Messages

3551

General Mach Discussion / Re: Spindle/ C Axis using CSMIO/IP-A

« on: October 16, 2018, 02:17:41 PM »

Hi Mick,
the encoder resolution of 2048 lines/rev is the simulated encoder.

The servo encoder and the servo drive have much finer resolution that that. I think the servo encoder is 17 absolute and therefor has a potential
resolution of 170,000 counts per rev.

You could theoretically increase the simulated encoder resolution up to the same 17 bit. Given that the CSMIO closes the loop then the simulated encoder
resolution is the limiting figure. The downside is that the CSMIO has limited signaling speed, and in any event signaling over 500kHz between controller
and servo drive is DIFFICULT at best there is therefore a practical limit to the resolution beyond which the signaling speed limits the rotational speed.

The second issue is the 'zero error window' My servo has a programmable window, 4 encoder counts (out of 8000) by default where the servo drive
determines that the actual position is close enough to the commanded position that it will not try to close the error any further.  You can reduce the
zero error window however the servo will 'hunt' when its close to its commanded position, sometimes you will hear it as a buzz. I use the servo drive
to close the loop and therefore use the servo drives manufacturers programming facility to do this. In your case you will have to use the 'zero error
window' feature or its equivalent, if it has it, in the CSMIO.

My experience is that for practical purposes that a resolution of 0.18 degrees or 10.8 arc minutes is realistic even if greater resolutions are theoretically
possible. Thereafter gear reduction is the only feasible way forward. Consider a harmonic drive.

Craig

3552

PoKeys / Re: Pokeys57CNC PWM outputs in Mach4

« on: October 15, 2018, 02:17:09 PM »

Hi,
you could also generate PWM from an analogue voltage, couple of transistors and an op amp.

Craig

3553

General Mach Discussion / Re: Topic: Parallel Port help

« on: October 13, 2018, 08:59:35 PM »

Hi,
I presume you are running, or at least trying to run a parallel port?

Post a screen shot of the results of DriverTest.exe (in the Mach3 folder)

Craig

3554

General Mach Discussion / Re: Question before my next Mach3 question.

« on: October 13, 2018, 06:08:58 PM »

Hi,
I use my mill, among other things, for making circuit boards, essentially an engraving operation.
For that I require my spindle go flat out all the time, ie 24000rpm. I don't want or need speed control...
just turn it on and off is all I require.

Even for milling of aluminum I often run at 24000 rpm with small diameter endmills, there again I don't require
agile speed control. If I require a somewhat slower speed because I'm using a larger diameter tool then I can reach over to the
VFD and turn it down a bit. Having programmatic control over spindle speed is nice but you can do a lot of work without it.

May I suggest that you not get to hung up on speed control. If Mach can turn the spindle on and off that might be enough.
Who cares whether you have Forward/Reverse? Do you have any lefthand cutting tools?

If you have a pot mounted on your VFD to change speed that may be adequate.

I would guess after you've done some serious work you'll realize that speed control is desirable but not essential.

Craig

3555

General Mach Discussion / Re: Spindle/ C Axis using CSMIO/IP-A

« on: October 13, 2018, 05:50:43 PM »

Hi Mick,
if I understand you are using the original VDF/spindle motor currently? How does it perform?
Induction motors and VFDs are a poor choice for indexing/C axis work but for normal turning operations
are more than adequate.

As you know I have a servo for a slow speed/high torque spindle. My initial use of it was in velocity mode and I would present
the servo drive with a +10/-10 V signal.....easy.

More recently I have been experimenting with the same servo but in Step/Direction mode and using it as a continuous
running spindle. Mach4 has a quite extensive suite of APIs that make this possible.

My most recent experiments have revolved around having the 'normal' spindle defined (Step/Dir) AND an Out-of-Band axis.
In Mach4 you can have up to six Out-of-Band axes which can be jogged. Thus I have two Step/Dir input pairs available for my
servo spindle. I select one pair as required for the machining operation at hand.

The trick is that when the spindle is in free running mode that it will lose reference. Thus when I finishing the free running operation and wish to
index my spindle I have to home it and then I am able to jog to a given angular position. What I am working on is having Mach keep track
of the encoder during free running mode so that it does not lose reference.

My most recent experiments have gone a step further. I have the same normal free running spindle, I have an indexable (via jogging) Out-of-Band spindle
and have a genuine C Axis which has coordinated motion with the other axes for things like rigid tapping. Thus I have three separate modes of operation
programmatically selectable.

All in all it has absorbed a great deal of time and programming effort. Given that 99% of my milling requires just a free running spindle the question must
be asked 'does all the complication of an indexable and/or C axis make sense?'. Probably not... however it has kept me off the streets and I have learnt
a lot about Mach4 and programming it. If what is learnt in pursuit of your hobby is considered valuable, then this has been worthwhile.

Craig

3556

Mach4 General Discussion / Re: What happened to the MPG flyout in Mach4?

« on: October 13, 2018, 12:42:24 AM »

Hi,

Does that feature still exist in Mach4? If so I I see there's a Jog tab with the same functionality but a different interface

The flyout has gone the way of the dinosaur. The jog tab has all the same functionality.

You may not yet be in a position to use it but when you are check out the jogging APIs, you'll be able to use those to define
and make your own jogging commands/macros/buttons.

Craig

3557

PoKeys / Re: Pokeys57CNC PWM outputs in Mach4

« on: October 12, 2018, 09:30:22 PM »

Hi,
you say the laser expects PWM not analogue. When PWM  is passed through a lowpass filter it becomes an analogue voltage.
Thus it is my expectation that the laser ACCEPTS PMW and uses that to generate an analogue voltage to do its work.

May I suggest an experiment. If your laser is expecting a 5V PWM signal then using a battery or small DC power supply
and a potentiometer generate a varying 0-5V signal.

If you are dead set on using PWM is the spindle speed output. I assume your machine does not have a spindle? If so the PWM signal which
is normally used to control the speed of a VFD would be available for use. Have a look at the spindle API's is API.chm.
This is an example and may be useful:

LUA Syntax:
rc = mc.mcSpindleSetCommandRPM(
      number mInst,
      number RPM)

Description:
Set the commanded RPM for the spindle.

Craig

3558

PoKeys / Re: Pokeys57CNC PWM outputs in Mach4

« on: October 12, 2018, 05:49:42 PM »

Hi,
have you given any thought to a Frequency-to-Voltage converter, there are such ICs, and tend to be used in instrumentation and communication applications.
They work on the idea that if you present a square wave signal of 1kHz say it might produce 1V whereas if you present it with a 2kHz signal it will output 2V.

The reason I make the suggestion is that the signal (excluding the acceleration ramp up and de-acceleration ramp down) are variable frequency signals.
Thus if your B axis has a tuning of 1000 steps per unit then and a max velocity of 60 units per minute:

G1 B1000 F60 would for the duration of the move (excluding ramp up/ramp down) of 60 X 1000 =60,000 pulses per minute or 1Khz.
G1 B1000 F30 would cause a pulse rate of 500Hz.

If you had a V-to-F converter IC on your B axis output you would have a variable voltage set by the axis feedrate.

Note that this strategy doesn't require any special support from your controller....it just outputs what it believes are a simple pulse stream indentical to
that required to drive a stepper for instance.

If memory serves I believe it might be the C25 or maybe the C62 BoBs which use this idea to generate an analogue voltage for a VFD rather than the more traditional
PWM.

Craig

3559

PoKeys / Re: Pokeys, mach4 no go?!

« on: October 12, 2018, 03:38:15 AM »

Hi,
that's good news....it means the PoKeys can signal the drivers with the arrangement you have.

The question is why are the motors not moving?

There seems to be a couple of possibilities.
1) The PoKeys is not producing Step pulses
2) The drivers are not set up correctly and not responding to the pulses they are being sent.

We need to devise some tests or strategies to determine which.

I think the simplest is to measure either the current or voltage of the Step output. If the output is producing pulses it will be
on for half the time and off for the other half. I would expect the voltage (or current) would be about half what the active Dir
output would be.

Try issuing an MDI like:
G0 X100  and then put your multimeter (in normal voltage mode) between the PoKeys output and 0V. What result do you get?

Craig

3560

PoKeys / Re: Pokeys, mach4 no go?!

« on: October 11, 2018, 04:27:57 AM »

Hi,
so long as you don't use the 10A range any of the other ranges have the resolution to read 10mA or so accurately.

Shouldnt step dir also be ok then?

Yes, I agree, so it is important to measure it and find out why its not working.
My guess is that you don't have the PoKeys and/or Mach setup correctly and there are no signals coming out of the PoKeys,
we would know foe sure once you measure it.

I've posted eight times and on each occasion I've asked you to measure the current into the DIR pin, fist when going in one direction and
then again when going in the other. I'm sick of asking.