Author Archives: Victor Waegenaere

Week 6: Last improvements and test

Script to make same direction in path

The chain link we tested in the tensile testing machine has one design flaw. When sliced using Cura, the inner wall of the chain link is printed clockwise and the outer wall is printed counter clockwise. This resulted in a specific point on the chain link on which the fiber is not continuous but turns around. As a result, all links printed with fibers broke at the location of these turns.

To make our print stronger, python script was used. This script analyses the gcode and determines whether or not the path is clockwise or counter clockwise. If it is counter clockwise the program reverses the printing direction.

Reversing the printing direction proved a little harder than expected. This was because the E values in the gcode first had to be changed into a value for only that distance (since E values in gcode represent the total extrusion) before they could be moved around. Also the G0 (travel moves) commands had to be moved a little, since the final G1 (printing move) command per round ends up at the same position as the G0 before that round. If the order is reversed, the first G1 command moves the nozzle to the position it is already in while extruding material. This was solved by turning the coordinates of the G0 commands equal to the location of the first G1 command per round instead of the last.

gcode swap

A part of the used gcode file is shown before and after running it through the script. The swap of lines can be seen.

The G0 command is needed to make this script work but can later be removed using the other python script.

Final Test

For our final print we chose the next specifications:

  • Length: 50 mm
  • Thickness: 8 mm
  • Insider radius: 7.5 mm
  • Outer radius: 20 mm
final results

Light blue (6731N, 686kg) and purple (7017N, 715kg): Chain link with fibers. Dark blue (3691N, 376kg), green (3203N, 326kg) and red (3930N, 400kg): Chain link without fibers.

The chain links with fibers broke at an average force of 6874 N (700.7 kg). The one without fibers broke at an average force of 3608 N (367.8 kg). The one with fibers is 1.9 times stronger then the one without fibers.

Week 5: Final design

Last week

This is the last week of the project. Next week we have to present our findings and final design on a science fair. Our goal this week is to optimize a print, which can be tested on its strength and compared with the same print without fiber.

Final design

The final designs will be made by using all the solutions and methods we have find during the past weeks. They will be tested to see the improvement of a fiber reinforced print.

First test print

Our first print that will tested is a chain link. The choice of a chain link is because it is very easy to attach it and make a test set-up for it. The chain link can easily be hung and we will augment the load which we hang at the other side of the link. The chain link was designed with the following properties:

  • Length: 50 mm
  • Thickness: 6 mm
  • Insider radius: 4 mm
  • Outer radius: 10 mm
chain link

The chain links, left without fibers and right with fibers. There is also a coin of 5 euro cent as reference.

Script to remove travel moves

To make it possible to print almost every gcode, because we won’t work with a cutting extension, we had to make sure that there are no travel moves. If it would have a travel move the fiber, that is attached to the nozzle and the print, will either break or pull the print when moving without extrusion. We made a Python-script which changes the travel moves into printable moves. After a few days of work it’s finally finished! Here’s how it works step by step. Note that this example is not perfect, since this first layer has different settings.

  • First the script opens a gcode file, and copies all the lines to a new file. It searches the the last line G1 before a travel-move G0. G0 is a fast movement without extrusion.
  • The G1 line remains the same in the new file on the right side.
Before After 1

The last line G1 before a travel-move G0 is marked in red.

  • The G0 is replaced by a G1, which is a slower movement. By calculating the length of the actual movement and multiplying this length with an extrusion constant we get an estimated E, which we add at the end of the new line G1. (marked green).
Before After 2

Here the change of G0 to G1 and the new E value are shown.

  • To reset the extrusion-settings we make a new line with G92, and add the last E value of the original G1.
Before After 3

Here is an example of how the G92 line looks. In this case the E value of the original G1 line was E41.41991.

  • And the code continues!

Introduction of reinforced FDM with fibers

The technology of 3D printers is evolving at very high speed. There are many different methods that are used to 3D print. One of the easiest and cheapest methods is fused deposition modeling (FDM). In the context of the minor “Advanced Prototyping” of the TU Delft, we will explore the possibilities of reinforced FDM prints. An Ultimaker 2  will be used in combination with the PCB and software of the Ultimaker Original. This combination gives us the freedom to adapted and expended our setup to print fibers together with the printing filament. This method should improve the strength and stiffness of the object that is printed. We will look at different approaches and fibers to find the best way of reinforcing.

Our group consists of four member with different backgrounds. Our studies are aerospace engineering, industrial design (one at the TU Delft and one at the TU Eindhoven) and electrical engineering. Hopefully our backgrounds will result in creative and new solutions on our problems. Joris van Tubergen is our expert, who will help and support us during the project.