Changing to a 12V 360W Power Supply

Why a 360W power supply?

I was trying to print ABS, but I couldn't get good bed adhesion.  The web tells me I need a bed temperature of 100C for printing ABS.  I could only get my bed up to about 80C, even when I let it heat up for an hour or so.

I thought there might be a problem with the wiring, so I checked the voltage to the hotbed while it was heating.  It was 10.4 V instead of 12 V.  So I checked the output of the power supply, thinking I might have some high resistance in the wiring.  Still 10.4 V.  So I adjusted the Vout using the trim pot on the power supply.  The highest I could get was 10.7 V with the heater on.   With the heater off, the output was 13.4 V.  So it was pretty obvious to me that I was running the power supply at its maximum capacity.

Some internet searchingfor under  showed me that I could get a 12V, 30A (360 W) power supply for under $20 (https://www.amazon.com/eTopxizu-Universal-Regulated-Switching-Computer/dp/B00D7CWSCG/ref=sr_1_3?keywords=12V+25A+power+supply&qid=1576126279&sr=8-3) if you are interested).  This power supply is physically a little bit larger than the 12V, 240W supply provided by Tronxy, but it fits in the power supply holder.  I haven't yet worked out the mounting issues, but I think I just need to get the right holes in the base and make sure I cut a new fan outlet in the top cover.


With the new power supply wired up, the bed easily and quickly heated up to 100C.  The hotend also heated up much more rapidly than it had in the past.  So I decided to autotune both the bed and the hotend.

With the procedure below followed, I can easily run 100C on the bed and 240C on the extruder.  This was a great upgrade!

Doing the Autotune

The autotune is accomplished with an M303 command.  For the heated bed:

M303 E-1 C8 S100

For the hotend:

M303 E0 C8 S230

Bed Autotune Parameters

The autotune parameters for the bed were:

Kp= 370.71

Ki = 41.90

Kd = 819.97

In oder to make autotune work, I made a couple of changes, which unfortunately required recompiling Marlin.  You can see my instructions for updating the firmware here.  

The changes I made to the firmware included:

1) Enable PIDTEMPBED

2) Disable BED_LIMIT_SWITCHING

Final PID parameters for Extruder

Set Kp = 8.15, Ki = 0.38, Kd = 43.16 (values came from an autotune cycle)