Ghosting, aka ripples (ringing, rippling) is a 3D printing defect that is common with FDM and FFF technologies. The issue is most noticeable on models with flat vertical surfaces. Ripples occur when the direction of movement of the print head changes due to mechanical vibrations of the printer design.
In this article, we will walk you through how to fix 3D print ghosting step by step. Read on,
5 Steps to Fixing 3D Print Ghosting (Ripples)
Step 1. Check the Mechanics
It is advisable to start the fight against printing defects that are of a mechanical nature by checking and tightening the screw connections. The screws may not have been sufficiently tightened during assembly, or could have loosened over time as you use the printer.
Backlash and reduced structural strength negatively affect print quality. Therefore, before tweaking with the printer settings, make sure that the ringing is not caused by improper connections.
Ideally, the screw connections should be pulled with a torque wrench. However, if you are working at home with conventional tools, avoid using excessive force as it can damage the thread, the keyway, or the key itself.
For example, for printers assembled from a structural profile, you first need to control the screws that fasten the profiles. See below the connection of the Z rails to the base on the Longer LK5 Pro printer.
It is also important to fasten the carriage plates to the profile. The procedure for tightening the screws here is not easy; you have to remove the X profile from the Z rails. The video below shows how to do this on the Ender-3:
You should also check the condition of the moving parts. Movement along all axes should be smooth, without chatter or extraneous sounds.
If the printer carriages have rollers, check their adjustment. When the carriage or table moves heavily, the adjusting roller is overtightened. In such a case, loosen it a little. If the rollers move away from the guide profile, you need to increase the pressure.
For example, if the X guide moves up and down easily, this may be the reason for insufficient pressure of the rollers on the Z guide.
In such a case, you will have to increasing the pressure of the eccentric roller.
Step 2: Check the Belts
The belt tensioning procedure varies from printer to printer. The easiest option is when the manufacturer allows tension adjustment without having to use any tools.
To adjust a belt that is tensioned by moving the roller mount, loosen the screws, manually move the mount and, while holding it, fix it.
For popular 3D printer models, you can find community-developed models of screw belt tensioners.
There are also other ways to tension belts. For example, you can shift the motors, as in the case of the FlyingBear Reborn. Finally, for some budget printers, you cannot tension the belts at all. A good example of such a printer is the Kingroon KP3S. The printer’s belt is rigidly fixed with cable ties, and the motor and roller do not move.
In the case of the KP3S, to increase the tension of the belt, you have to remove it from one of the mounts, mark or photograph the current configuration just in case, remove the cable tie with the help of wire cutters and move the loop one or two teeth.
There are also some tensioners that are installed on a straight section of the belt. These tensioners are rigid, adjustable and springy. These modifications may not be available everywhere as they reduce belt free play and may affect the size of the printable area.
Spring tensioners are not the best choice, as they can “play” when changing direction, changing the tension.
An example of a 3D printed adjustable belt tensioner.
It is difficult to give a single recommendation on the belt tension on any printer. Therefore, you simply need to follow this rule: if you pull a correctly tensioned belt over a long section, it should oscillate a little, but not buzz like a string.
Excessive belt tension can lead to increased belt wear, deformation of printer components and another print defect – small ripples over the entire area of even vertical surfaces.
Belt tension effect. The left model in the top illustration is before adjustments. The print settings are the same in all cases.
Step 3: Make Sure the Printer is Stable
Not only is the condition of the printer important, but also how well it is installed. If the surface is uneven or wobbly, the vibrations of the printer and the support together or separately may also affect print quality. If the printer “rides” on the surface – you can install damping feet or a rubber mat on it. Another option is to reduce the speed and acceleration of printing.
An example of simple damping feet for an extruded profile. Photo by Thingiverse.com.
Step 4: Adjust the Speed, Acceleration, Jerks
Print defects may occur due to the printer’s speed settings. Let’s talk briefly about what each parameter is responsible for:
Speed (Speed, Velocity)
The Speed parameter refers to the speed of movement of moving parts. Speed is measured in mm/s.
Acceleration
Acceleration determines the intensity of the increase or decrease in speed, i.e. acceleration or deceleration. For example, 1000 mm/s2 means that in one second the speed can increase by 1000 mm/s.
Jerk
Jerk specifies the maximum speed change (from 0mm/s to the specified velocity) that the printer can go to the speed defined under jerk setting without adhering to the acceleration speed.
The absolute change in speed (considering both axes), from the end of braking to the start of acceleration, is the jerk.
In general, the more jerks, accelerations and speeds, the faster the print and the greater the likelihood of defects. The value of jerks is usually 10-30 mm/s. Acceleration and jerk settings are stored in the printer firmware, but can be changed through the EEPROM* settings or using a special command in the print job.
*EEPROM is a read-only, rewritable memory that stores a number of printer settings. Some of the settings include:
- The number of motor microsteps per millimeter of movement\
- Heating element calibration values
- Maximum movement speeds, accelerations, etc.
Typical acceleration values for consumer 3D printers are 500-5000 mm/s2. The greater the acceleration, the faster the printing, and the greater the requirements for the rigidity and reliability of the printer design.
To determine the maximum allowable accelerations, you can use the calibration model provided by the Calibration Shapes plugin for Cura. Since version 1.7, Cura has an Acceleration tower model.
If extrapolated to other print speeds, the ripple pattern will remain similar in intensity. However, at a lower speed the defect area will be shorter, and at a higher speed it will be longer.
Step 5. Saving the settings
Acceleration and jerk settings in Cura are applied directly to the job being prepared. After the optimal values of these parameters are determined, it is advisable to write them to the permanent memory of the printer. If the printer is equipped with a monochrome graphics screen (for example, the basic version of Ender-3), the menu contains acceleration and jerk settings: Control -> Motion l -> Acceleration and Control l ->Motion l -> Jerk.
After changing these parameters, you must save: Control l ->Store Settings.
Increasingly, common graphical touch screens usually lack the ability to fine-tune the printer. In such a case, there are two alternative options for recording the values of accelerations and jerks in permanent memory.
The first option is to manually generate a control code. To do this, using a simple text editor such as the standard Windows Notepad, create a text document, put commands in it, change the file extension to .gcode, write the file to a memory card and print it.
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Next, write these control commands in the text document you have opened:
M204 X3000 Y3000
M205 X30 Y30
M500
Finally, save the file by changing its extension to .gcode instead of the default .txt
The first command is to set the accelerations to 3000 mm/s² for the X and Y axes. The second command is to set the jerks to 30 mm/s respectively. The third is to write to memory. Printing this G-code file will cause the specified settings to be stored in the printer’s permanent memory. After executing this file, all subsequently launched print jobs will be executed at the specified speed, acceleration, and jerk settings.
The second option is to insert these commands into the slicer start code so that they are applied before the next job is printed.
Another Ripple
There is another print defect similar to the one described. The main difference is that the vertical waves are straight. They do not follow the contours of holes and protruding parts of the part. Also, the waves are distributed evenly over vertical surfaces, rather than concentrated in places where the direction of movement changes.
Causes of constant ripples include excessive belt tension, poor quality pulleys and motors. If the ripples are uneven but intermittent, this may indicate worn or damaged guides, linear bearings, or rollers, depending on the design of the printer.
Conclusion
A defect in the form of fading ripples (ringing, ghosting, rippling), which is clearly visible on even vertical surfaces, is usually due to mechanical vibrations of printer parts. To combat ripples, check the condition of the printer fasteners and the tension of the belts. Also, adjust the speed, accelerations and jerks.
It is advisable to select the optimal parameters by printing test models. The resulting values can be used in the slicer settings or stored in the permanent memory of the printer.
We hope our article has helped you learn how to fix ripples in 3D printing.
