Stepper Spindle

[ennio64]

In web builder , when axes beyond XYZ (e.g., A) are enabled, it should be possible to add 'Stepper Spindle (Experimental)' to the spindle selection menu. This would make configuring the Stepper Spindle more intuitive and user-friendly.
Thanks!

[terjeio]

I have added it to an upcoming version of the Web Builder for you to test.

[ennio64]

Tested and working.
Thank you very much.
Now, I've realized it would be important to have the ability to define the gear ratio in the spindle settings.

>>I have verified that in order to manually rotate the stepper spindle after sending the M5 command (e.g. part change), it is essential that the axis driver is disabled.
This is achieved by configuring the StepperDeenergizeMask parameter ($37). If the spindle is connected to the A axis, set $37=8. The driver is reactivated automatically: even by sending a command such as G0 A... or G1 A... F.... It is therefore not essential to reset $StepperDeenergizeMask=0, even if it can be useful to avoid unwanted deactivations. It is important to note that, after $37=8, the M3 or M4 commands do not work immediately. For the spindle to restart, you must first reactivate the A-axis driver with a movement command.<<

Solved: blackpill_alt2_map.h have Enable pin common for all steppers. Deenergize with $37=0 and reactivated with $31=1.

[ennio64]

Stepper Spindle RPM Test Results

I tested the stepper spindle speed using encoder feedback and found that the actual RPM does not match the commanded value. The discrepancy increases with higher speeds, indicating maybe a scaling issue.

Command M3 Sxxx	Measured RPM (with encoder)	Error %
100	99	-1.0%
200	196	-2.0%
300	291	-3.0%
400	384	-4.0%
500	476	-4.8%
600	565	-5.8%
700	658	-6.0%
800	739	-7.6%
900	832	-7.6%
1000	907	-9.3%
1500	1300	-13.3%
2000	1660	-17.0%

settings.txt

[terjeio]

Which driver? There are two implementations; one uses polling, the other is interrupt driven. The polled implementation is not the best one and could be the reason for the deviation.
To enable interrupt driven the driver has to support the HAL timer API, few drivers does.

[ennio64]

STM32F411 the board [blackpill_alt2_map.h] there is the settings.txt file attached

[ennio64]

I did some testing and now the RPM setting is exactly the same as the one detected by the encoder mounted on the stepper. However, I encountered a problem when threading (sync without the encoder).

[VER:1.1f.20251108:]
[OPT:VNMSL,500,1024,4,0]
[AXS:4:XYZA]
[NEWOPT:ENUMS,RT+,ES,LATHE,LATHEUVW,TC,SED,PID]
[FIRMWARE:grblHAL]
[SIGNALS:HSEP]
[NVS STORAGE:*FLASH 16K]
[FREE MEMORY:40K]
[DRIVER:STM32F411]
[DRIVER VERSION:251023]
[BOARD:BlackPill Lathe]
[AUX IO:1,3,0,0]
[G54:0.000,0.000,0.000,0.000]
[G55:0.000,0.000,0.000,0.000]
[G56:0.000,0.000,0.000,0.000]
[G57:0.000,0.000,0.000,0.000]
[G58:0.000,0.000,0.000,0.000]
[G59:0.000,0.000,0.000,0.000]
[G59.1:0.000,0.000,0.000,0.000]
[G59.2:0.000,0.000,0.000,0.000]
[G59.3:0.000,0.000,0.000,0.000]
[G28:0.000,0.000,0.000,0.000]
[G30:0.000,0.000,0.000,0.000]
[G92:0.000,0.000,0.000,0.000]
[TLO:0.000,0.000,0.000,0.000]
[PRB:0.000,0.000,0.000,0.000:0]
[SPINDLE:0|0|4|*SDRVE|Stepper|0.0,1000.0]

Generate with Lathe Wizard (IOsender 2.0.46)
G18 G8 G21
M3S200 G4P1
G0 X1.713
G0 Z0.500
G76 P0.500 Z-10.000 I-0.250 J0.100 K0.371

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[GC:G0 G54 G8 G18 G21 G90 G94 G97 G49 G98 G50 M3 M9 T0 F0 S200.]
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ok
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continue step by step

Same problem with G33. During threading, the feed stops about 3 mm from the target and then proceeds step by step.

[nickshl]

@terjeio how motor should be connected to to use stepper spindle plugin? Is it suppose to be connected to A, B, C axis? Or to the spindle control? For example Devtronic_CNC_Controller_V2_map.h board has Spindle Direction and Spindle PWM and it make sense to reuse those pins for stepper spindle control instead using A or B axis.
I am trying to decide if I should to replace 500W BLDC motor on my mini mill to 750W AC Servo motor(with dir and pul control). But it make sense only if I'll be able to use it as an rotational axis with synchronous motion for rigid tapping.

[terjeio]

Currently the highest "numbered" axis is used, A in a XYZA configuration, B in a XYZAB configuration etc...
Later I may make it independent of any axis, but I cannot guarantee that. It is likely I will add an option to "hide" the claimed axis before that since some users switch between spindle and axis mode.

[nickshl]

@terjeio that wasn't my question. Devtronic_CNC_Controller_V2_map.h have up to 5 axis and spindle control. I want to connect servo to the spindle terminals, not A or B axis terminals. I guess it possible to make it up to 6 axis(currently up to 5). If 6 axis selected, then PWM spindle should be unavailable and spindle control pins should be assigned to 6th(C) axis: Spindle Direction -> C Direction, Spindle PWM -> C Step. But in this case there will be unused A and B axis which will affect ioSender and SmartPendant interfaces.
Is there a way to change board configuration file in such way, that in the case Stepper Spindle selected, last axis will be bonded to Spindle Direction and Spindle PWM, not to corresponded axis Direction and Step?

[terjeio]

Is there a way to change board configuration file in such way, that in the case Stepper Spindle selected, last axis will be bonded to Spindle Direction and Spindle PWM, not to corresponded axis Direction and Step?

Only by assigning the pins as an axis step/dir outputs - and I know it is not perfect.
I took advantage of the step injection interface when I added the (for now experimental) stepper spindle. A new HAL interface has to be added if non-axis outputs are to be used, or the output from the claimed axis has to be excluded from reports. The latter might be the best option since, as I wrote above, some users runs the axis both as a spindle and as a rotary.

[ennio64]

Regarding the problems highlighted with the G33 and G76 thread cycles, relating to the feed rate stopping a few millimeters before the target and then proceeding in small steps, after further testing I discovered that the cause is related to the advanced acceleration options: - Third-order acceleration (jerk) - G187 acceleration profiles When these options are enabled, both G33 and G76 exhibit the problem. Disabling them, the thread cycles arrive at the target regularly. So the problem is not with the G33 or G76 commands themselves, but with the interaction between the thread cycles and the acceleration model. A temporary solution is to disable jerk/G187 during thread cutting.

[terjeio]

A temporary solution is to disable jerk/G187 during thread cutting.

The next major commit, due in late January, disables jerk for probing, jogging and spindle sync. It will also allow selecting axis letter for axes > 3 at compile time making configurations like XYZC possible.
Source code for the STM32F4xx and F7xx drivers can be downloaded here if anybody want to try it.