Avoid Harmonic Ridges by Auto Tuning PID

[Khalid Khattak]

Hi Guys,
Just want to share my experience of getting Harmonic ridges/serrations on my print surface. I thought first it is due to vibrations or other loose mechanical component in my 3D printer. I checked all and nothing bad found in mechanical settings. Then during the print i stopped the Heated Bed and saw that all the ridges vanished on the print surface.
Actually PID tuning of the Hotend and the bed thermistors is key to success. The variations in the glass bed surface due to poor tuning of the bed temperature sensors (thermistors) caused the minor thermal expansion/contraction of the glass plate which pronounced in the print surface. I did autotune the PID settings and now the temperatures are constant reading and ridges are vanished.
Happy printing

[magicmushroom666]

I'd be surprised if the cause was due to the heat bed movement with temperature. I'm controlling my head bed bang bang style, so it switches on and off at around 5 seconds each, much worse than a badly tuned PID and I dont see those affects at all. My bed however is powered by a seperate supply through a relay. Its likely that the cause is the voltage drop changing on something due to the heatbed current changing. The heat bed is a very large load, and if any cables are shared with it, such as 0V cables I'd expect to have trouble.

The supply for the heat bed should be taken direct from the power supply terminals, with seperate cables from those terminals for everything else.

[Khalid Khattak]

I'd be surprised if the cause was due to the heat bed movement with temperature. I'm controlling my head bed bang bang style, so it switches on and off at around 5 seconds each, much worse than a badly tuned PID and I dont see those affects at all. My bed however is powered by a seperate supply through a relay. Its likely that the cause is the voltage drop changing on something due to the heatbed current changing. The heat bed is a very large load, and if any cables are shared with it, such as 0V cables I'd expect to have trouble.

The supply for the heat bed should be taken direct from the power supply terminals, with seperate cables from those terminals for everything else.

I have silicone bed 220V. It abruptly rise the temperature of the glass from within 1minute from 23C to 110C I am controlling with Solid State Relay!!! My glass is fixed at three locations.... I just 3D printed another statue with tuned heat bed and it came out very clean. There was no noise issue and i came to cnclusion that rapid temperature rise at certain intervals was the reason of those harmonic imperfections.

[Eaglezsoar]

Khalid Khattak, if you find out anything different please let us know. This is an important issue.

[Khalid Khattak]

Eaglezsoar, In my case the untuned PID of the heat bed was the cause of these ridges. As I am using Silicone 220V bed which has abrupt rise in temperature. This rise and fall of temperature from the setpoint was huge which causes those ridges. Now after PID tuning all is perfect.

[3D-Print]

Awesome. jfettig and other have posted (can't find the page yet) a huge variation in if the bed when heating and it makes fits that stable heating minimizes that bed fluctuation.