Messages

7431

Mach SDK plugin questions and answers. / Re: Mach3 MDI Controlled by other Programs?

« on: August 25, 2016, 03:19:22 AM »

Hi Highspeed1964,
I have used MATLAB fairly recently. I was astounded by how powerful it is.

I used it (demo version only) to simulate a control system I am building for a servo.
You can graphically introduce integrators, differentiators, gains, delays, non linearites
and all sorts of other stuff. It can simulate the system and display it like an oscilloscope
or step response or a Bode plot and more other ways than I can describe. AND this was
only the 'control' module, there are a hundred or so other modules you can add including
symbolic maths equations and another code generator where you tell MATLAB what CPU
youre using and it programs in C your system. If you want technical or scientific computing
MATLAB is the way to go.

From what I could see however it would suck at CNC.

I imagine MATLAB 'objects' could be incorporated into Mach3 but I still have to ask why. If you
require the advanced mathematical simulation and/or matrix manipulation that MATLAB offers
well it could be done. The most mathematics I've had to indulge in CNCwise is trigonometry and
basic arithmetic which can be handled perfectly well by Visual Basic built into Mach3.

Craig

7432

Mach SDK plugin questions and answers. / Re: Mach3 MDI Controlled by other Programs?

« on: August 24, 2016, 03:15:37 AM »

Hi statfq,
is there a particular reason you wish to use Matlab? The VB scripting language built into
M3 has all the usual maths functions. Would they suffice for your calculation?

Craig

7433

VB and the development of wizards / Re: Counting Pulses on an Input

« on: August 24, 2016, 02:58:32 AM »

Hi kentCNC,
I'm only just learning too so regard what I say with caution.

I don't know whether M3 can count but it certainly does have 4 encoder inputs. Could you
mount an encoder on the end of your stepper or maybe on the far end of the ballscrew?
If you can the you have DRO's built in to M3 that can read and manipulate them.

Do you have reason to believe that you are losing steps? Loss of steps can be measured reasonably
easily with vernier calipers or a micrometer. That method wouldn't warn you however.

I have read quite a few posts where different people have tried to use M3 to correct for loss
of steps and I believe most if not all have failed, warning yes, correction no.

Any reasonable correction strategy requires a closed loop design which is the norm for servos
but in its infancy with steppers. The vast majority of steppers are used open loop. My machine is
open loop and yet I have never lost steps unless I was trying to do something crazy or otherwise
demand more than steppers can deliver.

My recommendation is solve the loss or potential loss of steps problem then any warning/correction
strategy becomes redundant.

Craig

7434

General Mach Discussion / Re: G31 alternative

« on: August 23, 2016, 07:45:21 AM »

Hi,
might be off topic but interesting none the less.

Some years ago one of the local linesman took a bad hit from 11kV. The first thing
the foreman noticed was the tyres of the truck carrying the 'cherry picker' sprouted leaks
and the water ballast in them started to squirt out. The current was passing thru Tony,
local guy and friend, thru the truck and earthing via surface conductance of the tyres.
 
Tony survived but was a very sick man for quite a long time. Most of the discharge had
passed around him, like surface conduction. Sharp bits like hands, elbows and knees were
badly injured but internal organs survived.

Evindently the probability of surviving a high voltage incident is actually higher than medium
voltage, 800-1700V. These voltages are found in traction systems like trains. Rectified 3 phase
(in New Zealand at least) is 580V. Any system using boost PFC correction like industrial
VFD's and some Miller Inverter welders have DC link voltage of 800V, the danger zone.

I deal with rectified 3 phase machines daily including some of those Millers. With those your
first mistake is your last and the capacitors are formidable!

Craig

7435

General Mach Discussion / Re: G31 alternative

« on: August 23, 2016, 06:38:24 AM »

Hi Tweakie,
I've always regarded LD50 (lethal dose 50% of the time) as 20mA.

In this case the open circuit voltage I measured was 130V but any moderate path to
earth drops the voltage bigtime. I can only guess but theres no way I could have stood
30mA and still write this to you...

You are correct that I should be much more concerned about this than I am or perhaps
appear to be.

Your concern is noted and appreciated.

Craig

7436

General Mach Discussion / Re: G31 alternative

« on: August 23, 2016, 06:24:48 AM »

Hi Rob,
great find on the info, I have bits and pieces but nothing as complete as this.

Supposedely these steppers can run at 3000 rpm with gear reduction 300 rpm. When I first
set the mill up I experimented and got axis speeds of 2200mm/min which equates to 440rpm
at the coupler and 4400 rpm at the motor. I ran everything at max to do it and of course they
got hot and were prone to stall. In more recent times I run 1200mm/min for a motor speed of
2400 rpm at 75% current output and they run comfortably and reliably pretty much irrespective
of whats loaded on the table.

The drives I have I think must be an earlier model as they don't have microstepping, full and half step
yes but otherwise look identical. Thanks again for the info.

Craig

PS just read your latest post and yes I've had a few close encounters with 230, and about 3 months
ago while at work I slipped probing a 400V circuit, it hurt!
We have a sign up saying "DANGER this will kill you and really, REALLY hurt while you die"

I can disconnect each motor and drive individually but when mounted I can't break the common
earth. Provided  I do one at a time I could measure return current in each, will do it and report
back, not this weekend as I have to work but maybe the next.

7437

General Mach Discussion / Re: G31 alternative

« on: August 23, 2016, 05:26:11 AM »

Hi Rob,
you're right of course, roll up my sleeves and get stuck in, I certainly have the gear, inductive current probe
to 5Mhz, differential voltage probe to 25Mhz with common mode range of 1400V....

The point is I just don't want to!  I'm happy making chips and have a new coil winding script to try out
and then there's the board for my 'you beaut' servo drive not to mention finish grinding the micrometer
head mounts then there's that straight edge and end clamps for a measurement jig and..... You know
how it goes interesting projects and must do jobs always come up and solving this leakage problem
is mere safety, I sniff at it!!!

Truth be told when I first discovered this problem is when I demounted the spindle and promptly got
quite a tingle from the mill frame. Additionally I laid the remote pendant down on the bed and managed
to take out one buffer channel in the BOB. Fortunately the fault didn't progress back into the PC but still
damage was done.

The solution is of course to demount each stepper so I can measure earth return current but I have just
not got around to it yet. Pretty slack and cavilier of me...

Craig

7438

VB and the development of wizards / Re: Mach3 doesn’t read some VB Script.

« on: August 22, 2016, 07:55:21 AM »

Hi Samrai,
I've had the same difficulty but with setOEMDRO(143,0.0), ie trying to reset an encoder.
In fact I've encountered several encoder DRO's which it appears that I cannot directly
set but can read with getOEMDRO(n).

Haven't yet had any great insight as to why, but then I've only just started to write my own scripts.

Craig

7439

General Mach Discussion / Re: G31 alternative

« on: August 21, 2016, 08:26:12 AM »

Hi Guys.
thanks for your replies, welcome and instructive.

Rob, when I meggered (is that a term you use?) the motors were certainly disconnected from the drives.
I went thru much of the procedure you outlined, disconnected every circuit that goes to the machine and
bought each one online one at a time. The culprits are the steppers, not identical but all near enuf to 10mA
a piece.

Heres the odd bit, the leakage occurs with small variation only wether the axis is driving or not. Even when
stationary the drives still PWM current to the motors.

I've been thru the wiring again and again. All circuits from the BOB to the drives are opto types, I had the
limits and home switches disconnected, in fact removed, the spindle was dismounted and on the other side
of the room!

Vexta specify a 500v isolation result and max rated input voltage of 150V for the motors. The drives themselves
are 230V input. Their size tells me that they have inverter powered DC link. I have not pulled one to bits yet but am
thinking that the DC link may not be isolated from earth. Certainly most AC servo drives are not isolated (what
a surprise that was!!!). I was guessing that the leakage was in the drives but each drive frame is earthed back
to the common rail and I could not for the life of me see why leakage would flow in the mill frame earth.

Since I did that testing I have bought a Tectronrix current probe. One day soon I'll apply it to this problem,
I promise!

In absence of anyother explanation I concluded it was induced current, aka homopolar current in defiance of
Kirchoff. I thorougly agree it way too high but I'm not throwing these things out... they're superb in every
other respect.

I am very careful about power supplies fighting one another. I repair welding equipment or a living and have
seen numerous occasions where weld voltage, a very beefy power supply, blow up boards and their power
supplies should it inadvertently get connected.

Craig

7440

VB and the development of wizards / Re: Mach3 doesn’t read some VB Script.

« on: August 21, 2016, 03:44:25 AM »

Hi Samrai,
I have just started to write my own scripts, its a challenge.

Encountered exactly the same problem you've described because the
script was stored in MachMill not MyMill.

Use Windows Explorer to check that the macro is in the profile you actually use.
...Mach3\macros\<your profile>\M.....

Craig