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3d Printing Supports Guide: How to Properly Add Supports to your 3d Prints

3d Printing Supports Guide: How to Properly Add Supports to your 3d Prints

(Source: hubs.com)

All 3D printing hobbyists have had to deal with drooping overhangs or unstable prints, which leads to the inevitable deep-dive into 3D printed supports. As additive manufacturing machines, FDM 3D printers deposit material in subsequent layers, requiring a strong foundation for each pass of molten filament. For overhangs or highly detailed parts, supports are critical.

Support structures necessarily increase the estimated amount of material required for a print and can increase prints times. Efficiently designing or modifying models can sometimes eliminate the need for supports, but it’s likely that you’ll have to incorporate supports into your prints at some point. Our guide covers the basics of adding supports to your 3D prints.

What are overhangs and why do they need support?

Overhangs refer to any portion of a print that extends beyond the boundaries of the lower layers. This can include flat surfaces or curved details that decorate upper layers of the model. These parts typically require extra support, but not all overhangs require additional material. If an overhang is situated at an angle less than 45 degrees from the vertical line beneath it, then it should be sufficiently supported. Note that this may change depending on the material you’re using or the size of the overhang.

FDM 3D printers deposit material at a slight offset between layers to avoid warping or excessive weight at an angle across layers. The weights of some overhangs can be supported by this offset, but each model and filament type has a limit.

What about bridges?

Unlike overhangs, bridges are supported with at least two points of contact with the previous layers. For bridges of lengths at or under 5 mm, the connecting points are typically sufficient to support the filament as it is being deposited.

At this distance, the printer can bridge molten filament across short distances before it sets with minimal sagging. However, for bridges longer than 5 mm, the filament will droop too much before setting and may even fall. Thus, 3D printing support structures is required.

Testing your printer’s limits

As noted previously, 45 degrees from the vertical is a good rule of thumb for determining which overhangs do not need extra supports. However, this is a general rule, and the difference between good and great 3D prints is knowing exactly what your printer can and cannot do. Printers that are poorly calibrated or filament that is highly flexible may lead to sagging under this limit. For this reason, we strongly recommend running overhang and bridging tests before jumping straight into your prints.

There are numerous testing models on Thingiverse designated to “stress test” your printer’s ability to handle bridges and overhangs. Most will include overhangs ranging from 20 degrees to 70 degrees at small increments such as 5 degrees.

Take note of the angle at which the printer starts failing. This is the maximum overhang angle that can be included in models without additional supports. It is a good idea to run this test when using different filament types or after calibrating your printer.

Considerations when adding supports to 3D prints

Increased print times and material costs

Simply put, supports are additional parts being printed on your model. 3D printing support structures will necessarily increase printing duration because more material will be deposited. The extent to which these are changed are greatly dependent on the style, number, and length of supports. Optimal support design can significantly limit the impact of added supports.

Additional post-processing time

Unless they are integrated into the model design, 3D printed support structures must be removed after the print. For hobbyists, this requires extra time and caution to ensure that the final print does not show blemishes where the supports were previously. For small businesses and manufacturers, this quickly adds up to additional printing costs.

Potential risk of damage

The removal of supports does not just pose an aesthetic or time problem—it can also damage the print itself. This is particularly worrisome for delicate or large prints. Because of this risk, it is crucial to carefully design the model to reduce the amount of support removal required and ensure that the model parts supported by the additional material are strong enough to secure when removing supports.

Support structure geometry

Most 3D printing support structures fall into two categories based on their geometry: tree-like and linear/accordion.

Tree-like supports

Tree-like supports have a branching structure that supports an overhang. This type of 3D printing only connects to some portions of the overhang and spreads its weight load to the lower layer.

This geometry can be advantageous in that it is easier to remove and causes minimal damage to the underside of the overhang upon removal. Because of how this style of support connects the upper and lower layers, it can only be used for overhangs that are not flat, such as fingertip or arched overhangs.

Linear or accordion supports

If you have seen 3D printed supports before, chances are that you have come across linear supports. These are by far the most common. This type of support is characterized by the use of vertical pillars that touch the entirety of the overhang and can be modified for any bridge or extension. However, they tend to use more material and harder to remove than tree-like supports.

Breakaway vs. dissolvable supports

Breakaway support structures

3D printers equipped with only one extruder print breakaway support structures by default.

With one extruder, users have to print supports using the same material being used to print the rest of the model. The density of the support structure can be changed, but there is little control over the rest of the support’s printing properties. Because both the supports and the model are printed using the same filament during the same print process, supports must be removed by hand (either breaking or cutting) after the print is complete.

Dissolvable support structures

If your printer is equipped with two extruders, you don’t have to rely on breakaway supports. Instead, one extruder can be loaded with PLA to print the model, while the other can be loaded with a water-soluble material such as PVA to print the supports. Once printing is over, the support structure can be “washed away” without causing significant damage to the print.

This method is helpful for complex and highly detailed prints, but care should be taken with larger prints with heavier bridges or overhangs.

Removing breakaway support structures

There are a few things to keep in mind when removing 3D printed breakaway supports to avoid damaging the final print.

First, identify which 3D printing support structures are easy to access using your hands. Gently put pressure on these supports with your fingers to snap them without putting too much force on the print itself.

For supports that are harder to access, such as those under curves, tools such as needle nose pliers, putty knives, or Exacto knives are preferred. When using a blade, we recommend heating it prior to removing the support as it can slice through the plastic more smoothly. Exercise caution when breaking supports using a knife and keep your fingers out of the blade’s path.

Sandpaper can be used to remove remaining pieces of supports. Wet sanding with high grit sandpapers (220 to 1200) can remove plastic and smooth the model surface. Apply water to the part and sand in smooth, light motions until the desired finish is achieved.

Prints using PLA may develop stress marks where supports were removed, leading to scratches or blemishes. Sanding or varnish can help remove these marks.

Incorporating 3D prints with optimal model design

Integrating supports into design

To avoid the post-processing required to deal with supports, some 3D print hobbyists simply add supporting elements into the model itself. This is particularly helpful for figurine or toy design, which can include extra components that do not disrupt the aesthetic of the piece. For example, a figurine with an arm extending out can include draping fabric or a staff to support the extended arm (which acts as an overhang support or bridge, respectively).

Integrating 3D printing support structure into the design of your models requires practice and may not be suitable for all applications. While incorporating supports that don’t need to be removed can save time and material costs, it can also reduce the functionality of practical prints. There are a few other options for dealing with overhangs and bridges that cannot be supported by the print design itself.

Using chamfers

Instead of printing support structures, chamfers can be used to reduce the strain of large overhangs by reducing the angle to 45 degrees. Chamfers are gently sloping, often beveled edges that require minimal to no additional support. If you have a curved overhang with a delicate edge that extends beyond the 45-degree limit, consider changing it to a chamfer to avoid unnecessary supports.

Reorienting the model

(Source: formlabs.com)

Some complex prints will require supports no matter what. However, not all models need to be printed in the orientation that they’ll be placed in or used. For example, an asymmetrical print that requires supports may be printed at an angle with a base that can be removed after the print is complete to ensure that the supports are only connected to pieces of the model that are easy to access. In the photo shown above, the supports on the right do not touch the gear teeth. While there are still many supports to remove, they are easier to access and are less likely to impair the functionality of the print.

Slicer settings for 3D printing supports

Many slicers have options that can help you identify the optimal 3D printing support design, allowing you to use supports that do not waste material and are easily removable. Your slicer software should provide several options for tweaking supports. Most slicers can auto-generate supports, and they also provide a manual mode for directly adding or removing supports as needed. Slicers like Cura have a suite of features that provide ample detail on the supports included in a given model, such as placement, strength, print surface effects, and density.

Using auto-generated 3D printing support structures for complex models

To determine the best way to add supports to your model, you have to figure out what your printer’s tolerance is for overhangs and bridges. We noted that running test prints is a great way to do this. You can also rely on your slicer to help you figure out whether your model might have overhangs that are too severe for your printer to handle without supports.

Once the model has been imported into Cura and positioned on the virtual build plate, parts of the print may be highlighted in red. Red parts indicate that the slicer has identified unstable parts. Be sure to rotate the model in the digital view to identify any unstable parts. Small red areas around the base of the print or at the very top of supports are not typically worrying; these parts should be supported by the print base or the larger parts of the model.

Enable auto-generated 3D printing support structures to ensure that red parts can be printed successfully. In Cura, this is done by enabling “Generate Support” under the Support section. You likely did not see any changes in the model view after generating supports.

To see the generated support structures, change the view to Layer View. Support material will be displayed in teal in this view. Moving the layer slider will reveal how the supports interact with the model during printing.

Cura generates linear 3D printing support structures by default. In Cura 3.2, users can add tree-like supports instead of linear supports.

Moving 3D printing support structures

When you enable support structures, the “Placement” setting appears under the Support section. This allows users to have broad control over the positioning of the support structures. By default “Everywhere” is selected, which creates supports across the entire model area. You can also select “Touching Build Plate.”

Selecting Everywhere can be helpful for models that have complicated or numerous overhangs along the model length as parts of the model itself can be used as the foundation for the support structures. However, this can also lead to the model being completely covered by support structures, which makes it difficult to nearly impossible to polish the model after printing.

Selecting Touching Build Plate can avoid this issue but may not be suitable for very large prints or those with overhangs only at the top of the model. For these, consider re-orienting the model as needed.

Using the Support Roof setting

Because an overhang is printed on top of printed support structures, they sometimes have a poor surface finish. A support roof refers to a dense skin at the top of the support structure that does not compromise the surface finish of the overhangs too much. When you enable this setting in Cura 3D, you can get a better surface finish.

However, these roofs are harder to remove than typical supports. This option should only be used if the surface finish of the overhanging part is critical to the function of the finished part.

Using the Support X/Y Distance setting

When 3D printing support structures are too close to the model’s outer wall, they can leave marks on the surface. The Support X/Y Distance setting under the Support section can mitigate this issue.

The Support X/Y Distance setting controls the minimum allowed distance between the model’s vertical walls and a support structure along X–Y axes. If your 3D printing support structure is damaging or sticking to them, increase this value by increments of 0.2 mm until the walls are smooth.

Double check all overhangs along the outer walls after changing this value. If supports are moved too far to support small overhangs, they may droop.

Altering the Z Distance setting to make supports easier to remove

If you find that removing the support material is difficult, increase the Z Distance value by small increments until it comes away cleanly. Cura can add or exclude supports at specified layers. Note that Z Distance must be set at increments of the layer height. For instance, if a 0.2 mm Z Distance setting for a print with a layer height of 0.1 mm is too much but a Z Distance of 0.1 mm is not enough, you cannot modify the Z Distance value further.

Support structure patterns

Cura generates 3D printing support material using one of seven patterns. This pattern can be changed using the Support Pattern setting.

For most prints, the default Zig Zag pattern will yield the best balance between strength and ease of removal. The other pattern options are Triangles, Lines, Grid, Concentric, Concentric 3D, and Cross. Experiment with other options to determine which works best for your specific model.

Adding support structures to your prints will be a necessity at some point. Supports can save a complex print, but they require additional material, time, and effort to manage. By carefully evaluating the orientation and design of your print, you can eliminate the need for excessive supports. Fine-tuning the support structure settings in your slicer can also make them easier to remove. Start testing out your new-found support knowledge and get printing!

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