3D printing FAQ

As the proud new owner of a printer and total 3D-printing newbie; I thought it would be a good idea to try and compile questions and problems I have come across into a sort of “Intro to 3D printing”. Below is a list of topics this article will cover, with links for quick access:


3D printing has become more and more popular and accessible over the past few years. You can’t go to a maker faire without at least a dozen printers being there all day, printing away freebies. When you start using your own printer, there are some specific questions you might ask yourself; but for the neophytes, or those of you who might have stumbled upon this page by mistake, I’ll start with this question:

What is 3D printing?
As indicated by its name, this technique allows you to print 3-dimensional objects. There are various techniques, but this article will focus on the most commonly used among hobbyists. 3D printing offers a quick way to prototype or customise things. It is also a cheap way to make prosthetics, missing or discontinued parts, and so on. With the current status of research, it won’t be long before 3D-printing metal, food, or human tissues is common practice. Today though, most prints are made out of plastic, and this is what we are exploring here.

3D printing is an additive process, where very small layers (or “slices”) are combined to make an object. SLS (Selective Layer Sintering) works a lot like a 2D inkjet printer, but it prints on layers of powder instead of paper. You would see examples of SLS in professional environments, because the machines are costly and take up a lot of space.

Fused Deposition Modelling (FDM) consists in melting plastic into a series of layers (usually around 1/5 – 1/4mm high) to create an object. This is the technique that usually comes to mind when mentioning 3D printing. FDM is widely available and enables the making of personal utensils, toys, jewels,… It can produce anything from a simple container to complex, intricate objects.

How much does it cost?
The cost of a 3D printer can vary a lot from £300 to tens of thousands of pounds, depending on the precision, the type of printing (SLS or FDM), the manufacturer. For a home printer however, you’d expect to pay between £300 and £2,000; the more expensive machines being reserved for industrial production. The cheaper options usually come as kits that you have to assemble yourself. If you’re looking for a printer that works out of the box, you’d probably pay a minimum of £700.
Materials aren’t cheap; but unless you’re planning on printing life-size car parts, 1kg of filament should last for a few months (expect to pay £20-£30 for a spool of 750g to 1kg).

Can I print a 3D printer?
No, not with a basic 3D printer. You would need a machine that prints metal, but I believe these are still scarce and costly. You would also need to produce the circuit to run the firmware. It seems like 3d-printing circuits will soon be possible with conductive filament (trying to solder components would probably melt some parts of it, though).
Even though you can’t print a fully functional printer with a printer, you can improve your kit by printing some parts, or why not some LEGO bricks and build a printer with a 3D Doodler?
Instructions on how to build a LEGO 3D printer with Mindstorms can be found on Instructables.

Now you have a printer, or are still looking to make up your mind, you’ll need to know about consumables. For 3D printing, plastic comes in the form of spools or coils of filament that is melted in the extruder and then laid onto the print bed to form the layers of your object.

What kind of material do I need to print things?
Fused Deposition Modelling commonly uses 2 types of plastic: ABS (Acrylonitrile butadiene styrene) or PLA (Polylactic acid). Other materials such as Nylon, TPE, PET, HIPS, or Thermosense exist, but their properties and behaviour in the printer can be related to either ABS or PLA. Each of these require different extrusion temperatures. PLA and related materials will print at an average temperature of 220ºC, ABS and related materials will have to reach over 240ºC. In most cases, ABS will require a heated bed (see Printing and Finishing touches for more information).

Assortment of 3d-printing filament - from richrap.blogspot.co.uk

Assortment of 3d-printing filament – from richrap.blogspot.co.uk

Which one is the best?
Your choice of material will largely depend on which one your printer supports. Some machines support both PLA and ABS, others only work with one or the other. ABS is a chemical compound and can produce fumes at high temperatures, whereas PLA is made from corn starch (so it is more eco-friendly and also biodegradable). ABS is a little bit more flexible than PLA and would be better for printing hinges, for example. For more info, see ABS or PLA? Choosing the right filament.

Where can I buy it?
Online! Whether you choose to go for ABS or PLA, you’re more likely to find bargains on the web. Although not the cheapest, Faberdashery and ColorFabb, among others, offer a wide variety of colours and good quality materials.
To be able to see the filament before you buy it, I would recommend visiting a hackspace, maker faire, or 3d printing store, such as Makers Café or iMakr store (London, UK).

Can I reuse wasted filament?
If your latest print didn’t go as planned, or you saved up a lot of scraps and would like to re-use them, there isn’t an easy and immediate solution. You would have to crush your object to then melt it back into filament. Filament extruders are starting to emerge and multiply on the market, but at the moment, they’re almost as expensive as the printer itself. Some DIY solutions exist but are also costly.

Can I make my own filament?
You can, with one of the filament extruders mentioned above. If you’re not up for sourcing the parts yourself, Filabot, EWE, and OmniDynamics, among others, sell kits or pre-assembled ones.

Multicoloured prints from filament made with Strooder

Multicoloured prints from filament made with Strooder

You then need to source ABS or PLA pellets and colorants. Unless you buy these in bulk (at least 25kg), the cost of the raw materials and the machine, will be equivalent to buying a ready-made spool. Plus, small quantities are harder to source.
For more details, see How to make DIY filament for your 3D printer.

How fragile is a printed object?
Once cooled, a 3D printed object gets quite hard. It is worth noting though, that PLA is a bit brittle and has an tendency to snap whereas ABS is softer and will bend a little. The solidity of your object will also depend on the thickness of its walls and the amount of filling. Flexible materials are very unlikely to break.
Both PLA and ABS are insoluble in water, however PLA starts to soften at 60ºC, which would cause the object to be deformed. It is therefore not recommended for items that will be used in high temperatures.

3D Models
Now you’ve given in, selected your printer, and bought some filament. What next? You need to tell the printer what to print, in other words, you need a digital model of your chosen object.

So, how do I get my ideas from my head to the printer?
To start with, you need a 3D software capable of exporting a .STL file (any 3D software worthy of that name should be able to do so). STL stands for Stereo Lithography and is the standard file format for 3D printing.
There are a lot of options, free and paid for. Among free and Open Source 3D software you’ll find: FreeCAD, OpenSCAD, OpenCascade, TinkerCAD, Blender. The first 3 of that list are more targeted at industrial design, OpenSCAD uses code to generate 3D shapes, and TinkerCAD runs in the browser. Blender is more focused on 3D modelling and animation, so you would get more realistic renders. The latter has my preference since I’ve got previous experience with it, but the choice of software will depend on your intent and affinity for it.

3D model for tooth brush holder, design by LauchLab on Thingiverse

3D model for tooth brush holder, design by LauchLab on Thingiverse

There are of course many more available, but I haven’t had a chance to try them all! To get you started with 3D modelling, check out the documentation and tutorials available on YouTube. Start simple.

What if I’m not good at modelling?
Don’t start by modelling a complicated object, maybe a square pencil holder would do. 3D modelling takes a lot of time and patience, even for the simplest of objects. Try using the predefined shapes to start with (cube, cylinder, sphere…). Once you’ve got the hang of it, shape up your object with LEGO, play dough, or clay and take pictures at different angles that you can re-use as a guide for your digital model.
And if you really can’t wait and want to print super cool things right away, you’ll find a growing online community eager to share their creations. Check out sites such as Thingiverse or MyMiniFactory. Some online services will also offer to model and print objects for you. Also check your local hack/maker space for 3D-printing events and workshops.

What about scanning?
Scanning is also an option, if you don’t know where to start. The boom of 3D printers, also saw the emergence of 3D scanners on the market. Again, the prices vary drastically, from a few hundred pounds to tens of thousands. You can even find free smartphone apps that will do 3D scanning. There are 3 identifiable types of scanners: handheld, desktop and full body. The latter takes up a lot of space and is generally reserved for shops (although it is possible to make one with a Kinect).

3 different types of scanners - from left to right: handheld, desktop, full body.

3 different types of scanners – from left to right: handheld, desktop, full body.

The drawback with 3D scanners, is that they might pick up elements from the background and add some noise to the 3D model. Cleaning up the file in your 3D program of choice is required. Moreover, generating a 3D model from captured images can take long time.

What’s biggest/smallest thing I can print?
If you don’t have the budget to get the largest FDM printer (1.3m3 print volume), don’t worry. When printing big objects, you’re not as constrained by your printer’s size as you might think. Before slicing your 3D model, you can cut your model into pieces to print separately. You can then model slots to clip your parts together, like a jigsaw puzzle, or use superglue (or even a 3D Doodler). So, providing the assembled object isn’t too precarious and abides by the laws of physics, it can be pretty big: bikes, cars, guitars… It all depends on how long you’re prepared to wait for the print to finish!

For small prints, you’re limited by your printer’s precision. Layers can be as thin as 0.1mm. However, if you’re scaling a model down for a small print, it is recommended to get rid of some of the details that won’t be visible at the size you’re printing. This will save some time and prevent lumps in your final object. Some research printers have printed objects only as wide as a human hair, but I doubt these would be useful to makers.

Even though it wouldn’t work with FDM, another interesting solution for big prints is to optimise the print volume by folding the model. The process is described in the video below and was developed by Marcelo Coelho Studio.

Software and file formats

I like the look of what I’ve modelled, how do I print it?
First of all, you need to make sure your model is watertight. Depending on the program you’re using, there will be different commands to reveal non-manifold areas (i.e. areas that have holes, or extra faces and edges). You will then need to scale it to metric units, to be sure it will be printed at the size you want it to be. From there, export a .STL file.
Before exporting the file, you might want to consider changing your object’s orientation. (It could be an advantage to print a thing on its side, to get a greater surface, and therefore better first-layer contact, on the print bed.)

And that’s it?
Not quite. From the .STL file, you will need to export a .gcode file which contains all the coordinates the extruder needs to move to, for each layer of your item to be printed. It also contains all the printer settings, such as temperature, speed, cooling options, infill settings and so on. To export such a file, you will need a slicing software such as Slic3r or Cura.

What settings do I need for my printer?
Your slicing software will have 2 types of settings: some that are specific to your printer, such as the type of filament it uses, its diameter (usually 1.75mm or 2.85mm), the number of extruders, the temperature, the size of the print bed, its centre, etc. Once saved, these are unlikely to change.

Infill patterns available in Slic3r, at 60% - top left to bottom right: Honeycomb, Concentric, Line, Rectilinear, Hilbert Curve, Archimedean Chords, Octagram Spiral

Infill patterns available in Slic3r, at 60% – top left to bottom right: Honeycomb, Concentric, Line, Rectilinear, Hilbert Curve, Archimedean Chords, Octagram Spiral

Settings will then vary, depending on the type and size of the items you’re printing. You might want to adjust the speed, whether to print a skirt (the perimeter around your object), a brim (make the first layers slightly larger), or a raft (recommended for ABS, this consists in printing a few layers of support material under the print), the percentage and type of infill, etc. These settings might involve a lot of trial and error at the beginning, but after a few different runs, you’ll get a good idea of what works and what doesn’t.

How long is the print going to take?
Of course, the printing time will depend on how big and complex your object is, if you need to generate supports, and how much you want to fill it.
I didn’t have time estimates when I ran my first prints, and on one occasion I really thought I was going to be up all night for a 10 hour print! Luckily, the progress was exponential and it ended up lasting 5 hours. Knowing how long your print is going to take upfront is a huge advantage, as you can imagine.
My printer gives me the percentage of the file processed, as well as the time elapsed but does show me how long the print is going to last. Therefore, you need to use your slicing software beforehand to get an idea. I believe Cura give you a time estimate; with Slic3r, however, you have to import your G-code into Printrun/Pronterface. So far the timings given have been pretty accurate (the only trouble is that you have to export different G-code files for different fill settings if you want to see which one is reasonable).

Printing and finishing touches

My print is a bit deformed, what happened?
If the first layer doesn’t stick to the platform properly, it will cause warping, meaning consecutive layers won’t lay flat, creating an uneven shape. It is recommended to use a glue stick, or apply Kapton tape to your print bed to ensure a better adhesion. Materials like ABS will require a heated bed (maintained at about 90ºC throughout the print), and have to be left to cool down before being taken off.

An example of warping - from 2print3d.com

An example of warping – from 2print3d.com

If the object collapsed during the process, or has any overhanging parts that didn’t print properly, it will need support material. Support can be created with the slicing software, before exporting the G-code. Note that additional support can be difficult to detach when printing with PLA and could leave marks. You might consider re-orienting your object to minimise the amount of support needed.

Can I print multiple objects in one go?
Depending on the size of your print bed, you can print a few objects at once (say, LEGO bricks). Instead of printing the whole set layer by layer, though, you might want to print an object one after the other. Your slicing software will have such a setting. In Slic3r, for example, you can find it in Print Settings>Output Options>Complete individual objects. Note that you will have to account for your extruder size and any overhanging fans or parts (i.e. if one of your printed objects is higher than 20-25mm, it might get in the way of the extruder).

If you’re printing individual objects, or one that has gaps, such as the one shown below, you will need to adjust your retraction settings beforehand, to avoid stringing. This forces the printer to pull the filament back when the extruder goes over open spaces.

Design by pemoews on Thingiverse; printed by yours truly

Design by pemoews on Thingiverse; printed by yours truly

My object isn’t smooth, what can I do?
The first ting to do is to check that you had optimal settings for your print (thin layer height, good retraction, good adhesion,…) To see how you can improve your print, check Slic3r’s tips on fighting ooze.
To improve the smoothness after print, you can sand your object. Use a piece of sandpaper by hand, as mechanical sanding could melt the plastic. This works well on PLA. ABS, however, can whiten with this process.

ABS smoothing from RepRap Blog

ABS smoothing from RepRap Blog

For chemical smoothing, you can use an acetone bath on ABS only. On PLA, you can use ethyl acetate. A silicone coating could be used on both materials. Please bear in mind these chemicals can be dangerous and take all necessary measures before working with them.

Can I print in multiple colours?
Yes. SLS would allow for a fully multicoloured print. With FDM, however, options are more limited. One of the options is to pause your print and change the filament in the middle of the process; but you risk causing drippings and deformations on your object, and it only works if you want layered colours. If you were considering a more random colouring, then a multicolour filament could do, but there are very few available commercially.

Twister filament range from 3D printing systems

Twister filament range from 3D printing systems

Other printers come with dual head extruders which can alternate between 2 colours on the fly. Finally, another solution would be to print separate parts in different colours and assemble them.

Can I paint my object?
Another solution to get a multicolour object, is to print it in its main colour and paint it. Acrylic paint is recommended. Here are a few tips from MakerBot.
You can also give some texture to your piece by “flocking” it. This process consists in applying an adhesive to the surface of the object, and then coat it in flocking fibres (soft fibres that give a texture similar to felt).

That’s it for now! I hope this has given you a bit more insight into 3D printing; and if you have any other question that you’d like to add to the list, feel free to comment!

Related links, articles and books
What is 3D printing?
55 3D printers at Maker Faire Rome that you’ve never seen before
Mastering 3D printing, Joan Horvath
Preparing Blender files for 3D printing
Life-size 3D printed Iron Man suit took 14 months to complete
Multi-colored 3D printing from a single extruder
Printcraft – print items made in Minecraft
3D printing created this drone, complete with circuitry
Amazon files patent for 3D printing delivery trucks


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