Week 5 - 3D printing and scanning

The fifth week is dealing with 3d printing. There are three tasks, which we are working on.

Test the design rules of the printer

We have three Ultimaker 2 3D printer in the Lab. These are Fused Deposition Modeling printers, which basically melt plastic and put it in place. As printing material we are using PLA with a thickness of 2.85 mm. This stuff is based on corn starch but not for consumption though. For interesting 3D printing projects, I strongly recommend the webpage thingiverse. There are a lot of projects and files, which one can download stl-files for printing. It is free and some files one even can and modify. In the picture below you can see some things, which have been printed here.

I decided to use three test pieces from thingiverse, to get an idea of the accuracy of the printer.
My first approach was Test 1.

The program for using the Ultimaker is Cura, which is free available on the Ultimaker page. It reads the stl-files and allows to define the parameters of the print. But most important, it slices the object. As you can see in the left picture above, you can define the filling, the layer thickness, the speed of the filament, the temperature of the nozzle and so on. There a plenty of parameters to play with but fortunately also an easy setting for a quick entry in 3D printing. These settings give good results. For additional testing I printed the Test 2 and Test 3.

The right picture above shows the results of the tests. Our printers are able to print little overhangs up to 45 °. The diamteres of the small holes 3, 4 and 5 mm are 0.5 mm to small. While printing in air, means covering a gap, the print comes out stringing. The smaller the gap (here 2 mm), the more stringing. The distances are also a bit shorter, than expected. For example 2 mm is 1.6 mm, 4 mm is 3.5 mm and 16 mm is 15 mm on the print. Nevertheless, the Ultimaker is for the price a very good printer and you can do awesome pieces with it. When it comes down to where precission matters, then this would not be the tool of the first choice.
It happens, that the 3D prints come out in a way, which is not expected. A good guide for 3D printer errors is this page.

Design and 3D print an object

In this assignement we should take care, that the object which we are designing, can not be made subtractively. I decided to make a fan, which is warped and has a round tip that makes it impossible to fabricate this with the 2.5D machines. At least, not that easy. Anyway, in the first picture on this page you can see In addition this has two more advantages for me: it helps me later, when I want to build my final project (Booty-dryer) and it is also a good practice to work with Solidworks...and I am saving the environment by not printing anything to throw away. While researching the web for making a fan, I found this Video. Thanks to the Solidworks-tutorials, I don't need to start from zero on this one.

Since the part is very big and this is about learning to use the 3D printer, I have decided to scale it down to 50%. This will take almost 3 hours time by 100% filling and 60 μm layer thickness.

It went pretty well but it needs to be a bit more grinded. Good to see in the picture on the right, is the support structure of the print. Cura has this function, that allows print parts which would have an overhang or parts of a structure which basically would 'hovering' free in the air in printing a support structure, which can be then removed. The whole piece needs to be grinded and sanded though.

3D scan an object and optionally print it

This turned out to be not as easy as expected. Scanning something should't be that hard but if you are using Sense 3D it is. The scanner works so bad that it's basically not working at all. I tried different combinations of light and different object sizes but I had all the time the Lost Tracking message. I figured a setup out and after some advice from the fablabdetroit fellas, regarding lighting and reflective surfaces, I managed to scan a basketball.

At least I got 50% of my basketball, so I can print it twice to get a whole one. Seriously, the Sense 3D scanner is very sensitive and I lost tracking all the time. With a bit more time, one could figure out the best environment and settings to work with it. My impression is, that a high contrast is helpful. Furthermore, if the position of the scanner is fixed and the object moves like on my rotatable chair, it gives better results.

The best aproach is to have the scanner on a stand or having another person around.

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