a +2.5V to +5V pulse, it works with the Shopbot controller without needing to change the polarity of the step signals.

There is one problem that I haven't taken the time to explore. The PRT-Alpha controller has an Alarm input for each motor that receives a signal from the Oriental Motor Alpha stepper driver. When I tested the G203v with my PRT-Alpha, I just left the Alarm input unconnected. Sometimes I got a false alarm error. For reliability, the Alarm would have to be correctly terminated (either +5VDC or 0VDC), but I haven't 'scoped that signal to see which polarity is expected.
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  #17  
Old Sat 10 January 2009, 05:41
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
Nita, you didn't need to go very far to pickup that PRT-Alpha, did you.
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  #18  
Old Sat 10 January 2009, 11:25
Nita
Just call me: Nita
 
Raleigh
United States of America
J.R. Hatcher,

We've bought our PRT Alpha back in 2006 for hobby purposes. Didn't have quality time and patient to put one together so we ended up buying.

Mike,
Excellent, thanks for the information. Will it be exact cutting ratio?
Is motor same part# as ShpB0t indexer?
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  #19  
Old Sat 10 January 2009, 17:49
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Nita,

I don't know which motor Shopbot is supplying right now. It doesn't really matter, because you just change the unit value to match the motor that you select.

On the Shopbot, using SB3 software, the unit value for an indexer is in steps per degree. You divide 2,000 steps per revolution by 360 degrees and then multiply that by the gear ratio. If you're using a 3.6:1 geared motor, the math is (2000 / 360) X 3.6 = 20 steps per degree. A 7.2 geared motor has 40 steps per degree. A 36:1 motor has 200 steps per degree.

(When you enter the Unit Values, be sure to enter the multiplier for that axis as 1 when you use a Gecko stepper driver. The Oriental Motor Alpha stepper motors need a multiplier of 4 or 5 depending on the model.)
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  #20  
Old Sat 10 January 2009, 18:51
Art
Just call me: Art #2
 
Lancaster,Texas
United States of America
You can see my tail/head stock at http://www.turningaround.org/4_axis_mill.htm
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  #21  
Old Sat 10 January 2009, 23:52
Nita
Just call me: Nita
 
Raleigh
United States of America
Guys,

Does the Shopb0t indexer comes with Gecko or Oriental driver?
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  #22  
Old Sat 10 January 2009, 23:58
Nita
Just call me: Nita
 
Raleigh
United States of America
J.R. Hatcher,

Sorry, overlooked your message..

Yep, they are not that far from us...
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  #23  
Old Mon 12 January 2009, 07:33
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Currently, Shopbot lists two indexers on their price list. Both are for the PRS-Alpha machines (meaning that they include an Oriental Motor Alpha motor/driver). Item 15102 is a 6" indexer for $3,075. Item 15104 is a 12" indexer for $5,995.

Your cost to build an indexer with a Gecko G203v, an Oriental Motor PK296A2A-SGxx motor, an AnTek supply and a Harbor Freight wood lathe should be less than $750. Add to that basic cost the cost to mount everything and you might have a total cost of about $1,000, depending on what you buy and what you make yourself. Just the Oriental Motor motor/driver package would cost about $1,700, depending on which model motor you selected.

Personally, after having used both a geared Oriental Motor Alpha motor/driver and an ungeared Oriental Motor Alpha motor/driver, I cannot see the advantage of spending as much for ONE motor/driver as it would cost to buy four PK296A2A-SGxx motors, four Gecko G203v stepper drivers and an AnTek power supply. All stepper motors, if driven incorrectly, will lose steps - including the Oriental Motor Alpha stepper motors/drivers. A basic stepper motor that has the shaft exiting both the front and rear (like the PK296B2A-SG3.6 motors or the PK296-F4.5B motor that I have sitting on my test bench) could have a $75 encoder from U.S. Digital installed. With an encoder installed, a small microcontroller like the Atmel AT89C2051 chip could monitor the steps going to the motor and the steps generated by the encoder. If the steps going to the motor exceeded the steps coming from the encoder by a set number, the microcontroller could signal the Break-Out-Board and stop the cut. That solution would cost less than $100 per motor, so four encoder equipped motors with Gecko stepper drivers and an AnTek power supply would still cost about the same as one Oriental Motor Alpha motor/driver.
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