Spheres or spherical objects can be challenging in 3D printing. Read on for some tips to improve the print quality of spheres in 3D printing!
Fused deposition modeling (FDM) 3D printers work by moving nozzles along the X, Y, and Z axes, extruding filaments at specific locations, and gradually creating parts layer by layer.
While FDM printing is very advantageous in some respects, including its ease of use for beginners, the layer-by-layer printing process also has its limitations.
A significant drawback of FDM 3D printers is that they produce "steps" on curves that intersect the Z-axis.
Other aspects of the printing process can also limit print quality, such as Z-shaped seams and inconsistent extrusion.
In particular, spheres are among the most difficult geometries to print in 3D because they are more susceptible to the effects of stepped lines.
If the printout requires support, there will be even more impact, because the smooth, curved surface of the sphere means that the marks of the support points will have nowhere to hide.
All of the above reasons may result in a rougher surface finish than usual.
FDM printed spheres will never be perfect, but there are several ways to minimize defects and achieve the cleanest possible surface finish.
In this article, we will discuss some techniques for printing spheres using FDM 3D.
design
The first step in printing a sphere is to design it correctly, and there are actually two ways to do this: either split it into two or keep it as a whole.
Dividing a spherical shape into hemispheres makes printing easier and eliminates the need for supports; however, it increases post-processing time when you need to reassemble them and you must be mindful of the possibility of warping at the heated bed contact surface.
If your spherical shape is part of a larger design, consider printing the portion of the design separately and reconnecting it later.
Alternatively, you can keep the spherical shape in the model, but carefully consider the orientation when slicing.
Dividing a spherical object into two parts is very simple.
First, open your favorite 3D design program and find the center point of the spherical object.
Then, use a splitting tool (planar or 2D sketch) to divide the model into two parts.
Finally, export each section separately for individual printing.
It is best to print one hemisphere at a time to avoid nozzle retraction issues as it moves between blocks.
If you preserve the spherical shape as a solid, no special design preparation is required.
Simply export the model as usual, but be aware that you must handle the protruding part at the bottom of the sphere in the slicer. Let's move on to the slicer settings!
slice
Slicing the model is the next important step in printing spheres, although adjusting the slicer settings is key to any successful printing.
Better, smoother printing on the print bed means less sanding and post-processing time.
To print spheres that look smoother, a very versatile but useful setting is to use a smaller layer height.
In short, higher resolution means fewer noticeable steps because more layers are used to build the curve.
Although this increases printing time because an additional layer is needed to achieve the same height, the smoother surface obtained through such a simple setting adjustment will be worth it!
For example, Cura's adaptive layer height and other features can achieve finer details and faster printing speeds; this setting is also available in other slicers, although the names may differ.
In short, this function changes the layer height of the entire slice model so that less detailed parts will be printed with thicker, faster layers, while more detailed parts will be printed with thinner layers.
This is particularly useful for spheres because it creates a smooth transition between floor heights, resulting in a natural, more rounded appearance while reducing the number of stair steps.
The key part of printing a sphere is the support; theoretically, a perfect sphere only needs to contact the printing platform plate at a single point.
However, 3D printers cannot print in mid-air, so the bottom of the sphere needs a support structure to support the sphere during printing, otherwise it will roll.
You can avoid this need by dividing the model in half, as each hemisphere can be printed on its flat base.
Typically, when the support material is removed, the support may leave marks or a rough surface.
To minimize the impact on the sphere's surface, try increasing the distance between the support material and the overhang. (The relevant settings in Cura are "Support Z Distance" and "Support X/Y Distance".)
Using a raft or edge could also be a good idea to further enhance bed adhesion for spherical parts.
The support structure and the spherical area of the contact printing platform plate are surrounded by rafts and edges to keep them grounded to the bed.
This is important because without edges or rafts, the support structure may fall off in the middle of the print!
The infill and the outer wall are the main components of the print, as they occupy the interior infill and the exterior surface, respectively.
The amount of infill and outer walls is less important to the surface appearance of a sphere, but should be set according to the intended use of the part. For example, these settings can affect how light passes through the object, which can be helpful if you are printing something like a moon lamp.
For infill, a lower than usual infill density can be used unless the part requires strength for its internal structure. This will avoid any risk of the infill pattern seeping into the walls. Lower infill density also means less printing time.
If you want a certain degree of transparency, try using a smaller number of exterior walls (about two).
In other words, considering that too little shell and too little filler may cause sagging at the intersection of the filler gaps and the shell.
To prevent this from happening, consider using three or more exterior walls when the infill density is around 10% or lower. If you want a more robust-looking surface and stronger components, increase the number of exterior walls.
For a sphere, regardless of its intended use, the number of wall layers should always be the same as the number of top and bottom layers. This is because if one number were greater than the other, the weight of the sphere would be uneven.
If your spherical part is not a regular sphere, you also need to consider the part's orientation.
If you cannot divide the part into two sections, the lower half will require a lot of support, so please remember that removing the support may damage any details.
If your sphere is part of a larger model, try adjusting the placement of the model to minimize the support required for the sphere itself.
For slicing settings, it's recommended to use a vase or spiral pattern. The vase pattern only prints the circumference of spiral objects, making it ideal for cylinders and other hollow circular shapes. This will also reduce material consumption and printing time. Please ensure you remember to activate the support; otherwise, printing may fail.
print
There's not much to discuss when actually printing spherical objects, but before you start printing, check the printer's regular maintenance.
This means ensuring that your belts, nozzles, heated beds, etc., are functioning properly.
To ensure your spherical shape doesn't become like an egg, be sure to tighten the belts on the X and Y axes.
A loose belt will make the print head or print bed move more loosely, so the perfect circle will look a little oval.
Don't forget to make sure your nozzles are clean and clear, as clogged nozzles can cause inconsistent extrusion and make the surface quality look worse.
As with any printing, remember to level the heated bed before you start printing so that the first layer prints nicely and evenly.
Finally, consider using materials such as ABS to print spherical objects.
While the success rate of printing on other materials such as PLA should be similar, ABS has a simple layer smoothing option, so the end result may be more impressive.
If you have a dual extrusion printer, try printing the support material using a soluble material such as PVA, as this will prevent surface damage when the support is removed.
Post-processing
Finally, the sphere needs post-processing. Fortunately, there are many post-processing techniques available, depending on your print, materials, equipment, and level of experience.
For spheres, some good options include grinding, using solvents, polishing, and coating.
The first step you should take is to remove all support material from the printout. Carefully use a tool to remove the last remaining support fragments stuck to the model.
If you print the model in two parts, you may not need to remove the supports; instead, you can use adhesives such as super glue or a 3D pen to bond the hemispheres together.
When aligning the two halves to achieve a smooth transition, strive for perfection.
Next, use sandpaper to sand the model from low grit (coarser) to high grit (finer).
If bonding two hemispherical parts, ensure a smooth transition between them and evenly sand all areas of the spheres for optimal surface finish.
If you are using ABS to print a model, you can use solvents such as acetone to add a smooth, shiny surface to the model.
The solvent's role is to slightly melt the surface to blend the layers and remove visible lines.
If you are using PLA to print parts, you can use an epoxy coating (such as XTC-3D) to smooth and finish your objects.
Finally, you can polish, paint, or coat the model for a final touch.
Drawing spheres can cover up any final imperfections on an object, add or emphasize details, or change colors.
To achieve a smooth shine, try using a rotary tool to rotate the polishing material at high speed, or you can polish it by hand.
That's how to print a spherical object that looks great anywhere!
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