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The 3D Printing Workflow is the process comprehending all stages from the idea to the fabrication of a final part using additive manufacturing technologies. This white paper will help you understand which are the necessary steps to be taken in each stage of this process in order to be able to better plan for it, optimizing time and resources.
The main stages to be considered within this workflow for FFF 3D printing, in all of which we will dive deeper in this document, are:
- Modelling or obtaining a pre-made model
- Generating an STL file
Modelling for 3D printing
The first step in any additive manufacturing process is obtaining or producing the 3D model that is to be printed.
Modelling is the process of representing a 3D object in a mathematical way, and can be done manually, using a CAD software or by 3D scanning objects to represent them digitally.
Another option would be using a pre-made 3D model, which can be obtained from a variety of sources, since several online marketplaces for 3D content allow individual designers to sell or share for free the content they have created.
Generating an STL file for 3D printing
Once the CAD model is ready, a vital stage during the 3D printing workflow is converting it into an STL (stereolithography) file. STL uses triangles (polygons) to describe the surfaces of an object, without any representation of colour, texture or other common CAD model attributes.
Although, some considerations must be taken into account when exporting the model to an STL file. As the process creates a mesh of triangles, the resolution can be controlled by changing the density of the mesh:
- If the mesh density is too low, the model will show triangles on its surface when printed.
- If the mesh density is too high, it will increase the size of the file and the printer will not be able to print the finest details of the part.
The exported resolution of the STL file can be adjusted in the CAD software.
*Repairing an STL file:
Sometimes, the STL can present problems related with the mesh. The most common issues that an STL can show are :
- Holes or gaps in the mesh
- Flipped normals
- Intersecting and overlapping triangles
- Bad edges
To solve these issues, additional software such as Magics by Materialise (paid), Netfabb by Autodesk (free version), 3D Builder (preinstalled on Windows), Meshmixer (free) or Meshlab (free) can be used.
Slicing for 3D printing
Once the STL file has been correctly generated, it needs to be loaded into a slicer software such as BCN3D Cura.
The slicing software is used in the additive manufacturing processes to convert a 3D model into specific instructions for the printer, by turning the STL file into a G-code with printer commands:
The slicer divides the object into horizontal layers, and for each layer describes the necessary movements to extrude the plastic. Apart from the coordinates of the extruder, the software includes information about the temperature, the speed, the material flow, supports… etc. If these instructions are precise and have the right parameters, the prints will achieve top quality.
All slicers available in the 3D Printing Market can achieve similar smooth surfaces for normal structures, but the quality of overhangs and bridges is directly affected by the slicing software used.
The main parameters to be modified are:
- Nozzle size
- Printing profile
It is also important to correctly place the part in the printing surface and optimize the orientation in order to take advantage of the anisotropy or to minimize support structures.
The process of FFF technology consists of building objects by depositing melted material layer-by-layer, using thermoplastic polymers as raw material.
The printer takes a filament of a thermoplastic material and pushes it to the print head using gears. The print head will melt the filament at an adequate temperature and will depose it through a nozzle along the XY-plane to create one layer. Once the layer has cooled down, the platform moves down the height of one layer and deposes the path of material to build the second layer. The process continues until the full model is completed.
In this stage, correct maintenance of the printer and accurate calibration are vital to produce high-resolution parts.
For most of the additive manufacturing technologies, it is required to post-process the printed parts in order to get them ready for use. However, in the case of FFF parts it is not always mandatory, and its main purpose would be to hide visible layer lines, to remove supports or to mitigate the anisotropic behaviour. Removing supports is the most important type of post-processing of the parts that have complex geometries. There are two types of supports:
- Standard supports, which are made with materials which are not dissolvable and have to be removed mechanically. They are printed faster than the dissolvable supports but do not generate a smooth surface finish.
- Dissolvable supports are removed introducing them into a bath of solvent. The most common solvable support materials are:
After support removal and depending on the material used for the print, there is a big range of post-processing techniques that can be applied to the part:
- Cold welding
- Gap filling
- Priming and painting
- Vapor smoothing
- Epoxy coating
- Metal plating
You can find a more detailed description of these techniques in our white paper.
After all steps have been completed, it will be necessary to test the part. Depending on the final application of the 3D printed piece, the functionality, the mechanical and/or chemical performance, the aesthetic or all of these characteristics will have to be validated through specific tests.
Implementing this workflow will help you with introducing FFF 3D printing in your business’s day-to-day processes in the simplest way, as it contains all the steps needed to 3D print a model, achieving the best possible results along the way.