Heat bed stops heating within a few degrees of target temp

Hello,

I own several printers but recently have been "upgrading" a couple of them to SKR 1.4 turbo boards with 2209 drivers. There are two printers in question so Im sure its likely in the Marlin config. the printer specs are listed below.

Printer 1:
Model: Modified Rep Rap Guru Prusa i3 v2 (bought on Amazon about 4-5 years ago.
Board: SKR 1.4 Turbo
Marlin: 2.0.6.1 custom built from 3dwork.io and then further modified to suit my needs
Hot End: semi stock (direct drive) (have replaced several parts over the years but have kept with the original design)
Heat Bed: silicone heat pad 200x200 12v 220W (as advertised) attached to "old" PCB heater and then borosilicate glass (original I might add) and then Fysetc spring steel PEI print surface

Printer 2
Model: Modified Power spec Ultra 2.0 3d Printer
Board: SKR 1.4 Turbo
Marlin: 2.0.6.1 custom built from 3dwork.io and then further modified to suit my needs
Hot End: Stock (second extruder was removed to facilitate a BL Touch)
Heat bed: original aluminum plate with attached PCB Heater, borosilicate glass, and the Fysetc spring steel/PEI build plate

I have the same issue with both of these printers. If I am heating to 60°C then the bed gets to about 57 and shuts off. While measuring current draw on the modified Rep Rap (have not measured current draw on the modified Power Spec) it shows about 18A and then drops to nearly 0. Sometimes it will continue to heat at a very low current and eventually make it to 60°C bust most times it gets to about 57°-58° and errors out. now, that being said.... if I heat to 100°C it will go as far as 91°-92° in a reasonable amount of time and then slows to a dead crawl again, often not making it to temp at all.

I have attached my config.h and config_adv.h files for review. I would love to get this sorted before I go and do the "upgrade" to my Creality CR10S.

Thanks in advanced.

Devan Phillis KD8MST

Did you run PID autotune? [marlinfw.org]

Edited 1 time(s). Last edit at 10/28/2020 07:00PM by dekutree64.

Dekutree64,

I am running it right now, I had thought about running it previously but thought it was only for a wavering temp... the more I read the more I realize that the exact issue I'm having is a result of bad PID settings as well.

I'll post how it works out.

Thanks,

Devan Phillis KD8MST

Here is how my PID Tuning turned out..... for the modified Rep Rap Guru

E0 old values/new values
Kp: 22.2/19.19
Ki: 1.08/1.26
Kd: 114/73.25

E-1 (bed) old values/new values
Kp: 10.0/44.67
Ki: .023/7.95
Kd: 305.4/167.23

and results are..... WONDERFUL........it slams up to temp in no time flat and seems to stay there. a longer print will be in order to really test it.

Again, Thanks.

Devan Phillis KD8MST