Messages

2401

Mach4 General Discussion / Re: Macro Mach4 for THC CAP04

« on: June 19, 2019, 03:54:04 AM »

Hi,
I'm no expert on plasma but I believe that all the functionality required for THC is ALREADY contained within Mach4 Plasma
screenset, ie you don't need a macro, its already there as a module.

Craig

2402

General Mach Discussion / Re: Mach3 - MPG - Precise control as it is on an industrial CNC...

« on: June 19, 2019, 03:38:12 AM »

Hi,

this has been done for a very long time with the Mach software.  Based on that, I fail to understand the "real time" issues related to Windows. 

Mach, or indeed any program on a PC, does not run continuously. It will run for a few milliseconds and then Windows will rush away
and do anther job or even several jobs and then come back to Mach and run for a few more milliseconds. This is the nature of
Windows and little or nothing you can do about it.

Your steppers/servos require non-interrupted pulse streams, the machine would stutter and stall if it relied on Mach alone
to generate pulse streams given that Mach runs 'in fits and starts'. For this reason Mach builds up a string of moves
and stores them in a buffer so while Mach is idle waiting for CPU time the motion controller 'has something to go on with'.

Its that 'something to go on with' that characterizes ALL Windows based CNC programs. While it works pretty well,
jogging in response to an MPG is one area where the 'something to go on with' idea catches you out.
The CSMIO works as well as it does because it can directly process MPG pulses to step/direction pulses without Machs
intervention. It is however the only controller that does that, to the best of my knowledge, and until Hood pointed it out
I didn't know that.

All the genuine realtime hardware controllers are very expensive, ten times and more what Mach costs.

LinuxCNC however is free and the hardware required is modestly priced. I personally am not a fan of Linux but you may
differ.

I use a VistaCNC P1A pendant, first with Mach3 and then with Mach4. The pendant is USB connected to the PC and has its
own plugin. In response to the pendants plugin Mach plans moves and communicates them to my ESS which in turn
generates the pulse streams required to move the axes. I have no trouble, if I select 0.1mm per click, the axes move 0.1mm
per click. What can happen if I select 1mm per click and spin the MPG fast the 'clicks stack up' faster than the machine can move,
and the machine runs on after I have stopped spinning the MPG to catch up on the backlog. It is very un-nerving. If I increase
the jog speed the machine can move that much faster an the problem is much reduced. I don't like that idea much, usually when I'm
jogging I want modest movement speeds to prevent overruns, inaccuracy and crashes. For this reason I tend not to use 1mm
per click, but I find 0.5mm per click or 0.1mm per click better matched to my machine speed and my brain function!

There is a thread running on the Mach4 board which talks a bit about Ethercat. Ethercat is essentially real time communication
for which Windows PCs have struggled because they are not real time capable. What changed here is a VERY clever
innovation provided by Interval Zero called RTX64 which adds a real time processing core to your existing Windows machine.
Further is sounds like its coming to Mach4 soon......and we hope affordably.

https://www.machsupport.com/forum/index.php?topic=41233.0

Whether it would solve your problem is not immediately clear to me but it might interest you.  Googling Interval Zero and
RTX64 will yield some very interesting and informative videos.

Craig

2403

Mach4 General Discussion / Re: Lathe Electronic Leadscrew / Gearbox

« on: June 18, 2019, 03:14:09 PM »

Hi,
for Mach to measure an display spindle rpm it requires a signal. It can accommodate one channel of an encoder.
It measures the time between successive pulses and calculates the rpm based on the time delay. With an encoder channel
producing many, maybe hundreds of pulses per rev the time between pulses is vanishingly small and the potential inaccuracy
in measuring such small time intervals is large.

As a consequence the recommendation is, and the PMDX-416 may in fact require, an index signal, that is one pulse per rev.
Hook up your encoder but use only the index channel.

Thereafter setting the speed of the spindle is all  about Gcode.
g1 z-1 s1000    for instance would cause the Z axis to advance 1 inch (assuming z=0 currently) with the spindle at 1000 rpm.
Note that the spindle is not synchronized however, it is known as an 'out of band' axis. So with the numbers I have proposed
the average feedrate is 0.001 inch/rev, however the z axis will accelerate up to cutting speed and then at the end of the move
decelerate to zero. Thus in those accel/deccel phases the feedrate will not be 0.001/rev.

If you wish to maintain the spindle and the z axis in exact lockstep or synchronization then an ordinary 'spindle' or out of band
axis is insufficient. You would require the spindle to become a coordinated axis....the C axis.

Is that necessary? Have you had a look at Gcode for turning jobs on a lathe? The vast majority dont not have such
tight synchronism between the Z axis and the spindle.

Have a look at the properties of G93 called 'inverse time feed mode'. Have a look also at the Constant Surface Speed feature
of Mach4. Excepting threading its not strictly necessary to achieve synchronism between the Z axis and the spindle.

May I suggest do that first and  once you have explored the performance of that THEN consider what advantages that perfect
synchronism offer relative to the complexity of achieving it.

Craig

2404

Mach4 General Discussion / Re: Lathe Electronic Leadscrew / Gearbox

« on: June 18, 2019, 03:18:43 AM »

Hi,

My understanding when i bought them was that they were not a true servo but a stepper motor with encoder feedback into the driver.

That is essentially correct. You don't need, or indeed want, any other encoder. The PMDX-416 only has five inputs. You do not
have spare inputs for things like encoders, in fact you don't really have enough for home and limit switches as is. You will also
need an Estop and a probe, so there is two of the five available gone.

You may want to consider the PMDX-416's bigger brother like the PMDX-424 as it has a few more inputs or if you want
more still inputs an ESS, or UC300, or 57CNC.

The important point is that Mach and the PMDX-416 will issue pulses to the stepper drive to travel 1 inch say, and
the stepper drive will ensure, barring overload or other fault, that the axis gets there. You can program the drive such that
should the stepper fail to stay in sync with Machs planned trajectory the drive will issue a 'following error' fault.

To do lathe threading you will need an index signal on the spindle..

Craig

2405

Mach4 General Discussion / Re: Lathe Electronic Leadscrew / Gearbox

« on: June 17, 2019, 03:06:13 PM »

Hi,
this post should be on the Mach4 Discussion Board, I imagine Tweakie will shift it.

If I understand correctly you are trying to control the leadscrew of your lathe? If that is the case it is the Z axis
in CNC lathe parlance.

You hook your stepper driver to the Step/Direction pins of the Z axis in your PMDX-416. There is no need for an external
encoder. Mach4 nor the PMDX-416 is not a feedback controller, thus while you could use a couple of spare inputs on the
PMDX-416 to 'read' the encoder and Mach could display that if you wish. What Mach or your controller cannot do is
use that information to 'adjust' your stepper motor drive. That is a 'closed loop' and is not possible with your combination.

Instead you have an 'open loop' situation where Mach/PMDX-416 will send a precisely timed stream of pulses to your
stepper driver to move your Z axis (leadscrew) inexact lockstep with the X axis (cross slide).

The only place where an encoder will be useful, and even then only the index channel of the encoder, is when it monitors
the spindle. An index pulse is required to synchronize the spindle and Z axis ( leadscrew) when threading.

You say you are using a 'hybrid stepper motor'. Would you post some more information about it, in particular is it a closed
loop drive or not?

Craig

2406

General Mach Discussion / Re: Mach 3 GCode problems

« on: June 17, 2019, 01:59:48 PM »

Hi,

I tried to load Mach 4 but I can not find a plugin for my controller as yet.

That controller does not have a Mach4 plugin.

Craig

2407

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 16, 2019, 03:07:33 PM »

Hi,

I assume a G4 would work in the g code?..

Yes, g4 in Gcode would cause a delay whereon you can change direction......but if you omit the g4 from your
code you blow up your relays and/or your drive. You should have a script in Mach4 that runs every m3/m4/m5
operation so that an inadvertent missing g4 doesn't wreck things.

That would apply to either SSR OR relay solution.

Craig

2408

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 16, 2019, 02:35:55 PM »

Hi,

and if you ever fire both sets of relays at the same time lots of smoke will be let out.

That is correct, if you do not correctly program and time the activation of the SSRs you risk having all four on at one time
and disaster will strike.

If however you have an input relay and a DPDT relay on the output (for motor reversal only) then you need to sequence
the input relay BEFORE switching the reversal relay or risk blowing the contacts off the reversal relay, ie you have
to correctly program and time the activations of the relays.

Correct programming is required in both cases.......either solution works and either fail if you don't time activation correctly.

Craig

2409

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 16, 2019, 02:18:57 PM »

Hi,
because you have four independent SSRs you have in effect a DPTT (double pole triple throw relay) where  with all four
SSRs off results in the motor being off.

Is it strictly necessary to have a fifth SSR in the AC input circuit?

Craig

2410

General Mach Discussion / Re: Mach3 - MPG - Precise control as it is on an industrial CNC...

« on: June 15, 2019, 09:49:49 AM »

Hi,

The ESS still doesn't support every feature, does it?

Well yes it does, although it does not handle jogging as the CSMIO does.

ESS (in Mach4) offers:
1) Realtime THC
2) Spindle PID
3) Baklash Comp
4) Single point Lathe Threading
5) Laser Rastering/Vectoring
Plus all the usual homing/limits/gantry squaring/probing that we assume all controllers can manage.

Craig