Need Help! - X/Y motors all of a sudden chattering/struggling under no load

Only thing I notice is this:

setp hm2_7i76e.0.dpll.01.timer-us -50

I would change this to:
setp hm2_7i76e.0.dpll.01.timer-us -200




 

I think I may have found the culprit. As I mentioned previously the only two things that I did differently when this all started was switching the breaker in the subpanel off/on and adding G61 to the beginning of the g-code. Well I just removed G61 and restarted LCNC and ran the same tests and it ran perfectly.

The reason I thought I should test this is because the whole reason I started using G61 is because once I would reach a certain speed my sharp corners would start rounding. From my research G61 was one of the options to eliminate this. Well now that I realized that the chattering only happened on corners it made me wonder if there is a connection. Apparently there is.

From my research G61 is used for exact stops which can help at higher speeds, especially at sharp turns like corners. It kinda makes sense why it chatters on arcs. From what I learned G61 causes an exact stop check after EVERY move the machine makes before moving onto the next move. Well an arc is made up of many nodes so am I correct in thinking that the machine would stop at each node causing a chattering? If this is correct, why would it chatter at a sharp corner where there is only one node? So this kind of makes sense but kind of doesn't.

Could there be some setting in my INI/HAL that may be causing G61 to chatter? I have read that G64 is also an option to help with sharp corners being rounded but not sure what the best parameter to set it to. That is why I chose G61.

Does anyone have any suggestions?

PCW wrote:

Only thing I notice is this:

setp hm2_7i76e.0.dpll.01.timer-us -50

I would change this to:
setp hm2_7i76e.0.dpll.01.timer-us -200
 

Thanks for the suggestion. What exactly does this do? 

It sets the DPLL sample time (for the stepgen position feedback in
this case) to 200 usec before (- sign means before) the nominal
LinuxCNC read time.

If this is too short relative to shifts in latency that cause "baseline drift" it's
possible to fail to latch the position before actual read causing a following
error spike of velocity/servo_thread_period. These will show up as random
thumps in motion.

It sounds like your issues are more acceleration related however

tommylight wrote:

From the Gcode quick reference:
G61, G61.1 Exact Path Mode
Meaning it will stop at the end of every segment, then accelerate and stop on the next, and so on.
That explains the chatter as the machine is stopping and starting consistently.
Use G64
G64 P0.1
Means the machine can deviate from the exact path by 0.1mm .
For anything on wood, 0.2 or even 0.3 should be OK.
If using inches, adjust accordingly .

Thanks. That helps.

 

PCW wrote:

It sets the DPLL sample time (for the stepgen position feedback in
this case) to 200 usec before (- sign means before) the nominal
LinuxCNC read time.

If this is too short relative to shifts in latency that cause "baseline drift" it's
possible to fail to latch the position before actual read causing a following
error spike of velocity/servo_thread_period. These will show up as random
thumps in motion.

It sounds like your issues are more acceleration related however

Good to know. Thanks

So I have ran a few more jobs without the G61 and the chattering seems to be gone. I will try the G64 next.

Hey I have a quick off topic question that came up during all my testing. When I hit a E-stop during a job, how do I clear the E-stop relay so that I can continue the job or even just restart the job? When I hit the E-stop a amber light comes on on the relay. I cannot seem to get the amber light to go out unless I close and re-open LCNC which is a pain because I then have to re-home the machine. A lot of wasted time.

Well I know this diagram is not standard or ideal but it is easier for me to read. The E-stop relay is the thin green relay on the DIN rail. 

The file is too large to upload so here is a link to it on my Google Drive.
drive.google.com/file/d/1rknAbOJF4_oHykb...ApW/view?usp=sharing

Thanks