PID autotune for heated bed

[crimp3d]

Hello all,

I'm looking at PID autotuning my heated bed (older M2, dual PS: 12V/19V). I recently changed my V3 hotend to the V3b and while I was at it, autotuned it and updated the config files instead of manually inputting the values through Simplify3D each time. This worked well and the new hotend seemed to come up to temp much quicker. I want to try printing ABS (again) and I remember the heated bed taking quite a long time to come up to temp.

I tried to PID autotune the bed with 'M303 E-1 S100 C8' within Simplify3D but it started autotuning the extruder. I take it that the bed is not PID enabled in (my) Marlin? Perhaps I am overlooking it in the configuration file(s)?I did notice the TEMP_SENSOR_BED, #define BED_MAXTEMP 150, and #define BED_MINTEMP 5 definitions, but I obviously need to be looking for something else. Do i need to 'build' this into my Marlin configuration file?

Thanks,
Pierre

[jimc]

pierre, please dont quote me but i believe the bed is NOT pid controlled. its been a long time since i was into the firmware on the m2. i remember it simply being off or on. it really should not take too long to heat up, my bed is 12v as well. with abs i am only bringing it up to 96c. thats all thats really necessary.

[crimp3d]

Thanks for the feedback; I won't loose too much sleep over it then. I'm just running autotuning for my V3b hotend for ABS and venturing into printing with ABS.

Pierre

[crimp3d]

Update...

I was able to get the a couple of prints off with S3D set at a temp of 95 for the bed (as well as the S3D controller), with a minimal amount of warping (I'll try more hairspray). However I tried a couple more prints today with the bed temperature set at 100 and even though the bed reaches the temp after a while, as soon as I started printing then the temp plummeted to 88 and I knew the ABS was not going to stick, and it didn't.

There was not a lot of movement of the bed, so disturbance in the air flow around the bed was kept to a minimum. I stand to be corrected if this may be a greater cause of the temp drop than I think it is. The door to the room is closed, the room is well insulated and basically no drafts (it was getting might toasty yesterday, while printing).

I've read that having an enclosure is helpful, but is it really necessary?

Aside from that, any helpful hints on why the temp drops so much would be appreciated.

Pierre

[jimc]

that sounds more to me like you have a bad connection. the place where the connection always goes bad is where the power brick for the 12 side plugs into the rambo. check the plug. they really like to melt down right there. also check the bed power wires going into the bed and the loop out the back of the printer. things like to fail there as well because of the constant flexing.

[crimp3d]

Thanks again, Jim, for the feedback. I'll take a look, and post an update.

Pierre

[insta]

Having done both -- PID on the bed makes it harder to hit the target temp. It's a bigger deal to PID the hotend, since the hotend will continue to heat-creep after the heater is shut off, but the bed is so massive and heats slowly enough that it won't cause issues to bang-bang that only.