In this article, we will discuss a topic very appealing to every 3D printer user. Precisely, the impact of the Jerk parameter on our printer and what benefits you can have from this setting in terms of printing speed and quality.
3D printer jerk explained
When it comes to optimizing your 3D printer, one of the aspects to consider is definitely the printing speed. The duration of a print is already eternal, so why not optimize this parameter properly? You may be wondering, “just raise the speed in the slicer“, yes ok you are right. But how far can we raise it without imploding the printer? Take some time and calmly follow these basic concepts related to movement speeds.
When the printer moves an axis from one point to another, it will do so with a speed set by the slicer. You will find it expressed in mm / s or in mm / m, we will use mm / s. Fortunately, the movement will not be from 0 to 100 instantaneous instead two other parameters come into play, Jerk (mm / s) and Acceleration (mm / s ^ 2).
The very famous jerk, expressed in mm / s, is nothing more than the speed that the motor reaches as soon as the impulse is given. To be clear, if we have set a jerk at 15 mm / s and a print speed at 60 mm / s, the printer will not do 0-60 mm / s instantly. It will go from 0 to 15 mm / s immediately. Then, after an acceleration, it will reach the set speed. We, therefore, should understand the importance of this value. If set incorrectly it could create artifacts on the print or damage the machine itself. The printers currently on the market (DIY kits) reach an average of 50/60 mm / printing speed with a good definition.
Jerk or mechanical problems?
First of all, it is necessary to establish whether your problem is caused by incorrect jerk settings or rather by a mechanical problem. The following image shows the comparison between a model that does not have defects ( model on the right) and one that has some artifacts ( model on the left).
Look at the letter X and notice how, on one side of the letter, you can see signs comparable to an echo. Then compare the edges of the square part of the two models. You will notice that the edges appear differently in the two models. These are the most common artifacts caused by incorrect jerk settings. To exclude any mechanical issues it would be advisable to check :
- Belt tension and condition: the belt must not be elastic, must not be too tight, nor too loose.
- Mechanical clearances: bearings, bushings, screws, nuts, guides, worn parts in general.
- Status of the frame and of the printer in general: tension and any play of the screws or broken frame parts.
Jerk settings 3D printer
Firstly we need to determine if our current jerk setting performs well and does not create any artifacts. There are 2 main cases:
Jerk too high
The printer moves chaotically, and you will see lots of vibrations. An average value that is set in the firmware is 15/20 mm / s. If the 3D mechanics are very robust, you can try raising the default value up to 30 mm / s and see how it behaves. The benefits of holding a high Jerk result in 90 ° right angles without annoying bulges and reduced print times. On the other hand, if it is too high, it will create the Ghosting / Rippling effect. You realize it immediately because, in the vicinity of letters or holes, the machine vibrates so much that it affects the layout of the loop. The definition of the printed object is lost and there is the risk of making the motors lose steps.
Jerk too low
It is suitable for those machines that have a weak and “ballerina” structure. A value of 5/10 mm / s is just perfect and allows you to get prints with a good definition. Don’t go too low, or the corners will be very blunt, and you will notice an overabundance of material where it changes direction. The printer goes significantly slower, will be less noisy, and less mechanically stressed.
3D printer jerk calibration
If the printer is robust and doesn’t present andy vibrations, then we have to properly configure the jerk settings. There are different ways of doing this. The slicer software does not seem to be directly responsible for the problem. Instead, it can be “configured” to mitigate or even solve the problem.
In this case, a suitable solution to solve the problem seems to be to set a value for the Jerk parameter lower than the default one.
That said, the only efficient way to solve the problem is to make test prints, modifying the parameter a little at a time (steps of +5 -5), and compare the results each time. The STL model was specially created for this purpose. You can find it HERE.
If the Jerk parameter is too low, the sharp edges will likely be rounded and/or show other defects. If too high, it could create “dangerous” oscillations. However, keep in mind that the goal is to obtain a cube that resembles this one as closely as possible.
Note: The Jerk parameter is a definition in physics … but in the case of 3D printers, it is used to indicate (since it is the firmware that manages the behavior of the printer) the maximum value of the instantaneous speed change.
Control jerk from 3D printer
Your printer may offer among the menu items, the possibility to change this parameter. It is not necessary to save the new value in the EPROM memory. Do some tests until you find the correct jerk acceleration value and save them. If not, you will be forced to redo it after each power-up of the printer.
control jerk doing Gcode instructions
If your slicer offers the possibility to add Gcode instructions at the beginning of the print, then you can add the M205 command. Pay attention to what type of firmware you are using because the G-codes may differ.
Control Jerk by modifying the firmware
It is the longest and most complicated procedure. Not everyone knows how to download, configure, compile, transfer the firmware to their own printer, and in fact, it’s not really an everyday thing. (But if you want to check out this article on how I compiled Marlin) .