Blog 16: How does a 3D Printer work?

Introduction:

3D printing or additive manufacturing is a process of making three-dimensional solid objects from a digital file. In 3D Printing, an object is created by a 3D printer by laying down successive layers of material until the object is created. Each layer can be seen as a thinly sliced cross-section of the object. The 3D printer uses computer-aided design (CAD) to create three-dimensional objects through a layering method. 3D printer codes are generated using CAD software that gives the command to the 3D printer to print. These codes are known as GnM cods 3D printing involves layering material, like plastics, composites, or bio-materials to create objects that range in shape, size, rigidity, and color.

The term 3D printing covers a variety of processes and technologies that offer a full spectrum of capabilities for the production of parts and products in different materials. Essentially, what all of the processes and technologies have in common is the manner in which production is carried out layer by layer in an additive process which is in contrast to traditional methods of production involving restrictive methods or molding/ casting processes.

In the 1980s, 3D printing techniques were considered suitable only for the production of functional or aesthetic prototypes, and a more appropriate term for it at the time was rapid prototyping. As of 2019, the precision, repeatability, and material range of 3D printing have increased to the point that some 3D printing processes are considered viable as an industrial-production technology, whereby the term additive manufacturing can be used synonymously with 3D printing.

In the previous blog, we learned about Parts of a 3D Printer. In this blog, we will see how a 3D Printer work.

3D Printing Process

Layer Height

Layer height is the thickness of each 3D printed layer of an object. This can also be called the Z Resolution which is referring to the process of creating each layer as the print bed moves down to allows for another layer.

A smaller layer height yields better quality objects with stronger strength properties. This is due to better interlayer adhesion, reducing gaps and creating a smoother overall finish for the object. This is most apparent when printing curves, where you can see the stepping of the edges.

Smaller layer heights however require more printing time, therefore the selection showed have careful thought before the printing process begins.

Print Speed

Print speed refers the traveling speed of the extruders as they travel during the printing process. It is express in mm/s and also determines the print quality of an object. A balance must be met in terms of print speed when making adjustment before the printing process because it does affect other settings. For example, faster speed will require more temperature awareness since increasing the speed will usually reduce the quality of the print. As a side note, we must not confuse print speed with travel speed, which is the speed at which the extruders when not directing printing.

Software terms

Slicer

Slicing software is a category of 3D printing software that is used to convert a basic 3D computer object into something that the printer can understand and print accurately. There are various options of slicing software but they all work with the same output. They can take a 3D object, and convert the surface into miniature triangles, that come together to make the object. The amount of these triangles also determines the accuracy and detail of the 3D object that can be printed.  Within the application, you can get detailed controls about the printer, how to print the object, orientation, material settings, and all settings possible for the 3D printer.

After setting the desired parameters, the slicer software can then slice the 3D object into the desired layer height and visualize the printing process. When this is completed, the object file is then converted into G-code, which is a data type used in many manufacturing processes that stores information about how to print or in the case of a CNC machine, how to mill an object. This G-code is what drives the extruders in the 3D printer to accurately create the object.

Infill

Slicing software gives you the option to print a fully solid object, or a hollow one and everything in-between. This is accomplished by setting the infill amount. This is usually how the internal structure of an object is to be printed and the settings range from 5% infill to 100%. Furthermore, you get four main infill pattern types which are a honeycomb, wiggle, rectangle, and triangular.

Honeycomb offers the greatest strength with minimum material, and triangle offers better lateral load strength, which gives the outer shell of the object better strength to handle horizontal forces applied to the object. Wiggle is mainly used for flexible materials and rectangular doesn’t have any specific advantages.

Skirts and Brims

Brims, skirts, and rafts are parts that are used to create better bed adhesion for the 3D printed object before the printing process and to check that everything is set up correctly.

A skirt is an outline of the print area of the object but doesn’t directly touch the object. It is used as a primer, to check whether there is excess material in the nozzles, that they are calibrated correctly, and to ensure consistent material flow.

A brim is directly attached to the object, but goes a little further out and involves more outlines than the skirt. Its main purpose is to hold the object and to ensure the first layer is printed correctly.

Common Troubleshooting Terms

Warping

Warping can be described as the shrinkage of a 3D printed object at the corners of the base, mainly attributed to temperature changes. It is due to the process of non-uniform cooling where certain printing layers cool faster than the heated parts. When this occurs, the cooler layers end up distorting the geometry of the object since cooling causes shrinkage and this action affects the immediate molten layers. As the areas cool and harden, they pull on other layers as cooling increases. The main reason for warping is that heated thermoplastics need uniform cooling after being extruded to allow an object to accurately settle while maintaining the desired geometry. If the printing bed is not heated or the ambient temperature of the print chamber is not modulated then this leads to different cooling rates. To prevent warping issues, ensure that the FFF 3d printer has a heated bed with a metal plate. This distributes the heat throughout the bed and means a more uniform temperature distribution. This will minimize the effects of warping in the first layers of the object.

Cracking

Cracking is caused by the same issue as warping, being the non-uniform cooling of a printed object. The difference between cracking from warping is cracking occurs at different locations in the printed object. To offset the possibility of cracking, a printer with an enclosure allows eliminating the ambient temperature fluctuations that may occur that could lead to cracking of a 3D printed object.

A few Applications of 3D printer:

• Consumer products (eyewear, footwear, design, furniture)
• Industrial products (manufacturing tools, prototypes, functional end-use parts)
• Dental products
• Prosthetics
• Architectural scale models & maquettes
• Reconstructing fossils
• Replicating ancient artifacts
• Reconstructing evidence in forensic pathology
• Movie props

Advantages:

1. Flexible Design

3D printing allows for the design and printing of more complex designs than traditional manufacturing processes. More traditional processes have design restrictions that no longer apply with the use of 3D printing.

2. Rapid Prototyping

3D printing can manufacture parts within hours, which speeds up the processes. This allows for each stage to complete faster. When compared to machining prototypes, 3D printing is inexpensive and quicker at creating parts. As the part can be finished in hours, allowing for each design modification to be completed at a much more efficient rate.

3. Print on Demand

Print on demand is another advantage. As it doesn’t need a lot of space to stock inventory, unlike traditional manufacturing processes. This saves space and costs as there is no need to print in bulk unless required.

The 3D design files are all stored in a virtual library as they are printed using a 3D model as either a CAD or STL file, this means they can be located and printed when needed. Edits to designs can be made at very low costs by editing individual files without wastage of out-of-date inventory and investing in tools.

4. Strong and Lightweight Parts

The main 3D printing material used is plastic, although some metals can also be used for 3D printing. However, plastics offer advantages as they are lighter than their metal equivalents. This is particularly important in industries such as automotive and aerospace where lightweight parts have significant importance and can deliver greater fuel efficiency.

Also, parts can be created from tailored materials to provide specific properties such as heat resistance, higher strength, or water repellence.

5. Fast Design and Production

Depending on a part’s design and complexity, 3D printing can print objects within hours, which is much faster than molded or machined parts. It is not only the manufacturer of the part that can offer time savings through 3D printing but also the design process can be very quick by creating STL or CAD files ready to be printed.

6. Minimising Waste

The production of parts only requires the materials needed for the part itself, with little or no wastage as compared to alternative methods which are cut from large chunks of non-recyclable materials. Not only does the process save on resources but it also reduces the cost of the materials being used.

7. Cost Effective

As a single-step manufacturing process, 3D printing saves time and therefore costs associated with using different machines for manufacture. 3D printers can also be set up and left to get on with the job, meaning that there is no need for operators to be present the entire time. As mentioned above, this manufacturing process can also reduce costs on materials as it only uses the amount of material required for the part itself, with little or no wastage. While 3D printing equipment can be expensive to buy, you can even avoid this cost by outsourcing your project to a 3D printing service company.

8. Ease of Access

3D printers are becoming more and more accessible with more local service providers offering outsourcing services for manufacturing work. This saves time and doesn’t require expensive transport costs compared to more traditional manufacturing processes produced abroad in countries such as China.

9. Environmentally Friendly

As this technology reduces the amount of material wastage used this process is inherently environmentally friendly. However, the environmental benefits are extended when considering factors such as improved fuel efficiency from lightweight 3D printed parts.

10. Advanced Healthcare

3D printing is being used in the medical sector to help save lives by printing organs for the human body such as livers, kidneys, and hearts. Further advances and uses are being developed in the healthcare sector providing some of the biggest advances in using the technology.

Disadvantage:

1. Limited Materials

While 3D Printing can create items in a selection of plastics and metals the available selection of raw materials is not exhaustive. This is due to the fact that not all metals or plastics can be temperature controlled enough to allow 3D printing. In addition, many of these printable materials cannot be recycled and very few are food safe.

2. Restricted Build Size

3D printers currently have small print chambers which restrict the size of parts that can be printed. Anything bigger will need to be printed in separate parts and joined together after production. This can increase costs and time for larger parts due to the printer needing to print more parts before manual labor is used to join the parts together.

3. Post Processing

Although large parts require post-processing, as mentioned above, most 3D printed parts need some form of cleaning up to remove support material from the build and to smooth the surface to achieve the required finish. Post-processing methods used include water jetting, sanding, a chemical soak and rinse, air or heat drying, assembly, and others. The amount of post-processing required depends on factors including the size of the part being produced, the intended application, and the type of 3D printing technology used for production. So, while 3D printing allows for the fast production of parts, the speed of manufacture can be slowed by post-processing.

4. Large Volumes

3D printing is a static cost unlike more conventional techniques like injection molding, where large volumes may be more cost-effective to produce. While the initial investment for 3D printing may be lower than other manufacturing methods, once scaled up to produce large volumes for mass production, the cost per unit does not reduce as it would with injection molding.

5. Part Structure

With 3D printing (also known as Additive Manufacturing) parts are produced layer-by-layer. Although these layers adhere together it also means that they can delaminate under certain stresses or orientations. This problem is more significant when producing items using fused deposition modeling (FDM), while polyjet and multijet parts also tend to be more brittle. In certain cases, it may be better to use injection molding as it creates homogenous parts that will not separate and break.

6. Reduction in Manufacturing Jobs

Another disadvantage of 3D technology is the potential reduction in human labor since most of the production is automated and done by printers. However, many third-world countries rely on low-skill jobs to keep their economies running, and this technology could put these manufacturing jobs at risk by cutting out the need for production abroad.

7. Design Inaccuracies

Another potential problem with 3D printing is directly related to the type of machine or process used, with some printers having lower tolerances, meaning that the final parts may differ from the original design. This can be fixed in post-processing, but it must be considered that this will further increase the time and cost of production. 

8. Copyright Issues

As 3D printing is becoming more popular and accessible there is a greater possibility for people to create fake and counterfeit products and it will almost be impossible to tell the difference. This has evident issues around copyright as well as quality control.