Checking the capabilities of a 3D printer with simple test models

One of the most popular models presented by manufacturers of low-cost 3D printers are printed vases. They have incredibly fancy designs and are made of bright, colorful filaments. They induce very positive emotions in people who are unfamiliar with 3D printing – vases are very nice, and their geometry makes us think that their creation was no mean feat. Meanwhile, it is quite the opposite: vases are the simplest models to print, they always look right, regardless of the device on which they are printed. The problems begin when you need to print something more complex, preferably one with supports, which then must be removed. Here are some simple ways to check whether a 3D printer is indeed as good as the manufacturer or the distributor suggest…

You could say that an FDM technology 3D printer finds it much easier to print models in an uninterrupted and continuous manner, whereas when the printing halted is for a moment and the 3D printer moves to a different part of the plate to start it again with the next / previous layer, the possible problems start to occur. Therefore, when printing a vase, which except for the base has no infill inside of it, the 3D printer performs a continuous movement from the bottom upwards along the geometry of the model. Even if you set the wall thickness at +1 mm, 3D printing the vase is still very simple, as the device operates at all times around one area and performs almost no retraction.

When a model is made up of several independent fragments which come together in the model’s upper part, or when printing several independent models at once, the 3D printer must move from one fragment to another, around the plate, at the level of a single layer. At this point, there are a number of details which have a significant impact on the quality of the printed model…

The first fundamental problem is the proper leveling of build plate with respect to the printhead. In other words, the distance between the table and the head in the bottom left corner of the plate must be the same (or very similar) to that in the upper right one. If you do not make sure it is so, one piece of the printout may adhere to the surface of the plate well, and another one could detach from it and cause problems at a later stage of printing, when the material starts to roll up due to shrinkage. The next issue is a correctly set retraction. When the head is moving from point A to point B, the extruder pulls up (retracts) the filament in order to prevent it from dripping out of the head at the time. If the retraction is too small, there will be tiny filament strands, connecting the particular parts of the model, which you will need to manually remove after the printing is finished. If it is too high, the filament will not be able to flow out quite in time and the printout will be full of holes, which will not only look unattractive, but most of all will weaken the model.

The last essential aspect is the speed of the head’s movement between the various parts of the model (the so called “travel speed”). If the speed is too high, it may cause the head to inadvertently damage a part of the print, crash into it or dissever it from the plate. These strokes are usually small, however, they occur continuously and weaken the adhesion of the model to a plate. If the speed is too low, it means longer 3D printing time and the mentioned problems with retraction (long travel speed = greater retraction).

There are countless test models available on the Internet, the so-called “torture tests”, which are designed to bring all the best and the worst out of a 3D printer. To be honest, I’m not a big fan of them either. In the end… they are not really helpful. We usually print completely different models, and we can check the quality a particular 3D printer in a much simpler and more illustrative manner.

The first test we normally carry out on the new 3D printers, is printing the whistle with a ball inside. This simple model has one crucial element – the ball is printed on a very thin layer of plastic. Once the print is finished it is enough to slightly pry the ball, through the opening, and it should readily break away from the base of the whistle. If the 3D printer’s travel speed is too high, in the course of printing the head may knock the ball and cause its detachment or dislocation, which in turn leads to crooked printing of its successive layers. The ball is no longer a sphere but an unspecified shape. If this happens you already know that the default speed set by the manufacturer must be reduced. Especially for models any more complicated than a whistle.

Another standard model is a high heel shoe. It is used to once again test the travel speed, while printing the heel, as well as the way in which the 3D printer builds the supports. From experience we know that although in the case of the heel it usually works very well – in 9 cases out of 10 the supports will easily detach from the model without causing damage, then in the case of the shoe’s front, where the inclination angle is small, in most cases you will experience problems.

The supports test verifies our not only the capability of the 3D printer, but above all the software we get in the package. I must admit that the open-source software handles this much worse than proprietary programs. At least in this case…

The hardest – and also the most perfect test which I checked of how a 3D printer generates and prints the supports, is the model of the robot from the first part of RoboCop films – the ED-209. The model is very complicated and requires generating a huge amount of supports, which then must be laboriously removed.

The model takes quite a few hours to print out (depending on the size and the speed of a particular 3D printer). If after printing and removing the supports it looks as in the photo below, it means that the 3D printer can handle (almost) every model.

The third standard model which we always use to start working with a 3D printer, is a model of a PCB plate. It consists of several elements, of different shape and height. Additionally, one of them is equipped with an inscription on top. In this model, we primarily test whether the walls of each of the components are printed smooth and even or wavy. Two of the elements are hollow (they are marked in red in the picture below) – on some devices they are printed properly, on others they are printed over. Not all the 3D printers can also cope with inscriptions…

There are many more similar tests – what we always try to establish is the accuracy of digital model’s reproduction by the 3D printer, any whether any problems occur in the course of 3D printing and if it is easy to remove supports (if there are any). We also pay attention to the speed of the device and its reliability. If the 3D printer tends to pull the prints up from the plate, or the filament gets jammed, we know that it is not suitable for professional use, where printing may last several dozen hours. If you are afraid to leave the office (or home) when the 3D printer is still printing, it means you do not have good equipment…

Nevertheless, the simple tests described above would help you see what might await you in the future. If a whistle model is printed perfectly – try to print 4-6 of them at a time. You may find out that while increasing their number on the work plate, the 3D printer will begin to pull the particular balls up while printing them. If there is already a problem with a simple model, it will certainly persist with more complex printouts.

And when looking at test prints from a particular 3D printer, remember that it is not a great achievement to print a beautiful vase…

Source: centrumdruku3d.pl