Spiky hotend and bed temps

Question

I recently rebuilt my A8 printer to have a metal frame and replaced the board with a GT2560 reva+. I'm having problems with the temp readings from both my hotend and hotbed. Using marlin 1.1x and Its possible I have something configured incorrectly. I can get successful prints with good quality but sometimes I get thermal runaway during a print.

Both cold and at temp (200c) have fairly large temp spikes. I didn't have this problem with my old board. I had much smoother temp curves. I'm using the default PID values for Ultimaker Kp 22.2, Ki 1.08, Kd 144.

I have tried to use PID autotune but get drastically different values every time I run it and using the results gave worse results (sometimes giving a heating error during the autotune). I checked all the wiring and nothing looks frayed or damaged.

First pic is cold temps. Second is trying to do a PID tune. Third and fourth are during a print.

Are you sure the fourth is during a print? Looks like PID auto tune to me. — Valmond, Feb 14 '18 at 09:08

score 2 · Accepted Answer · edited Feb 14 '18 at 07:48

2

I had a similar problem and there could be three reasons(if the connections are ok):

thin wires to the hotend
one of the MOSFETs was fried
the termal sensor wasn't good enough insert into the hotend

Try to measure the hotend heating element voltage while printing.

edited Feb 14 '18 at 07:48

mac

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answered Feb 14 '18 at 06:29

Coder_fox

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One of the mosfets on the board was bad. Just replaced the board and the problem was solved. – B.Schoch Feb 24 '18 at 16:34

score 1 · Answer 2 · answered Feb 15 '18 at 08:58

This really looks like a bad connection, so try with your old board to see if the broken connection is on the board, or it's the temp sensor or the wires.

I had exactly this problem with a bad connection from the temp sensor.

If you didn't break anything, it's the board that's fried / badly connected.

Spiky hotend and bed temps

2 Answers2