Bed Heater Intermittent Heating (V-Core 4 500mm)
I am having an odd issue with a v-core 4 500x500 printer I inherited. The 120V 1200W bed heater is intermittently shutting off when it heats up from cold, and causes the printer to shutdown from the bed heater taking longer than expected.
The bed heater stops getting power and is accompanied by a click noise, like a contact closing or opening. After several seconds to minutes, if the printer has not shut down, another click is heard and the bed will once again begin heating up. This on/off cycle will continue until the bed has reached the target temperature (80 C), though sometimes rarely it will turn off again while near the target temperature. The rest of the printer remains powered. The original issue with the printer is that the ground and neutral wires from the outlet were swapped and going to the wrong leads on the power supply. This has been corrected but the issue remains. After replacing both the power supply and SSR, the same intermittent heating occurs. While the bed is not heating, the SSR still recieves a 24VDC control signal and the red light will remain on. If the bed is disconnected, the relay reads 15kOhms resistance when receiving the 24VDC signal, and there is no continuity when there is no signal. While the bed is heating, the expected 1.5VAC drop between the ends of the relay is present. I am unsure what else could be causing the problem, and I am unsure what the clicking noise is being generated by, as I would expect the SSR to not make noise. If it were a fuse, I would not expect the bed to operate at all. I don't see any contactors anywhere in the printer. The photo is the graph of the bed heating up. After each click, I set the target temperature back to 0 and after a few minutes it clicks and can heat again. The 3rd and 4th peaks I did not lower the target and the printer shutdown, all while the control signal remained at 24V. The 5th peak occurred close to the target and the PWM control signal was around 70%.
The bed heater stops getting power and is accompanied by a click noise, like a contact closing or opening. After several seconds to minutes, if the printer has not shut down, another click is heard and the bed will once again begin heating up. This on/off cycle will continue until the bed has reached the target temperature (80 C), though sometimes rarely it will turn off again while near the target temperature. The rest of the printer remains powered. The original issue with the printer is that the ground and neutral wires from the outlet were swapped and going to the wrong leads on the power supply. This has been corrected but the issue remains. After replacing both the power supply and SSR, the same intermittent heating occurs. While the bed is not heating, the SSR still recieves a 24VDC control signal and the red light will remain on. If the bed is disconnected, the relay reads 15kOhms resistance when receiving the 24VDC signal, and there is no continuity when there is no signal. While the bed is heating, the expected 1.5VAC drop between the ends of the relay is present. I am unsure what else could be causing the problem, and I am unsure what the clicking noise is being generated by, as I would expect the SSR to not make noise. If it were a fuse, I would not expect the bed to operate at all. I don't see any contactors anywhere in the printer. The photo is the graph of the bed heating up. After each click, I set the target temperature back to 0 and after a few minutes it clicks and can heat again. The 3rd and 4th peaks I did not lower the target and the printer shutdown, all while the control signal remained at 24V. The 5th peak occurred close to the target and the PWM control signal was around 70%.
3 Replies
I would definitely hunt down the click, the timing of it coinciding with the lack of heating means it is important.
Can try the screwdriver against ear trick, I'd check the SSR and the bed itself. It should have a fuse, but maybe it has a thermal circuit breaker making the noise?
I think it must have a thermal breaker, i verified that the clicking cannot be coming from the SSR or power supply
I decided to stick a large block of metal to one of the protruding features that connect to the wires on the bottom of the bed heater and had my first successful heating in weeks
wonder if whatever that component is is under-specced or failing