3D printing for repair: in practice

This article was written as part of the RE.FAB TOUR project, funded by the Walloon Region. Stay tuned for regular articles on 3D printing for repair. Find the whole series here, as well as resources for further study and training!

3D printing: the basics

First of all, the hardware: you’ll need access to a 3D printer (in a fablab, for example), filaments (the material that will be printed), and a computer with some specific software. In this article, we’re talking primarily about FDM or fused filament deposition technology. This is the most accessible technology, and can be used for a wide range of repairs. To repair or redesign a part, you’ll also need tools to disassemble and measure the part to be reproduced.

The 3D printing process itself is relatively straightforward. In three main steps, you can go from a digital 3D model of your part to a physical object.

The main steps in 3D printing.

1. First of all, you need a 3D model of the part you want to print. This model can either be redesigned using design software (see our tips on this page), or retrieved online, directly from the manufacturer or via a part-sharing platform. The ready-to-print 3D file is an .stl file. If we make the analogy with a paper printer, this corresponds to the .pdf file you wish to print.
2. The next step is to prepare this part for printing. This requires a second piece of software called slicer. The aim of this software is to transform the .stl file into a .gcode file that can be understood by the 3D printer. This file contains all the machine instructions that the 3D printer will follow. It’s at this stage that you’ll need to define the various printing parameters, such as the printer used and the material chosen, which strongly influence the quality of the printed part. Continuing our analogy, the cutting software corresponds to the dialog box that appears when you click on print your pdf document.
3. Finally, it’s just a matter of launching the print itself. As with paper printing, if you haven’t made any mistakes in the previous steps, this is the easiest part!

From 3D printing to repair

Once you know how to print in 3D, it’s only a short step to knowing how to repair using 3D printing. To this end, as part of the Sharepair project in which Repair Together participated, TUDelft has developed a methodology, published in a guide that we have translated.

Repairing with 3D printing: the 3DP4R methodology.

First and foremost, and as with any repair, you need to understand where the fault comes from. Which part has failed, and more importantly, why? If you don’t understand the cause, there’s a good chance that it will happen again, even with the best repair intentions!

1. The first step before embarking on design is to analyze the part in more detail. The main question to ask here is: “Can my part be repaired using 3D printing?”. The process for answering this question has been detailed in another article. If the answer to this question is yes, the analysis of the part can continue. This analysis will enable us to understand in greater detail what role the part plays in the failed object, what parts it interacts with, what mechanical functions it performs, etc. Understanding the part and the reasons for the failure is essential to the success of the rest of the repair.
2. At this stage, we’re ready to get to the heart of the repair. This second stage is in fact the most specific to the repair and the most essential in determining whether or not the repair will be successful. It involves preparing the 3D model to be printed. There are two ways to do this: either redesign the part, or retrieve it online. The best practice is to start by looking at whether the second solution is possible. There’s no point in reinventing the wheel if a model already exists. However, there are limits to this solution (detailed in another article). The other solution is to redesign the part from scratch. If there’s one thing you need to know at this stage, it’s that redesigning is not the same as copying. Indeed, if a part has broken, it’s probably because it was fragile. What’s more, the original part was generally made using a different manufacturing method and different materials. It will therefore be necessary to adapt the design to match the new constraints of 3D printing. In concrete terms, this generally involves reinforcing the part, and often simplifying it.
3. When it comes to the actual manufacturing stage, there are few specificities linked to the fact that the part is intended for repair. As with all 3D printing, it’s a question of determining the right printing parameters, such as the printing direction, so that the part meets expectations.
4. Finally, once the part has been printed, it still needs to be tested. The part often has a mechanical function or interacts with other parts, and we need to make sure that it fulfills its function.

Ready for a successful repair using 3D printing?

A golden rule is that the first impression is rarely the right one. The key word is: iterate, iterate, iterate! Most of the time, you’ll need to adjust one dimension or another, correct one defect or another, or adapt the print parameters, which will require a few tests and prints.

So just because you know how to print in 3D doesn’t mean you’ll be able to make a repair using the same technique. Nor should we forget to ask ourselves the question of the relevance of using this technology for repair. Sometimes, a spot of glue will do the trick! To find out more about how to repair with 3D printing, take a look at the resources in our directory, our dedicated tutorial, or our upcoming training courses.