tuning Bed and Extruder heaters + M109 question May 22, 2016 11:54PM |
Registered: 8 years ago Posts: 177 |
Re: tuning Bed and Extruder heaters + M109 question May 23, 2016 04:53AM |
Registered: 10 years ago Posts: 14,672 |
Re: tuning Bed and Extruder heaters + M109 question May 23, 2016 06:09AM |
Registered: 8 years ago Posts: 177 |
Re: tuning Bed and Extruder heaters + M109 question May 23, 2016 07:09AM |
Registered: 8 years ago Posts: 475 |
Quote
dc42
PID adjustment
For the hot end, if you are getting overshoot then just reducing the S parameter will probably be the simplest way to cure it. Otherwise, here is one approach to tuning the PID constants:
1. Set S to 1.0, P to 20, B to 30, and I, D and T to zero.
2. Command the hot end to a high temperature, say 250C. As soon as it reaches 160C, command it to 0C. Watch the temperature to see how much it overshoots. Set the B value to about 5 to 10 higher than the amount of overshoot.
3. Command the temperature to 250C and wait. It won't ever reach 250C because of the zero I and T terms. When the temperature has stopped increasing, read it off, also use M573 P to get the average PWM. Set the T value as follows:
T = average_pwm/(temperature_reached - room_temperature)
4. Now follow classic Zeigler-Nicholls tuning. With the temperature set to e.g. 200C, increase P up to the point at which the temperature shows regular oscillations. Call this value Posc. Measure the period of the oscillations, call this Tosc. Then:
P = Posc/3 (increase/decrease this if desired to increase/decrease the overshoot)
I = 2P/Tosc
D = Tosc * P/3
M109
M109 should wait until the temperature has been reached. If it doesn't, that probably means that no tool had been selected when the M190 command was executed. You need a T0 command before the M109 command.
Re: tuning Bed and Extruder heaters + M109 question May 23, 2016 09:11AM |
Registered: 10 years ago Posts: 14,672 |
Quote
PRZ
In the step 3, shall the result of M573 be timed by 255 (or 256), according this message [forums.reprap.org] ?
Re: tuning Bed and Extruder heaters + M109 question May 24, 2016 09:32AM |
Registered: 8 years ago Posts: 177 |
Re: tuning Bed and Extruder heaters + M109 question May 24, 2016 10:29AM |
Registered: 8 years ago Posts: 475 |
Re: tuning Bed and Extruder heaters + M109 question May 24, 2016 01:55PM |
Registered: 10 years ago Posts: 14,672 |
Quote
aussiephil
Well either I didn't get it or that just won't work when dealing with high power fast heating setups.
Example, at step three I easily shot past 250 and reached 260 before I set it to zero again..... Hotend is a Dyzend with 300c thermistor and 24V 60w heater cartridge.
The time to heat from 10c to 160c was approximately less than 20 seconds.......
Re: tuning Bed and Extruder heaters + M109 question May 24, 2016 07:28PM |
Registered: 8 years ago Posts: 177 |
Quote
PRZ
Indeed, your parameters looks ok for the power. Maybe proportional coefficient is a bit high.
Did you insulated with Kapton the heating block (that will change a bit the T parameter) ?
PID control on the bed gives me a lot of improvement over bang-bang control, but our configuration is not quite comparable.
Quote
dc42
Quote
aussiephil
Well either I didn't get it or that just won't work when dealing with high power fast heating setups.
Example, at step three I easily shot past 250 and reached 260 before I set it to zero again..... Hotend is a Dyzend with 300c thermistor and 24V 60w heater cartridge.
The time to heat from 10c to 160c was approximately less than 20 seconds.......
60C is much higher than most people use. E3D hot ends use 25W, other hot ends use typically 40W. You could try repeating step 3 commanding 200C with P reduced to 10. Wait for the temperature to settle before calculating T.
Alternatively, try halving P, I, D and T in this command (or use it as-it but set S to 0.5): M301 H1 P10 I0.10 D100 T0.50