Messages

3931

Mach4 General Discussion / Re: work zero in mach 4

« on: August 02, 2018, 05:01:46 PM »

Hi,
if you are observing MACHINE COORDINATES in your DROs then I would expect Z=0 to be at the top of travel
and moving downwards would go more negative.

If you are observing WORK COORDINATES then I would expect a positive number say 100 mm at the top of travel and
as the Z axis goes downwards it would decrease until the surface of the material at Z=0 and below the surface
of the material would be negative. Thus if you stopped at Z=-1mm then the tool is cutting 1mm off the top surface
of the material.

Craig

3932

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: August 02, 2018, 04:42:29 PM »

Hi,
in some respects resolution beyond 10,000 count is beyond the mechanical accuracy of our machines
and is of academic interest.

However multiturn absolute encoders are increasingly common and with a little battery pack don't lose
position when depowered. With a 24 bit encoder such as the Delta A3 series you could have 8 bits for
complete revolutions, ie +127 and -128 revolutions and still have 16 bit resolution within any one revolution,
that is 1:65536 or 0.32 arc min. Enough for any purpose I would have thought!

Craig

3933

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: August 02, 2018, 03:08:32 PM »

Hi,
the power calculation:

angular frequency (radians/sec) =4000 X PI X 2 / 60
                                              =410.9 rad/sec
Power= torque X angular frequency
         =2.1 X 410.9
         = 879.6 W


As a double check:
Power = Voltage X Current
          =130 X 6.8
          =884 W

My contention that a 750W servo would suffice seems correct, if you can get 1kW or greater servos for the same money then why not?
I think 1 horsepower axis motors should be ANY AMOUNT for a hobby machine as it is!

Craig

3934

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: August 02, 2018, 02:59:19 PM »

Hi Mick,
the prices you quoted for Schneider units are considerably better than is obtainable in New Zealand.

I think the critical number in the pic of your existing servos is the continuous rated torque. Provided any servo that you choose can match
or exceed that then the machine will have all the grunt that the manufacturer intended. It may well be that you can find a servo of even greater
torque but at a lower speed. You could as Hood suggests gear it suit and make the match near perfect OR accept that your machine in hobby
service may be somewhat slower than it was.

If you do the calculation it may prove that the maximum axis speed of the by using the max servo speed is ridiculously high anyway. In production
machines where cycle time is critical acceleration (read torque) figures as highly as maximum speed (read rated motor rpm), if anything  slightly
more torque would prove more satisfying with respect to following accuracy than high speed.

That you are investigating AC servos and coming to the conclusion that they can be had if, not cheaply, at least affordably will allow you to advance
your project very considerably and in a very satisfying manner, AC servos will eat the SEM's for breakfast.

Craig

3935

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: August 02, 2018, 09:05:48 AM »

Hi,
I work in he electrical industry and have been offered Schneider Electric drives, probably not at cost but at a great discount on the list price.
They look like great units but are still two and three times more than Delta and DMM.

The sad reality is that US, European and Japanese drives are very expensive, even second hand are still more than Delta and DMM are new.

Great to hear from you Hood. I seem to recall that there was a bloody big golf game in your neck of the woods last week.....you didn't get hit on the head
with a golf ball did you?

Craig

3936

Mach4 General Discussion / Re: G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 02, 2018, 03:39:45 AM »

Hi,
just re-reading this thread....Mach4 can and does use an index signal to measure spindle speed but it does not try to control the speed
as a result of the feedback. Nor does Mach attempt to use the feedback for synchronization purposes.

My understanding is that Warp9 had released lathe threading code, unfortunately it had a bug is the synchronization part. When they revisited that they decided to
increase the functionality of their plugin by offering multipulse per rev signaling and offering PID feedback control over the spindle. It is this major increase
in functionality that has delayed the lathe threading code by at least six months now.

The reason I mention it at all is because it highlights the division between a Mach function and a controller function.

Mach has a there-and-back communication delay of about 10ms. That would be way too slow to have an effective feedback control over a spindle, it would need
to be about 100 times faster for a feedback loop to be effective.

An external motion controller like an ESS does not suffer from the extended communication delay, it can respond in microseconds. Warp9 have never made any pretense
that their devices offer feedback control. It is quite a departure for them to work on PID feedback control of the spindle. My understanding is that the ESS will modulate
the PWM output to effect speed control so it is still a long way short of the sophistication required to close a position loop, none the less I am impressed.

Andy (Warp9) indicated that the company was intending to release a low level API which would allow users to program their own feedback solutions. Given the
glacial pace at which Warp9 convert intentions into reality I'm not getting too excited yet. I believe Andy announced this because this PID control of the spindle
is an example of what such an API is capable.

It may be, and is certainly hoped that the developments at Warp9 with regard to lathe threading may dovetail with an API and so we may get a 'python lump'
of new features and functions.

The timely response requirement is such that lathe threading will have to be a control board function, even if Mach's communication loop could be improved ten-fold
it would still not suffice for lathe threading. Even worse is that Windows is not a realtime system so even if Mach could magically communicate at the required speed
Windows would not.

So while Lua offers the possibility of programming for feedback control the underlying communications between Windows, Mach and the hardware are just to slow
for anything but slow processes like thermal control.

Craig

3937

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: August 01, 2018, 07:18:56 PM »

Hi Mick,
you might also consider second hand, thats how I got my servo. I got it, 1.8kW and matching
DSD020 drive for $800NZD, about $550US, including freight. Note this unit was already in New Zealand
otherwise the freight could have been another $150US. I had to buy/make the cables, not insubtantial,
don't overlook them if you are buying. Good cables and connectors are essential and good ones aren't cheap.

This thing does 6.2Nm continous at 3500rpm and can position to less than 5 arc min and accelerate to 3500rpm
from standstill in under 2 sec. Its almost too good for a mere spindle motor but I wanted the torque and AC servos
are about the highest 'torque density' out there. I can bury a 16mm four flute mill tool in 316 stainless to the extent
my machine flexes before the servo stalls. It KICKS ANUS!!!

Craig

3938

Mach4 General Discussion / Re: G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 01, 2018, 07:06:27 PM »

Hi,
at work at the moment so not able to check on my machine, but yes. There is a dedicated input
ISIG_INDEX, from memory, which Mach treats as an index pulse from the spindle.
It can be treated as a single pulse per rev or multi pulse per rev.

Note that it is a single input.....it wont give you MPG type results. Its perfectly adequate for speed monitoring
purposes but not really suitable for position.

Craig

3939

Mach4 General Discussion / Re: G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 01, 2018, 06:13:14 PM »

Hi,
the Mach settings I alluded to allow Mach to get spindle speed, Mach DOES NOT synchronise motion
for threading for instance, that is a motion controller function.

Craig

3940

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: August 01, 2018, 06:10:29 PM »

Hi Mick,
I notice the Kinco motors in 1kW are 130mm frame, might pay to check they will fit in.
Also they are slower, one 5Nm@2000rpm and the other 10Nm@1000 rpm.

Note also that Kinco do 20 bit absolute encoders which I don't think will be compatible with the CSMIO,
choose the model carefully or you will end up having to replace the analogue controller with a step/direction unit whether
you like it or not.

Craig.