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Basics
The Spindle is the main effector on your CNC Mill/Router. It holds the end mill or drill bit, makes it turn and remove material.
While manual control is sometimes fine (turn it on before starting your G-code, off when you are done), it is so much neater to have G-codes to control it automatically: simply put an ON G-code at the beginning of your G-code file, and an off G-code at the end of your G-code file, and you don’t have to think about it anymore.
The spindle module supports different types of spindles which are described in the following subsections.
[!NOTE] NOTE the spindle module is NOT compiled into the normal smoothie build, you need to use the CNC build.
General
The spindle module has an option which lets you enable or disable the entire module:
spindle.enable true # set this to false to disable the spindle module
G-code
Available G-code commands:
M3will start the spindle.M3 S5000will start the spindle and set speed to 5000 RPM.M5will stop the spindle. Last set RPM is remembered and used for nextM3command if S argument is not given.M957will report the current spindle speed and PWM value. This returns not the actual value but the value that was set through M3.M958will report the current PID parameters.M958 Px.xxx Ix.xxx Dx.xxxwill set them (to save the new values, you need to edit config file manually).
PWM Spindle
[!NOTE] The PWM spindle is generic for all spindles that use a direct PWM signal to control the spindle speed directly with a MOSFet. It needs a feedback sensor to adjust the speed using a PID control.
Example config options
spindle.type pwm # sets the spindle module to PWM mode
spindle.pwm_pin 2.5 # Big Mosfet Q7. Pin must be hardware PWM capable.
spindle.pwm_period 1000 # default 1000, sets the PWM frequency
spindle.feedback_pin 2.7 # Pin must be interrupt capable.
spindle.pulses_per_rev 1.0 # default 1. Defines the number of pulses occur for each rotation
spindle.default_rpm 5000 # default 5000. Defines a default RPM value in case no RPM value is provided.
spindle.control_P 0.1 # default 0.0001. P value for the PID controller
spindle.control_I 0.1 # default 0.0001. I value for the PID controller
spindle.control_D 0.1 # default 0.0001. D value for the PID controller
spindle.control_smoothing 0.1 # default 0.1. This value is low pass filter time constant in seconds.
[!NOTE] Check the pinout to verify if a pin is capable for a certain functionality!
[!TIP] Hobby servo ESC as spindle control Since I’m experimenting with hobby ESC+motor combos (1:8 scale 3 phase 4068 like motor) I wanted to share its config. ESCs act like hobby servos - 20 ms period time, 1.5-2ms duty cycle time -, so instead of having modified the spindle code, I’ve created a switch for commands M3/M5. Due to the very small duty cycle window, you won’t have much control over the motor: S7.5 is neutral, S12.5 is “fastest” after calibrating the ESC manually with bCNC (read ESC’s manual; below S7.5 is breaking for now).
The following code is working, setting neutral upon boot - ESC init.
switch.servo.enable true # Servo module for PWM control switch.servo.input_on_command M3 switch.servo.input_off_command M5 switch.servo.output_pin 1.23o! # spare pin with PWM capability, 3.25 should also work from EXP2, maybe needed to set it to 1.23o! switch.servo.output_type hwpwm #switch.servo.pwm_period_ms 20 #set PWM period to 20ms (50 Hz) switch.servo.startup_state true # turn on the output to have neutral for ESC switch.servo.startup_value 7.5 # this is default_off_value switch.servo.default_on_value 7.5 switch.servo.failsafe_set_to 0
[!NOTE] If you want to learn more about this module, or are curious how it works, Smoothie is Open-Source and you can simply go look at the code, here.
Analog Spindle
This module is used to control a VFD with a PWM that is converted to a 0-10V analog signal by an additional circuit. That circuit also provides an optocoupler for switching the VFD RUN signal. It is also the mode of choice if you run a brushless motor spindle driven by an ESC, in that case, you will not need any additional circuitry.
[!NOTE] The analog spindle is generic for all VFD’s that use a 0-10V speed reference signal, so it doesn’t need a special implementation for a certain VFD. The downside is that the signal is not completely linear and may be interfered with by noise. If you can use a VFD that supports Modbus/RS485, it’s highly recommended to use that technique!
Example config options
spindle.type analog # set the spindle type to analog, can also be used for ESC spindles controlled by a PWM
spindle.max_rpm 24000 # set the max spindle speed that is achieved at 100% PWM
spindle.pwm_pin 2.4 # the pin which emits the PWM signal
spindle.pwm_period 1000 # the PWM frequency
spindle.switch_on_pin 2.6 # the pin which is used to enable the VFD (optional)
PWM to analog converter circuit
[!NOTE] If you’re using a brushless motor + ESC that takes the PWM directly as a speed reference, you don’t need an additional circuit.
VFD adapter board PCB
Used to talk to your VFD via an analog signal
This is an example of a small extension PCB that contains a circuit to convert the 3.3V PWM signal into a 0-10V analog signal.
VFD adapter board schematic
For the curious
This is the related circuit diagram for the converter
VFD adapter board wiring
How to connect it to your Smoothieboard and VFD
This example shows how to wire the Smoothieboard to a Huanyang VFD using the PCB shown above.
[!WARNING] Unfortunately, the circuit does not create a completely linear output signal. As you can see in the graph, the signal is better at the beginning and at the end.
[!NOTE] If you want to learn more about this module, or are curious how it works, Smoothie is Open-Source and you can simply go look at the code, here.
Modbus Spindle
This module is used to control a VFD using an RS485 communication bus. It provides a Modbus implementation and is easily extendable to support a wide range of Modbus compliant VFDs. But it also can support VFDs that are not compliant with the Modbus standard such as the widely used Huanyang VFD that is popular and cheap on eBay.
[!NOTE] The modbus spindle needs a separate implementation for every VFD model. At the time of writing only the Huanyang is implemented, but it is very easy to extend the module for many other models.
Example config options
spindle.type modbus # set the spindle type to modbus/RS485
spindle.vfd_type huanyang # set the VFD type, this is necessary because each inverter uses its own commands
spindle.rx_pin 2.6 # TX pin for the soft serial
spindle.tx_pin 2.4 # RX pin for the soft serial
spindle.dir_pin 2.5 # RS485 is only half-duplex, so we need a pin to switch between sending and receiving
Huanyang VFD Modbus Parameters
In order to get the Huanyang VFD accepting commands via ModBus, you need to change a few parameters:
[!NOTE]
- PD001: 2 (Source of run commands: communication port)
- PD002: 2 (Source of operating frequency: communication port)
- PD163: 1 (Communication address: 1)
- PD164: 1 (Communication Baud Rate: 9600)
- PD165: 3 (Communication Data Method: 8N1 RTU)
RS485 extension board
Like an analog spindle, the Modbus spindle needs an external circuit, but that is much simpler.
VFD Modbus signal adapter PCB
Used to talk to your spindle over RS485 differential signals
This is an example of a small extension PCB that contains a circuit to convert the 3.3V UART signal into an RS485 signal.
VFD Modbus signal adapter schematic
For the curious
This is the related circuit diagram for the converter
VFD Modbus wiring
How to connect it to the Smoothieboard and the VFD
This example shows how to wire the Smoothieboard to a Huanyang VFD using the PCB shown above.
[!NOTE] If you want to learn more about this module, or are curious how it works, Smoothie is Open-Source and you can simply go look at the code, here.