Author Topic: trajectory buffer - missing vectors after STOP and START  (Read 2578 times)

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Offline etet100

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trajectory buffer - missing vectors after STOP and START
« on: August 02, 2015, 01:36:01 PM »
Hi. Sorry for my poor english (i'm trying to do my best).

I'm working on USB motion controller. I noticed that after stopping program (Stop button) and starting it again (Cycle Start) some trajectory
vectors are lost. For example:

G2 X5 Y5 I5 J0
G1 Z6 F200
G3 X0 Y5 I0 J6
G1 X0 Y0 Z5 F1200

If i run program and then stop it almost immediately, mach stops filling trajectory buffer (GMoves Movements[0x1000]) after (for example)
70% of first arc. When i start it again it doesn't continue to generate first arc but go
straight to second or even third line of gcode.

I also noticed that it's probably correlated to "MainPlanner->ExBufferHi" value. The higher value it is, the more vectors are lost.

Could someone help me ? Thanks in advance.
« Last Edit: August 02, 2015, 01:45:27 PM by etet100 »

Offline garyhlucas

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Re: trajectory buffer - missing vectors after STOP and START
« Reply #1 on: August 02, 2015, 01:51:27 PM »
Never use stop while the machine is moving. Use Feedhold instead. If you stop a program you need to be very careful how you restart. I always single step on a restart and watch carefully where the machine is versus where it need to go.

Offline etet100

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Re: trajectory buffer - missing vectors after STOP and START
« Reply #2 on: August 03, 2015, 02:38:52 AM »
It look's like you are right. Issues with trajectory buffers are gone when i'm using feedhold.

Hovewer, in lpt mode i always used stop (or even emergency stop) and never experienced any problems. It was
very convinient. Is there any way to continue (automatically) correct path after stop or estop ?

Offline garyhlucas

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Re: trajectory buffer - missing vectors after STOP and START
« Reply #3 on: August 03, 2015, 03:39:30 PM »
I suspect that when using the printer port where Mach3 is generating every step it knows exactly where the stop happens as long as no steps are lost, like from a crash.  However stopping with an external controller when the path has not completed leaves Mach 3 not knowing where the tool is. Using feed stop issues a command that tells the motion controller to bring the machine to a stop so position is maintained.

Offline etet100

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Re: trajectory buffer - missing vectors after STOP and START
« Reply #4 on: August 17, 2015, 02:15:05 AM »
Thanks. In this case, further work on external pulse generator does not make sense. Using the parallel port is much more convinient.