Designing for 3D printing can be quite different than designing for other purposes. Something that looks beautiful in your CAD program could be extremely difficult or messy to print which creates a frustrating experience for any Maker.
To create an easily printable object, there are five key design rules to keep in mind:
1. Design To Avoid Supports
What are supports?
Supports are extra material that act as “scaffolding” to hold a design in place if there is nothing beneath it to build on. Depending on your design, supports may be necessary to prevent filament from drooping when it’s printed. After the print is complete, the supports can be broken off and cleaned up to leave you with your final design. In most cases, the supports are automatically generated by the slicing software that converts your STL file into a format the 3D printer can read, called G-code. If you’d like to ensure a specific support structure is created, you can design it into your model directly, but in most cases, the auto-generated support structures do the trick.
Benefits of Reducing Supports
Although supports are sometimes necessary, there are a lot of benefits to designing in a way that avoids them altogether. Here’s a few reasons why you should care about reducing supports:
Saves time and money: Designs that require a lot of supports waste material, since the supports are removed and likely thrown away once the print is complete. Additionally, adding supports means the product will take longer to print (more material = more time), and we’ve seen supports increase print time by up to 100% in extreme cases. When you add in the time required to clean up the supports post-print, the difference in time to completion can be significant.
Lowers probability of printing errors: Supports add more complexity to the design which raises the probability of errors when printing. It’s common for longer, more complex prints to fail much more frequently than short, simple prints. Keep it simple to raise your chances for a successful print!
Creates smoother surface finish: Using supports typically creates a rougher surface and again, creates more work during post processing to smooth it out. In some cases, the surface may be damaged beyond reasonable repair when using supports. The picture below is an example of a 3D printed part that is printed without supports (left) and with (right).
Design by mold3d
If you can’t avoid using supports but do have access to a dual extrusion printer, we recommend using a soluble supporting material like HIPS, which is discussed in more detail in our filament guide.
How to Reduce Supports
This is a good way to remember what shapes are safe to design without supports and which to avoid. Thanks to one of our top designers who wrote a more detailed article on Supports and the YHT Rule. The basic rule goes as follows:
- Anything in a “Y” shape is safe to print without support because it’s a gradual slope which still has enough material beneath it to keep it from drooping. This is another way to think of the 45 Degree Rule, which states that in general, overhangs with a slope greater than 45 degrees will require supports. The more gradual the angle, the better. This is why cone shapes are generally safe.
- Designs that take the form of an “H”, where the middle overhang connects to either side is called bridging. Typically, bridges shorter than 36 mm long print with a droop of 0-0.5 mm, bridges 36 to 60 mm long print with a droop of 0.5-2 mm, and bridges longer than 60 mm long print with a significant droop of 2-5 mm. These rules aren’t set in stone, however, since it depends on your material and print settings.
- Anything with a “T” shaped overhang will not have any support and will almost certainly create errors in your print. There just isn’t enough to hold the material up in this configuration.
Split the model into multiple parts
Another way to avoid supports is to split up your model into multiple parts so they can each print flat. To help with this, the Onshape Part Studio has a tool that splits up designs easily. If you haven’t done this yet, refer to Onshape’s blog on A Guide to Successful 3D Printing for more detailed instructions. After you print the parts, you can bond them with an adhesive like cyanoacrylate (super glue) or a solvent. This can be especially useful for complex designs and larger prints.
Orient your model properly
Sometimes, supports can be reduced simply by rotating your design into the appropriate orientation for printing. For example, in the case of the ‘T’ print above, the need for supports can be completely removed by laying it flat on it’s back. You don’t always need to make changes to your model to improve results.
Anchor your print
Anchor parts of your design that would go beyond 45 degrees and attach them to a different part of the model to avoid overhang. For example, in the first picture below you can see the arms are attached to the back. This is a good method to avoid overhang and allows you to print the design as a whole whereas the model below have their arms straight out which will create some problems when printing.
2. Design For Printing Tolerances
There are limitations on how much detail a 3D printer can successfully reproduce, which means you need to take these physical limits into account when creating intricate designs.
Here are some suggested guidelines on detailing for an FDM printer:
- Most FDM printers claim to print a minimum layer resolution of about .05mm, but realistically most designs work best with .1mm per layer.
- The suggested minimum text size on the top or bottom build plane of your model is 16 point boldface and 10 point bold face for vertical walls on most FDM printers
- The suggested minimum wall thickness for designs depends on the specific layer thickness used by the printer and the specifics of the design (how large it is, how much weight it will hold, etc.), but a wall size of 1mm or larger is generally safe for most FDM printers.
- The minimum spacing between interlocking parts is .4mm on most FDM printers.
Prints with narrow parts can often get overheated during printing and warp the design. To prevent overheating in one place, you need to disperse the heat and allow the hot end of the extruder to move away from your object to give it time to “cool off”. You can do this by creating a thin object away from your 3D print that is the same height so that as you’re printing your design, the hot tip moves away to print the other object away from your design. This will create an extra tower whose only purpose is to divert the hot end of the extruder while printing to prevent overheating
Photo by simplify3d.com
4. Design for your Material
Depending on the intended use of your printed piece, your choice of material can affect certain aspects of your design, and needs to be taken into account for the best results.
For example, if you’re designing parts that are meant for mechanical purposes, you need to consider the strength and flexibility of the material it will be printed with and ensure your design will meet your desired specifications. Additionally, if your parts are meant to fit together with other items or other printed parts, you’ll need to take into account how much your material will shrink and warp after cooling.
For a quick easy comparison of the properties of the most common types of filament used in FDM 3D printers, check out our handy 3D printing filament guide.
5. Choose Your STL Export Settings
If you’re designing for an FDM printer, you’ll most likely be exporting your design as an .STL file which creates a representation of your design in triangles. High poly counts create more detail in the print but can create file sizes which are difficult for your slicing program and 3D printer to handle. Typical file sizes range from 200KB to 10MB, but different printers have different capabilities so it’s important to know the limits of your printer. The goal is to create a file that’s as small as possible while still maintaining the detail in the design.
Sell or Share Your Designs with Pinshape
Once you’ve used Onshape to create your masterpiece, what’s next? If you’re interested in selling or sharing your designs online, that’s where Pinshape comes in. We’re a 3D printing design community and marketplace where designers can upload and download 3D printing designs to sell or share with the community. With our Pinshape App on the Onshape App Store, you can sell your designs on Pinshape without leaving your design page!
All you have to do is download the app, create an account or login through Facebook and select which items you want to share in the drop down menu. If you want to learn more about how to use the Pinshape App with Onshape, visit our blog on how it works. Our community would love to see what you’re working on and we’re excited to have Onshape designers join our community!
Whether you are designing for printing yourself or to share with others, we hope these tips helped!
Have fun and happy printing!
For more tips on design for 3D printing, see Pinshape's 3D Printing Design Guide.