M03 doesn't wait until rpm reached

[ToastyCH]

Hello togheter,

Im useing a diy milling machine.
Board grblhal2k, vfd hy-620 connected via rs485

When I start a gcode like this:

M03 S24000
G0 X0 Y0
G01 Z-5 F500

My machine starts the spindle but continues imediatley. So my insert reaches the workpiece before reaching 24k rpm. (I can see the spindle ramping up in ioSender)

In my eyes the right behavior would be that grblhal waits till the spindle reaches the desired rpm. And the continue with the gcode.

I created an github Account to post this idea. So I have no idea how everything works here. If i can provide more data, please let me know.

Best regards

Toasty

[LoganFraser]

Wait for AtSpeed rpm detection would be ideal, but even a post-processor addition of the spindle delay setting after every rpm increase would be useful, especially in ops that have different ramping to milling RPM settings.

[terjeio]

Setting $340 is available? If so set it to the deviation allowed as a percentage of the programmed speed. $392 can be used to set the delay before an alarm is raised if the spindle fails to reach the speed.

[Dietz0r]

Setting $340 is available? If so set it to the deviation allowed as a percentage of the programmed speed. $392 can be used to set the delay before an alarm is raised if the spindle fails to reach the speed.

Spindle on delay is available and set appropiately but does not delay gcode execution.
It just checks for RPM at the set time. I can reproduce this on VFD with RS485 and on PWM mode.

It was surmised that it's a conflict of the "Saftey Door Input" function.

[terjeio]

If $340 is set to 0 the $392 delay is ignored (for M3/M4 commanded spin up it is the delay before an alarm is raised, for safety door it is delay before the code continues after the door is closed).

[ToastyCH]

Im sure i set $392 to 8 seconds like my vfd. Im not sure what $340 is set on my machine. Will check it as soon as I can get back to my machine and the reply here.

[Dietz0r]

Just checking in from the machine.
$340 was indeed still set to 0.
With $340 = 1 it waits until the spindle reaches 20000rpm (programmed 22000rpm) and then continues.
So that is confirmed working and indeed user error on my part.
Maybe the option discription is a bit missleading and the waittime could/should be decoupled from the tolerance setting for machines without rpm feedback from the VFD (like 0-10V controlled spindles)?
e.g. if $340 = 0 tolerance is set wait atleast the time specified in $394 ?

as always thanks for the quick replies @terjeio

edit: swapped $392 for $394, misstyped

[ToastyCH]

I've also checked my $340. It was also set to 0.

Now the machine waits. Even though i think the machine doesnt wait till my actual rpm is reached but maybe my "feel" is just wrong.

But like this i can work with😀

Thank you very much terjeio!

How ist this supposed here? Can I close this idea?

[S2000Stefan]

Hello ToastyCH,

When I start a gcode like this:
M03 S24000
G0 X0 Y0
G01 Z-5 F500
My machine starts the spindle but continues imediatley. So my insert reaches the workpiece before reaching 24k rpm. (I can see the >spindle ramping up in ioSender)

To insert a delay when spinning up the spindle, please write the following line after the M3 command.

M03 S24000
G4 P5
G0 X0 Y0
...
Where P stands for the time in seconds. In this case 5 seconds.

Best regards
Stefan

[ToastyCH]

Hello Stefan, yeah a dealy would work. But then I always got to remember to write the command in the gcode. As I know me, Im sure i will forget it once...

If the machine would wait, that would be much "safer"for me. Or do people want to start cutting before the spindle ramped up?

[S2000Stefan]

Hello Toasty,
so i have entered this line in the postprocessor then "it" always thinks of it for me. :)
But I have heard that there is a much more elegant solution in grblHAL.
I'll take it easy then. ;)

[terjeio]

But I have heard that there is a much more elegant solution in grblHAL.

It is available for ModBus controlled VFD spindles that can report the current RPM, or if there is an spindle encoder connected to the controller and the controller is configured to read the RPM from that. There are also a couple of drivers that can fake "spindle at speed" by ramping the PWM output (compile time option - not tested much).

[tcurdt]

So IIUC this is the logic?

$340=1 (wait for spindle)
$392=12 (delay in seconds until timeout aka ALARM14)

Would be great to have this better documented here.

[terjeio]

Would be great to have this better documented here.

Agree. Until then you can always get at least some help from the inbuilt documentation. See the first few paragraphs here.

[tcurdt]

That's the docs I would love to see improved :)
(BTW: Happy to provide a PR to the wiki once I understand things)

It says "The timeout delay defaults to 4 seconds and is currently set from the SAFETY_DOOR_SPINDLE_DELAY symbol."

SAFETY_DOOR_SPINDLE_DELAY?

It defaults. So the timeout can be set? via $392?

[tcurdt]

So gsender decided to switch from grblHAL to grbl (grrr!) that's why I didn't see the inline help.
Still it would be nice to have something along these lines added to the wiki:

$340=10 (percent of difference in spindle speed allowed before alarm, enabled if > 0, also enables waiting for spindle on M3)
$392=12 (delay in seconds until timeout for spindle speed aka ALARM14)