Heater heater_bed not heating at expected rate

General Discussion
1

Basic Information:

Printer Model: Voron 2.4 R2
MCU / Printerboard: Octopus 1.0
Host / SBC: Raspberry PI
klippy.log: Zip File Attached
klippy (9).zip (2.1 MB)

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Describe your issue:

…
Been printing fine with PETG. Need to print some projects in ASA, so I completed the side panels and add four fans to help with chamber warming. I added two outside the bedrails, printed two more mounts in ASA and added two for the middle of the bed.

After adding the fans for the middle of the bed I continually get the “Heater heater_bed not heating at expected rate” message, even when I heat with the fans off, and it seems to take longer to heat. I set the bed temp to 115 and clicked the box to show power on the graph and it seems to be consistent at 60% until just about 113 degrees. Then there are some power fluctuations and finally the power drops altogether.

Klipper Bed Temp
Klipper Bed Temp670×444 29.3 KB

I’m trying to decide if this is a configuration issue or a hardware failure. I had been able to print some small ASA parts with no problem until I added two fans for the center of the bed. No idea where to start here.

2 
[heater_bed]
heater_pin = PB10
sensor_type = Generic 3950
sensor_pin = PF3
max_power = 0.6
min_temp = 0
max_temp = 120
control = pid
pid_kp = 40.842
pid_ki = 1.341
pid_kd = 310.906

With the max power capped at 60% (line 5) and a requested temperature of 115 °C, your bed’s heater is likely simply too weak.

1 Like
3

Would .75 be an appropriate value or is this more or less a trial and error sort of thing?

4

Usually you set it to 1 or don’t set it at all.

#max_power: 1.0
#   The maximum power (expressed as a value from 0.0 to 1.0) that the
#   heater_pin may be set to. The value 1.0 allows the pin to be set
#   fully enabled for extended periods, while a value of 0.5 would
#   allow the pin to be enabled for no more than half the time. This
#   setting may be used to limit the total power output (over extended
#   periods) to the heater. The default is 1.0.
1 Like
5

For cast aluminum beds I run power at .8 to prevent warping the bed with a high power heater. I also insulate the bottom of the heater with foil backed insulation to reflect the heat upwards where you want it.

I’m not sure what the fans are doing but if they will be blowing on the bed or bed heater then PID tune it with them on. I just use a single 40mm Noctua air recirculation fan that pulls air from the top of chamber and out near the bottom of the chamber..

I don’t have a Voron but same basic principles apply to any printer.

6

To avoid bed warping/potato chipping in my custom printers, I follow the approach used by Voron.

I anchor the bottom left corner (0,0) and let the other three corners slide in guides as the bed expands when it heats up.

I have this now on five printers (including my original Voron) and I haven’t had any beds warp in any way through years and thousands of hours of use.

3 Likes
7

Did this, except I have the right rear screw tight.

8

The fans circulate the air under the bed around the chamber to assist in warming the chamber.

9

Hi Myke,

Could you please share a link, or links?

???
I’m at a loss! (and you got 3 likes!)

Thanks, hcet14

10

It’s called a “kinematic bed mount” and there’s a pretty good explanation here:

On my Custom printers, the heated bed is mounted on brass standoffs and I use a laser cut acrylic sheet for mounting electronics to it. In the image below, the blue square is the bottom left origin (0,0) and is the exact diameter of the standoff’s screw, the three red ovals (1.5mm between the centres of the circles at each end) are at the other three corners in which I’ve put a plastic bearing over the standoff’s screw to allow them to move freely.

image
image1300×1135 24.3 KB

People simply recognize my genius.

4 Likes
11

To defy the root of the cause of warping is the best solution. :+1:

2 Likes
12

? :wink: plus the 10 characters

1 Like
13

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