When creating a 3D model on a 3D printer, you may encounter poor print quality. Changing the slicer settings does not work, and the printed part appears shapeless, showing delaminating structures, gaps in layers, and other similar defects. This means it’s time to calibrate the extruder.
Calibrating the extruder of a 3D printer
Extruder calibration is a change in printer settings to write new parameters for the filament bar pulling speed and to change the temperature mode of the hotend. The printer is calibrated if numerous attempts to reconfigure the slicer have failed to improve print quality.
If the calibration procedure is rejected, it will be impossible to achieve accurate reproduction of a spatial object from a digital model. It is connected with the fact that the range of slicer settings does not allow for complete elimination of disturbances occurring in the control commands of the printing device firmware.
Warning! Before starting the calibration check the slicer settings, namely the filament type and the rod diameter as well as the nozzle cleanliness. Incorrect configuration may be the reason of bad printing quality.
Signs that you may need to calibrate the extruder
When inspecting the printed models, you may see defects:
- Individual layers are thin, depressions are noticeable, layers are missing and there are gaps between them. This is a signal that not enough plastic is being fed. This is how insufficient extrusion occurs.
- The opposite problem is overextrusion. If too much plastic is squeezed out through the nozzle, there will be overlaps and overhangs on the edges of the model, and the contour of the part will be distorted.
To get more or less acceptable print quality, you have to change the filament feed rate, also known as “flow” or flow rate, in the settings. Considerable shifts to one or another side signal incorrect calibration.
Adjusting the 3D printer’s extruder: a step-by-step guide
The process of calibrating the extruder is not that simple: you need to understand the G-code, be able to work with the sections of the slicer that give access to the software firmware settings, know the procedure for measuring the parameters and entering new values into the printer’s memory.
For making measurements you must prepare:
- A caliper or metal ruler;
- A pen and paper;
- Filament with minimal shrinkage;
- a computer with Repetier Host software installed.
Connect the printer to the PC by inserting the USB cable that comes with the printer into the USB port.
Calibrating the extruder
Before attempting to change the programming codes, you should check the operation of the mechanical components. If there is a problem with the filament supply, it might cause a problem with your printer. The first step is to adjust the pressure roller (if allowed by the printer’s design). If the pressure mechanism works correctly, there is no wear and tear of the rod pulling gears, you should pass to the next stage of calibration – adjustment of filament quantity, which is supplied by stepper motor.
To do this, remove the guide tube and cut off the tip of the wire sticking out of it.
Warning. The printer has a protection that prevents the stepper motor from turning on if the hot rod is cold. You must either turn the protection off with M302 P1, or warm up the extruder to operating temperature by sending G-code M109 S225.
The next steps are as follows:
- connecting the printer to the PC;
- Start the Repetier Host slicer;
- Send G-code G01 F200 E100, which means “squeeze out 100 m of plastic at a speed of 200 mm per minute”;
measuring the length of the extruded bar.
If the received value is less or more than 100 mm, it is necessary to correct the settings of the stepper motor. To do this, you need to find the value set in the printer firmware by running the M502 command. For example there is a number 95,5 written in the program.
Now calculate the new value by the formula Y × L / l, where
Y – the number found in the program (95.5);
L – the length of the rod, which was set (100 mm);
l – the length to which the filament is actually stretched (e.g., 98 mm).
95.5 × 100 / 98 = 97.4 (round to tenths).
This will be the new value Estepps/mm.
To record the correction, find the Estepps/mm option in the menu and enter the value. Run the M500 command to save it to the printer memory.
The calibration is finished. Repeat the filament check feed for verification.
The thermistor temperature is calibrated with the following command: M303 E0 S235 C8 U, where:
- E0 – extruder number (0 means 1st extruder);
- S235 is the heating temperature 235 °C;
- C8 – number of cycles;
- U is the key to save the parameters.
When calibration is complete, be sure to give the M500 command, which ensures that the calibrations will be saved in the printer’s memory.
To simplify the procedure, instead of working with the console, where commands are usually entered, you should create a file with the extension .gcode:
- create the file in Notepad;
- write the commands in it:
- M106 S127
- M303 E0 S235 C8 U
- M300 S500 P1
- click “Save as” and name it calibrovka.gcode.
This file will need to be run on the 3D printer.
Reference. The first command will turn on the fan at 50%, which will increase the accuracy of the calibration, and the last command will make the printer beep to indicate the end of the calibration.
Filament Feed Calibration
You begin adjusting the filament feed by printing a test cube. The settings in the slicer are:
- flow rate: 100%;
- no fill;
- number of wall lines: 1;
- without cover (number of cover layers – 0).
The checkboxes of such parameters as “Alternating wall” and “Vase mode” are unchecked.
It is necessary to find the average value of wall thickness. To do this, each of the walls is measured in at least three places with a caliper. The obtained values are added and divided by the number of measurements. For example, the result is 0.45. We substitute in the formula for the flow value 100 % × p / k, where:
p – nozzle diameter;
k – the coefficient of the average value of measurements that is obtained after measuring the test cube.
100 × 0,4 / 0,45 = 88,(8)
The obtained value is rounded to tenths and entered in the program settings.
The correctness of the settings is checked by printing out one more test cube and making measurements. The final result should be equal to the number p.
Errors and how to avoid them
After restarting the printer, the calibration is not saved. Reason: No command was given to write changes to the EEPROM. When the calibration is finished and the parameter changes have been made, you need to run the M500 G-code.
After the manipulation the print quality has changed slightly or even worsened. The reason: The measurements were made incorrectly. You will need to cycle through the measurements and calculate the average value to increase the accuracy, this will minimize the measurement errors.
Calibrating the extruder will make it possible to achieve high quality 3D printing. Do not neglect this step of printer setup. Pedantically following the calibration algorithm and carefully measuring the necessary values for calibration will ensure the most accurate results.