Design4Repair

People often throw away their electrical household appliances when they are still repairable. The amount of electronic waste could be reduced significantly as some appliances may only need a replacement part.

With the advances in 3D printing technology, this technique can be used to prolong the lifespan of these products.

However, not everyone has had experience with using CAD and 3D printing, therefore this instructable provides most of the basics and general information you would want to know before starting with product repair and designing your own product parts.

In addition we have developed four different design strategies. They can be found under Step 6, which you can navigate to when you feel confident enough to continue!

You can click the hyperlinks of each strategy to find the instructables. This guide contains the common aspects which are shared between the different strategies instructables and the preparation required.

However, certain guides have slightly more specific requirements so do be aware of this too.

Supplies

Each supply type or point of attention will be assigned its own step in this instructable.

This instructable ends with a step that explains how to find which strategy to use for your project, so that you can immediately start your design process after reading through the basics on this page!

Step 1: 3D Printer

Access to a 3D printer is a must, preferably owning one yourself, because the strategies will probably require multiple iterations. Every 3D printer has different specifications. Before following one of the strategy guides make sure that: 

• The bed size is big enough and tall enough for the part you want to print (you can split up a print into parts, however, this may lead to a weaker part, more modelling work and/or further post-processing).
• You take the required preparation steps for your printer in case you are using a different material than PLA, e.g. adding a heat chamber or a direct drive. Do some research to the filament your are using in advance to make sure you will be able to produce some good quality parts!
• Your printer is calibrated and can print accurately. (Put your printer to the test!)

If you do not own a 3D printer there are two options to be able to print anyway:

• The first option is to ask if anyone around you has access to a 3D printer which you can use.
• If you do not know anyone with a 3D printer, you can go to a print service with your 3Dmodel/design. This option however does cost more money, since you would have to pay for both material, service and likely postage.

Step 2: 3D Printer Filament

Most parts can be replaced or repaired using regular PLA but other materials could be considered if:

• Your design could include snap-fits, in which case ABS may be beneficial, since it has lower stiffness.
• If the part you are designing should be flexible, you could also consider using TPU.

Please note that both ABS and TPU require specific conditions for good printing results. Lastly, if you want to use multiple materials in one print/part, keep in mind that different types of filament sometimes cannot be combined in the same print, since some materials will not adhere to each other.

Check whether the materials you want to use can be printed on top of each other here.

Depending on what the product comes into contact with, different factors need to be considered. If the part comes into great contact with heat and corrosive liquids, 3D printing is likely to not be suitable.

Step 3: CAD/3D Modelling Program

CAD Software

Most CAD programs can be used for creating a replacement part, so in general use any CAD software you feel comfortable with.

The most important thing for any program you use is the ability to use exact dimensions to create geometry.

If you are going to follow the Parametric Design strategy, you will need to use a program in which you can properly link variables together, such as Rhino Grasshopper or openSCAD.

Suggestions of CAD programs to use:

• TinkerCAD
• TinkerCAD is an online CAD software which is more simple, giving users access to use a shape library which they can use to build an object.
• Would work for simple parts that need to be replicated.
• Many tutorials available online, for example.
• Register and access TinkerCAD here.
• Fusion360
• Fusion360 is a CAD software that can be used for 'freeform, parametric, sheet meta, direct, surface and mesh design.'
• There are many tutorials online on how to use Fusion360 if you are a beginner. Such as this video.
• Register and download a free trial of Fusion360 here.
• OpenSCAD
• OpenSCAD was used for the parametric designs in this set of instructables.
• OpenSCAD may seem quite complicated at the start, however by being open source it is accessible for many.
• OpenSCAD provides a user manual as well as tutorials on WIKIBOOKS which are in depth and easy to follow in multiple languages.
• Download OpenSCAD here.

Most of the parts in this instructable series were made using openSCAD and/or SOLIDWORKS.

Basic knowledge of how to use the CAD program is also required, and basic, easy to follow tutorials can be found online.

Slicers

In addition to the CAD program, you will also need a slicer software. This program will convert the model that you make into a printable file for the 3D printer. There is usually a specific slicer that is recommended for the 3D printer that you have.

The most commonly used, free slicers are:

• Ultimaker CURA
• Prusa slicer

Most of the parts in this instructable series were sliced using Ultimaker CURA.

Step 4: Tolerancing

With directly replacing a part it is very important to consider the tolerances between that part and any that it interacts with.

The tolerances you need for your prints will depend on several things, such as:

• The print settings you are using in your slicer software.
• The type of part you are creating.

For example, parts that have a tight fit have a much smaller tolerance compared to parts that are able to move.

Please refer to this guide to learn about tolerances.

Test the tolerances of your printer using this video.

Some tolerancing rules

• In general, the starting point for tolerances in these repair projects would be around 0.2-0.4mm, to get parts to fit.
• The tolerance needs to be applied to each edge of your part, that will be touching another part. For a tolerance of 0.3mm this means that for one cylinder to fit over the other, there should be at least 0.3mm between the outer surface of the inner cylinder and the inner surface of the outer cylinder. This means that on a radius, the tolerance is 0.3mm. When these tubes are given a square profile instead, there should be 0.3mm between either side of the squares, meaning that in height and with, or, 'across the diameter', the tolerance should be 2 times 0.3 = 0.6mm.
• If you want to test the tolerances with your own 3D printer and slicing settings, you can create some easy test prints by modelling small shapes that fit into each other like a puzzle, or in a way that resembles the part you are working on. In addition you can find files on Thingiverse.
• If you feel like your print almost fits and a new iteration will take a lot of time to adjust, you can try using the boiling water trick. It may help to hold your printed model in boiling water for 5 to 10 seconds before immediately trying to get it in place again. The boiling water will soften the plastic a bit, giving you the opportunity to push the part in place before the plastic hardens again. Be careful if you do this with small parts and use pliers and gloves accordingly!

Step 5: (dis)assembly Tools and Measurement Tools

Measuring tools

Depending on the shape of your part you may require a variety of measuring tools. We recommend a set of (digital) callipers for accuracy, however other measuring tools like rulers or protractors may be helpful as well.

Sometimes parts can be hard to measure with standard measuring tools, but not all hope is lost, since 3D printing allows you to create your own measuring tools, see step 2-4 of this guide.

At last there is also the option to use 3D scanning, but we advise to only do that if you have no other choice because it is less accurate and requires additional software and processing. (This instructable goes into detail of the 3D scanning process.)

(Dis)assembly tools

In addition, if disassembly is required, then tools such as screwdrivers, pliers and wrenches may be required. When disassembling, make sure to organise all of the parts well and keep all screws/nuts/bolts safe. It might also be useful to take pictures during the disassembly process to help you re-assemble the product once you are done replacing your part.

We recommend recording the disassembly so you have a video to help you put everything back together again.

Step 6: Finding the Most Suitable Strategy for Your Repair Project

Now that you are aware of the most common things in design for repair, it is time to find the best strategy for your project!

To know which strategy is the most suitable for designing your repair part, you can follow this flowchart.

After going through multiple questions in the flowchart it provides you advice of which strategy of the four is most suitable for repairing your broken part.

If you would like to look at each strategy yourself, here are the links to each one of them:

• Simplifying
• Recreating the part but reducing detail and optimising it for 3D printing.
• Universal Design
• Creating a new part that is based on the dimensions available.
• Partial Repair
• Designing an insert to fill a gap/hole or to reinforce a part.
• Parametric Design
• Creating adapters where specific dimensions can be changed to fit different parts from different brands together.

Step 7: A Helpful Video With the Basics

We would like to advise you to watch this video which briefly goes over all of the basics for 3D printing!