Just out of curiosity, what are your guys’ heat up times like for your heated beds? My 650W psu gets my ubis hotend to 230C in 2-3 minutes, and the bed to about 70C in 5 minutes, but then it’s a long wait until my bed reaches the 85C I set it to for ABS.
Same for me, about 15 until i hit ABS temps. PrusaPCB into 3mm glass. The PrusaPCBs are just about powerful enough to get to ABS temps, but sadly, many of the successor products have inherited the same problems. Many of the electronics boards are also right at their current limit with the 12A beds.
And, by the way, the PSU wattage doesn’t really influence the power output of your heated bed. Just sayin’.
I had a feeling the PCB beds and electronics boards were the limiting factors here. I was pretty sure the PSU wattage wasn’t affecting the situation, but had a feeling someone would ask if I didn’t post it. My printer used to be enclosed, which dramatically improved the time it takes to heat the bed and ABS print quality overall, but I have yet to make an enclosure big enough ever since I rebuilt my printer in a larger size.
Insulating the bottom of your platform can make a big difference with this. Corrugate cardboard or just a few layers of folded paper towels work better than anything else. When I need to get particularly hot (130C for PCABS), I put another piece of cardboard over the top while it’s heating.
We use the Helios boards from Panucatt. They get to 60C in less that 1.5min, 120C in less than 5 minutes.
400w silicone heat bed from alirubber run on 24v, attached to 1/8" aluminum heat spreader, 3mm borosilicate glass on top. Thermistor reads 110c in 5min but it bounces for another minute or so. But the thermocouple attached to my multimeter says its another 4min until the glass surface is stable at 110c.
550W silicone heated bed at 110v switched with a solid state relay straight from the wall outlet. I hit 110C and above in less than 2 minutes. I built with this setup from the get-go on @Chris_Purola_Chorca 's advice and I’ve never turned back. I will never ever have a heated bed with anything else.
@ThantiK I never had the guts to go 110v. I saw a lot of posts when I was building mine of melted SSRs. But I have seen several now from people I trust like you. I think I might revisit this option on my Big Bot.
@Eclsnowman , I’ve got a 20A opto-isolated SSR which is rather good quality. I think the people that are melting SSRs are hooking them up wrong or overvolting, etc somewhere.
I’m currently getting some decent temperature setup times with a PCB heated on 3mm glass no insulation which does improve heatbed thermal loss. On my other printer I use a cork laminate to insulate the bottom of the platform.
Timings without insulation:
Hotend - 220ºC - 2min aprox
Heatbed - 100ºC - 9min aprox
Heatbed max - 124ºC
FET - 45ºC - 20ºC over ambience (no cooling)
PSU - 240W
@ThantiK are you running pid or bangbang?
@Eclsnowman PID of course. No PWM. I recently learned that RepetierFirmware uses some sort of PWM control; I use Marlin which doesn’t do that.
You can PWM if you really want to, but you need a special SSR.
Here’s the special SSR: https://github.com/mosfet/kossr
And coincidentally the connector on my heated bed burnt to a crisp today. Luckily the house didn’t burn down.
I halved the trace on a 6x6 heatbed, making it two parallel resisters, then fed it with 13.8v at 28amps using a 40amp relay. It goes from room temp to 105 in less than two minutes.