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Messages - joeaverage

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4781
Hi,
great looking project.

Option one which includes enclosing the servo/stepper and ballscrew within the feedback loop has a lot to reccommend it.
You will require that the controller be 'closed loop activated', at a cost and you will have to do some low level
programing to make it work.

Option two is pretty straight forward.

I note the you intend on using steppers albeit closed loop steppers. To be honest I wouldn't do that. The steppers are still
steppers, no amount of feedback makes them any more accurate, faster or more powerful. The manufacturers
of them are playing on your fears about losing steps. If open loop steppers are going to lose steps due to overload
or not having the required torque then closed loop steppers will lose steps for EXACTLY the same reason. The closed loop
will try to correct it but fail because the steppers are OVERLOADED closed loop or not. Given the premium you pay
you are not getting any advantage.

Look instead at genuine AC servos, now you are talking real a real solution and not those Clearpath things, they are way
to expensive for what they are.

Craig

4782
General Mach Discussion / Re: mach 3 not working?
« on: April 15, 2018, 07:47:45 PM »
Hi,
sounds like your machine is interpreting the Gcode in mm when the Gcode was composed in inches.
That makes the part come out 1/25th of the correct size.

Read up about G20/G21

Craig

4783
Hi,
yes the flexibility of AC servos is amazing. They all have 'torque mode' for instance. Not really applicable to CNC but it means that you produce an analogue voltage (or PWM)
and the servo produces a matching torque irrespective of speed. You can imagine that would be just the thing in a printing press where you want a certain tension in the roll of paper no matter how
fast it is passing the roller.

Another useful feature in my Allen Bradley servo and I think its commonplace among AC servos is dual mode. It means for instance the primary control mode might be position control
via step direction pulses but changing on input to the driver and it will revert to secondary control which might be analogue voltage controlled speed mode. In fact this is what I'm working
on for my servo spindle in my mill. Mostly analogue voltage controlled speed mode is adequate but if I want to do rigid tapping I need position control. With this feature change one digital
input and I can have either.

All in all very impressive and I'm still finding out new wrinkles.

Craig

4784
General Mach Discussion / Re: GoTo Zero not working
« on: April 15, 2018, 06:09:02 AM »
Hi,
never thought to ask are you using a parallel port?
Can you post a screen shot of the DriverTest.exe page?

Craig

4785
General Mach Discussion / Re: GoTo Zero not working
« on: April 15, 2018, 06:02:48 AM »
Hi,
still can't think of anything that would tie them together.

I'm thinking you may have a bad case of midband resonance which can and does produce some wildly unpredictable results.
What stepper drivers are you using?
What microstepping regimen are you using?
What power supply, voltage and type, are you using for the steppers?

Craig

4786
General Mach Discussion / Re: GoTo Zero not working
« on: April 15, 2018, 05:50:01 AM »
Hi,
well can rule out some sort of power supply interference.

I cant think of any reason that an M3 command would make any difference to a subsequent G0 move.

Craig

4787
General Mach Discussion / Re: GoTo Zero not working
« on: April 15, 2018, 05:38:21 AM »
Hi,
thinking also about the situation you describe where it seems to work if the spindle is running but plays up when the spindle isn't running.
You're right it shouldn't make any difference.

Does the power supply run both the spindle and the stepper drivers? I suspect it does.
Is the power supply a switching supply or analogue, I'm guessing a switching supply?

My guess is that the load on the power supply with the spindle running is sufficient to somewhat 'quiet' the switching supply such that the stepper drivers work better.
If that's the case you have a crap power supply, do yourself a favour and get a kick-arse analogue supply, they work so much better and so much more forgiving.

Craig

4788
Hi,
the UC300 will be fine. The truth is that beyond 100kHz you need to be pretty damn good with your signaling electronics and cables otherwise the signals just don't arrive at the
servo drives.

I have an 1.8kW Allen Bradley AC servo and drive I bought second hand I bought to make a high torque low speed spindle for my mini-mill. I can signal it at 200kHz single ended, ie just a normal
hook-up, or up to 500kHz with differential signaling using the sort of electronics that computers signal each other. To run it at maximum speed , 3500rpm at maximum resolution, 8000 count per rev, requires a
pulse rate of 466kHz. Its doable but I use electronic gearing to knock that back to 93 kHz (divide by 5) and make the signaling situation that much easier.

The only real advantage of the ESS being able to go at 4MHz is if you wish to read a high resolution encoder at high speed.

I might point out that this Allen Bradley servo is the first AC servo I've ever had a chance to experiment with and they make DC servos look like absolute s*********t. They are just so much more controllable
and flexible, I'm not going to bore you with the details but when you get your hands on one you will ask yourself 'why didn't I get into these years ago?'.

Craig

4789
General Mach Discussion / Re: GoTo Zero not working
« on: April 15, 2018, 05:07:28 AM »
Hi,
may I suggest slowing it way way WAY down until it works properly and THEN start to speed it up until you find the limits.

All we know for sure at the moment is that you are trying to go too fast....by how much we don't know yet and wont until you slow it down enough to find the limits
of performance. Then it appropriate to ask 'is this right...or is there some fault?'

Try speed of 500 and an accel of 100.

Keep upping the accel until it starts missing steps or stalling, then back it off 25% Then work on increasing speed until a fault occurs.

Note you need to use G0 MDI commands so that you are testing the same thing...jogging is not scientific enough to give you useful comparisons.

Craig

4790
Hi,
the UC300 has a kernel speed, it can be 25kHz, 50 kHz or 100kHz. You set it in the UC300/Mach3 plugin.

An Ehternet SmoothStepper from Warp9 can go at 4Mhz, 40 times faster than a UC300 can!

Craig

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