3. Impression 3D#

In this unit, we have to :

  • Explain what we learned from testing the 3D printers
  • Explain how we identified the design parts parameters
  • Shown how we made our kit with words/images/screenshots
  • Included our original design files for 3D printing (both CAD and generic (STL, OBJ or 3MF) files)
  • Included images and description of our working mechanism

3.1. Getting started, dowloading PrusaSlicer#

First things first, we need to download the software PrusaSlicer on the following link. This software will allow us to prepare the FlexiLink we modelized last week for 3D printing. By following this tutorial, you will learn the basics for using the software and the 3D printers.

3.2. Preparing the file for PrusaSlicer#

Back on OpenSCAD, we need to export our file in STL. To do so we can go to File > Export > Export as STL.

Once we exported our file we are ready to use the software PrusaSlicer.

3.3. Using PrusaSlicer#

Once you launched the PrusaSlicer software, you need to add an object on the plater. To do so, you need to press on the cube with a + and then select the STL file we exported earlier on OpenSCAD.

Now that your object is in place, the Print Settings are the next important part to look at. The two most important parameters are the Filament and the Printer. The filament used in the FabLab is Generic PLA and the printer is the Original Prusa i3 MK3S & MK3S+ 0.6 nozzle. The other parameters are explained in the tutorial.

To check how long the printing will take, you can press on the Preview button, it’s the sliced cube at the bottom left of the screen. You will then be able to see the estimated time for the print in the bottom right corner. A good aim for a small FlexLink is about 15 to 20 minutes.

Once you are ready to export the file to make the print, you can click on Export G-Code on the bottom right corner. This will export the file in gcode which is the type of file the printer need to execute the printing.

3.4. Using the printer#

To start printing, we first need to add our G-CODE file in the SD card of the printer. To do so, we can take out the SD card of the printer and put it in the adaptater that is available in the printing room. Then we can plug in the adaptater to our computer. Once this is done, we can drag our G-Code file in the SD card and then make sure to extract the SD card properly from the computer. We can then put the SD card back in the printer. Before starting printing, we need to make sure that the printing board is clean by cleaning it. Once it’s done, we can start printing our FlexiLink.

3.5. First print#

For the first print, the piece took approximatly 20 minutes to print. The FlexLink was working fine at first but unfortunately, after playing with it for a bit, it broke down.

3.5.1. Seconde print#

To reinforce the weakness of the piece, we can add a rounded corner where the joint broke. Thanks to Sergio and his round_corner module, that is has followed :

module round_corner(side, height){
    translate([-side,-side,0])
        difference() {
            cube([side,side,height]);
            translate([0,0,-1])
            cylinder(r = side * 1.02, h = height + 2);
    }
}

By adding two round corner on either side of the beam of the satelite, the whole piece looks like so :

After printing it and playing with it I can confirm that the satelite is a lot more sturdy and didn’t break. Here is the final print :

3.6. Compliant mechanism#

The compliant mechanism we decided to do with my study buddy Alexandru is a kind of catapult that shoots an object vertically. The first sketch we made looked like this (it was litteraly made in 15 seconds) :

The objective is to use our satellites FlexLinks with some basic structure and the platform that was the modified code in module 2 to make out catapult.

3.6.1. Parts used#

To make the compliant mechanism, we used : 2 beams with holes, 2 satelites, 6 pins and a platform.

The beams with holes were printed with 20 holes and look like this :

The satelite used are the same than the one in the module 2 and same goes for the platform. The pins are simple cylinders, with 4 of them of a height that is equal to 3 times the height of the beams/satelite height which is equal to 24 mm and 2 pins with a height 2 times as big so 16 mm. For the radius of the pins, to now the exact size we need for the pins to go through the holes, we printed a few ones with different raidus. Since the holes of the beams and the satelite have a radius of 4 mm, we printed pins with a radius of 3.9, 3.8 and 3.7. We tested which one of the pins were the best and we found out that the 3.9 was too fat and didn’t fit, the 3.7 was too thin and fell through the holes too easily, and finally the 3.8 could be inserted in the holes with a bit of resistances. The 3.8 was therefor perfect since it didn’t fell through the holes and could be inserted in them. A better option to now the perfect size of a pin would have been to print a stick in a conic form a bit like a ring sizing stick that could be inserted in the holes to now the perfect size for a pin to fit in.

A link to the file that was used to create all the pieces can be found here.

3.6.2. Final result#

By combining all the different printed parts, we managed to make ourself a small catapult :