Guide: How to Design 3D Prints for an FDM Printer
With the explosion of 3D printing in the past few years, at-home 3D printers are becoming more and more affordable. This means that more and more people are relying less on ordering 3D prints and instead joining the 3D printing movement as makers armed with their own FDM printers.
This means that a whole new population of people is looking for high-quality designs to print at home, but not all prints are FDM printable. So, how do you design an FDM compatible 3D print?
What is an FDM printer?
Before you can design for an FDM printer, you need to understand how it works. 3D printers carry out additive manufacturing, which means that materials are joined to create objects from 3D model data. This is different from traditional subtractive manufacturing where material is cut into and removed in order to create a final product.
A Fused Deposition Modeling (FDM) printer is the most common type of home 3D printer. This kind of printer works by feeding filament through a nozzle where it is melted into a liquid and laid out, layer by layer, onto the printing platform where it immediately cools and hardens. The nozzle repeats this process of melting and laying out the material in the filament until the entire print is formed. Here’s a video of an FDM printer in action!
Why should I design for FDM?
The easiest and most direct answer for this is cost and convenience. Commercially 3D printed designs are much more expensive to produce than those generated on FDM printers. Secondly, but equally important, is the demand for FDM printable products is high. The 3D printing industry is taking off and a lot of that interest is coming from makers who own their own printers and need high-quality designs to print on them.
What makes something FDM printable?
There are a few common things to keep in mind in order to make your design FDM printable:
1. Design for the right materials: At home printers most commonly use acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) plastic filaments. It’s important to keep the properties of these materials in mind whenever you’re designing your prints, because certain design elements will need to be adjusted. For example, a wall hook that is very sturdy when commercially printed in ceramic might have to be adjusted to be thicker in places in order to support a coat whenever it is printed in PLA.
Similarly, it is important to consider the melting point of the filament being used. A cookie tray might be FDM printable, but since it’s melting point is 221°F in ABS or 302°F in PLA, it is not usable to actually bake cookies.
2. File Type: FDM printers can print .STL and .OBJ files (which are converted to Gcodes by a slicing engine before printing).
.STL files include information about the surface geometry of a 3D object without any coloring or texture attributes.
.OBJ files contain surface data, a MAT index and texture file.
3. The 45 rule: Because each layer needs to build off the last, angles of more than 45 degrees generally require supports to be printed along with the design. Although needing to add a few supports to a design before printing isn’t a big deal, it is important to keep the number of supports at a minimum to facilitate ease of print and to keep the cost of producing the print affordable. It isn’t ideal for a maker to have to use $5 worth of support material to print a design in addition to the material that will actually go into creating the design (Check out our video tutorial on the 45 Rule here).
Another things to consider here, is that you might want to design two versions of the same file – one with supports and one without – since some of your customers may prefer to generate their own supports, while others might prefer to just hit print.
4. Design for the printer size: FDM printers range from build area between 120 mm x 120 mm x 120 mm on the small side (as seen in the UP Mini) to 305 mm x 305 mm x 305 mm on the large side (as seen in Type A Machines, Series 1). Users can adjust the size of downloaded files to fit their printer, but on the stream option this isn’t possible. For that reason, it’s important to keep the maximum print size in mind whenever you’re designing files for the stream option.
5. Pay attention to your detailing: There are limitations to details that can be printed on an FDM printer. Don’t make detailing so fine that they can’t possibly be printed.
Here are some detailing guidelines to keep in mind for an FDM printer:
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, but the more space the better.
6. Watch your polycount: A high polycount design can produce very detailed printed models, but it can be hard to work with due to its massive file size. To make the files easier to access try to keep the poly count as low as possible without losing the essential detailing. The maximum model size for Pinshape is 50MB, but again, the lower the better. (View our video tutorial on polycount here.)
You can lower the poly count by decimating the file size in programs like Blender or Meshmixer (View our video tutorial on how to decimate .STL and .OBJ file size here.)
7. Mind your meshes: Make sure that your meshes are manifold (watertight). This doesn’t mean that you can’t have spacing between multiple parts – you can – but you need to make sure that there are no holes in your design where solid parts should be. Holes in your mesh will render the design not printable. (View our video tutorial on watertight meshes here.)
You can check for holes by using tools like Solid Inspector (a free plugin for Sketchup), which will show you the holes in your mesh. You can also run your file through Netfabb, which will close any holes in our mesh.
8. Keep it real with your renders: Keep in mind that your renders should reflect how the model will actually print. FDM printers use all one color filament – there is no multicolor option. Renders with coloration on them can make it look like the print will be textured when in fact it will come out as a smooth service. This can leave makers feeling misled and upset with the outcome of the print purchase.
9, Pro Tip: Try running your design through Magics, Netfabb or Meshmixer to repair any errors in your design (i.e. non-manifold meshes) before uploading the file to Pinshape.
Remember: Material Matters!
Since the maker is taking on production for the design, help them out by designing with material usage in mind to cut down costs and print time:
Follow that 45 rule to reduce the need for support material!
Scale down the bounding box size – a smaller design is less expensive and time consuming to create. Keep in mind that, if you allow downloads of your design, then makers will be able to resize the design how they want. A streamed file, however, is pre-sliced, so makers won’t be able to make changes like this.
Combine separate files into a single one, separated by 2mm between each part. This will make it easier for the maker to print the files all in one go. Remember that for an FDM printer all the parts need to be touching the build plate, so make sure to have all of the different parts placed at the same starting height.
Follow these pointers, and you should be well on your way to FDM printing success!
Have more questions or pointers on how to design for FDM printers? Post them in our forum!
