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Jerk & Acceleration


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What is the Acceleration Setting?

The Acceleration setting measures how fast your print head speeds up, limited by your designated 3D printer speed in your slicer settings.

The higher the setting, the quicker the print head will get to its maximum speed, the lower the setting, the slower the print head will get to its maximum speed.

A lot of times your top speeds won’t be reached when 3D printing, especially smaller objects because there is not much distance travelled to make full use of the acceleration.

It’s very similar to a car’s acceleration, where if a car can go a maximum of 100 kph, but there are a lot of turns in your journey, you’ll find it hard to get to the maximum speed.

In the Cura slicer, they state that enabling ‘Acceleration Control’ can reduce printing time at the cost of print quality. What we can hopefully do on the other side is improve our Acceleration at the benefit of increasing print quality.

Your slicer doesn’t actually have much to do with acceleration, in so far as emitting G-code to say where the print head should go and at what speed. It’s the firmware which sets limits to speed and deciding how fast to accelerate to a given speed.

Each axis on your printer can have different speeds, acceleration and jerk settings. The X and Y axis settings are generally the same, otherwise your prints can have different features dependent on part orientation.

There are limits on how high you can set acceleration, especially when printing at angles larger than 45 degrees.

What is the Jerk Setting?

It’s quite a complex term and has different descriptions based on what firmware you are using. It’s basically an approximation value that specifies the minimum speed change that requires acceleration.

The Jerk setting measures the speed at which your print head moves from its still position. The higher the setting, the faster it will move off from a stable position, the lower the setting, the slower it will move off from a stable position.

It can also be known as the minimum speed your print head will slow down before initiating speed in a different direction. Think of it like a car driving straight, then slowing down before a turn.

If Jerk is high, your print head won’t slow down as much before making the directional change.

When the print head is told to change speed and direction in the G-code, if the difference in speed calculations is less than the specified Jerk value, it should happen ‘instantaneously’.

Higher Jerk values gives you:

  • Reduced printing times
  • Fewer blobs in your prints
  • Increased vibrations from rapid changes in direction
  • Smoother operation around corners and circles

Lower Jerk values gives you:

  • Less mechanical stresses to your printer
  • Smoother movements
  • Better adhesion for your filament at direction changes
  • Less noise from your printer
  • Less lost steps as you may get with higher values

Akeric found that having a Jerk value of 10 gave the same printing time at 60mm/s speed as a Jerk value of 40. Only when he increased the printing speed past 60mm/s to around 90mm/s did the jerk value give real differences in printing times.

High values for Jerk settings basically mean the change of speed in each direction is too fast, which usually results in extra vibrations.

There is weight from the printer itself, as well as from the moving parts so a combination of weight and fast movement doesn’t go too well for print quality.

The negative print quality effects that you’ll see as a result of these vibrations are called ghosting or echoing. I’ve written a quick article on How to Solve Ghosting & How to Fix Banding/Ribbing which goes through similar points.

Which Problems Do Jerk & Acceleration Settings Solve?

Adjusting your acceleration and jerk settings has a whole host of issues that it solves, even things that were not known to you as an issue.

It can solve the following:

  • Rough print surface
  • Removing ringing from prints (curves)
  • Can make your printer a lot quieter
  • Eliminate the Z-wobble in prints
  • Fixing the layer line skips
  • Stop your printer from running too violently or shaking too much
  • Many print quality issues in general

There are plenty of people who went and adjusted their acceleration and jerk settings and got some of the best print quality they’ve ever had. Sometimes you don’t even realize how good your print quality can be until you actually get it for the first time.

I’d definitely recommend trying this fix out and seeing if it works for you. The worst thing that can happen is it doesn’t work and you just change your settings back, but with some trial and error you should be able to reduce issues and increase print quality.

The video below by The 3D Print General goes into the effects Jerk & Acceleration settings have on print quality

How Do I Get the Perfect Acceleration & Jerk Settings?

There are certain configurations which are tried and tested in the 3D printing world. This is great because it means you have to do very little testing to get the best settings for yourself.

You can use these settings as a baseline, isolate either acceleration or jerk, then increase or decrease it little by little until you get your desired quality.


Now for the settings.

For your Jerk setting you should try 7mm/s and see how it goes.

Jerk X & Y should be at 7. Acceleration for X, Y, Z should be set to 700.

You can go directly into your menu on your printer, select the control setting, then ‘motion’ you should see your acceleration and jerk settings.

  • Vx – 7
  • Vy – 7
  • Vz – can be left alone
  • Amax X – 700
  • Amax Y – 700
  • Amax Z – can be left alone
Acceleration & Jerk Settings on Ender 3 Control Box

If you would rather do it in your slicer, Cura allows you to change these values without flashing your firmware.

You’ll just have to go into Cura settings and click advanced settings, or custom settings to view your jerk and acceleration values.

Usually you want to do this one by one. It’s good to start off with the jerk setting.

If lowering your jerk makes things too slow, you can up your print speed somewhat to compensate. If just lowering the jerk doesn’t fix your problem, then lower the acceleration and see what difference it makes.

Some people leave the Jerk settings at 0 & have an acceleration of 500 to get good prints. It really depends on your printer and how well-tuned and maintained it is.

Binary Search Method for Getting Good Jerk & Acceleration

The binary search algorithm is commonly used by computers to search programs and it can be used in many applications such as this one here. What it does it give a reliable calibration method by using ranges and averages.

How to use the binary method:

  1. Establish a value that is too low (L) and one that’s too high (H)
  2. Work out the middle value (M) of this range: (L+H) / 2
  3. Try printing at your M value and see the results
  4. If M is too high, use M as your new H value and vice versa if too low
  5. Repeat this until you get your desired result

It can take some time but once you find the settings that work best for your printer, it can make the world of a difference. You’ll be able to be proud of your prints and not have weird, wavy lines and artifacts plaguing your print quality.

It’s a good idea saving them as a default profile in your slicing software. So the next time you come to slice your next print, it will be automatically input into the settings.

I advise you to write down what the settings were before you change it so you can always change it back in case it doesn’t work. If you forgot to it isn’t a big deal because there should be a default setting to make it go back to the original settings.


These settings do vary from printer to printer because they have different designs, weights and so on. For example, 3D Printer Wiki  says to set Jerk to 8 and the Acceleration to 800 for the Wanhao Duplicator i3.

Once you’ve tuned your settings, use this Ghosting Test to analyze the levels of ghosting and whether it’s better or worse.

You want to look for ghosting of sharp edges (on the letters, dimples and corners).

If you have vibrations on your Y-axis, it will be seen on the X side of the cube. If you have vibrations on your X-axis, it will be seen on the Y side of the cube.

Slowly test and adjust to get the settings just right.

Description

Some of the default firmware settings are great for showcasing the speed capabilities of the printer, but are not optimized for print quality. Specifically, the Jerk and Acceleration settings are set too high by default.  These setting control the change in speed when changing directions.  High values will result in vibrations as the motors change directions which results in the ghosting or echoing effect as seen below.

Process

Using the control box

  1. Use the dial on the control box to navigate to Configuration -> Acceleration.
  2. Change the Print X and Print Y from the stock value of 1000 to 800.
  3. Change the Jerk from the stock value of 20 to 8.

Using Repetier-Host

  1. Connect to your printer with Repetier-Host
  2.  Under the Config menu option, choose “Firmware EEPROM Configuration.”
  3. Change the Jerk and Acceleration settings.  Set X and Y Acceleration to 800 and Jerk to 8.

Testing

Test and adjust until you’re happy with the results.  Vibration on the Y axis will be visible on the X side of the block, while vibration on the X axis will be visible on the Y side of the block.

 


 

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