Messages

461

General Mach Discussion / Re: Odd glitch in movement?

« on: April 29, 2014, 04:34:54 AM »

Question - as it is I now know it will work at 3300mm.min on 1mm sheet very nicely. If I then go for thicker metal, say cutting at 700mm.min, will the acceleration have less 'bite' than it does at this higher speed.?

Not sure what you mean by "bite" but if you mean "jerk" then...

(Jerk is not just an arbitrary term btw - it's the pukka name for the rate of change of acceleration).

As acceleration is constant in Mach - so is Jerk. (There used to be a planner that used S-curve accel to reduce jerk - but that's another story).

Or to put it another way - any lack of rigidity presents the same issues at any speed.

Not sure if that answers your question.

462

Modbus / Re: How to Address Modbus Outputs if you have more than 20

« on: April 29, 2014, 03:54:05 AM »

No need to wait for Mach4, Mach3 macros take parameters.

Yes - an understanding of C would certainly help.

Cheers

Ian

463

Modbus / Re: How to Address Modbus Outputs if you have more than 20

« on: April 28, 2014, 11:08:40 AM »

Hi shangJie

Thanks for getting back. Good you're getting it sorted.

Just for completeness - this would have been the detail of my suggestion. The Arduino Mega has 54 outputs and can be programmed with open source software to be a MODBUS slave.

You could then send the number of the output you wanted activating via MODBUS using a single register and the GCode S word (normally for spindle speed but it's just a number) so no VB macros needed. Then your Brain would be ONE rung like:

CmdSpindleRpm ->NOP -> MODBUS register

Anyway - you're up and going so no worries

Ian

464

General Mach Discussion / Re: Odd glitch in movement?

« on: April 28, 2014, 10:47:16 AM »

CV rounding < accel > Jerk.

i.e. accels right there somewhere between CV rounding and Jerk. What's the best accel for your machine? Looks like your close on finding it. To me those cuts look pretty darn good. Good work.

Ian

465

General Mach Discussion / Re: "run from here" problem

« on: April 28, 2014, 03:43:39 AM »

ARE you SURE (;-) ? Something seems off. IF your Cam adds in the #1000 =31 in the preamble of the program Then #1000 gets set to 31 at program load.

When you press RFH and inside of that button you reset #1000 =1 it resets the #1000 to 1

BUT when the RFH preruns the Gcode modes it will SEE the initial call of #1000 =31 and set it BACK to 31.

YES??  NO??

that would be YES - I am sure and a NO - the buttons don't write to 1000 anywhere

The 1000 var never changes, what it's set to by your CAM post stays. It just tells the button code which of 31/28.1 to use. I COULD have hard coded (say) 31 into the cycle start button, but that would mean you'd have to change the code in the button if you wanted to use 28.1 instead. By putting 31 or 28.1 into 1000 and copying that in the button instead, it means the same button code will work for either. Simples.

466

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 12:08:38 PM »

Remember your dumbbell shape is not "awkward" because it's particularly special in having small circles, it's just an example of a shape with tightish turns. ANY shape that requires sharp direction changes is going to need good accel. I know I keep harping on about the accel but it truly is the key.

Poor accel causes larger changes in cut speed. ANY change in cut speed will change the voltage across the arc. That change in voltage will be interpreted by your THC as a HEIGHT change. That's what causes dive. That's just how it works. Yes THCs use various methods to try to mitigate this but the plain fact is that you're better off not taxing them too much in the first place.

467

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 11:14:22 AM »

No particular need for a separate layer for small holes. Remember turning THC ON/OFF BETWEEN cuts is not an issue. Turning THC ON/OFF DURING a cut usually IS an issue.

LOL - yes your long dumbbell with small circular ends could pose that problem. You don't maybe think you think too much do you Dave?

Of course when you have that great accel this sort of problem will magically disappear anyway. (hopefully  ) 

Ian

468

General Mach Discussion / Re: "run from here" problem

« on: April 27, 2014, 10:04:51 AM »

Ian, you are such a tease 

But in my defence I would offer two things to the prosecution... (i.e. Terry)

1) I DID say back in reply #45 that THERE IS a way to do this. i.e. Not IS THERE a way to do this? I thought you'd picked up on that.

2) I thought you would enjoy the challenge.

3) I think it's fair to say that you've (in your words) "yanked my chain" plenty and will no doubt continue to do so  so...

Anyway - here's the deal. Simples really (G31 type TOM as an example)

1) get your CAM to output #1000=31 in the init section.
2) say your current TOM probe output is like

G31 Z-1

instead, get your cam to output it like

G#1001 Z-1

Now arrange for #1000 to be copied into #1001 when you're running and when you do a RFH arrange for 1 to be copied into #1001. So a run does what it says on the tin - but a RFH doesn't process G31 it processes G1 instead - which it handles fine.

You can do this in various ways - ONE way is to add code to your cycle start button

setVar(1001, getVar(1000))
doOEMBUTTON(1000)

and your RFH button

setVar(1001, 1)
doOEMButton(1016)

That's the basics of all it is really - which you could play around with if you're interested (oh sorry - you're not  )

DISCLAIMER: I make no claim that this will sort all RFH bugs out. It solved the problem (for me) that you raised in reply #43. YMMV. Do I use it much? not really.

Cheers

Ian

469

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 07:38:51 AM »

BTW, if I need a small hole in thick material, it needs to slow down, I have found 70% seems to work but as that is programmed in sheetcam! how does anti-dive deal with that?

IMHO THC has pretty much no value on small holes - in fact in my experience it causes more problems than it ever solves. Remember THC is there to cope with the changing height of the metal. Almost by definition - small holes - don't cover enough metal to see any particular change in height. Add to that the fact that THICK metal is going to be even LESS prone to changes in height over short distances and it becomes clear that THC brings little if anything to the party.

470

General Mach Discussion / Re: Odd glitch in movement?

« on: April 27, 2014, 07:32:32 AM »

PS, IAN sorry for taking over your post(;-) but I cut that type material every day on a DIY type machine.

Hey Terry - not my post - be my guest - Like I've said, you've probably forgotten more about plasma than I'll ever know.

Turns out though that with specific regard to the question about the firedoor and dumbbell I've found this:

It would appear it's caused by a bug in Mach's CV when using Angles >. It only affects G1/G2 blends and not G1/G3. So that's why you're seeing your notches where they are in the firedoor and why you have asymetric blends on the dumbbell. It goes from the present version back through to the dawn of time so looks like we're stuck with it.

However, as Terry and I have both said you shouldn't be needing CV options anyway so it shouldn't be an issue here. Note that this doesn't solve your rounding - it will just make it consistent - your rounding is still down to speed/accel. At least though, now ALL your joins should be rounding you shouldn't get the notching.

Cheers

Ian