When it comes to 3D printing, you can either design the part you want to print in CAD software (see our guide on designing parts for 3D printing), or you can search online libraries such as Thingiverse and download the files directly. Load the file into your slicing software and this will change your model into a set of instructions for the printer. Send this to the printer (usually via USB, SD card or WiFi), hit print and there you have it.
Sounds simple, yes? But how do you make it the best it can be? How do you make sure it will print successfully? Read on for a few tips and tricks to getting successful prints.
The way that you position you part on the bed is important. For FFF printers there needs to be a large contact area between the base of the part and the print bed to ensure that the part will remain stuck in the same place throughout printing. Take this part for example:
This is a bag clip, made for resealing pasta, biscuits or anything else. You can see that there is only a small area connected to the build plate. This could very easily move as further layers are printed which would leave nothing for the rest of the model to attach to. How could we improve this?
This version of the model has a much higher contact area with the build plate and so will print much more reliably.
Build Plate Adhesion
Some printers have a rough tape-like surface to the build plate in order to help your part stick. Others, generally heated beds, are glass. With glass build plates, use of a PVA based glue stick such as Elmers is recommended to give the print a surface to stick to.
You can also use a raft or a brim. These are settings you select in your slicing software. Rafts are a full base of plastic underneath the model, whereas a brim is just a single layer of plastic underneath the edges. Both will simply snap off after the model is printed. See parts below for examples.
Rafts and brims are good for thin or slightly curved surfaces, but they are only to help the first layer stick to the bed. Orientation is the more important factor when it comes to printing parts successfully.
Overhangs and Support
Overhangs are areas of the design that are not entirely on top of the layer below. Most printers will cope well with small overhangs, and can even cover short gaps, known as bridging. Bigger gaps require supporting – more on this soon. Take a look at our next example below:
This spiral pen pot demonstrates both overhangs up the sides and bridging on the top. On each layer the printer must go a little way past where it was last time to create the spiral effect. Professional printers can print this as shown in the picture above without trouble.
This bridging capability also allows for printing articulated models and moving parts as in the photo below.
This model fire engine prints in one part with no supports and has moving wheels with a rotating and lifting ladder. As before, professional printers can handle this kind of print easily.
For dealing with gaps that are too big to bridge, see below.
For parts with empty voids, such as the drawers above, we use support to avoid printing large areas on fresh air. The support is printed with the part and then is removed manually with pliers or cutters afterwards. Some printers are dual-extrusion and have the ability to use a soluble material for the support. This allows for much more complex geometries to be printed.
The easiest way to put support on your model is simply to enable the setting in your slicing software. Support can leave a rougher surface when removed, so you may need to change the orientation of your part in order to make sure that important surfaces are support free or use soluble support.
Layer height is one of the most used terms in 3D printing. But what exactly does it mean? Put simply, layer height is how much the z axis moves between one layer and the next.
Layer heights are often found in the range of 50-200 microns (0.05-0.2mm). A bigger number here means that the print will be quicker, as there are fewer layers, but the surface quality of the print may be reduced.
Consider a 20mm cube. At 0.2mm layer height, this would be 100 layers to get 20mm tall, as each layer is 0.2mm thick. At 0.1mm layer height, this would be 200 layers, and thus take twice as long to print. Below you can see a representation of the layers at 0.2mm and 0.1mm.
Because the layers are squashed closer together in the 0.1mm part, the printed part looks smoother. For early prototypes, or design iterations that you want to be able to compare quickly, use a big layer height to save on material and time. Once you are in the final stages, use a small layer height to give a high quality look and feel to your part.
Infill is the amount of material inside the model. If a part is not being produced for strength, then print times can be massively reduced without affecting the look of the model. Using less infill also uses less material. The images below show a range of infill densities:
The higher the infill, the more plastic is inside the part, and so the longer the print takes. However using a very low (< 10%) infill can leave you with large areas to bridge and cause problems if there are any holes or embossed detail in the top surface.
Infill is a compromise between strength of part, level of detail and print time. It is always worth scanning through the layers in the software before sending to print to check that all areas are adequately supported.
Material Selection and Other Settings
There are a myriad of other settings that can be changed in the slicing software to tweak the print. These can be experimented with if desired, but the inbuilt profiles should work well enough for most applications. These profiles are set per material, dependent on a number of factors such as extrusion temperature, bed temperature, print speed and so on.
You do not need to concern yourself with this if you do not wish to, simply select the material you are using, chose your layer height and infill and click print! The material settings will be applied automatically for you.
Hopefully now you have a greater understanding of the main preparation techniques required for FFF 3D printing. We hope you enjoyed it!
We hope you found this article interesting/useful. If you are thinking of buying a 3D printer, please check out our range of FFF 3D Printers
Read the next part in our “how to” series: How to Prepare Your Model For 3D Printing Part 2: SLA.