Repairing or retrofitting a Wells Index

[Aley]

I just bought a Wells Index model 700 knee mill with a Bandit control. The upsides are that the price was too good to pass up and the iron is in decent shape (once I cleaned off some light rust on the table from the machine sitting outside under a tarp before I bought it); the downside is that it was sold for cheap because the control is bad.

At this point I'm trying to decide what my best options are for the machine. As I see it, I have four choices:

1. Repair the Bandit control. It's a 1979 vintage with 1981 firmware (or so it would appear from my cursory inspection), but parts are apparently still at least somewhat available. I'm a bit worried that this could lead to a lot of expense if I get into the repair and find that there are more problems that I was able to identify at the outset, though, and I'm told that the parts that are available tend to be rather expensive. Plus, when I get done I still have an obsolete control that may not be able to be drip-fed through the serial port, and might therefore be pretty marginal for my use. I haven't been able to find much information at all about the Bandit, although the folks at Wells Index can probably sell me a manual.

2. Retain the existing steppers and drives and try to do enough reverse engineering of the old control system to find the step & direction inputs to the the drives, then run them from a PC and one of the inexpensive control programs. I haven't looked closely enough at the old control to even know yet whether this is even a workable idea. However, if I can track down the signals I will end up with drives that are already matched to the steppers without having to go buy them. I don't know how much work it would be to trace the signals without the computer working, though, and I also don't know if the drives are any good. One of them has a damaged trace that I'd have to repair (it looks like it shorted, which matched the previous owner's description of what happened when they tried to repair the machine before they sold it) and another has been shorted and repaired previously.

3. Retain the existing steppers and run them with Gecko drives and a PC-based control. The problem with this is that I don't have specs on the steppers (they have no nameplates at all). I did get one spare stepper with the machine, but although it's the correct size it's visibly different inside the end cover and may not even match what I have. If its specs are to believed it requires 8.6A, which is more than a Gecko can supply; this would presumably lead to diminished performance.

4. Retrofit the machine with servos and PC-based control. This is of course the most expensive option, although it would probably give me a nicer machine than any of the other options.

A fifth option would be to retrofit the machine with a Centroid control or similar, but that would be pretty solidly outside my budget right now so I haven't done any really serious consideration of it.

My ultimate goal with this machine is to use it for prototype and short-run production jobs. I don't need anything fancy from the control; I use FeatureCAM to create nearly all of my programs since I have access to it at work, and therefore conversational programming is not particularly important to me. I suppose rigid tapping might be nice, but I'm not sure I'll get that with any of the options I'm looking at and it's not a real requirement at any rate. I'm also not in a pressing hurry to get this mill running since I can go into work and use the Brigeport EZ-Plus at work after-hours, so the time required either to troubleshoot and fix the old control or retrofit a new one isn't much of a concern.

I'm sure plenty of people here have had the same question about what to do with an old machine, and I've love to hear input from others about what they've done.

Dave

[HuFlungDung]

Hi Dave
Your story reminds me of my not so distant past

I started out in cnc with a Bandit cnc on a lathe and a Bandit cnc on a Wells Index mill. Typically, the control would run okay for a month or so at a time, and then it would get flaky, or quit working altogether. Lots of pin connectors to keep clean, lots of boards to keep pulling and reseating so the contacts made good.

I upgraded the mill 10 years ago, with a Shadow cnc, which is a spin-off of the Bandit, but still has only 10K lines of memory, compared to the Bandit's 1k. The Shadow was kind of designed around the concept that devoted Bandit users would want to be able to run exactly the same style code after their retro to the newer control.

If you have the correct RS232 port installed, either the Bandit or the Shadow will execute from a remote PC. The processing time is slow, though, so heavy 3d programs tend to run a bit slow, as the control cannot process segments fast enough to keep the feedrate up.

On my Wells Index, servo motors were used, even with the Bandit. However, the Bandit used tach resolver feedback, whereas the Shadow uses more modern encoder feedback. If you look inside your Bandit, I think its the 4th card in the cage that is named "resolver logic" and it will have a little piggyback card on it.

You can contact Control Solutions in Bozeman, MT, or the affiliate, Albright's CNC Support Service, for more info on the Shadow, and also some repair parts for Bandits. Also in Bozeman area, Wendland Browning Services offers some Bandit repair service.


I upgraded the lathe to a PC based cnc using Camsoft and Galil card. Actually, I went with new servo amps, the PC and Galil motion card, used a few buttons from the old cabinet. I used the original motors in it, but upgraded the encoders. Going this way considerably reduced the amount of wires in the cabinet.

PC is very nice, but its not cheap, the way I did it. Camsoft CNC professional was $5k, Galil card and stuff $2.5K, encoders and amps, another 1.5K. Plus, many hours of work to redo the wiring and create the user interface within the Camsoft framework.

Its nice to have all your program storage right there at your machine, with an optional cadcam also available right on the PC at that machine. I don't use the Camsoft cad system, but any gcode file can be created in any cadcam and then run right there, anyways.

I'd guess you'd have to spend between $7500 to $10,000 whichever way you'd want to go.

It can be such a pain trying to use old motors and drives with unknown specs, that its sometimes just better to toss and replace with new stuff that someone can service, if you need it. Actually, most newer electronics is pretty reliable, so that takes care of a lot of the headaches that went along with the old technology that used so may discrete components.

[Aley]

It's good to know that the Bandit control can be drip fed. I had suspected that this might be the case, but I know that many older controllers didn't have this capability so I didn't want to make the assumption. At this point most of what I do is 2.5d and isn't so complex that it wouldn't run OK even with some latency between blocks, but the stuff I do is only going to get more complex as I get better with the CAM software.

My machine definitely uses steppers. They appear to be triple-stack NEMA 34s. The fourth board in the card cage is labeled MOTOR LOGIC and has ribbon cables that run to the back of the cabinet to the stepper drivers. (Interestingly, the fellow at Wells Index with whom I spoke told me that the unit originally shipped with high-power stepper motor drives that were located in the bottom cabinet, which sits under the normal Bandit case and is nearly as big as a small refrigerator, but these were apparently retrofitted at some point to the more standard Bandit stepper drivers.)

The more I think about it, the more I come to the conclusion that fixing the Bandit control would just be a Band-aid anyway. I think I'd find it limiting over the long term and eventually end up retrofitting. The real advantage to repairing the original control then becomes the ability to make a little money with the machine and get it to pay for its own retrofit. :-)

The money required to get set up with Camsoft probably won't be in the budget for a while either. I've considered options like EMC and Mach2 for PC control; I guess I need to learn more about servo cards vs. step & direction servo drives before I get too serious about buying the parts.

[HuFlungDung]

Even though I've never run Mach2, I'm sure it will beat patching up the Bandit. That one line LED window is not the most informative user interface

You might take a quick check to see if there is a round connector on the side of the control cabinet. That is the RS232 comm port. If its present, and has a ribbon cable going inside to one of the cards, then it likely has the option for DNC.

The guys I mentioned above can make up a cable for you, to match that port to your 9 pin serial.

Does this machine have any kind of rpm changer, power drawbar or tool changer on it?

[Aley]

I powered up the computer portion of the control this morning. With the drivers and all the wires going to the mill disconnected I was not able to get anything except the illuminated pushbuttons on the front panel to light. I didn't do a bunch of work on it, but it doesn't give me a warm fuzzy feeling that it didn't power right up. Of course, it may need one of the connections that is currently not connected to power up correctly, so I certainly haven't proven that the computer is bad, but it leaves me wondering.

This afternoon I pulled the drivers to see about reverse-engineering them to work with a PC control. Two things I realized are that they're labeled for 8A max per phase (with a 45VDC input), and they're set up for unipolar. The wiring going from the control to the machine includes two wires from the drivers to the motors that are clearly not the original, as well as four more that are original; this leads me to believe that the original high-power drives supplied with the machine were bipolar, and the low-power drives that are currently fitted are low-power by virtue of being unipolar. IIRC bipolar will give somewhere around 30% more torque at a given speed, although I think it may be limited to a lower top speed at a given voltage.

Since I could run Gecko G201s at 7A/phase at the original 45VDC (and using the original unregulated power supply even) and wire the motors bipolar, I think I can end up with a machine that's got more force to the axes than I could achieve with the Bandit control. I don't know if I can up the voltage to get better high speed, but at this point fast rapids are not the greatest of my worries.

It's starting to look therefore like my best option at the moment would be to use a PC with Mach2 (or EMC, or TurboCNC - I already have a couple of computers set aside for my two lathe projects that will run TurboCNC), three Gecko G201s (or G210s, depending on the speeds I need and can achieve), and associated parts. I'll still need to build or buy a relay board to do spindle control (most of the spindle control parts will come from the original cabinet, but I doubt there's a 5V relay there), coolant, and run the lube pump (which I could probably do just on a timer if I don't want to wire it through the PC). Total cost could be under $500 for a decent-performing machine, depending on whether I buy a better computer than the ones I have and how I do the various pieces.

I used the single-line LED "interface" (I use the term very loosely here) on my Compact 5 CNC lathe for a while. What an improvement it was to go to a video screen! And that on a machine that I never program from the panel, but simply upload programs from the PC and run. :-)

The Bandit control does have the connector, and when I initially pulled the boards to photograph them (viewable at http://www.cibola.biz, BTW) I checked the chips. It has a set of 1458 and 1459 ICs, which are RS232 line drivers; therefore I'm sure it has RS232. Maybe that'll be an asset when I start looking for a buyer for the leftover parts from the control after the conversion. :-D

The machine has a lever to change spindle speeds; unless I put a stepper on it or fit it with a VFD the computer won't have control of the spindle RPMs, just the on/off of the spindle. That's actually how the brand-new Bridgeport EZ-Plus at work does it (except that the operator has to turn on the spindle before the program will start running - the computer doesn't even do that for you), which surprised me on that machine but seems to work well enough for the stuff I do on it. I can see situations where it would create problems (running a 1" dia. end mill in steel at 4200 RPM can't be good if you forget to change the speed after using a small cutter) but on the aluminum parts I typically do I can run any of my tools at maximum speed without breaking anything. I guess I could put on a spindle encoder to give the computer feedback about the speed, but if I go to that much trouble I'll probably just fit a VFD.

My machine does not have a tool changer on it. It has Universal Kwik-Switch tooling, so there's no drawbar needed. The tool holders are on the expensive side ($250 for an ER-series collet chuck and $150 each for end mill holders), but the seller of the machine threw in six end mill holders and six collet holders when I bought it. The collet holders use a type of collet I'm not familar with and I haven't hunted enough to see whether I'll be better off buying those collets or just buying a couple of ER16 collet chucks and associated collets; I'll worry about that more once I get the machine running.

I don't think I mentioned that the shop I bought the machine from was going to haul it off for scrap since the control was bad, and I ended up buying it for $100. I wish I could find that kind of bargain every day! Considering that the iron is in pretty good shape and they threw in a dozen tool holders, I think I might have done OK. :-D

Dave

[Aley]

In case anybody cares, I've decided on a direction to take with this machine.

After discussion with a number of people I've decided to scrap the original Bandit control. Wells Index has the schematics available for a very reasonable price, and I could almost certainly repair it, but even if it's working perfectly it's pretty marginal for what I want to do with the machine.

Instead I'm going to refit the machine with Gecko drives connected to the original steppers. The steppers are NEMA 42 (not the 34s that I'd originall thought), which are pretty big for Geckos, but judging from the motor specs that Wells Index supplied me they should be able to handle it OK. The steppers will get wired in series configuration, which keeps the phase current within specs for the Geckos, and I'll run them at 80V to maximize performance. I could run them a few volts higher without excessive heating, but that would be outside of the specs for the Geckos and the increase in performance would be pretty marginal at best.

The steppers are currently connected to the ball screws with a 2.5:1 belt reduction, which I'll keep. Originally the machine was set up for full steps, which yielded a resolution of .0004" per step. I'll use G210s with the step multiplier set on X2, so I'll end up with a resolution of .00008" per step. At 20 kHz from the controller that will give me rapids of 96 ipm, which is only a tick slower than the original 100 ipm rapids with the Bandit control. I might be able to get slightly faster rapids by using X5 on the step mutiplier, but I doubt that the motors have enough torque at speed to move the table much faster than 100 ipm anyway.

I'm planning to use TurboCNC on an old Pentium 166 computer that I bought some time ago for a lathe conversion. I'm still working (slowly) on the lathe, so in the meantime I'll swipe the computer. I'll probably experiment with other control software since I have a golden opportunity to do it, but I already own a license for TurboCNC and it's already installed on the computer so it's the quickest way for me to get up and running.

FWIW, Wells Index has been incredibly helpful with this process. They've given me tons of information, done a bunch of research to find out how the machine was configured when it was shipped in 1979, and have generally spent a bunch of time on helping me get everything I needed. For me, that's worth knowing next time I'm looking for a machine.

Thanks for all the input on the machine and the control. Having this forum available has made it a lot easier for me to make the decision of what to do with the retrofit.

Dave

[Al_The_Man]

There is always a raft of Universal Kwik-Switch tooling on ebay, both 200 & 300. And it usually goes cheap.
Al

[Aley]

When I bought the machine the seller threw in a dozen Kwik-Switch 200 holders. Six of them are end mill holders that I can use, but the rest are Acura-Flex collet chucks with no collets. :-( Those collets on eBay always seem to go for a lot of money. I'll probably end up buying a couple of Collis Rapid-Switch collet chucks set up for ER-series collets. Those are really expensive as well, but at least I can use ER collets in my other machines too.

Buying new Kwik-Switch or Rapid-Switch tooling is a lot more expensive than the R8 stuff I'm used to. Anybody know what taper the Wells Index has if I remove the Kwik-Switch master holder?

Dave

[HuFlungDung]

Dave,
On my machine, the quik switch nose is part and parcel of the spindle and cannot be removed. Maybe yours is different, you could inquire of Wells Index if there is any doubt.

[little bubba]

We're running a Wells with a '78 bandit controller on it, and it does get expensive to replace those boards, though they are very easy to get through wells, you need to talk to a guy names Rick Robertson (smart guy, knows these things inside and out). The driver boards are about 900 and the logic boards usually run around 400(ther is a core charge of course). The collets that the holders you got are probably Acura-Flex (AF) collets, you find them on e-bay once in a while, usually in odd sized, but they squeeze pretty good so going .016 oversize usually isn't a big problem.

[Aley]

Rick Robinson (or maybe it's Robertson - I don't have my file in front of me right now) is the fellow at Wells Index who's been helping me. I've been really impressed with their customer service - we've dealt with Hardinge quite a bit with a Bridgeport that we recently bought, and after that Wells Index' service is a breath of fresh air.

I got six Acura Flex holders and a total of two AF collets with the machine. I'm running ER series collets on other machinery, though, so I'll probably stick with ER and get rid of the AF holders. $250 each is a lot to pay for a collet holder, though - that's what the Kwik-Switch ER collet holders are going for new. I have yet to see any ER collet chucks with Kwik-Switch arbors on eBay - most are Acura Flex, with a few other types like DA thrown in.

I stripped all the boards and other electronics out of the control cabinet last night so that I could put the cabinet outside to free up room in my shop. I'm going to sell nearly all of the electronics from the control, with the exception of the magnetics in the lower cabinet (reversing motor starter for the spindle, transformers and relays) that will get reused in the retrofit.

Dave

[little bubba]

Why not try and find a few 3/4" AF collets, or within a /64th, and stuff one of those extended shafts with the ER collets in them. There is a company somewere in this country that deals with used AcroLoc parts(Boat Anchors'R Us ?), and they carry used AF collets, if I remember right, they were only about $10 bucks a piece. This would eat up a bit of your Z-axis travel though, or like we did, a collis JT adaptor isn't that expensive and we just stuck a drill chuck on it, drilling and reaming only. Or you just need to be creative, Honestly I don't like any toolchanges on a single tool changer, mistakes can easily be made, so I put in a special effort to limit the tool changes. Right now, a 3/8" 90degree carbide mill drill for two different size hole, plunge and interpolate, then a #6 center drill with an 82deg chamfer for the rest of the holes. Its pretty easy for the operator, if the tool is on the right hand side of the part, mill-drill, if its on the left, center drill. Hope that helps a bit.

BTW their service is really good, I've had that guy call me back while he was on vacation and also on the road (overnight) doing service calls, they have also been really good on warranty's and returns.