Introduction: Repair Using 3D Printing: 3 Reproduction

This guide is part of a series: Repair using 3D printing. This series of guides describes the process of reproducing a broken part by 3D printing a viable substitute. Please refer to the series’ main guide to follow the complete process. This guide includes a step-by-step explanation of the particular sub-process within Repair using 3D printing. First time readers are advised to read the whole guide, experienced readers can use the quicklists in each step to guide and speed up their next attempts. Skip to step 2 to get going!

Step 1: Background Info

The final step in the process is the actual reproduction of the part, from the 3D model that you have created in the first two steps. Now, as 3D printing can still be an experimental process, I will not go into detail about the printing and machine operations itself. If you own a printer yourself, you have probably figured out all the ins and outs about it and calibrated it to perfection. See it as driving a car; you will probably know exactly how your car will react and how it drives, but anyone with a license can drive most cars first time around.

For regular, inexperienced users however, 3D printing is actually really accessible: 3D printers are becoming widely available through public workspaces such as FabLabs, Makerspaces, Libraries and various technology-related instances. Furthermore, owners of 3D printers can register on platforms such as 3D hubs, and make their printer available as a paid service! Then there are also the professional 3D printing services, which offer access to industrial machines, materials and superior quality but at a cost. I will therefore focus on low-threshold access to desktop 3D printers, as I mentioned in the Main guide as well. I have provided a list of useful services in the next section.

3D printing, as you probably already know, is a manufacturing technique where material (hot plastic) is ‘printed’ layer-upon-layer, building the 3D shape from bottom to top. The 3D printer has a spool of material, called filament, that is fed into the printer head. The hot end of this printer head heats the material and presses it through the nozzle and deposits a precise line of material onto the previous layer. The printer head is continuously repositioned throughout the process; following a specific path you will create using slicer software. The hot material cools down and fuses to the previous layer, creating a solid part. The thinner the layers and the line of material extruded, the more accurate and detailed the product will be, at the cost of longer printing times. Generally, a print the size of a coffee cup takes about 5-6 hours, depending mainly on printing speed and layer height settings.

Step 2: What You Need

As in the remodeling step, you will need your computer again to prepare your freshly created 3D model for printing. As you probably already have done, your model should be checked for integrity and exported to the .STL file format. As a result, a triangulated version of your model, consisting of only the surfaces of the volume by means of interconnected triangles, will be the basis for your 3D print.

This model will be ‘sliced’ into the layers and toolpath for the 3D printer, so it knows how to construct your model. You will either need special slicer software for this if you are preparing the printing job yourself, or this happens behind the scenes of your printing service. If you are printing yourself, you probably want to use Cura for this, unless the printer requires special software (look for this at the respective manufacturer’s website). Cura is free, open-source and compatible with a wide variety of printers. Download it here.

Furthermore, you obviously need a, or access to a 3D printer. It is likely that you have found these guides through your interest and awareness of 3D printing and probably available printers around you, but I’ve included a useful list of services and platforms to find a printer near you. The amount of local printers surprised me a lot!

Locating a nearby printer

Depending on where you are, it might very well be the case that you already know someone or a place that owns a 3D printer. This probably is your best bet already, see if you are allowed to print your model there! As 3D printing material for desktop printers is fairly cheap, you might even succeed for a very small fee or for free (Indicate you are printing for repair; a sustainable initiative!) Local shops, workspaces, libraries, technology-related (educational) instances or even your neighbour might have a 3D printer readily available. Ask around! Otherwise, the following online platforms provide information about available printers and printing services nearby. 3D hubs being the largest platform, where printer owners can enlist their machines as a ‘3D printing hub’, for you to directly order your model is an ideal place to start! A price quote, information about the printer(s), available materials and the printer’s location are all part of this service.

3D hubs

MakeXYZ

You can also check online if a FabLab or Hackerspace (community-driven workspaces for hobbyists) near you has a 3D printer; these are often available to everyone, for a small fee, as a workshop or under subscription.

FabLabs in the Netherlands and Belgium

List of Hackerspaces (check if they have a 3D printer)

Online printing services

Another option is to order your 3D print online at a professional 3D printing service. You upload your model on their website, select a material and the part will be delivered up to your doorstep in a week or so.

Such services often have industrial machines and therefore offer different material and superior quality, but at a cost. As I focused on desktop printers in my research project, I do not have experience with any of these services, but I assume that they are significantly more expensive but with better quality results. I can therefore recommend to only look at professional printing services if you need very specific materials, finishing or have other quality-related requirements. For most cases, desktop printing can have more than decent results, at a fraction of the cost! I’ve also included tips for post-processing your print, to improve the finish on your part if you desire. The following services are a couple of the most popular 3D printing services. Read more about 3D printing services on All3dp.com.

ShapeWays

Sculpteo

i.Materialize

Step 3: Preparations

Before setting out the printing job, make absolutely sure that your model is intact and eligible for 3D printing! Especially if you have 3D scanned your part, make sure that you ran the error analysis in Remake. If you want to be sure, you can import the exported .STL into Remake again, and run the error analysis again. You can also open the .STL in most CAD programs, your slicer software or Windows’ built-in 3D Builder app.

If you have created the model yourself in CAD, you probably do not have to worry. You can always load the model into your slicer software already, and see if it succeeds to import. Also, check if there are any thin parts in your part; they should be at least 1-2 mm thick to be printable. If you are not certain about the printability of your part, take a look at the knowledge base of 3D hubs.

Next, if you are printing at a printing service, upload or deliver the model to them, and get advice about your printing job. Some services offer a model integrity check, price quote or even a design optimisation. (Local) printer owners can help you with the material selection and preparing the print job, and might even print it for you. Nevertheless, continue to the next steps to learn more about this yourself!

Step 4: Slicing Your Model

Before printing, the 3D model has to be prepared for the specific printer. So-called slicing software cuts the model into very thin layers, according to the settings you provide. These layers are then traced in a path for the printer head to follow, each layer at a time, from bottom to top. This toolpath, along with temperature, extrusion speed and various other settings make up the instructions for the printer, on how to print your model! You upload this ‘GCode’ to your particular machine, often via an USB stick or SD card.

Besides printer settings and slicing, slicing software like Cura often contain printing optimisation tools. Three of those I consider very helpful: Support structure, bed adhesion and the Infill setting.

  1. The first is probably the most important; parts are rarely directly printable without any supporting material between the printing bed (the surface the part will be built upon) and any overhanging geometry, as this will fall down otherwise. If you print layer-upon-layer, you will need a previous layer to print upon, obviously. In case geometry is floating in the air during printing, support structure is automatically generated by Cura! This additional material is printed in layers as well, but can be broken off easily after printing. It often leaves markings on the connecting part, however.
  2. Secondly, the first layer is crucial in the printing process; it has to stick to the bed, or the part will deform from the printing heat. Cura can generate an extra band of material on the first layer, around the contour of the part, that help your part stick to the bed better, called a Brim.
  3. Furthermore, the Infill setting in Cura can help reduce the printing time and material (cost) greatly when you have large, solid volumes. The solid does not have to be printed entirely solid in most cases, instead you can select a pattern and percentage to which Cura will generate a raster of material called infill, to substitute the otherwise solid printed volume. Generally, infill as low as 20% is strong enough, as the outer ‘shell’ will always be printed solid.

When you load your model into Cura, it will automatically start slicing. If you set the view to ‘Layers’ after it is finished slicing, you can review the toolpath and generated support structures. Also, you get a quote of the estimated printing time and amount of material needed.

Orientation of the model

In most cases however, you will have to reorient your model to minimize the support structure. Also, be aware of the build direction; As the layers are stacked over the vertical (Z) axis, the part is significantly weaker in this direction. This is due to the layer adherence, that is weaker than the material connections within one layer. This makes the part anisotropic, or not equal in all directions in terms of material properties.

The best orientation is often debatable. I can recommend three main things to look for:

  • Lay flat. Keep the part as low to the bed as possible, reducing the support structure to a minimum. Also, prevent overhang above other sections of the part, as this will fill up with support material as well. Aim for overhang angles of a maximum 45 degree angle.
  • Intricate details on top. As support material will probably affect the visual quality of your part where it makes contact, keep fine details on top.
  • Build direction. If you are printing a mechanical part, try to align the load-bearing features to the XZ plane, so the individual layers rather than the stack will take the forces. Think of a beam, if you print it vertically, it will be a large stack of small layers, eager to snap under load. Instead, print it flat to have the strength of the individual layers over the whole length

Step 5: Selecting the Right Material

Now you have prepared your model, the last thing you do before printing (if you haven’t already) is to select an appropriate material for your particular case. I’ve mentioned this already in the Decomposition guide, as it is one of the critical choices in your printing job!

You should be selecting a material based on your findings in the decomposition, as you’ve found a lot of clues about the part’s function. Again, the material you select should be fitting these functions, otherwise your part will fail or not comply with the initial requirements.

Therefore, I’ve created an online tool that will help you to select an appropriate 3D printing material for your case! A series of questions about your part will phase out incompatible materials and advise an optimal choice.

Material selection tool

As there is only a limited selection of materials available for 3D printing, and chances are that your particular printer might not even print one of these, this is only an advice. Make sure you judge the outcome yourself, and the reasoning behind it! If you are in doubt, contact an expert on 3D printing for advice. For now I’ve included five of the most common rigid plastics for desktop printers: PLA, ABS, PET, Nylon and PC.


A more elaborate list (and comparison) of 3D printing materials can be found on All3dp.com. If you have the option, you might as well pick a nice colour for your print. The majority of materials come in a broad selection of colour options, from white and black to all kinds of vibrant colours, transparent ones, metallic and even glow in the dark!

TIP: printers with dual extrusion (two materials): PVA

Newer printers now have the option to load two materials and can therefore print a model in these two materials at once! This is very helpful when you load the material PVA as a secondary: PVA is an alcohol-based, water-soluble material that can be used to print the support structure out of. You can then simply dissolve the support structure in water, leaving almost no marks from otherwise hard to remove supports.

Step 6: Printing!

Now you’ve reached the actual printing job! If you are printing at a service, simply select the right material and upload your model. You will probably get an indication of the cost and time it takes to deliver your product. Good luck!

In case you are printing yourself; I briefly explain the procedure. (Make sure you have read the documentation of the printer or had instructions of the printer’s owner if it is the first time!) After slicing your model in Cura, write the Gcode onto an SD card and insert it in the printer. Make sure there is enough material left in the printer, or load a new spool (consult the printer documentation, or owner how to). Start the printer and check it every once in awhile to see if it prints without errors. Especially check the first couple of layers, to ensure that they stick to the printing bed well!

After a couple of hours, depending on the size of your part, your new part should be ready! Check for any printing errors, remove any support material with a sharp knife and sanding paper, clean the print with some water and soap and you are probably ready to reinstall your freshly created spare part onto your broken product! If you are interested in additional tips to make your part even look better, check out the next step about post-processing.

Troubleshooting

If your print is not perfect the first time around, consider the following troubleshooting tips:

  • Is there any material in the way when reinstalling the new part on the product? - See if you can remove any material: drill out holes, cut away material using a sharp knife or sand it down to make it fit.
  • Does your print not fit, connect or line up? - You will have to go back to your model and alter the failing geometry. Consider ‘cutting’ away material and remodeling details that are not fitting. Print again.
  • Is the print too small or large? - Measure a clear reference on your original part and take the exact same measurement on your print. Divide the print’s dimension by the original; this is the scale factor you will have to apply on your model to scale it properly! Print again.
  • Are there any details lost, or is the part ugly because of support material? - Consider a different orientation for printing. Intricate details should be facing up, preferably! If you have a bold surface touching the printer bed, consider making it entirely flat to eliminate any support structure underneath. You can also look for a dual extruding printer, that prints the support material in water-soluble PVA!

Step 7: Post-processing Tips

Like any DIY project, there are numerous ways to post-process your makings. Similar to model making, you can sand, polish, coat and paint your print to make it look better, if you like. Cleaning up your model from any printing traces and residue is often necessary anyways!

  • Sanding and polishing: most materials allow for fine sanding and buffing up, to remove the layers somewhat. Be careful with this however, especially with PLA, as sanding too hard burns the plastic and leaves black markings!
  • Coating: you can also cover the part in a thin layer (food contact safe) epoxy resin Filler: Or, you can ‘plaster’ it with automotive filler paste or a crack filling primer paint. This can be sanded down to perfection, ideal for painting!
  • Painting: You can also paint the part if you like. Consider the filler tip, as removing the traces from the layers is otherwise very hard to do. Paint the part using either the acrylic or enamel paint you use for painting scale models, or a standard procedure with (automotive) spray paint: primer and sanding, paint, clearcoat.
  • ABS: Acetone treatment. There are special techniques for polishing ABS to shiny using Acetone (nail polish), but it is somewhat dangerous. Numerous instructions exist online, such as on Ultimaker.

Step 8: Done!

Thats it! If all went well, you have successfully created a 3D printed substitute for your repair case! All that is left is to reinstall the part onto the product; do this in the exact reverse order you removed the original part from it. As I advised you to do, you probably took notes and pictures about this procedure, be sure to follow these steps and don’t miss anything. Double-check your reassembly before connecting any power source or start using the product again! Obviously, this is again at your own risk.

As my research project is probably still ongoing I am very interested in your experiences! If you like, share your story in the comment section or PM me! This not only helps me improve this series of guides, but also might help other repairers in their case!

If you have any feedback on the guides or tools as well, feel free to contact me as well.

Good luck!

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