: Use Digital Calipers to check if a 20mm test cube is actually 20mm. Major deviations suggest worn-out belts or incorrectly calibrated E-steps.
Before handing over cash, perform a hands-on audit of these critical areas. If buying online, demand video proof for each: buying a used 3d printer
: Power the unit on and preheat both the nozzle and the bed. Use the printer's display to verify they reach and maintain target temperatures without fluctuating wildly, which could indicate a failing thermistor or heater cartridge. : Use Digital Calipers to check if a