1. Pid Tune Marlin
2. Marlin Bed Pid Tuning

PID tuning refers to the parameters adjustment of a proportional-integral-derivative control algorithm used in most repraps for hot ends and heated beds.

PID needs to have a P, I and D value defined to control the nozzle temperature. If the temperature ramps up quickly and slows as it approaches the target temperature, or if it swings by a few degrees either side of the target temperature, then the values are incorrect.

To run PID Autotune in Marlin and other firmwares, run the following G-code with the nozzle cold:

Getting Started. Welcome to the TH3D P.I.D. Auto Tuning Guide! This will take you through the steps to P.I.D. Tune your printers hotend. If you have the new Unified Firmware you can go to Control Temperature PID Autotune Then set to 240 if you have a stock hotend and 250 if you have an all metal. The heat manager can also be changed to use PID which can yield better results after running the PID Tuning command for a set temperature. (PID is a control loop feedback mechanism with many uses. A general description of PID is beyond the scope of this article. ) Tune the PID control system to the temperature you most frequently use.

This will heat the first nozzle (E0), and cycle around the target temperature 8 times (C8) at the given temperature (S200) and return values for P I and D. An example from http://www.soliwiki.com/PID_tuning is:

For Marlin, these values indicate the counts of the soft-PWM power control (0 to PID_MAX) for each element of the control equation. The softPWM value regulates the duty cycle of the f=(FCPU/16/64/256/2) control signal for the associated heater. The proportional (P) constant Kp is in counts/C, representing the change in the softPWM output per each degree of error. The integral (I) constant Ki in counts/(C*s) represents the change per each unit of time-integrated error. The derivative (D) constant Kd in counts/(C/s) represents the change in output expected due to the current rate of change of the temperature. In the above example, the autotune routine has determined that to control for a temperature of 200C, the soft PWM should be biased to 92 + 19.56*error + 0.71 * (sum of errors*time) -134.26 * dError/dT. The 'sum of errors*time' value is limited to the range +/-PID_INTEGRAL_DRIVE_MAX as set in Configuration.h. Commercial PID controllers typically use time-based parameters, Ti=Kp/Ki and Td=Kd/Kp, to specify the integral and derivative parameters. In the example above: Ti=19.56/0.71=27.54s, meaning an adjustment to compensate for integrated error over about 28 seconds; Td=134.26/19.56=6.86s, meaning an adjustment to compensate for the projected temperature about 7 seconds in the future.

The Kp, Ki, and Kd values can be entered with:

In the case of multiple extruders (E0, E1, E2) these PID values are shared between the extruders, although the extruders may be controlled separately. If the EEPROM is enabled, save with M500. If it is not enabled, save these settings in Configuration.h.

Pid Tune Marlin

For the bed, use:

and save bed settings with:

For manual adjustments:

• if it overshoots a lot and oscillates, either the integral gain needs to be increased or all gains should be reduced
• Too much overshoot? Increase D, decrease P.
• Response too damped? Increase P.
• Ramps up quickly to a value below target temperature (0-160 fast) and then slows down as it approaches target (160-170 slow, 170-180 really slow, etc) temperature? Try increasing the I constant.

See also Wikipedia's PID_controller and Zeigler-Nichols tuning method. Marlin autotuning (2014-01-20, https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/temperature.cpp#L250 ) uses the Ziegler-Nichols 'Classic' method, which first finds a gain which maximizes the oscillations around the setpoint, and uses the amplitude and period of these oscillations to set the proportional, integral, and derivative terms.

Saving PID settings

You will need to commit your changes to EEPROM or your configuration.h file for them to be permanent.

Marlin Bed Pid Tuning

To save to EEPROM use:M500

Modifying Marlin Autotune parameters

The default Marlin M303 calculates a set of Ziegler-Nichols 'Classic' parameters based on the Ku (Ultimate Gain) and the Pu (Ultimate Period), where the Ku and Pu are determined by searching for a biased BANG-BANG oscillation around an average power level that produces oscillations centered on the setpoint. (See https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/temperature.cpp#L238 )

You can transform these 'Classic' parameters into the Zeigler-Nichols 'Some Overshoot' set with:

Or the Z-N 'No Overshoot' set:

If you click “Yes,” also read the explanation that follows and click “OK.”.Eject the installation disk image. If in doubt, select “Install for this user only.” Then click “Install.” System Preferences closes and reopens.If you are installing Hazel for the first time, it asks if you want to install some sample rules. Games for mac. Click “Yes” or “No,” as you prefer. You can do this by clicking the Eject icon next to the disk image icon in the Finder’s sidebar.Optionally drag the disk image file to the Trash.The Hazel preference pane should display automatically.

Note that the multipliers for the autotuning parameters each have only one significant digit (implying 10% maximum precision), and that the other schemes differ by factors of 2 or 3. PID autotuning and tuning isn't terribly precise, and changes in the parameters by factors of 5 to 50% are perfectly reasonable.

In Marlin, the parameters that control and limit the PID controller can have more significant effects than the popular PID parameters. For example, PID_MAX and PID_FUNCTIONAL_RANGE, and PID_INTEGRAL_DRIVE_MAX can each have dramatic, unexpected effects on PID behavior. For instance, a too-large PID_MAX on a high-power heater can make autotuning impossible; a too-small PID_FUNCTIONAL_RANGE can cause odd reset behavior; a too large PID_FUNCTIONAL_RANGE can guarantee overshoot; and a too-small PID_INTEGRAL_DRIVE_MAX can cause droop.

PID Tuning by Commercial PID

If you have access to a PID controller unit and a compatible thermal probe that fits down into your hotend, you can use them to tune your PID and calibrate your thermistor.

Connection of the output of the PID to your heater varies depending on your electronics. (I used a 1K2:4K7 voltage divider to drop the 22V output of the PID to 5V for my bread-boarded VNP4904)

After the PID is connected you can use it to measure the nozzle temperature and correlate it with the thermistor readings and resistances.

Conversion from the commercial PID values of kP in %fullscale, Ti in seconds, and Td in seconds is as follows:

As an example, a $30 MYPIN TD4-SNR 1/16 DIN PID temperature controller and $10 type-K probe can hold a particular Wildseyed hotend with a 6.8ohm resistor at 185.0C+/-0.1C using 12V with about a 43.7% duty cycle, or 0.437*12*12/6.8=9.25W. Invoking the autotuning on the controller produces these parameters: P=0.8%/C, I=27s, D=6.7s. Converting these to Marlin PID values:

Differences between the results can be caused by physical differences in the systems, (e.g: the thermocouple is closer to the heater than the thermistor,) or by different choices of autotuning parameters (e.g.: the MYPIN TD4 autotuning process is a proprietary black box, while Marlin uses Zeigler-Nichols 'Classic' method.)

The Temperature/resistance table below was developed by using the PID+thermocouple system to set temperatures on a sample hotend by controlling the heater while measuring the thermistor resistance. These values can be used with Nophead's http://hydraraptor.blogspot.com/2012/11/more-accurate-thermistor-tables.html or Marlin's https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/createTemperatureLookupMarlin.py to create calibrated thermistor tables. The PID column collects the autotuning values produced by the PID controller for the indicated temperature. The kP,Ki,Kd lists the converted parameters.

Swings in temperature for your 3D printer’s hot end, such as the Ender 3, is just plain no good for quality print results. Steady, controlled heat is what you are looking for and getting it right can be great for your print results. PID auto-tuning is a way to control the temperature by using an algorithm to determine the values that the printer uses to heat and maintain temperatures. Below you will find the instructions to set your PID values. This method is going to change the values that are stored in your printer, and used every time it heats. This method is great for setting the PID values if you use very similar filament, and cooling most every time you print. If you use a lot of varying filament, or use cooling on some and not on others, you will want to modify your slicer printer settings to set the PID values for each configuration. Lets take a look:

• First off, use a terminal command processor to send commands to your printer – such as OctoPrint, Repetier Host, or Simplify 3D.
• Start your printer in a cooled state, with the material you are going to use (such as PLA) primed in the hotend – either from a previous print or heat the printer and push through a few inches of filament and let it cool back down
• Start the cooling fans if you intend to use them as part of the results you want from the PID test. Send the command M303 E0 S205; to the printer for a temperature of 205C – change the S value to whatever target temperature you are looking to get stable heating for like this:

• The printer will take about 5 minutes or so and run through the auto-tune test.
• When it is complete, Marlin will spit out the test values for P, I and D looking something like this near the end of the output:

• Now tell your printer that you have new defaults, sending in new values for the PID values that you received from the test. In my example I send it the values like this

• And it returns a success looking like this:

• Next up, you will want to save your settings to the firmware, or the next time you cycle the power, you will lose the settings, so send the save settings command like this:

There you go, you should be all set to go with stable PID settings that make your printer produce better prints . A couple of quick things to note:

1. I have seen some varying settings and re-running the whole thing a few times will give you interesting variations in the values returned. The first time I ran this on a printer, the resulting values produced oscillating temperatures (around +-4 degrees C) which is a little too much. You are looking for tight temperature ranges – I was happy with the settings above that roughly stayed very solid in the 204-206 degree C range. Re-running the test a few times you may find a set of values that really tighten it up for you as well.
2. Remember, if you are swapping in another brand of filament, a different type of filament (like going from PLA to PETG), or using fans vs. no part fans, you will want to either re-run this test and store them in firmware to use until you change them again, or send the M301 command in your printer profile with each of the values for P, I, and D for the configuration each time you go to print. This method takes a little more work, but ensures that the settings are correct for the config you are intending to use.

That’s it for today, if you have a comment or tip leave it below – we would love to hear from you. Happy printing!