In the modern world of experimental aviation, an individual designer/builder has access to a remarkable level of new precision technology that has become available within the past decade. We have come a long way from the era of paper plans and “band saw and file” fabrication techniques.
Two major technological advances are powerful CAD (computer-aided design) systems and numerically controlled fabrication. The combination of these two technologies is extremely powerful because it allows us to go directly from digitally modeling a design in CAD to the actual physical part without requiring a human with fabrication skills to interpret drawings and build the part.
Automated manufacturing systems fall into two broad categories. The first is numerically controlled machine tools and cutters that automate the traditional process of cutting parts out of pieces of stock material. They generate finished parts by starting with billet stock or sheet stock and cutting away material to produce a part. CNC milling machines and lathes for billet material, and laser and waterjet cutters for sheet material, all fall into this category. Automated cutters are in widespread use in many areas of manufacturing including the aerospace and kit airplane industries.
The second type of automated manufacturing is known as “additive manufacturing.” Additive manufacturing systems start with a material feedstock and build up a part by fusing the feedstock into shapes. There are a variety of additive manufacturing systems that use differing materials, forms of feedstock, and methods of fusing the material, but they all fall into the general category of “3D printing.”
High-end additive manufacturing is just starting to be adopted in the aerospace industry. Systems that produce additively made metallic parts are just reaching the stage where they can be used to produce safety-critical parts of vehicle structures and systems. Major engine manufacturers are now using 3D printing to make turbine blades and other components of jet engines. This level of additive manufacturing is not yet available to individuals or small companies because of the high cost of the equipment needed to produce flight-quality metal parts.
I was able to iterate this design several times within about two days to get to this working design.
The 3D printing available to individual builders has not yet reached the point where it can be trusted to fabricate structural components, but it is exceedingly useful in other ways. The 3D printers available to individuals at reasonable cost typically produce plastic parts by feeding material filament through a heated head that fuses layers of plastic together to build a part. Some people have had success with printing high-strength nylon or carbon-filled materials to produce useable final parts for low-stress, non-safety-critical applications. More typically, the physical properties (strength, thermal stability, etc.) of standard 3D printing filament materials (PLA, ABS, PETG) are insufficient for final-use parts.
Even though we cannot yet make most final-use parts with 3D printing, it is still very useful in other ways. I have been using 3D printing and CAD on my most recent project to aid in both the development of my design and in the building and assembly itself.
Parts Development
When developing a complex part or a part that needs to fit accurately with other parts, it is very helpful to be able to mock up the part to verify fit and develop the design without investing the labor and cost of actually fabricating multiple iterations of a complex part. 3D printing is extremely useful here because you can develop a preliminary design in the computer using CAD and then print a plastic test part that can be used to verify fit and test assembly.
This makes it possible to develop and iterate the design of a part relatively quickly and at low cost. We can go through multiple iterations until the plastic test part shows that the design is mature enough to fabricate the real metal or composite part. I have used this to good advantage on my current project to preview the design for machine parts before committing to fabricating the final parts.
Tooling
3D-printed parts can also be used as tooling. Having the ability to quickly make custom tools and templates fundamentally changes the builder’s mindset. While in the past, the question was, “What can I find to do this job?” or “How can I use standard tools to do this?” the question becomes, “What custom tool can I make to do exactly what I need for my specific problem?”
Measurement
One example of a custom tool made possible by 3D printing is this holder that lets me use my smartphone accurately as a digital level.
Virtually all smartphones these days have a built-in digital level that’s normally used simply to control the orientation of the screen. There are a variety of free or very low-cost apps that allow you to use your phone as a digital inclinometer or digital level. The problem with this is that most phones, particularly if they are in protective cases, do not have a clean indexing surface that allows you to measure reliably using the Level app. I developed a 3D printed fixture to solve that problem. It holds the phone accurately in a consistent position and has both a flat index surface and a built-in V block that lets me use my phone to accurately rig or level both flat items and tubes.
Material Forming Tools
While I have not personally used 3D-printed molds, I know of other experimenters who are 3D printing molds and forms that are then used to lay up composite parts. On my project, I have found it useful to make tooling to bend and shape sheet metal as shown in the following pictures.
The structure of my project has many spots where a sheet-metal gusset must wrap partially around a tube and fit snuggly over the tube outer surface. Bending the gusset involved clamping it onto a tube of the proper radius and then pulling and pounding on it until it fit. This was time-consuming and took a bit of effort each time to get a good fit. I solved that problem with this pair of tools that are used in a vice to bend the gussets to fit the outer radius of the tubes that they wrap around. The 3D-printed tooling allows me to get consistent, clean bends that match the outer radius of the tubes precisely.
The edge of a flat gusset riveted to a round tube protrudes, leaving an exposed edge. Sometimes this protruding edge is unacceptable, and it is necessary to curl the edge of a gusset to conform to the outer diameter of a tube so that the edge lies flush on the tube surface.
Curling the edges originally required me to pound them over a mandrel with a mallet to get the right shape. The 3D-printed tool set, used in a vise, curls the edges of the gussets to the proper radius quickly and precisely. The pins go through the rivet holes in the gusset to position it properly.
Hole Pattern Templates
I have also had considerable success making custom 3D-printed templates to accurately place and space fastener holes.
This custom-made hole template wraps around the tube and has an offset to fit cleanly over the plate. The V-notches in the ends mark the tube tangency centerline and the holes define an evenly spaced hole pattern for rivet holes.
Clamping and Alignment Tools
There are many instances where we need to clamp parts together and hold them precisely relative to each other to ensure an accurate assembly when assembling a structure. Custom 3D-printed alignment tools and clamps make it possible to assemble the structure accurately and are also valuable in distributing clamping loads to avoid damaging or distorting parts.
Here, for example, these two tubes needed to be held parallel to each other at a specific distance apart. These custom clamp blocks were easy to 3D print. They hold the tubes in precisely the right relation to each other. The full radius on each block holds the tubes in alignment and distributes the clamping loads uniformly into the tubes to avoid crushing or distorting them.
This is a nice article about using 3-D printing to build templates and fixtures for full scale aircraft construction. We also find that it is useful for building model aircraft parts like engine mounts and bell cranks for example, where the material properties are good enough. It can be a very good educational tool in an aviation STEM program.
Good article! As a 3D printing hobbyist and retired employee of industrial scale 3D printer manufacturer I’m a big fan but builders and pilots need to understand that there’s a giant difference between being able to print a part and that part actually being airworthy no matter how perfectly it is rendered by the printer.
I work with Barnaby to re-create some of his printed parts in aluminum for use on the actual aircraft. Anyone making printed parts should have such a relationship with a machinist or machining service so as to not be tempted to use a printed part in an inappropriate service. From a machining viewpoint having both a dimensioned drawing and a 3d plastic example is very useful towards getting the part that you want.