Nearly half was through printing my MPCNC plastic parts, I have had another heated bed failure on my 3D printer.
After around 60 hours of printing plastic parts for my CNC project, I have had another heated bed failure on my Sunhokey Prusa i3. This is apparently not an unusual occurrence. The first time I was able to get it going again with use of black electrical tape on the contacts. This time, I think I will just get a new heated bed from my new local supplier Spool3D in Calgary.
(Yes, I am shamelessly plugging this Canadian vendor, with whom I have no relationship. However, like many of you, I have been waiting for local 3D printing suppliers to show up in smaller markets. One finally has. His prices are reasonable, he carries stock, and I wish him well.)
As you can see on the left, I have printed the corner blocks and roller assemblies, as well as stepper motor mounts for the MPCNC and the measurements look good. The EMT conduit fits snugly. When I get the hardware, I will test the clearances for the screws and bolts.
Heated Bed Failure Not Rare
Unless you are printing only with PLA filament, and even then, you need a heated bed on your 3D printer. Most people print on flat aluminum plate or glass. Heating is created by running current through resistance. In most cases, the resistance is a pattern of copper which is either taped onto the bottom of an aluminum plate, or embedded as a printed circuit board on top of which you can place a piece of glass. There is also a layer of insulation (white shown above) which is taped over the heater to focus heat upwards into the bed.
As shown above, 12 or 24 volt power is supplied by your printer control board, and is attached to the heater with two wires, often with rivets, as shown with the black wires above. (The white wires are for a thermistor, or calibrated temperature sensitive resistor, which is also attached to your heat bed and lets you monitor and control the bed temperature.) The yellow tape shown above is Kapton tape (a trade name for polyimide film which remains stable across a wide temperature range, up to 400C. There are a variety of heated bed designs described here.
What causes heated bed failure? Probably the most common cause is quality of manufacturing in an immature industry. The heat bed can consume a lot of power, typically drawing up to 11 amps at 12 volts, well over 100 watts. In some cases, the connection between the wiring and the heating element is not great, crimps or rivets fail.
Anyway, I am off to buy a replacement heated bed so I can continue printing parts for my MPCNC.