Solved: Z Banding due to heated bed

[joboman]

Okay so I had z banding issues for the longest time, especially on small prints. I tried turning off the bed after the first layer and voila, issue solved! I can't PID tune to 92C since the process will time out, so I started at 80C and ran the PID tune to 92C. It gave me some really funky numbers from 50-1000 and the three numbers I was supposed to average out weren't similar at all. Using these values my heated bed will fluctuate from 85-93C which is causing the banding. BTW, 92C is almost the upper limit of my heated bed, maybe 95C.

So..

HOW DO I STABILIZE HEATED BED TEMP?

Thank you

EDIT:

If anyone cares, I couldn't get the right PID values but as suggested by a few members on this forum, I switched to dead-time control with incredibly stable results!

[JFettig]

Manually tune pid using repetier host while watching the power output graph.

[joboman]

Thanks for the prompt response, is there a guide for that somewhere? Never used Repetier Host, but downloading now

[JFettig]

No guide. It's hard to fully understand pid. I controls the steady state swing, D is the more reactive part. Leave p for now. Try I and D at 1 to start. Drop D if power rapidly fluctuates drop I if the wave doesn't stabilize or increase it if it never reaches stability

[Eaglezsoar]

I have looked at dead-time control on Repetier's site and I do not fully understand the firmware settings required to put the heatbed or hotend in dead time control or what
I have heard it called bang-bang control. Can anyone enlighten my old and getting older brain?

[joboman]

Hi Eaglesoar,

In your EEPROM settings there should be a heat manager value for both the hot end and the heated bed.

0 = bang-bang, 1 = PID control, 3 = dead-time control, I'm not sure what 2 is for.

the Kp, Ki and Kd values are your PID constants (if you have 1 for the heat manger value)
the Kp value is your dead-time constant (if you have 3 for the heat manager value)

the below link from repetier will explain how to find your dead-time constant and how to set it up, much easier than PID in my opinion.

http://www.repetier.com/dead-time-control/

PS. I use bang-bang for my hot end and dead-time for my heated bed.

[Eaglezsoar]

Thanks for your response joboman.

[DGBK]

I just switched to dead-time over the weekend. The results are much better for me. My heated bed only varies by about 0.2 degrees now. I'm still dialing in the hot end, but it is leaps and bounds better than the PID tuning. I feel like a dead-time tutorial would be great as a sticky in tips and tricks or even in newer manuals.

[Eaglezsoar]

I just switched to dead-time over the weekend. The results are much better for me. My heated bed only varies by about 0.2 degrees now. I'm still dialing in the hot end, but it is leaps and bounds better than the PID tuning. I feel like a dead-time tutorial would be great as a sticky in tips and tricks or even in newer manuals.

I agree, a sticky would be nice. As long as I have been on this forum, I have never seen a posting detailing how to setup dead time, or bang bang modes for the heaters.