3D printer: How the best filaments work and what they are - simply explained

3D printing is becoming more and more popular. This article explains how a 3D printer works, which filaments you use to print impressive models and some practical tips.

How does a 3D printer work?

3D printers are like sand by the sea. Accordingly, there are various techniques for how the printer creates a model. Basically, however, all printers can be assigned to one of four different techniques.

• On the one hand there is stereolithography ("SL" or "SLA"). The printer has a bath in which there is liquid photopolymer. Photopolymers are plastics that harden when exposed to light. The printers usually work with acrylic, epoxy or vinyl ester resin. The resin is cured using a laser. There is a plateau in the photopolymer basin, which moves down a little after hardening one level (deeper into the bathroom). After the model has fully hardened, the plastics have high strength and chemical resistance. The advantage of this process is its accuracy: the printer can also print structures that are micrometer-sized. Unfortunately, stereolithography printers are currently still very expensive.
• Selective laser sintering ("SLS") is also known. To understand how it works, imagine a pipe in which a plateau is built again. The plateau is at the top at the beginning. First of all, a roller is used to distribute a plastic, a plastic-coated molding sand, a metal or ceramic powder on the plateau. A laser then drives over the plateau and heats certain points in the powder so that they combine and the first level of the object is created. The plateau then descends a bit and the process begins again. So an object can be built up piece by piece. What is practical here is that the rest of the material can act as a support material and - unlike stereolithography - no support structures have to be printed.
• In classic 3D printing, fused deposition modeling ("FDM"), liquid plastic is applied to a surface in layers using an extruder, which hardens immediately. Then the surface moves down a bit (or the extruder up) and the next layer is printed. The printers are relatively inexpensive and can be assembled yourself with some know-how. However, support material must be printed for objects with "overhang", ie objects that are significantly wider at the top than at the bottom. In addition, the printing accuracy is relatively imprecise compared to stereolithography. For hobbyists and those interested, however, this is exactly the right procedure.

What filaments are there?

With fused deposition modeling, you print with so-called filaments. These are rolls on which thermoplastic materials are wound in wire form. However, there are some differences depending on the type.

• Polylactides ("PLA") are most commonly used in printers. The plastic is mostly obtained from regenerative sources, such as corn starch. Nevertheless, it is not biodegradable. The plastic is food-safe and water-repellent due to its methyl group. It is also flame retardant and resistant to UV radiation for a long time. The biggest advantage, however, comes from printing: there is no unpleasant smell.
• Acrylonitrile-butadiene-styrene copolymer ("ABS") is also used very frequently. This plastic is one of the most widely used plastics in the world. It is particularly resistant to oils, greases and high temperatures. In contrast to PLA, ABS is significantly harder. However, you should not inhale the smell of this plastic when printing. Liability is a major problem when printing. While PLA adheres well to a heated glass plate, some types of ABS adhere very poorly despite the very hot heating bed and double-sided adhesive tape. However, very nice models can be created with ABS. After printing, the models usually have a matt color. However, if you place the model under a glass dome containing a cloth moistened with acetone, the model will become quite smooth after some time: ABS is soluble in acetone, methyl ethyl ketone or dichloromethane.
• Polyvinyl alcohol ("PVAL" or "PVOH"), which is produced by hydrolysis of polyvinyl acetate, is very practical for models with an overhang. The special thing about this plastic is that it is water-soluble. For example, in a 3D printer with two extruders, you can print a model with PLA, but the support structure with PVAL. However, this plastic is unsuitable as a filament for printing the actual model, since the water is absorbed from the air and the models will not last long.
• High Impact Polystyrene ("HIPS") is mostly used as a support material for ABS. This plastic has a high impact resistance and hardness, but can be dissolved by limonene, which can be found in lemon oil, for example.
• Printing with PLA compounds is particularly exclusive. This is a mixture of PLA and particles from other substances. So you can also print with wood or copper, for example.
• Polycarbonates ("PC") are rarely used in printing. The advantage here is the very high melting temperature of 270 ° C to 300 ° C. This plastic also has high impact resistance and heat resistance.
• If you want to print gears or screws that have to endure strong forces and must not break, polyhexamethylene adipic acid amine, also known as "nylon" or "PA", is recommended.
• "Elastic" or "Flex" filaments, which are usually composed of different materials, can often be found on the Internet. The biggest advantage here is flexibility. This allows you to print flexible and rubbery models. As a rule, thermoplastic elastomers based on urethane ("TPU") are used as the main component.
• You can also print cups and plates. For this you need food-safe plastic. In addition to PLA, there is also polypropylene ("PP"), which is also slightly flexible. A food-safe combination of PLA and ABS is PETG, which is also easy to print and is very weather-resistant.

How does a printing process work?

First you create a 3D model with a CAD program and save it as an STL file.

• This STL file is then loaded into a slicing program, such as Cura or Slic3r.
• In the slicing program, you have the option of setting the properties of the model, such as the fill density or the use of support structures.
• The program then converts the 3D model into a G code. This contains all positions that the extruder should move to one after the other. In the meantime, the filament is extruded, creating a haptic model.

In the next practical tip we will give you an introduction to the CAD program "Solid Edge", with which you can create many practical 3D models.