What cannot be 3D printed? Time to debunk some myths!

General 3D printing misinformation: review of facts and fiction!

Each technology has some fundamental limitations, and 3D printing is no exception.

As soon as I owned and wrote about 3D printers, people started "spamming" me with mainstream articles about it (no pun: still I like them and still I learn from them!). So even our grandparents would soon be printing their glasses, their bikes, their firearms, their houses and even their own legs!

For sure, I am not the one that will disenchant this emerging technology: I am writing this blog and I regularly post new designs on Thingiverse repository.

But as I write this (april 2013), you just cannot buy a 3D printer and print anything, nor even expect it to work as advertised if you do not understand very clearly how the thing works. It is just not reliable enough for the average user (unless you have no special expectation, in which case this pay doh printer may avoid frustrating experiences). It is even quite hard to reach an acceptable quality even for people born with a screwdriver in their hand.
Update 2021 : we're closer to reliable, out-of-the-box 3D printers. Still they often need to be properly tuned, especially the low-cost ones. And time will not fix their other drawbacks. Please read on!

Which hobbed bolt for a filament feeder? My homemade one!

Driving the filament with hobbed / knurled bolts

My quite efficient hobbed bolt :)

As all owners of 3D printers know, one item of utmost importance is the so-called "hobbed bolt", "knurled bolt" or "driving shaft". It is one necessary "vitamin" (ie. non-printable) item that is coupled to a motor and which rotation drives the filament into the hot end (check the whole setup).

Now, molten plastic still does not flow easily through our tiny nozzles (~0.4 mm), and the force to be applied is quite high. Pushing the filament manually gives a good idea, as one hand is barely enough. Since necessary value may be 15 or 20 Kg of traction, this is where problems start to arise given the small filament diameters (3 mm or even 1.75 mm).

How to run a (Cura) Python plugin on STL files without Cura?

Here is a geekier post about how to tweak Cura plugins and convert them to standalone Python scripts that post-process your g-code without Cura nor Skeinforge.

After I designed and used my wood gradient plugin, people naturally started to ask for the source code. I was a bit lazy first, because it was made for Cura 12.08: the patch I released was not very convenient, and Cura had evolved with a better and simpler plugin system, and included my own plugin.

Then, I got the time to fix it. Here is how I converted it to a standalone Python script that runs on its own, asking nothing to nobody.

Molding and casting with a 3D printer

Printing a mold and/or lost wax casting

Or how a 3D printer also opens the way to semi-industrial homemade objects beyond artistic sculptures!

Indeed, a 3D printer can be used indirectly, to print a mold of the object and not the object itself. The print is used as a "shape", and the final object is made of something else that could not be printed directly such as aluminum or silicone.

Molding is also useful to produce small batches of objects (even out of plastic), in a way which is much quicker than by 3D-printing. 3D printers are only rapid prototyping machines not ready for mass production.

Ron Thompson explains clearly how he made his aluminum heating block for his gravity filament extruder:
here is a two-part oil-bonded sand mold, rammed around the above 3D-printed orange plastic shapes.

How fine can an Ultimaker print?

 Ultimaker impressive quality at smallest layer heights (40,50,75 microns)

I printed one famous treefrog on my Ultimaker for a friend and realized I have forgotten so far to speak about the overall quality you can reach with this printer.

It gets hard to feel the layers by sliding your nail (75 microns layer height).
The most prominent place where layers show up is between the eyes.
This print is not postprocessed (see the hair-like filaments not yet removed/sanded/burnt)

Review: what materials can be 3D printed?

What materials to 3D-print ?

Every now and then I am being asked about it, so here is a post on the many materials that can be 3D-printed at home.

Smooth transition, from carbon-fiber reinforced PLA to ABS

It is not complete and will expand with time. It is no buyer's guide either, nor a technical document. Read it as a short generic survey of usable materials. There is also a post dedicated to materials most suited to artistic goals.


As for me and many others, I print mostly with PLA filament (see below). Even though I have a set of other materials (wood, rubber, Nylon and so on), I did not test all the following myself, mostly because each material requires its set of specific time-consuming trials and errors to achieve good quality. Mastering all of them would take me months, if not years!

Short belt tensioner for NEMA 17 stepper motors

How to tension the Ultimaker short belts once for all?

Upside version of the tensioner

The short belts that drive the main rods from the X and Y steppers must always be kept tight. Otherwise the print quality really gets bad. Two symptom that are easy to spot is non-round cylinders or "bouncing" waves in the surface of the print.

The usual fix is to unscrew the 4 bolts, push the motor downwards with a thumb and tighten the screws very hard while keeping the pressure...

I just could not stand this anymore, so I designed this thing and this derivative (with an additional spring).

Auto shutoff at end of print

Kill your 3D printer when it gets lazy !

Given the heat a 3D printer can generate, even when idle, I would better kill it than let it powered unattended, both for the planet, and to reduce the slightest risk of fire. ;)

I stick here to the simplest and most straightforward modification, partly because it is already supported by the Marlin printer firmware.

By the way, the total cost is less than $10, and you will just need a few solder points!

Major wood FDM printing breakthrough !

Extremely efficient wood 3D printing system

This is incredible...

No need for a hot bed, no issue with massive overhangs, no stringing at all, no retraction, grinding nor feeding issues, not even noise, smell nor chemicals.

Free and easy sourcing of material, highly portable, robust, self-powered and auto-adapting printing system. And damn, they even master wood gradients and polygonal infill!

Now, on the downside: it comes without a user manual and the system is incompatible with g-code. And sometimes, it stings.

How nasty.

Poll: what are the features you added to your stock Ultimaker ?

What are your Ultimaker features?

Here is an on-going poll motivated by this post on the Ultimaker google forum. So please keep your comments for the forum!

I finally developed my own blogger poll system after failures with the official and restrictive blogger polls.