actually the 4th axis was a rotary the steps per inch was a slip.  The Tormach approach uses a lath  BUT it also has a rotary axis hookup that has a quick attachment to convert it to an indexer/interpolated 4th.

Their setup requires manual setup to convert but it only takes about 10secs or so to convert it.

IF you are providing the drive then this is a moot point as you can get the drive setup with a configuralble buffer system that wil wait on the brake. BUT you will have to be able to turn the function off IF you want to do interpolated 3d work.

I think most users are going to want it to do both functions once they start using the 4th(;-) it is like Crack once you get the 4th YA CAN"T LIVE WITHOUT IT. (;-)

BUT you will have to be able to turn the function off IF you want to do interpolated 3d work.
I think most users are going to want it to do both functions once they start using the 4th(;-) it is like Crack once you get the 4th YA CAN"T LIVE WITHOUT IT. (;-)

Yes on all counts.

I did some testing and have some quantified results. Settings:
Step per degree: 25.6
Step multiplier:    5x
Velocity:            82k
Acceleration:     14k

The test program did nothing but G0 moves with lock on before and off after - G0 move is next line in code after lock release macro. Macro has sleep(10) after DeActivate. No programmed G-code delays. Heaviest chuck I have (a customer's special wood holding chuck). The machine was literally slamming around in a way that it would never experience in normal use.

Encoder 1800line (7200CPR)

Absolute MAX following error on G0 moves ranging from 30 to 180 degrees each direction:
Without lock:       151 to 189
With lock @50psi  171 to 203

Notes: Above are MAX and occur only once during the run. Most times error is under 10 between moves with or without the lock.
With acceleration set to something reasonable, max error is in the 50's with most moves generating about 5. Negligible difference lock on or off.
Looks like custom firmware is not going to be needed.

Is that running with the macro to lock/unlock ? Using the macro it is a sure thing no problem

TO be seamless you have to eliminate the macro right?

Is that running with the macro to lock/unlock ? Using the macro it is a sure thing no problem
TO be seamless you have to eliminate the macro right?

There will always be error on a servo, so the goal was to see how much error was added by the lock. The test program contains lock and unlock macros, with no g-code commands between the unlock macro and the 'A' axis  move. The release Macro and a G0 'A' move back to back is the worst case scenario. The same program was run with and without air to the lock. Without air, the lock is inoperative and cannot add following error due to release latency.

If by 'seamless' you mean transparent to the CNC control software (MACH in this case), then yes, the Macro has to go away.

There are three basic challenges to making the 4th axis work as I want.

1) a way to run the A axis continuously.

2) operation of the lock function

3) ability to run a high res encoder at high RPM.

For use with Mach3, all of these have been solved. (1: swapaxis board  2: embedded macros  3: step mulitplier, smoothstepper, kflop)

For 'universal' use with other CNC setups, only the first is solved and I am working on the other two. Solving the second challenge for 'universal' use (my current focus) will also benefit Mach by eliminating the need for macros embedded in the G-code by manual editing or modified post proc.

Looks like custom firmware is not going to be needed.

Cool!

Every now and again we get lucky.  Always brings a smile to my face when it happens!

Cheers,

BW

NOW the big Question(;-)

If you have that much error using the macro with the delay that the macro creates, what will the error be without the delay from the macro???

"THAT" was where I ran into trouble(;-) I guesss it will depend on how much following error "your" drive allows before it errors out(;-)

I don't think using sleep in a VBscript contributes to following error. I don't know that for a fact, but sleeps are inserted to put Mach on hold while functions execute, otherwise it can get ahead of itself.  Another example is that you have to put G4 delays in the G-code or Mach won't update the variable monitor.

Inserting sleeps and 'while is moving' and so on are execution holds that have nothing to do specifically with the 4th axis or the lock. Those are in there because Mach needs them. Maybe a scripting Guru will chime here and quantify the time period of sleep(10), but it ain't much . .  few milliseconds I would guess.

I hear you on the fault issue, I had some Gecko 320s  . .  briefly. The drive I am using is a Dugong which has a settable following error up to the 10s of thousands. These drives are tractors. Not too fancy, but just big brutes. I'm using a NEMA34 DC brush motor with a 40A max draw and the Dugong just slaps it around. A momentary error of 200 on a 7200CPR encoder is not much considering the test parameters. Swinging a heavy chuck with stupidly fast acceleration and instant direction changes and long moves . . actually I had the thing pushed to a limit just below where the servo motor would go ballistic and break into violent oscillations. i.e. the test was intentionally not real world. The test settings were quite in excess of anything you would use in normal machining operation.  

Simpson36,

I don't know if I understood correctly, but maybe if you use some kind of sensor at the brake lever system cappable to stop the program execution using "feedhold"...

Maybe using two microswithes connected in a way that the cnc is in feedhold when the lever is in transit - the command is free only at the end of each move - braking or not.

Here is the latest video of the 4th axis. This one is by request also. I've had quite a number of queries about form tools ever since I mentioned it a while back. This vid demonstrates a form tool that I finally got time to make for cutting curvilinear form teeth. Also shown is the hideously painfull way I was making them before the form tool. The contrast is  . . . well, just take a peek.
http://www.youtube.com/watch?v=ViN4t4YI_T4

Thanks for the suggestions and comments on the lock operation. It is pretty much sorted out now. For Mach3, a couple of options are available already. It is just a matter of seeing how 'automatic' I can make the operation for the purpose of making the dual indexer/lathe capability easily implemented in a variety of setups, not just Mach. While I am waiting for the modifications to the Dugong, I am going to try other drives that already have the features I need to automate the lock function.

Also I am thinking now about making a trunnion table. That was the reason for the 'Super Duty' version of the 4th axis, so I may as well have one for myself. I do have applications for it. I would love to hear from people who are using or would like to be using a trunnion table. What's good What's bad. What would you like to see?

I was looking at Tormach's 'Duality Lathe' approach. Anybody have comments on that setup? Tormach has the lathe tools in a fixture that appears to be clamped to the spindle. My spindle is servo powered and has a spindle lock like the 4th axis. It occurs to me that a relatively simple fixture clamped to the spindle could hold a bunch of different tools in a carousel arrangement.

These pictures show how I set my X2 4th axis up for Tools. I mounted the quick change tool post on the side.