I have several big printers which will eventually join my “farm” but which have very slow bed heaters. 10 to 20 minutes before the printer actually starts. Boring.
I have a huge, 50 lb toroid 2/1 wired as an autoformer so it gives several kilowatts of nominally 62 VAC when enabled from wall plug power, nominally 127 volts AC 60 hz in the US .
I have it rigged ATM with 2 pairs of 60 amp SSR’s like crydoms, that can use the bed heaters 24 volt output of a printer as control.
Edit after testing:
Unforch, this idea won’t fly w/o a line powered clock so the switch on or off is always on the same zero crossing. Why? Easy if you think about it. The SSR’s switch any time for on, but wait for a zero crossing of the input line voltage to turn off. The difference in timing constitutes a DC component superimposed on the line voltage, which slowly builds up the magnetic field in the toroids ferrite core, eventually saturating it magnetically, at which point 99% of the inductance disappears, and a 30 amp breaker in the service goes down with a bang. Exacerbated by the lack of line sync. its possible for it to be enabled for 10 negative half cycles and 12 positive half cycles so this idea won’t fly in its presently unsynchronized form.
So, I measured the bed R, and bought a 600 watt 36 volt supply I could turn down until it was getting 600 watts, which turned out to be around 32 volts. That will speed it up considerably from the 20 minutes to 70C for PETG.
End of edit. Read on if bored.
Triggering one SSR to turn it on, and another SSR to feed the printer that turned it on, feeding that printers bed heater, so it follows the bed heater signal but feeds the bed needing heat with the 62 VAC in place of the 12 or 24 the printer might supply. So 2 SSRs per printer connected. Rigged for 2 printers but could do 4 if the breaker feeding that outlet stays up. I can if needed, bring in a new 20 amp branch from the service if needed. I’m a CET and can teach electricians how to do it. And have done that as the C.E. at a TV station for the last 20 years of my working life.
Has anyone else done similar to speed up the bed preheat times?
On a Sapphire 5 for instance, running PETG which needs a 75C to 90C bed, 80C from a cold start is 14 minutes with a 24 volt PSU. At least the center of the bed can be up to temp in 4 or 5 minutes.
Comments?