Modelling guide for 3D printing

Before carrying out the 3D printing process, it is necessary to face the modelling phase of the object, a process with its own challenges.
July 19, 2022/ Glancing EYE Staff
Additive manufacturing is part of the innovations that, in recent years, have increased their demand and acceptance. This technology offers numerous advantages, such as the reduction of the time spent on the production of a product, as well as the associated cost. However, to obtain quality results, it is necessary to have a digital model that serves as a base. In this sense, modelling for 3D printing is a support specialty with its own challenges. In the modelling or design phase, the requirements to be fulfilled in order to obtain a functional prototype or a high-quality final product are determined. Furthermore, since there are different forms of manufacturing or processes to follow during 3D printing, with FDM, SLA and SLS being the most common; it is necessary to choose the most convenient in each case.

Modelling for 3D printing

3D printing can help us bring our ideas to life. In order to fully exploit the potential of rapid prototyping or product creation, it is necessary to have high-quality 3D models. These models can be designed using a computer-aided design (CAD) software application. These type of applications are used in the design and modelling of products. It is true that the basic principles of 3D modelling in all design verticals remain the same, but there are some aspects of design that must be taken into account when modelling for 3D printing. In this case, the requirements are slightly different from 3D modelling for rendering. For this reason, our experts have developed a guide of good design practices to achieve perfection and precision in the 3D printing of prototypes or products.

Minimum wall thickness

The minimum wall thickness is defined as the minimum required thickness that the model must have at a given point. The minimum thickness of the printable wall depends on the printing technology and material chosen. It is advisable to carefully read the design guides for the corresponding material. It is worth remembering that in some cases the maximum wall thickness can also cause problems. You have to understand how to assign the wall thickness for each surface of the 3D model. This step can be a bit different in each 3D modelling software. We must visualize, analyze and think about the design. If you have weaker sections, it may be a good idea to add design elements to support and reinforce them. Additionally, we have to consider how the size of the object will influence the required wall thickness.

Printing material guidelines

Every print material is different. Materials can be brittle or strong, flexible or solid, smooth or rough, heavy or light, etc. Ideally, an object should be designed for a specific material. For example, if we want to print a 3D model in ceramic, there are specific design recommendations related to the material that we must take into account, such as supporting the protruding parts, rounding the corners, etc. The choice of print material only predetermines some of the basic design guidelines to follow. Some materials have good strength and toughness and therefore thin walls can be made from that material. However, for other materials like ABS, the walls need to be thick to prevent post-print cracking and tearing. Thus, the designer must structure the models according to the properties of the material to be printed. It also helps if technical staff on the team guide the designer through the real drawing/developing process.

Design to avoid or minimize supports

Although support algorithms are improving all the time, support material can leave unsightly and unwanted marks on the outer surface of prints. Removing the support material can also be time consuming. To avoid this, it is better to design the models to be 3D printable without support. Apply the 45 degree rule: if the overhangs exceed 45 degrees, they will need support material. Clever modelling tricks can be used to print the model. Create support/bridge objects (cones and other supports) by adding them to the model. Always try to integrate supports into the core design.
There are a few design aspects that need to be considered when modelling for 3D printing.

The model must be watertight

The model must be completely closed or watertight, as it is more commonly expressed. It is possible to achieve this by adding a 3D mesh suitable for 3D printing. The option to create meshes is readily available in most 3D design software applications. This process should be done before exporting the model as an STL file, as problem areas can be difficult to detect and fix once the model has been converted. This problem can also occur during the translation of files from one modelling system to another.

STL file resolution

For 3D printing, the most common file format is Standard Triangle Language (STL). In simple words, the design will be translated into triangles in 3D space. Most 3D modelling software applications have the option to export the designs to an STL file and set the desired resolution. Resolutions that are too low or too high can cause problems when modelling for 3D printing:
  • Low resolution STL file: It is important to note that a poor quality export will never deliver a good print. Low resolution means that the triangles in the STL file are large and the print surface will not be smooth. Like digital images, lower resolutions lead to a “pixelated” print.
  • STL file with resolution too high: A file with a high resolution will make the file too large and adds challenges during printing. Since it contains a higher level of detail, it will take a long time to print and some 3D printers may not be able to print it. It is best to try to keep the file size under 15 MB before uploading the model.

Printing technology limitations

The basic chemical characteristics of impression materials are different. Therefore, the technologies used to print each of these materials are also different. The best example of this is the interlocking pieces. On materials such as ABS, polyamide or rubber-like, interlocking parts can be printed. While in other materials such as gold, silver, bronze or resin, interlocking may not be possible. The reason behind this is not the material itself, but the technology that is used to print each of these materials.

Build a solid base

With typical desktop 3D printers, the model is printed layer by layer. Plastic printing filament (typically PLA or ABS) is melted and extruded onto a surface, known as a bed. It is essential that this first layer adhere to the bed during the print duration. Many times, prints fail during the first layer, due to lack of adhesion. Make sure you have a strong enough base designed into the model. This will ensure that the 3D printed models are strong, robust and durable. Make sure the base has the following characteristics:
  • Enough surface area to create a positive bond to the printer bed. Adding a raft in your printing software application can also help with this.
  • A base wide enough to support the model and prevent it from tipping over during the printing process.
  • A model base that is strong enough to resist deformation caused by different cooling rates.

Thicken the vulnerable areas

Extended model core appendages may break during or after printing if the contact point or bond is too thin. The areas where the thinner parts connect to the main body need additional thickness. During the production process, some materials are very delicate to print and can break during handling or cleaning. In some cases, an air blast is used to remove any support material.

Talk to an expert.-

To be at the forefront it is not necessary to develop at all levels, but rather to create good relationships with third parties. Our 3D Modelling experts can produce quality 3D Printing-ready files based on your specific needs. Contact us.
To be at the forefront it is not necessary to develop at all levels, but rather to create good relationships with third parties. Our 3D Modelling experts can produce quality 3D Printing-ready files based on your specific needs. Contact us.

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