Large Delta printer build - advice and suggestions welcome

[Trakyan]

We don't PWM solenoids or relays with coils. Solid State Relays ONLY for PWM, pal.

My first sentence was saying that it does NOT use PWM.

[AutoWiz]

My first sentence was saying that it does NOT use PWM.

But slowly switching on and off IS pulse width modulation just at a slow frequency.

[Trakyan]

It's not really a "frequency", it's switching fully on/off at a specified threshold. It has nothing to do with frequency it's always either full on, or full off depending on what side of the threshold your sensor is measuring. There is no regular, repeated pulse of varying width (or duty cycle) which makes PWM. This bang-band control how most ovens, hot water cylinders etc work. The time between switching is not pre-determined (unlike PWM, where each pulse is a fixed duration, just with varying on time) and the time between switching is measured in minutes if not longer. Even if the switching time was regular, if your period is measured in minutes or even seconds I don't think anyone will call that PWM. Have a look at the wikipedia page for bang-bang control.
https://en.wikipedia.org/wiki/Bang%E2%80%93bang_control