What does it take to design a part for 3D printing?

5 May 2022

3D printing technology can give the impression of disturbingly advanced, taken straight out of a sci-fi movie. Parts are being created out of thin air, layer by layer. Designing such components must therefore be very complicated and advanced, right?

Actually, not at all.

The design stage of 3D printing is basically analogous to the process of creating elements for CNC machines. In both cases, a virtual model of the part is necessary (prior to its production), with adequately defined geometry.

The difference between the two methods involves an additional, intermediate step, in the case of 3D printing. For the machine to read the model correctly, it requires software that cuts the geometry into planes and plans the layering. We call such a program a “slicer.”

We lay it down as a side note, because the “slicer” is an intermediary tool and does not really affect the process of designing the part.
So what actually influences the designing process the most? It mostly depends on what’s the starting point.

Re-creation project – reverse engineering

This is the classic scenario of reverse engineering, in which we rely on the original element, its mirror version (e.g., right and left car mirrors), or 2D technical documentation. We can call it a re-creation project.

Most straightforward elements can be recreated based on several key dimensions such as width, height and depth, hole locations and their diameters, etc. (e.g., shafts, bushings). So, here to create a design, all you need is a classic tape measure and a caliper. For greater accuracy, we can additionally use a feeler gauge or micrometer.

f you have photos or technical drawings of your part, it certainly does not hurt to provide such documentation to your contractor.

Much more often, however, the geometry of parts is so complicated that it requires special treatment.

Fortunately, 3D scanners come to the rescue. With their help, we can collect information about the surface geometry of those difficult elements. As a result, we obtain a cloud of the most critical points, which in the further processing stage are processed by the engineer into a virtual version of the object.

Creative project – work from scratch

If you start with a concept and don’t have the original, physical part, then the elements that will ultimately be connected to it (of course, only if there are any) will be instrumental. Model examples are electronic components, plugs, displays, standard fixtures, etc. (usually, solid CAD models of these components will suffice).

It’s super important to remember that the precision of fitting together such coexisting components often plays a key role! Therefore the tolerances of the contact surface must be determined right at the design stage.

It is easy to notice at this point that without the exemplary part, things get a bit more complicated. Based on our experience, we know that for the best possible result, it is worth preparing some assisting materials. It may be a graphic artist’s vision (which is not always feasible 1 to 1 in 3D printing), an overview model made of plasticine, or photos and graphics that will serve as inspiration and guidance on what effects we expect.

This is a unique design case where the customer needs to modify an existing part or add some element to the existing structure. We are then talking about a mixed project, i.e., work that begins with the re-creation stage – scanning the original detail or structure to get key geometries as a reference point. Then it turns into a creative project when we develop modifications desired by the client or add a cooperating element.

As seen from the three main categories described above, the starting point determines the amount and type of work.

But who will do it?

Your own design team

The most important suggestion that we can give to clients with their own design team (but with no experience in modeling parts for 3D printing) is about the very nature of this method. The material is not being removed here (like in sculpturing) but is gradually added – a bit like in clay molding. We repeat it like a mantra in almost every article to make our readers aware of this important aspect of 3D printing. Changing the way of thinking (from subtractive to additive manufacturing) will reveal new paths for designers and broaden design possibilities.

The limitations associated with subtractive production disappear, which allows for virtually any shape of elements in space.

In addition to this fundamental principle, we will share a series of practical tips and advice to follow when designing your parts:
  • Software – the right CAD program is the basis. At CubicInch, we use AutoDesk’s Inventor, but products such as Fusion 360, Solidworks, and FreeCad are also noteworthy.
  • Limits – this is quite obvious but still worth recalling. When designing a part, keep in mind the limitations of the machine. Make sure what dimensions the printing chamber has and what are the limits of the technology used by your contractor.
  • Holes – especially those located in the frontal plane, are quite a challenge for 3D printers and are more susceptible to deformation. You can overcome this effect by properly rotating the element before printing it. However, if your detail has holes in different planes, you should choose which of them are the most important for you
  • Tolerances – printed items are often part of machines or larger structures, so knowing the printer’s accuracy is very important. In the case of the MJF that we use, the producer declares +/- 0.03% (minimum +/- 0.3 mm for every 10 cm). Therefore, at the maximum dimensions allowed by the machine (approx. 30 cm), the accuracy is somewhere around +/- 1 mm. However, we make every effort to keep the machine calibration at the highest level.
  • Edges – Avoid sharp edges and corners. CAD programs have the function of smoothening the edges. So it’s a matter of a few clicks to get rid of any hard-to-finish geometries. Moreover, for CNC machining, the concave fillets result from the tool used, and the convex fillets are challenging to produce. In 3D printing (MJF), the curves are not a problem. However, they add attractiveness to your elements and are more pleasant to touch.
  • Threads – it is worth remembering that 3D printing technology allows you to make threaded connections. This opens up many possibilities and applications for designers and constructors. Depending on the application, we recommend modeling and printing the thread cut starting with size M4 (in MJF technology). For more demanding connections, it is worth considering threaded inserts.
  • Injection technology – if the parts you design are ultimately made in injection technology, remember about the limitations of this method – e.g., spatial structures that are empty inside or appropriate wall inclinations. Let your constructor know that the target technology will be injection, so that the final model prepared for 3D printing does not require tedious modifications.

    CubicInch engineers for the rescue!

    If you don’t have a team of designers on your side, don’t worry. At Cubic Inch, we offer a complete design package. Our engineers have the right tools and skills to take care of your case “from A to Z.”

    Regardless of your starting point, whether creative or re-creation work – we will help you prepare the necessary technical documentation and create a 3D model. Before launching the project, we will send You the visualization for approval, and using the FEM analysis, we will perform the necessary strength tests (if required). In short, we will bring your ideas into reality.

    Because it all starts with an idea!