Messages

1351

General Mach Discussion / Re: THC not working properly

« on: February 14, 2011, 04:54:20 AM »

Good you've made some progress. Looks to me as if some of the modio is done in the PP driver as well then. The thing with DoSpinCW is weird though because I use activateSignal(OUTPUT1) instead in M3, not a doSpinCW in sight and THC works just fine and dandy.

I wrote this little bit of code in a button to determine if the THC mode was actually on...

If isActive(THCON) Then
   MsgBox("THC is ON")
Else
   MsgBox("THC is OFF")
End If

When I press this button, even with the THC LED on, it tells me that the THC is off.  I'm at a loss.  There has to be something telling Mach to ignore THC commands even though THC is on.

The reason this doesn't work as you might have expected is... (and you're going to love this after your walk on water comment earlier) 

what you're testing here is whether ArcOK is on or off - not whether THC is on or off. THCON is actually the signal name for ArcOK. But then that's what it's called in ports n pins too so it shouldn't be that surprising perhaps.

Please get back with whether modbus is fast enough for THC UP/DOWN -  I'd be interested. Personally I think THC via PP is only just keeping up - but then if some of the modio is done in the PP driver, it may be no different - who knows.

Ian

1352

General Mach Discussion / Re: THC not working properly

« on: February 13, 2011, 12:16:19 PM »

AFAIK, the required THC functionality is coded "inside" the PP driver. That's one reason why THC doesn't work with the smoothstepper for example. I suspect, that as you're using the modbus for these signals and therefore not using the PP, then you're suffering from the same problem.

Ian

1353

VB and the development of wizards / Re: How to stop a movement when input is active?

« on: February 13, 2011, 12:07:24 PM »

That's good - thanks for the video too. 

Just a note though. If you prefer a macro, that's fine but you shouldn't even need to edit your code to insert that - ideally your CAM should be set up to insert it for you - either inline code or macro.

Ian

1354

General Mach Discussion / Re: Problems with axis accuracy - MachTurn

« on: February 13, 2011, 08:13:41 AM »

I don't think I am losing steps, but I was wondering about just how repeatable microstepping is - has anyone any experience of problems from this source?

Hi John. Microstepping should NOT be included in the "theoretical" calculation of accuracy. Purely from the motor accuracy perspective, full steps are usually stated as being within +/-5% accurate. Microsteps are less than that and are unpredictable. (Note the difference between accuaracy and resolution). Whilst full step accuarcy is purely down to motor manufacture, microstep accuracy is down to a combination of the motor/driver/PS/mechanics etc. As just one example, sometimes, a motor will not even move until it's had 3 or 4 microsteps, then it will "jump". It will do this sometimes and not at others - maybe.

Microstepping's purpose is purely to get smooth(ER) motion than full stepping.

Ian

1355

VB and the development of wizards / Re: How to stop a movement when input is active?

« on: February 13, 2011, 07:45:04 AM »

Yes you can use the G31 method if you want. It's one of those things that creates much discussion - G28.1 or G31 - which is better? They both have advantages and disadvantages. To use G31 you'd use the probe input in ports and pins. Then use something like G31 Z -100 instead of the G28.1 line in my previous code. The -100 is just an example - it doesn't really matter as long as your probe touches the metal at some point of course. You might want to add a feedrate in there to control the descent.

-ve is just shorthand for negetive.

Ian

1356

General Mach Discussion / Re: Pierce delay for plasma

« on: February 13, 2011, 06:59:57 AM »

Hi Matt - after having a play, I think you're absolutely right - in a way...

It seems that regarless of whether you're using THC, Mach executes the M3 and THEN executes the G4 dwell. However, IF you're using THC Mach will THEN wait, AFTER the dwell for ArcOK (if it has to). The reason I (and I suspect a lot of others) have never noticed this is that IF the M3 is very quick in turning on your torch AND the ArcOK is very quick and between them the time is MUCH shorter than the dwell, then everything APPEARS to work as it should. BUT - IF the time it takes to turn on the torch and to return the ArcOK signal is pretty close to the G4 dwell time OR worse LONGER than the G4 dwell then there is effectively NO delay. i.e. it's allready done the G4 BEFORE it even got the ArcOK.

This IMHO is clearly wrong and I would regard it as a Mach bug. What Mach SHOULD do of course is execute the M3 and then wait for ArcOK BEFORE it does the G4 dwell.

In reality, the only gcode commands that Mach will not execute if ArcOK is not there (and THC is on) are MOVEMENT commands.

Hope that all makes sense. You can test the above out by doing a "silly" long G4 and you'll see it IS being executed and not skipped.
One make do solution I guess is to add the time it takes the torch to come on + the time it takes it raise ArcOK + the actual pierce delay you need and code G4 for that. Alternatively I guess some suplemental VB in M3 to do a wait for ArcOK - something like:

'untested and crude - i.e. infinite loop if ArcOK never comes.
DoSpinCW
while not isActive(THCON) 'yes annoying isn't it, Mach's signal name for ArcOK is THCON for gawds sake.
wend  

Incidentally, a tip: I don't use DoSpinCW - it's slooooooooow, instead I use activateSignal(OUTPUT1) - it's waaaaaay faster to respond.

Ian

1357

VB and the development of wizards / Re: How to stop a movement when input is active?

« on: February 13, 2011, 04:00:31 AM »

Bob - I'm not sure if you have been told to do this via a VB macro by your school but this is not generally how this is done. IHS (Initial Height Sensing) from the hardware point of view is usually done by one (or more) of: Floating head, Ohmic sensing and capacitive sensing. It sounds from what you've said that you are using the floating head method with a microswitch. If so, you have the option of using either probe based IHS (G31) or home based IHS (G28.1). I'd suggest home based to start with.

In this method, you set your floating head microswitch as a home switch and set home to be -ve (in home/limits). You then use something like the following gcode at the start of each cut:

Code: [Select]

G28.1 Z3.00  (home downwards from safe height, 3 is just an example)
G92 Z0.0      (Homed, so set Z to 0)
G00 Z2.8000 (back off for switch travel - yours will likely be different - set distance appropriately)
G92 Z0.0      (set Z to 0)
G00 Z3.8000 (Move up to piearce height - see your plasma cutter manual)
M03             (fire torch)
G04 P0.3      (wait pierce delay - see your plasma cutter manual)
G01 Z1.5000 (descend to cut height - see your plasma cutter manual)
....               (commanded moves in x, y)

Hope this helps

Ian

1358

General Mach Discussion / Re: THC not working properly

« on: February 13, 2011, 03:28:53 AM »

Is this a licenced or demo Mach3?

1359

VB and the development of wizards / Re: Question for Breakin Wizard

« on: February 12, 2011, 04:59:24 AM »

“Use Rapids: This will allow you to cycle back and forth between tool feed speed and rapids for your repetitions. If this is selected, rapids will be used for the initial positioning for the router and bit.”

What is Rapids and what is the meaning of the above?

Rapids are where the machine attempts to do moves at the max velocity you've set in motor tuning. Rapids are G0 moves. This is as opposed to moves at your selected feedrate which are (for example) G1 moves. If you generate and examine the code from the wizard both with "Use Rapids" and without you'll see the difference.

“Alternate Sides Between Repetitions: Allows the Machine to do more of an X patter than a line back and forth at a diagonal”
 
What is the meaning of this?

if you don't select "Alternate sides" then the code generated describes a simple diagonal path. Try it to see. Use offline if you want to test it without machine movement.
if you DO select "Alternate sides" then the code generated describes a cross pattern. Try it to see.

Ian

1360

General Mach Discussion / Re: Pierce delay for plasma

« on: February 10, 2011, 09:20:44 AM »

Beat me to it about the G4 and the delay either being in ms or s  

Matt - is that just your memory - or have you actually missed out the G4 in your code.

Also - what do you have in your M3 macro?

This is pretty standard floating head IHS by homing stuff and should work fine. Can't comment on the behaviour of your particular THC as I've never used that one.

Ian