If its one of the printed circuit hotbeds basically it's one of two things.
The resistance is too high, should be in the 1.2 to 1.5 ohm range
The voltage is too low.
Measure the voltage from the PSU when the bed is on, if it's dropping significantly, and you are using an ATX power supply you may need to add a load on the 5V line,
Make sure nothing is adding resistance in the circuit, use heavy gage cables, the resistance is so low that insufficient cabling can change it significantly.
Put an insulator under the bed, so the heat radiates upwards.
All that said, details like what heated bed, what PSU, and how hot it gets would make diagnosing the issue better.
And can you describe falling to pieces, hot beds really only help lower layers adhere to the bed and stay flat during the print, it won't change things like layer bonding.
