How Do I Know If I Need To Do A PID Tune On The Hot End ?

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royg
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How Do I Know If I Need To Do A PID Tune On The Hot End ?

Post by royg » Tue May 16, 2017 2:20 am

I've noticed that the Hotend, after it first reaches the set temperature, the temperature then takes about 5 minutes to settle down. The hotend temp graph in Octoprint shows the temperature oscillating, initially about +- 4 degrees C, and progressively reducing, for the first five minutes after the hotend initially reaches the set temperature. It then maintains the set temperature very accurately for the duration of the print.

Is this behaviour an indication of the need to run a PID Tune on the Hotend ? Or, is this typical behaviour standard (or typical) for the Tevo supplied hotend ?

The Hotbed does not demonstrate this behaviour - it is being run via a Tevo Hotbed MosFET if that makes any difference..

Thanks,

RoyG
Tevo Tornado (MKS Gen L version) - Genuine E3dV6 - BLTouch
OctoPi (on an Odroid XU4)
Fusion 360, Cura, Slic3r, Ideamaker

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Re: How Do I Know If I Need To Do A PID Tune On The Hot End ?

Post by Lee » Tue May 16, 2017 2:04 pm

In short, a PID Autotune is never a bad idea.

If you think it's acting wonky, do a new one.
Printer: Tarantula w/ OctoPi on Pi Zero
Firmware: MK4Duo
Slicer: Simplify3D

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Re: How Do I Know If I Need To Do A PID Tune On The Hot End ?

Post by Cdn_Printer » Tue May 16, 2017 2:34 pm

Agreed, you should always do one.
Consider this. The current PID setting in your firmware are 'general' settings. Since all of our printers are different, including the output voltage of our power supplies, it only makes sense to run a series of PIDs to ensure your printer is performing at its best. If you change the bed or the hotend, guess what... PID time again.

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Re: How Do I Know If I Need To Do A PID Tune On The Hot End ?

Post by poppiesgdd » Fri Jan 12, 2018 3:59 am

Hello Roy .
acronymfinder.com has 88 definitions for PID including
pelvic irritation disorder, and many to do with computing
and electronics.
Could you please explain to us " new to printing " types
which one you are talking about just for clarity.
Thank you for all your other excellent contributions to
the best Tevo forum on the interweb .
A Gold star to Lee for starting this forum too .
Glenn.

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"PID Tune" and "PID Control". What are we talking about ?

Post by royg » Fri Jan 12, 2018 6:59 am

"PID Tune" and "PID Control". What are we talking about ?

First of all, we'll talk about what this "PID" abbreviation means. If we refer to Wikipedia, we see that "PID Control" refers to "A proportional–integral–derivative controller is a control loop feedback mechanism widely used in industrial control systems and a variety of other applications requiring continuously modulated control." (https://en.wikipedia.org/wiki/PID_controller) That's the technical explanation. If all that info makes sense to you, then the rest of this post is probably not much use to you.

On out 3D Printers, the designers of the Marlin Firmware have built-in "PID Control" to enable the 3D Printer's Main Board to accurately control the temperature of the hotend, and the temperature of the Heated Bed. PID Control enables the Hotend (or Heated Bed) to heat up to the set temperature with minimal overshooting, and to then accurately maintain the set temperature indefinitely.

What is PID Tuning ?


For the PID Control to work well, it needs to be tuned. That is, the PID software in Marlin needs to know things like ho powerful you heater element is, and how much heated mass is in the hotend, and lots of other stuff. To do this tuning, we need to provide values for three (3) PID parameters that are used by the PID Control software. These parameters are known as; Kp, Ki, and Kd. Working out the numerical values for those three parameters ( Kp, Ki, and Kd) can be done manually (which is difficult to do and requires a lot of challenging maths), or if you’re using Marlin Firmware, you can take the easy way out, and use the “PID Autotune” software that is included as standard in recent versions of Marlin.

How do you perform an PID Autotune on Marlin Firmware ?

I think that the best answer to this question is to direct you to two Youtube videos that discuss how to do a PID Autotune on 3D Printers equipped with Marlin Firmware.





These are Marlin tutorials – and not specifically Tevo Tarantua tutorials. That doesn’t matter, as the process is identical for any 3D Printer that is running Marlin Firmware.

What are the Commands being used in these Videos ?

In both videos, the presenter mentions a number of Marlin Firmware Commands that are used to: 1) execute the PID Autotune, 2) Save the resulting Kp, Ki, and Kd values to temporary memory on the 3D Printers mainboard, and 3) To permanently save the Kp, Ki, and Kd values that you have saved in temporary memory, into the EEPROM for permanent storage.

The commands used are standard Marlin commands, and the full syntax of those commands is available on the Marlin Firmware webite’s Documentation page; http://marlinfw.org/meta/gcode/

Are you still using the Tevo Factory supplied Firmware ?

If you have not installed other firmware on your printer since you’ve built it, then you most likely do not have Marlin Firmware running on your computer, as the Tevo Factory supplies a copy of Repetier Software as standard. The Repetier software supplied by Tevo does not have the EEPROM enabled, which means that you can’t save the PID Kp, Ki, and Kd values into permanent memory. Additionally, some people have reported that the Repetier Firmware does not respond to the Marlin PID Autotune commands. My recommendation is to use Marlin Firmware, as that firmware is under constant development, with new versions being released regularly, with many new features being included with each version.

Where do I get Marlin Firmware for Tarantula from ?

There are many links provided in various Forums, and on Facebook and Google+ groups, that link to various versions of Marlin Firmware that purport to be suitable for the Tevo Tarantula. Most of these link are to versions of Marlin that are way out of date, and in many cases the links are to firmware that contains bugs.

In my experience, and based on the recommendations of many Tevo users, I only recommend “Jim Brown’s Marlin for Tarantula” firmware. Jim has put a lot of work into making his configuration of Marlin as easy as possible to the user to configure to suit their particular Tarantula configuration.

https://github.com/JimBrown/MarlinTarantula

Download the firmware from Jim’s Github page. Jim has included instructions on his Github page, along with more instructions in the firmware files. Using the [Branch] dropdown list, I recommend choosing to download the “EasyConfig-1.1.x” version. Jim keeps his firmware in sync with the master Marlin Firmware on github, so as new versions of Marlin are released, those updates also appear in Jim’s firmware.

Marlin are presently keeping both Marlin 1.1.x and the newer Marlin 2.0.x versions under development side by side. At some point in time Marlin 2.0.x will become mature enough for us to move to the new version and 1.1.x will be retired. Unless you want to be involved in helping with testing Marlin 2.0.x, I’d recommend sticking with Marlin 1.1.x for a while yet.

When do I need to Repeat the PID Autotune Process ?

The PID Kp, Ki, and Kd values are only valid for your printer configuration as it stands at the time you ran the PID Autotune.

If you change any of the following, you need to repeat the PID Autotune Process:

1) You change the Hot End. (i.e. Replaced the factory hotend, with a new factory hotend, or you replaced the factory hotend with an E3Dv6 or other hotend).
2) You change the Heated Bed plate.
3) You change the Hotend Thermistor, or you change the Heated Bed Plate Thermistor.
4) You change the Heater Cartridge in the Hotend.
5) You’re using an E3Dv6 hotend, and you decide to install E3d’s Silicon Sock insulation around the hotend.
6) You install insulation under your heated bed plate.
7) You build an enclosure around the printer for printing ABS, etc.
8) You change to a filament that requires a higher or lower temperature. Each PID Tune is only valid for the specific temperatures that you ran the PIT Tune at.

In addition, (but with less scientific basis).....

I believe that my printer benefited from having a PID Autotune done at the beginning of winter, as my workshop is a cold and draughty place in Winter, and the cold drafts adversely effect the printers ability to maintain the set temperature. I also repeated the PID Autotune at the beginning of the Summer hot weather in November, and saw some improvement.

And lastly, when I ceased to print on masking tape on the aluminium heated bed, and instead started printing on a sheet of glass positioned on the heated bed, the printer benefited from a new PID Autotune for the heated bed then as well.

I hope that information is useful.

Regards,

RoyG
Tevo Tornado (MKS Gen L version) - Genuine E3dV6 - BLTouch
OctoPi (on an Odroid XU4)
Fusion 360, Cura, Slic3r, Ideamaker

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Re: How Do I Know If I Need To Do A PID Tune On The Hot End ?

Post by poppiesgdd » Fri Jan 12, 2018 9:36 am

Thank you Roy .
That is a brilliant answer for us new users
The amount of information you supplied in
such a short time floored me.
You get top marks from me for your answer.
Glenn.

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