Hotend issue after stopping a job

Controllers Smoothie
1

I am having a really odd issue that is difficult to diagnose. I *think* it is a Smoothie issue but I can’t be sure. Here is the sequence:

  1. Starting printing something. Hotend temperature rises to set point (e.g. 220C) and the print starts
  2. Stop the print mid-print
  3. Do something for a bit (e.g. fix a knot in the filament spool). Hotend cools down a bit (e.g. 100C)
  4. Start a print (doesn’t have to be the same job). Hotend temperature asymptotically approaches set point but never reaches it (e.g. 219C). Print never starts.
  5. Power cycle the Smoothieboard and re-start the print. Print starts and runs fine.

Note: If I run the print to completion (i.e. don’t stop it in the middle) then I don’t get this issue.
Also before you ask, yes I have auto-tuned the PID multiple times. No difference.

My best guess is that the code executed to stop the print is causing the Smoothieboard to get into a weird state. Here is what it executes:

M104 S0 ; turn off extruder
M140 S0 ; turn off bed
M84 ; disable motors

But as far as I know this is exactly the same code that it executes when the print finishes. So I’m stumped.

Any ideas?!?!?!?!?!?

Thanks in advance.

-larry

Imported from wikidot

2

FYI it is definitely not a PID issue. I’ve followed all of the on-line instructions PID tuning and tried numerous permutations. I’ve also tried manually changing the PID values to produce different under/over-dampening affects. As I said normally when I run it the temperature rises to the target rapidly and tracks it perfectly. It even works correctly if the print ends successfully and I immediately start another print while it is still warm. The behavior *only* occurs when I’ve stopped the print in the middle and then try to start another print. So I’m 100% confident it is not a PID issue.

3

Only an idea
You are trying to heat the head, with fan at full speed, (last stateof the stopped print)
the power is not enough to reach the set point.