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Author Topic: Tangential control bit - buggy behavior?  (Read 8829 times)

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Tangential control bit - buggy behavior?
« on: January 15, 2009, 02:57:31 PM »
See 2nd post in thread for description of buggy behavior.

I'm cutting a circle and using using tangential mode to make sure my cutting head is aligned properly.

The problem I'm running into comes down to the fact that I only know how to flip the tangential bit - I have been unable to figure out a way to test it or say "turn on"/"turn off" and it sometimes get flipped without my knowledge.   This leads to situations where I a piece of code winds up turning it off when I meant to turn it on. 

I'm afraid I'm missing something here - is there some way to turn this feature on or off, rather than just toggling it?  Alternatively, can someone suggest a way to test it in code so that I can determine whether or not it needs to be flipped?

Here's  a snippet of the code I'm using

Code: [Select]
G1 X6.5 Y5
M1000
G4 P.1
M1020 (macro to set tangential bit)
G17 G2 X5 Y5 R.75
G2 X5 Y5 I1.5 J0
M1001
G4 P.4

For reasons that are entirely beyond me, the first G2 command uses tangential perfectly, but the second doesn't.  The first M1020 command brings the knife direction indicator up onto the toolpath screen, and the pointer (and the actual knife) move perfectly.  When the 2nd G2 move starts, the direction indicator stays up, but it no longer moves.

I'm stumped.  Any help would be appreciated.

Thanks,
Matt
« Last Edit: January 15, 2009, 05:28:17 PM by Mattb »
Re: Tangential control bit - setting rather than flipping?
« Reply #1 on: January 15, 2009, 05:26:47 PM »
OK,

I came in halfway through this project and it seems that this issue wasn't adequately explained to me.  Setting the tangential bit is fine - I can do that in a VB script. 

Now that I have that squared away though, I think I've come across a bug in the way tangential is handled by Mach.

If I have two g2 moves in a row, tangential will only work for the first one, but it'll stay set for both of them.  If I do some other move in between there I then the 2nd move will again have tangential working fine.

I'm cutting paper with a blade, so I need a lead in to a circle - I'm cutting a 2nd circle inside the first for the lead-in, but I tangential won't work for both moves unless I do some other move in between which defeats the purpose of my lead-in.

Offline Hood

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Re: Tangential control bit - buggy behavior?
« Reply #2 on: January 15, 2009, 05:31:43 PM »
Never used that so dont know anything about it, but what would happen if you enabled a dummy axis such a C and in between your  two G2's put a C axis move? Might be worth a try but will make things a real pain if you have a lot of code.
Hood
Re: Tangential control bit - buggy behavior?
« Reply #3 on: January 16, 2009, 11:15:33 PM »
I'm trying to solve G1 resetting my feed rate on arcs in a new version of mach 3. I was reading through the user guide and stumbled across a section regarding the tang feature for cutting. It said it won't carry through more than one line of code for multiple arcs. You have to manually program the arc with a series of small G1 moves.

You say it is keeping the setting just not executing it. Why not try cancelling the setting after the 1st arc and calling it out again after the G1 you execute.

I'm kinda new at this ....just a thought.
Re: Tangential control bit - buggy behavior?
« Reply #4 on: January 19, 2009, 12:31:48 PM »
Quote
You say it is keeping the setting just not executing it. Why not try cancelling the setting after the 1st arc and calling it out again after the G1 you execute.

Thanks Scout - it's a good idea, and I've tried it - it just doesn't work.

I'm cutting fairly thick paper reasonably quickly- so G1 moves are just not an option - it winds up looking awful and the machine just about shakes itself to death.  I still haven't gotten around to trying the phantom axis idea- maybe if I get some free time this week.

What I wound up doing is just cutting a small straight line to lead into the circle - it's not perfect, but it's acceptable for now.
Re: Tangential control bit - buggy behavior?
« Reply #5 on: January 22, 2009, 11:38:01 PM »
I just went back to a legacy copy of Mach 3; no more issues with it cancelling my feedrates wen doing circular pockets. It's worth a try.
Also, the shuttering seems like an independent issue. Could be motor tuning or speed of feedrate vs cutting rpm?
Changed the dir and step values as high as possible in motor tuning as per someone elses post because large arcs (9' radius etc.) sounded like a dying cow. Movement is a little smoother but I am still missing steps occasionally. Maybe a higher kernal speed above 25mghz if my CPU will handle it?


Good Luck

T