I’m using and SKR Pro v1.2 board, and there are a few outputs I would like to control with G-Code.
Is any of this possible, or sensible?
PWM spindle control
I’m running a VFD for a 65mm 800w Spindle, I’ve read the documentation and I’m fairly certain that this is possible - I mostly mention this as it is one item that I would like to have PWM control for.
Spindle Water Coolant Pump
This could be a basic on/off 230V relay, so doesn’t necessarily need PWM control. What’s the common practice with these coolant pumps, can I wire it straight into the VFD power input, so when the CNC is powered the coolant pump is running? Is this a good/bad thing?
Flood coolant pump
I’m also planning on running flood coolant. The pump I have is a 3a 12VDC pump, but my power supply is 24V - The head height is something like 1.7m, so most likely overkill…Can I ramp it up/down and only to 12V (or less!) with the SKR board and a SSR?
I may be making this all too complicated.
I’ll chuck this question in here too - I’m planning on homing my Z Min with a tool height changer bit.
I have continuity from the casing of the spindle to the collet. Can I tie the DC - to the Safety earth and then run the Z-Min signal through the tool changer puck? Or am I likely to pick up interference?
The primary issue is that most VFD spindle speed inputs are controlled by 10V. You are going to get 3.3V or 5V or 12V out of the pins on the SKR Pro board. There are conversion modules. Here is one, and here is a topic that has some proposed DIY solutions.
As for your other controls, frequently we see people on this list use pins to control both SSR and mechanical relays. An M42 can set the state of arbitrary pins. In addition, it is not uncommon to use fan pins, and set the state using an M106/M107. Note that hardware fan pins are typically ground side switching and therefore don’t work for some applications.
I have continuity from the casing of the spindle to the collet. Can I tie…
This has been done. There are some topics on the forum showing how to modify some routers specifically for this purpose. I don’t remember those topics indicating interference being an issue.
can I wire it straight into the VFD power input, so when the CNC is powered the coolant pump is running? Is this a good/bad thing?
I have no idea on this one, so I’m pulling it out so hopefully someone else on this forum can answer the question. There are relatively few forum topics that explore VFDs (i.e. most people use a router).