Overview of 3D printing

Dirk Zacharias | 17. September 2019

3D printing is also known as additive manufacturing, rapid prototyping, rapid manufacturing or generative manufacturing. A component from a 3D printer is usually made in the same way. The material is applied layer by layer until the component has been completed. However, the manufacturing process varies depending on the individual 3D printing procedure used. The layers can be applied and joined together in that the layers are melted on top of each other, polymerised with UV light or bonded together by means of bonding agents.

In 3D printing, a 3D model in the form of a CAD file is used as the basis for the manufacture of a component. 3D printing is often used for the manufacture of prototypes, small volumes, special parts or replacement parts. There are 3D printers that are used to process different materials such as ceramic, concrete, food and so on. Which material and printer are selected depends on what the component is to be used for.

The different 3D printing methods

Different 3D printing procedures are used in additive manufacturing, depending on the type of component and the application for which it is to be used. Here, we would like to look at the most common 3D printing procedures.

Fused Deposition Modelling (FDM)

In the case of Fused Deposition Modelling (FDM), material that can be melted such as plastic is used and this is why it is also called the fused deposition modelling method. The plastic is heated until it almost reaches the liquid state. The plastic is then pressed through a fine nozzle to produce a thin thread. The thread is sprayed onto a surface in layers to gradually create the three-dimensional component. For FDM, different plastics can be used, depending on the application in which the component is to be used. FDM is frequently used in prototyping, medical technology, the automotive industry, aerospace engineering and for components used in complex testing procedures.

Selective Laser Sintering (SLS)

In the case of Selective Laser Sintering (SLS) the printer usually has three chambers. Two of these chambers each contain a moving platform, which move vertically in the opposite direction to the one in the other chamber. The material is kept in the first chamber and pushed into a second chamber by a roller. A laser melts or sinters the powder material at the desired position in the second chamber. After this layer has set, the platform in the first chamber moves upwards and the platform in the left-hand chamber moves downwards. The process then starts again. The surplus material is pushed into the third chamber. SLS is used for functional prototypes and end products. A great advantage of selective laser sintering is the complete design freedom.

Multijet Modelling (MJM)

In Multijet Modelling (MJM), also called the inkjet or Polyjet method, photopolymer (synthetic resin) is applied layer by layer and hardened with the help of UV light. For this purpose, two print heads that work in a similar way to an inkjet printer are used. Construction material and supporting material are applied alternately. The contours of the component are gradually sprayed onto the construction platform, whereby the component is hardened layer by layer as a result of exposure to the UV light. Additional supporting elements are built in order to enable the construction of protruding sections. With this printing technique, highly detailed objects with a smooth surface can be printed. Afterwards, the supporting material is completely removed. Due to the possible details on the component, polygraphy is being used with increasing frequency in the following areas:

•            Prototype construction

•            Medical technology

•            Models with thin walls

•            Model making

•            Electrical engineering

•            Precise mould and casting templates

•            Models with a delicate design

print2mold (P2M)

The print2mold method is an efficient combination of two manufacturing methods: 3D printing and injection moulding. With 3D printing, the tool for injection moulding that is printed is made of plastic or metal. The advantage of making the injection moulding tool with the 3D printed method is that it can be made considerably faster and complicated designs and details can be implemented more easily than if milling or electrical discharge machining is used to make the tool. Injection moulding is then used to make the actual component with the help of the 3D printed tool.

The print2mold method is especially useful if the prototype is to be made from the material already planned for large volume production of the component. Manufacturing with the 3D printing method would only be worthwhile up to a certain quantity and, in addition, the range of possible materials is limited compared to injection moulding. An injection mould can be made from plastic or metal with the 3D printing method, depending on the quantity, the complexity and the material needed. The advantages of additive manufacturing and injection moulding are optimally combined with each other.

The advantages of print2mold:

• the injection moulding tool can be delivered in 1 to 3 days
• free choice of material for the manufacture of prototypes or small volumes
• fine details are possible
• complex structures in the tool can be implemented by means of 3D printing
• up to 80% more cost-effective than milling or electrical discharge machining
• changes can be made to the final component due to very low costs for a newly printed tool

Selective Laser Melting (SLM)

The Selective Laser Melting (SLM) process is only used for the production of metal components. It is an additive procedure whereby the component is gradually built up with metal powder. This powder is melted at the desired position by a laser. It is a cost-effective method as a lot of material is saved and no additional tool mould is needed. SLM can be used to make complex workpieces with complicated inner geometries in one production step. Although the manufacturing time is short, the workpiece is very strong. Prototypes and medium-sized volumes can be fabricated quickly and cost-effectively. Selective laser melting is used where components are quickly needed and flexibility is required. In the case of selective laser melting, different materials can be pressed into the component in one working step. In the case of components subjected to thermal stress, copper conductors or interior cooling channels can be integrated in the component for better heat dissipation but this is not so easy in the case of manufacturing methods involving milling or electrical discharge machining.

Stereolithography

For Stereolithography (SLA), a plastic, consisting of photopolymers such as synthetic or epoxy resin, is used. A thin layer of plastic that hardens when exposed to light is gradually hardened by means of a laser. The workpiece is fabricated in a liquid bath filled with base monomers, with which a wiper applies a layer over the previous one. Moving mirrors control the laser so that it moves over the surfaces after a layer has been applied, hardening each layer before the next one is applied. The construction platform is lowered by a few millimetres after hardening and moved back to the position that is one layer thickness below the layer. In this way, the component is manufactured step by step. The component needs supporting structures in the liquid plastic bath as otherwise it would float away during the fabrication process. These support structures are made of the same material in the form of small columns and are removed mechanically after completion.

Development of the 3D printing market

Additive manufacturing methods are being used with increasing frequency in industry. The advantages such as speed and individuality, coupled with optimisation of the printing quality and the large variety of materials that can be used, are ensuring rapid growth of the market.

3D printing method according to material and manufacturing technique

Longer service life, maintenance-free and clean

igus only uses tribologically-optimised iglidur polymers that exhibit an especially low degree of wear and have a service life that is up to 50 times longer in moving applications than standard 3D printing materials. The results from the igus test laboratory confirm that the 3D printed components have wear characteristics that are comparable to those of our plastic parts made of iglidur material with the injection moulding method. Due to the use of iglidur polymers, the 3D printed components are maintenance-free, characterised by low friction and are ideal for moving applications.

Apart from the high quality and the possibility of using 3D printed components directly in an application environment, igus online tools provide customers with an easy way of making and procuring low-wear polymer parts.

The advantages of iglidur polymers in 3D printing:

• Service life up to 50 times longer than standard 3D printing materials
• Wear levels comparable to those of iglidur injection moulded parts
• Specially for moving applications
• Fast and cost-effective fabrication
• Short delivery times
• High degree of individualisation
• Easy manufacture of filigree models
• No tool costs or set-up costs

You can find out more about igus 3D printing here.

You can find out more about 3D printing and frequently asked questions here.