3D Printers Buyers Guide

3D printing is a manufacturing process where successive layers of material are laid down on top of each other in an additive process. Although 3D printing is often spoken of as a new technology, it has actually been around for over 30 years. Around a decade ago, patents around 3D printing began to expire and it was opened up to mass audiences, with previously large industrial machines now being available in more compact desktop designs

This guide will take you through the technologies found in desktop models today, and how they may differ to make a certain type of 3D printer better suited to any given job. It is worth mentioning that although this group of devices share the name ‘printer’ with many paper based traditional printers, they have very little in common - more can be learnt about ‘regular' printers in our Printers Buyers Guide.

Why 3D Print?

Every 3D printer builds parts based on the same main principle: a CAD model is turned into a physical 3D object by adding material a layer at a time. This is where the term additive manufacturing comes from. 3D printing is a fundamentally different way of producing parts compared to traditional subtractive manufacturing such as CNC machining or formative manufacturing such as injection moulding. In 3D printing, no special tools are required (for example, a cutting tool with certain geometry or a mould). Instead the part is manufactured directly onto the built platform layer-by-layer, which leads to a unique set of advantages, but also some limitations.

Advantages

Cost effective complexity - 3D printing allows easy fabrication of complex shapes, many of which cannot be produced by any other manufacturing method. The additive nature of the technology means that geometric complexity does not come at a higher price.
Low barrier to entry - as 3D printing does not need any specialised tooling, there are essentially no start-up costs. The cost of a 3D printed part depends only on the amount of material used, the time it took the machine to print it and the post-processing required to achieve the desired finish.
Easy customisation - you only need to change the CAD model to create a custom part. So each and every item can be customised to meet a user's specific needs without impacting the manufacturing costs.
Low cost prototyping - new designs can be tested at a fraction of the cost of other processes and at speeds that no other manufacturing technology can compete with.
Large range of materials - from plastics to speciality materials with properties tailored for high heat resistance, high strength or stiffness and even be biocompatible.

Limitations

Lower strength- 3D printed parts have physical weaknesses since they are built layer-by-layer. They are more brittle in one direction by approximately 10% to 50%, so plastic 3D printed parts are most often used for non-critical functional applications.
Limited accuracy & tolerances - the accuracy of 3D printed parts depends on the process and the calibration of the machine. For example, if you design a hole with diameter of 10 mm, the true diameter after printing may be ± 0.5 mm.
More costly at higher volumes - 3D printing cannot compete with traditional manufacturing processes in large production runs. As start-up costs are low, prototypes and a small number of identical parts can be manufactured economically. However, this also means though that the unit price decreases only slightly at higher quantities, so economies of scale are negated.
Post processing requirement - printed parts are rarely ready to use off the printer. 3D printers cannot add material on thin air, so support structures are printed with the part to add material under an overhang or to anchor the printed part on the build platform. When removed, they often leave marks or blemishes on the surface of the part they came in contact with. These areas then need additional operations (sanding, smoothing or painting) to achieve a high-quality surface finish.

Uses of 3D Printers

Many industries have now adopted 3D printing within their business models to benefit from the factors we’ve mentioned above. Just a handful of these are listed here.

Architecture

Typically, architects can spend days creating physical models to explain their designs to clients. Using modern technology, they can use their existing CAD drawings to rapidly create a model and print it in 3D. Not only do they save time but complex geometries that can’t be modelled by hand can be produced efficiently and at a low cost.

Prosthetics

Affordable desktop 3D printers are being used to create custom prosthetics for children at a very low production cost. Being such a low-cost option benefits children in particular because they grow out of their prosthetics quickly. Additionally, 3D printing allows children to choose custom options for their prosthetics such as superhero designs.

Medical

One of the key benefits of 3D printing is the ability to customise objects at no extra cost. The medical sector is taking advantage of this in various ways and one prominent field is that of hearing aids. The process begins by taking a 3D scan of the patient’s ear, which ensures an accurate 3D print can be made that has a perfect fit for that specific patient.

Product Design

3D printing enables product and industrial designers to create prototypes within hours as opposed to weeks through traditional methods. The cost to create a prototype can be in excess of £10,000 when you consider the tooling required for processes like injection moulding. With 3D printing, prototypes can be achieved at a fraction of the cost.

Aerospace

3D printing for aerospace purposes allows complex geometries to be created with no waste material and no tooling required. This results in innovative functional parts and huge savings. Larger jet engines can now be produced that are more efficient, lighter and powerful due to its 3D printed components.

Home Use

Desktop 3D printers can now be acquired for well under £1,000, which has gained the interest of many hobbyists. One of the main benefits is unlimited spare parts without having to rely on external sources. Uses can easily improve their designs and create new and better concepts.

How 3D Printers Work

So now we’re familiar with what it is and how it can be used, let’s look at how it works in detail. The process always begins with a digital 3D model - the blueprint of the physical object. This model can be created in a 3D design software package, of which there are many on the market. Typically the 3D digital model is then saved in either an STL or OBJ file format. Some models will also support GIF, JPG and PNG file formats too. The 3D printer then has software that slices the 3D file into thin, 2-dimensional layers and then turned into a set of instructions in machine language (called G-code) for the printer to execute.

3D Model

Sliced Model

Printing

From here, the way a 3D printer works varies by the process it uses to make the physical model. There are many types of 3D printing processes - resin stereolithography, sheet lamination, material jetting, vat polymerisation to name a few, however these tend to be more industrial means. The common desktop method is a material extrusion technique commonly called Fused Deposition Modelling (FDM) or Fused Filament Fabrication (FFF).

In FDM or FFF printing, a spool of filament is loaded into the printer and then fed to the extrusion head, which is equipped with a heated nozzle. Once the nozzle reaches the desired temperature, a motor drives the filament through it, melting it. The printer moves the extrusion head, laying down melted material at precise locations, where it cools and solidifies (like a very precise hot-glue gun). When a layer is finished, the build platform moves down and the process repeats until the part is complete.

FDM or FFF printing is the most cost-effective way of producing custom thermoplastic parts and prototypes. It also has the shortest lead times due to the high availability of the technology. A wide range of thermoplastic materials is available for this technique, suitable for both prototyping and some functional applications. As for limitations, this technique has the lowest dimensional accuracy and resolution compared to the more industrial 3D printing technologies. Furthermore, as extruded parts are likely to have visible layer lines, post-processing is often required for a smooth surface finish.

Support removal is typically the first stage of post-processing for any 3D printing technologies that require a support to accurately produce parts. Support can generally be separated into two categories; standard and dissolvable. Standard support material can generally be removed from the print with little effort, and cleaning of support material in hard to reach places (like holes or hollows) can be achieved with dental picks and needle-nose pliers. Well placed support structures, and proper print orientation, can greatly reduce aesthetic impact of support material on the final print.

With a dissolvable support, the support materials will differ depending on the types of filament being used, but all are removed from a print by placing the print in a bath of solvent appropriate to the material until the support elements have dissolved. The part will then be finished using techniques such as sanding, polishing, priming and painting to achieve the finished article.

3D Printer Resolution

When 3D printing, the resolution refers to the quality, or level of detail, at which your part is created. In general, the printer’s movement on both the XY and Z planes determines how fine the resolution will be, with smaller movements typically yielding higher resolutions. Resolution numbers will be shown in microns whilst the nozzle diameter will be shown in millimetres (mm). The lower these two numbers are, the finer detail is possible.

XY Resolution

The XY resolution of a part occurs on the horizontal plane, which runs parallel to the printer’s build platform or bed. The XY resolution is defined by the smallest movement that a 3D printer’s print head can make on this plane. The print quality of the XY resolution depends on how fine the movements of the printer’s motors are as well as the diameter of the print nozzle. As these numerical values decrease, the resolution becomes finer, and smaller features are able to be defined. It is important to note that the XY resolution may never be finer than the diameter of the print head nozzle (some printers have interchangeable nozzle heads with varying diameters to offer more flexibility). A good analogy for XY resolution is DPI, or dots per inch. Digital screens are made up of a grid of thousands of pixels. The more pixels the screen has in one square inch, the more detail it can resolve. Similarly, the finer a 3D printer’s motor can turn, the more “dots” in can fit in a square inch, resulting in more detailed parts.

Z Resolution

The other part determining resolution is the Z resolution, which occurs on the vertical plane. This is more commonly referred to as layer thickness or layer height. When a 3D printer creates an object from a design file, it first slices the part into hundreds or thousands of cross sections with the thickness of each cross section being equal to the layer height. The shorter the layer height, the more layers there are per vertical inch and the higher the resolution of your parts.

These layers can be visible and may even make the surface appear rough, particularly for curved or diagonal faces. Because this visibility is more prominent than the XY resolution, many manufacturers refer to print resolution as only consisting of the Z plane measurement. For a higher Z resolution, layers must be made smaller so that it takes more layers to construct the entire part and finer details and transitions can be made. Doing so increases the build time of the print, but it can also create a smoother transition along the face of an object.

Minimum feature size is a term that refers to the smallest “dot” a printer can make. This is determined by the diameter of the nozzle on the 3D printer and the height of one layer. Regardless of how close or far apart these dots are, however, keep in mind that any features on your model that are smaller than an individual dot will not resolve correctly when printed. To produce finer features, a printer with a smaller minimum feature size will be required.

3D Printer Features

Now we’re familiar with the process of how 3D printing works, it's time to look at the features of 3D printers. Before you buy a 3D printer, it helps to know what you want to print. 3D printers are available in a multitude of sizes which will have a bearing on the objects you print, but additionally they may have different nozzle sizes, finer layer resolution and better axis adjustability

Footprint & Size

Desktop 3D printers come in a variety of sizes and clearly the size of the unit will restrict the size of the prints that can be made, so this is the first thing you should consider. A larger size model will allow for greater flexibility in what you can create both in length, height and overall volume. It is also worth mentioning that although a printer will have a physical platform or bed size, you may not be able to use the entirety of it depending on the software you are using to create your 3D model. It is worth checking compatibilities of these prior to purchase. The differences may only amount to a centimetre or less, but are worth knowing if you plan to print items that require the whole physical bed dimensions

3D Printer Filaments

As we’ve seen FDM / FFF 3D printers use spools of filament to produce the 3D designs. These filaments can be made from a wide variety of materials so let’s take a look at some of the most popular ones.

PLA

In the realm of consumer 3D printing, polylactic acid (PLA) is easily the most popular filament type. First and foremost, PLA is easy to print with, has a low printing temperature and it doesn’t warp easily, meaning it doesn’t require a heated bed (although it definitely helps). Another benefit of using PLA is that it doesn’t give off an odour during printing. Another appealing aspect of PLA is that it’s available in a nearly endless abundance of colours and styles. Finally, as a biodegradable thermoplastic, PLA is more environmentally friendly than most types of 3D printer filament, being made from annually renewable resources such as corn starch or sugar cane.

Strength: High | Flexibility: Low | Durability: Medium
Difficulty to use: Low
Print temperature: 180°C – 230°C
Print bed temperature: 20°C – 60°C (but not needed)
Shrinkage / warping: Minimal
Soluble: No

Although PLA filaments are suitable for most uses, compared to other types of 3D printer filament, it is brittle, so it is best to avoid using it when making items that might be bent, twisted, or dropped repeatedly, such as phone cases, high-wear toys, or tool handles. You should also avoid using it with items that need to withstand higher temperatures, as PLA tends to deform around temperatures of 60°C or higher. For all other applications, PLA makes for a good overall choice in 3D printer filament.

There are too many more options for filament material to cover every possibility in this guide. The wide range available includes polycarbonate (PC), polyvinyl alcohol (PVA), polypropylene (PP), carbon fibre, wood, ceramic and metal filaments. Plus ones with specific properties like conductivity, magnetism, and the ability to change colour with temperature or glow in the dark.

Ready to buy?

Browse our range of 3D printers:

3D PRINTERS 3D PRINTING FILAMENTS

Alternatively, if you have any further questions you’d like answering about 3D printers, don’t hesitate to call one of our friendly advisors on 01204 474747 or contact [email protected].