Bandit Controller limitations

[Chris64]

Hello! First post here of many hopefully. I've been wanting to get into CNC for the last 20 years and I'm on the edge of buying a machine (after tinkering with building my own stepper motor system...it worked...just not that good). I have never used a real mill and certainly never a real CNC.

Anyway...to my point.

I'm looking at a Vertical Mill with a Bandit Controller (around $4-5k seems pretty typical). The only thing I can find regarding the Bandit controller is how to replace it (which may say a lot right there). Well that's beyond my budget to do.

I've read every post I could find here regarding the controller and I couldn't find anything that specifically stated why it's such an inferior machine...only that it isn't as capable as newer machines. I would expect that it is less capable than a newer machine, but what CAN'T it do?

I should also state that I'm a computer programmer by trade and what I'm hoping to do is feed the commands to the controller through a computer. I already made a program that I was pretty happy with for my stepper motor project. I've read through the entire ShadowCNC manual (assuming that it is the same) and this appears to be possible (although I'm not sure how it would handle multiple requests [buffering?]). Perhaps I will have to feed it whole programs which is still useable but a 1K project could get used up pretty quick with a detailed project (an engraved logo for example would need hundreds of paths easily).

So is it useable for a newb? Could it work the way I'm hoping? Any advice is welcome. I'm just looking for a cheap way to get into this hobby. My original plan was for prototyping idea's...but the idea of having a production capable machine is a big plus versus little desktop CNC's.

[HuFlungDung]

The only real problem with the Bandit is keeping it running, especially if it's your 'one and only' and you'd like to get something done every day. Lots of tarnishing edge connectors are the main culprit, it seems like 'up time' might vary from week to a month before it starts to act up. A regular maintenance seems to involve powering off completely, lifting the card cage, slide all the cards on and off the backplane a couple of times, same with connectors on the wiring harness.

The Bandit will do DNC. I do not recall off the top of my head what the maximum baud rate was for DNC, but 1200 seems like the right figure. This is slower than the maximum comm speed, which I believe was 4800 baud.

This means that short segment 3d or 2d programs will run at a limited feedrate, no matter what F you command, it might be hard pressed to average 20 ipm, more often, less than that. That is not out of line for an old cnc that might only achieve 100 ipm rapids.

Its a good old control to learn on, but it is bare nuts to operate, so you are starting on square one because the control is built assuming you are an expert programmer, and thoroughly understand the implications of using G92 to set the program reference point on the machine.

[HPbyGD]

On an other thought about the bandit controller. Is it possible to use the steppers and some of the parts out of the bandit to save some money to get an updated controller? If so what would it take to get it going again. I have a bandit controller that I took off and would like to make a simple CNC saw that only need two axis.
Gary

[Ben Colby]

Obviously the 1K limit for programs will cause you some problems. DNC is possible,
and I recall there were boards that were available that raised the baud up to 2500.
The Bandits G-code is not standard, but it does provide more automated-cycles than
any machine I've ever worked on. It also has a G79 canned cylce that allows you to
turn any sub-program into a Canned-cylce. You can for instance drill 10,000 holes
will 10 lines of code or less. I've been a machinist for over 20 years and programming
after say my first three years and the Bandit control is a personal favorite, however
many Fanuc-style programmers I have encountered have hated it.

The Shadow CNC is quite an update over the older Controller and would be much
more desirable. I prefer the Shizouka iron over all the others. Really stout.

The Bandits are getting to be 25 years or older now and of course all the baggage
that comes with a machine of this age should be expected.

[HuFlungDung]

Gary,
Are you sure it was steppers? I never had any experience with those, my Bandits used resolver based servo motor control, with tach and resolver. The motor logic was part and parcel within the controller, so it is a case of keep the original intact and running, or scrap it.

It may make some sense to go to the effort to save the motors. To modernize them (if they are servos), a person could remove the resolver and install an encoder on the end of the motor. That is about the extent of what I would bother to save. All the antique power supplies and cards within the controller would be better off replaced with something new (and quiet, and cool running). There might be a few bucks to be made off the old cards if you pawn them off to one of the shops that still services Bandit, if they have need for the cards.

[Chris64]

Wow! Thanks everyone...that is really great stuff to hear. Up until recently my work had a 30 year PBX and I had some flashbacks of restarts and cleaning contacts...yuck!

It says 1200 baud on the Shadow website...but again, I don't know how similar these two machines truly are. Parts seem plentiful for these controllers though and that's good...I think.

I believe it does use servos, not steppers.

As far as the travel speed goes I guess I undestand why it would have a delay between commands (due to the serial connection) but other then that I would expect it's travel speed to be the same once a command has been sent. Am I wrong?

Regarding the complexity of the programming, well I read through the whole documentation and let's just say "it's going to be fun." You definitely need a good plan of attack. But, it did all make sense at least.

Can anyone chime in on the possibility of adding a fourth axis? I really want to make a few gears amongst other things.

[HPbyGD]

I upgraded my Bandit with a shadow controller. On that the baud can be set up to 4800.
I am not sure if the orignal motors were steppers but I thought they were. I thought I made a mistake one time but I was wrong! hahahaha The machine is a Shizouka that was originally set up in the late 70's I believe. I believe that there is a small add on board that will up the baud rate on the old Bandits. I think that one of my old controllers has one in it.
Gary

[HuFlungDung]

Chris,
On a long feedrate move (during DNC) the Bandit will attain the correct feedrate. But when the program consists of many short moves, the controller tends to starve for data, because it must use hardware handshake, and that is much lower data rate than software handshake.

Even the Shadow (which I also have upgraded a couple of mills) will easily starve for data on complex 3d contouring at its somewhat higher baud rate.

4th axis on a Bandit might be possible, but I never went that route. I think its a bit overkill for what the control is capable of unless you wish to perform simple M function indexing via an external 4th axis controller.

[Chris64]

Chris,
On a long feedrate move (during DNC) the Bandit will attain the correct feedrate. But when the program consists of many short moves, the controller tends to starve for data, because it must use hardware handshake, and that is much lower data rate than software handshake.

Even the Shadow (which I also have upgraded a couple of mills) will easily starve for data on complex 3d contouring at its somewhat higher baud rate.

4th axis on a Bandit might be possible, but I never went that route. I think its a bit overkill for what the control is capable of unless you wish to perform simple M function indexing via an external 4th axis controller.

That makes sense. And for the 4th axis wasn't for anything too advanced. Just turning a table top index so I can cut gear teeth. I might even be able to remove one of the motors for this task but that might be a little ambitious.

[Ben Colby]

Many of the Shizouka Bandits used stepper motors, although I have run a few that
had servo's. The Kasuga (another Japanese Iron) Bandits I have run all seemed to
have servo's and a very nice spindle controller on some. The Shizouka's seemed to always take the heaviest cut.
I don't think the Bandits make a good choice as far as 3D (2 1/2D) milling, but for
general purpose machine shop work in short run quantities they still have a little
bit of use, as long as you can keep then running.

[little bubba]

We had a '78 Wells Index with a Bandit controller, it had steppers. When the only other CNC mill we had was an Acroloc(crashalot), it got a lot of work and made tons of money, I sold it off about 6 months ago since it was just sitting and collecting dust.

As for the limitations, well, its slow, I could never get any of the canned cycles to work or the tool length offsets. Not really a big deal, it took some creative programming, but it worked out quite well.

It wouldn't helicly interpolate, which was kind of a bummer, but at least it could make a straight 3 axis move.

The biggest drawback, boards burn out quite a bit, as HuFlungDung said, you will spend a bunch of time unplugging and replugging things in. If we still had that machine, I think I would retrofit it after one more board blew, it can get pricey.

[HuFlungDung]

The Bandit programming syntax is different than FANUC style programming. The canned cycles work fine, but you need to put the gcode at the end of the command line, and the cycles only activate after the next axis movement is made (even if it is zero move) after the cycle command.

Tool length offsets execute properly in format Tx00 where x= tool number.
T1 M6 is a tool call for a machine with a tool changer
T100 is a length offset call for T1. Be careful, the tool moves!
T010101 is the format for length offset and radius comp offset for tool 1, length offset register 1 and radius comp register 1. I usually only used this format for a tool call only when intending to use rad comp for a particular tool. Otherwise I stuck with the Tx00 most of the time.

/T1 START gets you into the tool length register, line 1.

/G1 gets you into the diameter comp register, line 1

A complete copy of the manual is indispensible to learn to run the Bandit.