Messages

2391

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 21, 2019, 06:29:19 PM »

Hi,
we actually stocked Allen Bradley relays of the same type, there must be an effective industry standard which different
manufacturers use to provide competing products.

They are still 'American Made' when that used to mean top quality. I have replaced these relays after 30 years service
reversing wire drive motors in sub-arc welders (150VDC motors)....they are truly rugged and reliable. Not to say you
couldn't wreck them by trying to switch direction with the motor at full speed without allowing a de-acceleration pause.

Craig

2392

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 21, 2019, 06:09:38 PM »

Hi MN300,
the relay to which you linked to from the Newark site is the indentical one to which I linked to on the Element14 NZ site.

Newark and Element14 and Premier Farnell are ALL the same company.

Craig

2393

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 21, 2019, 05:56:47 PM »

Hi,
there is an arrangement where you can use MOSFET/anti-parallel diode SSRs.

I have left out the connections to the opto diodes, they are switched as pairs, K1 and K4 together OR K2 and K3 together.

Craig

2394

General Mach Discussion / Re: Newbies

« on: June 21, 2019, 05:23:53 PM »

Hi,
Fusion 360 is free for a year to hobbyists. Its a great piece of advertising for Autodesk the company responsible for not only
Fusion 360 but Inventor, HSMWorks and AutoCAD.

It is worth registering and checking it out.

Craig

2395

Mach4 General Discussion / Re: SSR Relay Forward Reverse Help

« on: June 21, 2019, 05:05:54 PM »

Hi,

Could I have a bad SSR relay, how to test it ?.. I did check the ohms on the outputs of all the relays 3 showed 0 ohms but one showed 278.89 ohms when relays where not power on so should be Open circuit ..

Can you post an exact model code of the SSRs you are using? I noted that in the diagram you posted you showed the
internal representation of the SSR as a MOSFET with an anti-parallel freewheeling diode. If that is indeed the internal
structure of the SSR then you can under no circumstance reverse bias it because the freewheel diode 'shorts' the
applied reverse voltage.

As MN300 has pointed out a mechanical DPDT relay even with the addition of a SPST relay to isolate or turn off the spindle
is an easier proposition if you are not familiar with electronics. Unlike MN300 I think a suitable DPDT relay is not going to be cheap.
I have had many occasion to reverse DC motors as a result of working with welding equipment for some years.
We stocked open frame relays such as this for the purpose. They are not cheap but they are good and therefore did not come
back as a warranty claim on our work.

https://nz.element14.com/potter-brumfield-te-connectivity/prd-11dh0-24/relay-dpdt-125vdc-20a/dp/1386559

Note the price in this link is in NZD.

Craig

2396

Mach4 General Discussion / Re: Run G code from here starts cutting at transfer speed.

« on: June 21, 2019, 04:34:21 PM »

Hi,
I have build 4162 also, according to that the action of the <Run Gcode From Here> button is 'RunFromHere'.
Given that it is a stock Mach4 action we cannot see the code behind it

I remember always struggling with <Run From Here> in Mach3 until I understood all the implications of the instruction.
One of the important procedures required to <run from here> is to set the correct machine mode.

When you run a Gcode program at any given instant it might be that the spindle is spinning clockwise, ie that some time
in the immediate past an M3 has been issued, and presumably an S*********x to set the speed. The machine may be in incremental
mode, ie a G91 may be in effect and the current move being a linear interpolating cutting move G1 F*********x in effect.

If you start a Gcode program at some point throughout its length......what mode should the machine start in? You can't tell
without scanning through the Gcode that precedes it. There is an API function that does that called 'dry run':

Code: [Select]

LUA Syntax:
rc = mc.mcCntlDryRunToLine(
number mInst,
number line)

Description:
Process G code forward to a given line without motion.
It has a VERY important note that simply cannot be overlooked:

Code: [Select]

Notes:
Once the dry run is started, the function returns immediately. To wait on the dry run, you must check the state of the control.

I would presume that the stock action, 'RunFromHere', must include this API function or another very similar to it in order for
<Run Gcode From Here> to work. It sounds like from your description that Mach is not 'initializing' itself which suggests to me
that as Chaoticone has suggested may be because it is included in the <Set Next Gcode Line> and you have not used it?

Craig

2397

Mach4 General Discussion / Re: Lathe Electronic Leadscrew / Gearbox

« on: June 21, 2019, 10:52:27 AM »

Hi,

He wishes to drive the threading leadscrew with a closed loop stepper motor rather than gearing it physically to the spindle.

Yes, that could indeed be OPs intention.

If the index signal from the spindle encoder is hooked to the PMDX-416 and in turn to Mach then Mach has continuously updated
value of spindle speed. A small script in the PLC would allow the leadscrew stepper to be driven as a velocity jogged out-of-band axis.
The result would be that the leadscrew attains and maintains a speed in direct proportion to the spindle.

Note this approach is still not the same as a gearbox. The leadscrew would be velocity synchronized to the spindle but exact
posistional synchronization could not be assured.

If an index pulse is received by the PMDX-416 it will be transmitted to Mach, but there will be an indeterminate delay of several
or maybe tens of milliseconds. Mach will then do its calculation and issue P(osition)V(elocity) over T(ime) moves to the PMDX-416
with another indeterminate delay. The communication delays prevent the leadscrew stepper from maintaining exact positional
synchronization.

Exact positional synchronization can be achieved ONLY if the communication delays can be eliminated. When a G76 threading command
is encountered while Mach supervises actually the PMDX-416 takes over and does the synchronization itself without relying
on Mach with the inherent comm delays.

This could also be done with an Arduino, it would monitor the spindle encoder and produce step/direction pulses to the stepper
driver. That could be done continuously and within microseconds and positional synchronization could be attained.

Craig

2398

General Mach Discussion / Re: Ref all home does nothing?

« on: June 19, 2019, 01:47:35 PM »

Hi,
if I recall correctly its not necessary to use macros.......have you set up the 'home order' and unchecked the 'home in place'
setting in Config/Homing-Limits page?

Craig

2399

General Mach Discussion / Re: Mach 3 GCode problems

« on: June 19, 2019, 04:22:56 AM »

Hi,
yes.....good choice. I agree with Tweakie, Chinese CNC controllers are rubbish. The rest of the machine, all the mechanical
parts are usually pretty good, or at least as good as you could reasonably expect for the money but the electronics
lets them down badly and then to top it off they insist on using pirated software!

Mach4, an Ethernet SmoothStepper and a breakout board or two and you be set to do some great CNC stuff.

Craig

2400

Mach4 General Discussion / Re: Lathe Electronic Leadscrew / Gearbox

« on: June 19, 2019, 04:04:55 AM »

Hi,
g95 occurs in the Mill Gcode Manual.pdf but not in the Lathe Gcode Manual.pdf It suggests that g95 is not available
in lathe operations.

The time that you strictly require the Z axis and the spindle synchronized is when threading. The PMDX-416
handles threading and synchronization in real time and on it own board, Mach 'supervises' but because Mach is
not realtime capable it can at best supervise while the motion controller (PMDX-416) gets on with the real business.

g76 is used for threading.

Craig