Heated bed randomly takes longer to heat up sometimes

Sometimes my heated bed reaches full temp very quickly, within 10 minutes or so, but other times it can take an hour or so. This is on the same day, back to back tests. Room temp did not change between tests.

What could cause this strange behavior? Brand new ramps 1.5 board.

Wire size and lose connections is my first guess.
A quick test would be to carefully tough the wires when the bed is heating, if the wires are hot then the wires size is too small.

I would make sure that all bare power wires are tinned with solder and shaped to Maximize the surface area between the wire to the connector.

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Computer Programmer / Electronics Technician

Thank you! I'm really not a fan of the screw terminal connection...I would prefer to solder the heated bed wires into some sort of plug, then plug that into the board, if only that were possible.

The wires are *slightly* warm to the touch when the bed is heating.

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foul_owl

The wires are *slightly* warm to the touch when the bed is heating.

This could suggest the wires are slightly under size. Though warm is not bad, on the other hand hot would be considered real bad.

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Computer Programmer / Electronics Technician

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foul_owl
Sometimes my heated bed reaches full temp very quickly, within 10 minutes or so, but other times it can take an hour or so. This is on the same day, back to back tests. Room temp did not change between tests.

What could cause this strange behavior? Brand new ramps 1.5 board.

What is your power supply rated at? It is possible that it is "crow-barring" and then recovering. If, for instance, your first run of the day worked fine, and immediately thereafter your next one takes forever, that could imply a supply current inadequacy.

DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

Hi,
It might sound stupid, but check that your extruder nozzle is not too close to the bed when you heat it up, as the extruder's fan can cool off the bed at the beginning...specially true if your power supply is too limited in current.

Best Regards,