I've had my 24v silicone hotbed from Aliexpress for just over 18 months with daily usage.

I'm noticing that heat up times are getting longer, the PSU still cranks out 24v on the multimeter.

Do these have an operational life, or is there a means to test them to see how efficient they are running and when to replace? Both PSU and Hotbed?

I've not had one long enough only 4-5 months, but the adhesive is not very well bonded in the centre of the bed now. Doesn't seem to be a problem as the bed sits onto a metal plate with insulation above it so this pressed the silicone flat.

The only test I can think of is to measure the resistance of the heater. If it is changing over time then that probably indicates a problem. You can calculate the resistance you expect from the wattage/voltage.



So my heater is 500w, 240v so (240x240)/500= 115.2ohms expected resistance at room temperature.

Edited 1 time(s). Last edit at 01/18/2017 01:31AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Is the ambient temperature colder at this time of year?

Depends on where you live here... You bet.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I can't think of any reason why the resistance would increase significantly over time. Perhaps there is a poor connection in the circuit? If the PSU and bed heater are connected to the electronics using screw terminals, check that the screws are still tight.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Depending on the resistor wire used, it can technically oxidize over time, changing the resistance. That would only be an issue if there is a significant amount of O2 getting to the wire, which shouldn't be the case for an insulated silicone heater.

Thanks,

UK based and in the garage. So whilst it has been cooler recently, I can't see it impacting the heat up times that significantly. Over Christmas it was colder and operated fine- just started the past week. Reboots didn't have that much joy either.

Screw terminals are all tight.
Will check resistance and state of wires.