DIY Indexer

[pro70z28]

I've been looking at the capabilities of an indexer for the ShopBot. (Mine is an older PRT96, recently updated control board). I'm not getting any younger (65) and the thought of investing in a new set up is hard to justify. I thought about buying a used unit if someone has one gathering dust, but is in good shape. I was also wondering about building my own? I'm thinking if I bought a stepper motor matching the size I have on the ShopBot now, in theory I could build my own. Is it that simple or is there more to it than that? I'm a fabricator, by hobby, and have a metal lathe, mill, the ShopBot and a few other tools to get the job done. Just wondering if there are stories of other projects like this and what the results were. Sometimes the tool build can be as fun as using the tool once it's built. Thanks.

[Burkhardt]

Since the stepper resolution is too coarse and the torque too weak you will need a gearbox. Dependent on the target diameter of the parts you want to make between 1:5 and 1:50.
There are solutions with belt drive, planetary gears or harmonic drive. Look around on ebay, typically such 4th axis kits are around $300-400 incl. chuck and stepper. Tailstock is usually extra. Try to get one with larger 4-jaw chuck, this is much easier to use for wood blanks.

[Brady Watson]

As Gert hints, $340 including tailstock via Ebay (https://www.ebay.com/itm/282571170993?_trksid=p2380057.m570.l5999&_trkparms=gh1g%3DI282571170993.N36.S1.R2.TR2)

The caveat here is going to be your controller. Are you using the original 3G controls or did you upgrade to a 4G board or RBK? If using the original 3G controls, you need a motor less than 2A or you'll kill the driver. Something like this should bolt right up (check shaft sizes) and be under 2A: NEMA 23 Motor (https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-23-bipolar-18deg-116nm-1643ozin-15a-54v-57x57x56mm-4-wires-23hs22-1504s.html?mfp=149-step-angle%5B1.8%5D)

-B

[dlcw]

As Gert hints, $340 including tailstock via Ebay (https://www.ebay.com/itm/282571170993?_trksid=p2380057.m570.l5999&_trkparms=gh1g%3DI282571170993.N36.S1.R2.TR2)

The caveat here is going to be your controller. Are you using the original 3G controls or did you upgrade to a 4G board or RBK? If using the original 3G controls, you need a motor less than 2A or you'll kill the driver. Something like this should bolt right up (check shaft sizes) and be under 2A: NEMA 23 Motor (https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-23-bipolar-18deg-116nm-1643ozin-15a-54v-57x57x56mm-4-wires-23hs22-1504s.html?mfp=149-step-angle%5B1.8%5D)

-B

Brady, how would the eBay item you linked to work with a 2009 PRSAlpha with 2.2hp spindle?

[pro70z28]

The caveat here is going to be your controller. Are you using the original 3G controls or did you upgrade to a 4G board or RBK? If using the original 3G controls, you need a motor less than 2A or you'll kill the driver. Something like this should bolt right up (check shaft sizes) and be under 2A: NEMA 23 Motor (https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-23-bipolar-18deg-116nm-1643ozin-15a-54v-57x57x56mm-4-wires-23hs22-1504s.html?mfp=149-step-angle%5B1.8%5D)

The old board was DOA and tech support suggested replacing it with a v4g board. I installed it about a year ago.

[Brady Watson]

Brady, how would the eBay item you linked to work with a 2009 PRSAlpha with 2.2hp spindle?

You'd need to adapt an Alpha motor and drive to the mechanicals...not quite as bad as it seems.


The old board was DOA and tech support suggested replacing it with a v4g board. I installed it about a year ago.

You are good to go then up to a 3A motor without additional heat sink. You'll need an accessory motor cable, extra matching Gecko drive if your Acc slot is empty and change the current set resistor to match the motor.


-B

[pro70z28]

https://www.amazon.com/dp/B01H54UM8I/?coliid=I3R8O0TQ4X625O&colid=11LPAG0T1XVG6&psc=1&ref_=lv_ov_lig_dp_it

I found this on Amazon, but I don't se an amperage in the ad. There's others that say 3 amp, but they're 3 jaw chucks. I sent a request to the seller for more info. Where would I find a accessory motor cable? Is that a standard cable or is it propriatorey to ShopBot? I'll have to look to see if the 4th axis slot has a drive. I thought it did when I installed the board, but that's been awhile, might just be wishful thinking.

[Brady Watson]

https://www.amazon.com/dp/B01H54UM8I/?coliid=I3R8O0TQ4X625O&colid=11LPAG0T1XVG6&psc=1&ref_=lv_ov_lig_dp_it

I found this on Amazon, but I don't se an amperage in the ad. There's others that say 3 amp, but they're 3 jaw chucks. I sent a request to the seller for more info. Where would I find a accessory motor cable? Is that a standard cable or is it propriatorey to ShopBot? I'll have to look to see if the 4th axis slot has a drive. I thought it did when I installed the board, but that's been awhile, might just be wishful thinking.

There's no tailstock included with that...Think about how you are going to mount the indexer, then decide on the hardware. I found that buying a lathe with extension bed was cheaper/better than buying one of those things off Ebay. Then choose the stepper motor you want and belt reduction to the lathe shaft. If there isn't a drive in the 5th slot, just buy another matching Gecko. Same model as the rest of them.

You can get a PRT style Acc cable from SB. It has the 4-position Wago connectors on each end - plug & play. Get an extra motor side connector.

There's a little work involved, but nothing too serious. If you just want plug & play then you have to pony up for what SB sells them for. Otherwise you have to educate yourself and then work through it.

-B

[bleeth]

Maybe I'm missing something but the ad says you have a choice between 3 tailstocks.
"We have 3 type of this product, The default Tailstock is Type A , if you need it with Type B or C, please choose the type you need when you place your order.
Tailstock:Alive,with an axial direction spanner, adjustable travel: 50mm,Center Height: 65mm,Product weight: 2.1kg With K12-100MM 4 Jaw Centring Chuck "

[tlempicke]

I did this project last year and it was quite rewarding. I could not find out how to send a link but the thread titled
first project on cheap indexer
will have a link to the one that I used.
I put a bigger motor on it but as it turned out I did not have to. The one supplied with it would have worked just fine. What happened is that my PC board is marked for the resistor that sets the current to the motor. I soldered a resistor on to that not realizing that Shopbot just inserts the resistor into the terminals on the Gecko drive. As a result the drive went to maximum current which overheated the motor and drive both. As a testament to being tough both items survived just fine.
I fabbed up a mounting, and modified the belt drive just a bit. It was not quite tight enough so I made the holes oblong and tightened the belt.
It works well and I am currently planning a project that will make use of it.

[Brady Watson]

Dave - thanks missed that.

Tim - Here's your thread: first project on cheap indexer (http://www.talkshopbot.com/forum/showthread.php?24003-First-project-on-cheap-indexer) - I'd like to see pics of the head/tailstock you used as I am sure others would as well. Your pic strategically eliminated both from view...

-B

[pro70z28]

I have no problems fabricating whatever is needed on the mechanical side, it's the electronic side I'll have to be schooled on. I guess I already knew if there was a spare driver on the board, but I had to go look. Being a complete electronic illiterate, I'll need an indexer with tailstock, driver and cable. Everything else (electronically) is a matter of software/resistor adjustments, if I understand that right?

[pro70z28]

I should add, I do have a little idea how the 4th axis files are generated. I have a laser engraver with a chuck rotary and wheel rotary for engraving round jobs. However, it doesn't have a dedicated 4th axis drive, since there's no need for Z axis function during engraving on a laser. I unplug the y axis on the machine and plug the rotary attachment to the y outlet. Manually move the laser head to TDC of the workpiece and zero the z off the surface. Then I go into the menu and calculate the diameter of the piece to get the rotary dialed in. I've only done a couple rotary jobs so far. To check my calculations I've been putting masking tape on the part, and marking the start/stop positions say, 4" apart. Then I move the rotary 4" on the screen to see if it matches my start/stop points. I'm sure if I had more run time, the calculating would be an automatic process, but for now this is an ''engraving for dummies'' way to check my calculations.

[tlempicke]

Here is a like to what i bought. It has pics and specs.

http://www.ebay.com/itm/CNC-Lathe-Ro...72.m2749.l2649 (http://www.ebay.com/itm/CNC-Lathe-Router-Rotational-Rotary-Axis-A-axis-4th-axis-3Jaw-Chunk-Tailstock/282280057916?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649)

[Brady Watson]

I have no problems fabricating whatever is needed on the mechanical side, it's the electronic side I'll have to be schooled on. I guess I already knew if there was a spare driver on the board, but I had to go look. Being a complete electronic illiterate, I'll need an indexer with tailstock, driver and cable. Everything else (electronically) is a matter of software/resistor adjustments, if I understand that right?

If you have a PRT96, you need another G203V driver for that 5th slot. You'll need a current set resistor for the drive to limit how many amps it puts to the motor. With no resistor in there it puts out the full 7A...and will run like carp and super hot. Not a big deal you can read up on current set resistors on the Geckodrive site. Download the user manual PDF and there's a list to get you in the ballpark. The resistors have color bands on them...you can decipher what they are using an online resistor calculator - and find the one you need for the new drive after you know the value.

Aside from this, you just need the motor, cable and connectors. In VI change channel 4 to B. Ch 5 can be whatever. Turn on 5 axes in SB3 in VD command and set your UV for the motor depending on the reduction ratio. Go as high as you can on reduction...while it is possible to spin it like a lathe, ZERO useful work can be done doing that, so you might as well gear down for torque and resolution.

I have a couple of new straight gear 18:1 that work well as an indexer motor (has a little bit of backlash but ALL SGs do) but won't work if you get one of the units up thread. It's the same size as the rest of your motors.

-B

[pro70z28]

Thanks for all the info. Brady. So, it sounds like with enough reduction torque, amperage may not be the main consideration as the gear ratio would offset the smaller stepper?

While typing this it dawned on me... I retired my first CNC (a 4'x4' Multi-Cam) when I bought the ShopBot. Lightning fried a chip in the control board and they stopped parts support for that machine. I was told it could be upgraded, but the cost was nearly what the Shopbot was new, and I really wanted to step up to a 4'x8' table. That CNC is tucked away in the corner of the shop. Do you suppose I could rob one of the steppers off that machine? They are belt reduction stepper motors, but I'd have to dig it out for any info beyond that. Are stepper motors pretty standard, as in, if I match the amps with a resistor it should work? Still have the chuck to consider, so it may not be worth the extra fabricating time.

[myxpykalix]

Go to the last page in this "Indexer" section (first page when it was started) and move forward and somewhere along in there is a section where several guys posted their own DIY indexers from $100.00 and up and that ought to give you some ideas.

[pro70z28]

Thanks myxpykalix. I'll check that out.