Production of a prototype for a bending machine (Master thesis mechanical engineering)

As part of my master’s thesis at the Chair of Micro- and Nanoanalytics in cooperation with the Chair of Forming Technology at the University of Siegen, I developed and subsequently commissioned a bending machine for plastic forming in the scanning electron microscope.

The bending machine will be used to perform three-point bending tests to investigate the crack initiation of bent specimens in order to better utilize materials in bending forming. Forming processes are used in the manufacture of products in many areas of daily life: Cars, aircraft, ships, piping, sheet metal forming and many more.

For a detailed examination of the bending specimens during the bending test, I built the bending machine to fit the scanning electron microscope (SEM). Since there is little space available in a scanning electron microscope, the machine had to be relatively small and light – it fits on the palm of a hand. Initial bending tests in the SEM have already been carried out.

Rapid Prototyping

During the design phase, I used 3D printing as a rapid prototyping process. Compared to machining processes, this method has the advantage of fast production of parts based on CAD models. The first 1:1 scale prototype was designed and 3D printed during a planning and development project, also as part of my studies.

Especially at the beginning of the project, it was important to quickly get a good idea of the real dimensions of the components to be manufactured later. Thanks to the friendly support of the Fab Lab in the person of Fabian Vitt, the required components were printed quickly and without any problems. Thanks to the friendly support of the Fab Lab in the person of Fabian Vitt, the required components were printed quickly and without any problems. In this way, all those present can get a very good picture of the shape and details of the component that will later be manufactured through the 3D printouts. This is less possible with the otherwise often used printed construction drawings. 3D prototyping can lead to new fitting ideas and facilitate the identification of necessary optimizations.

A short animation video of the bending process:
https://lmn.mb.uni-siegen.de/in-situ-em/

Soviet hand drill repair

Pre Story

My father bought the thing at the flea market sometime. The price of 5 rubles (Ц. 5Р.) is incorporated in the handle, because at that time in the Soviet Union there was the planned economy and you could get a pack of butter for the same price in the big whole country.

Problem

The drill always did its job. It is particularly suitable for small jobs and you can dose the torque manually. Only at some point the drill got stuck somewhere and my father exerted too much momentum on the big bevel gear until a few plastic teeth sheared off, rendering the thing useless. The old bevel gear consisted of two parts: The front side with the teeth was made of a plastic casting and the back side was made of some kind of metal, which was somehow connected to the plastic (unfortunately no photo). So a new bevel gear was needed.

Solution

First, the teeth of the bevel gear had to be counted. There are 60 teeth. The driven bevel gear has 15 teeth, so there is a ratio of 1:4. In addition, all dimensions, such as the height of the teeth, their width and the bore diameter of the bevel gear had to be measured with a caliper gauge. The problem: the teeth are not simply arranged in a straight line, and their “focal point” is somewhere in the air. They are also wider at the outermost diameter than at the inner diameter of the bevel gear. So the geometry is a real challenge and you can’t just build the thing with a CAD program if you’re not a professional.
But what to do? Fortunately, I happened to come across a solidworks tutorial on the internet. It shows how to create configurable standard parts using the solidworks (SW) design library. And that worked well!

Procedure

Open Solidworks, open any assembly and throw out all the parts. Somehow it didn’t work out any other way for me. Then, on the right side of the screen, open the construction library and shimmy through the tree. Toolbox, ISO, power transmission, gears, degree bevel gear (driving).

Solidworks

For me, the ISO standard matched well with my Soviet part. Then the “Degree bevel gear (driving)” must be dragged and dropped into the assembly window. Now the “Configure component” dialog opens on the left. The module, the number of teeth, the pressure angle, etc. can be set. Here you have to experiment, have the bevel gear with the green check mark built again and again and measure it. (Tip: If you click on a component edge, the bottom info bar of SW conveniently shows the measured length directly).

SolidWorks-2

However, you cannot specify all dimensions and geometry properties in the configurator. And here’s where it gets a little tricky. If the tooth geometry of the blank created fits so far, the rest must now be added manually. I used the function “Attachment/Base rotated” to build a created sketch as a body of rotation to the blank (see screenshot). Again, I had to measure the old bevel gear over and over again.

SolidWorks-3

Once you are satisfied with the part, you need to export it to *.STL format for 3D printing. And off we go to the Fab Lab Siegen! Here Fabian helped me out, showed me the 3D printers and started the printing. Thanks a lot! 😊

Result

The first print was unsuccessful (of course). In 3D printing, for example, the holes are always slightly smaller compared to the model. The teeth were also too small, so that they could not engage deeply enough with the opposing teeth. These teeth also sheared off during initial attempts. In addition, the bracket for the crank was a bit too thin and is therefore broken off.

Gears printed

Drill machine open

But now it was possible to measure the printed bevel gear and improve the dimensions in SW and finally start a second attempt. However, the second time it went better than expected and the bevel gear installed beautifully. The hand drill runs very smoothly and if any problems should occur in a few years, I’ll just print out the bevel gear again 😉 .

Drill-machine-composed-1

Drill-machine-composed-2

A Child’s Book, or: Saving Plastic, Starting 3D Prints New

During the summer semester 2020, there was a printer in the Fab Lab that was constantly cancelled for testing. The printer with the name “Hades” had to serve as a test object for a children’s book. But what does a children’s book have to do with highly experimental, plastic-saving techniques? Let’s lunge a litte bit.

Earlier this summer semester, I decided to develop a children’s book for 3D printers. Together with my fellow student C. Ajiboye, this became a manual that tells a story on one side, one of Ursa, a girl exploring 3D printing through “Learning By Doing.” On the other side, there were explanations of how Ursa finds problems and what solutions it gives for each of them.
But the last page was special:

A WLAN-enabled (ESP32) microcontroller was embedded in this page. This one could feel touches via its touchpins. I then soldered these pins to copper surfaces and hid them under the page. One laser cut later, the copper surfaces could be seen shining through.

Thanks to these surfaces it was now possible to give commands to the ESP32. And thanks to the Octoprint servers, it was then possible to give commands to the printers. Yes, you read that right, this little book has a remote control for a 3D printer built in.

But What is the Point of All This?

Restarting a 3D print is not an easy task, so far there is not a single Octoprint plugin that dares to do this. The result is that when a print fails, which the sensors do not notice, a lot of time, sometimes days, and also up to kilos of plastic are lost. This book was intended to prevent that.

A book has many advantages: it’s quickly at hand, it’s often where you want it, and the software doesn’t change much. It is also lighter than a laptop and thus handier to use. What’s more, you don’t have to boot it up or preconfigure it. The interface is simply there.

But How do You Restart a Print With a Book Now?

A 3D print is stored in machine code. This “code” is written line by line and executed line by line afterwards. So a group of lines represents a layer, because a 3D print is done layer by layer. If a 3D print fails at one point, the commands could be executed again from this point. In the file, as well as in the real print, an exact height is defined for this. You could measure this height, but neither with the eye nor with a ruler you can find it exactly. With the 3D printer itself, on the other hand, you can find the exact height. Like calibrating old 3D prints, you can now use a piece of paper and the tip to determine to within 0.1mm where a print failed. So, with the book in your hand, you move the nozzle exactly over the pressure, lower it very slowly, and try to feel with a piece of paper placed in between when the nozzle touches the pressure.

The printer then knows exactly where this nozzle is located, if it is still referenced. Based on this height, the code is then split, the necessary initial steps are executed and then the printer prints again as if it had never stopped.

I Want This Too

After this semester I found the time to develop this project as a plugin for Octoprint. So you don’t need your own book and you can try it out in the web interface. But ATTENTION! This plugin is highly experimental and has also once caused damage to a 3D printer. I do not make any guarantees or take any responsibility for future damages and advise to always hover with your hand over the emergency switch until the first layer prints again and you are sure that the printer is working on the correct line.

Yours, Gerrit.

A Suitcase Filled With Heart

At the beginning there is a story. A reappraisal of feeling, put into words and released into the world. “Du dunkles Herz” (“You dark Heart”) by Tobias Gruseck comes as an appealing red booklet and is a story about a suitcase full of money that darkens hearts. But promoting literature depends on more than the content of the text. A myth around it is good, maybe an eccentric author, a scandal. Or a suitcase, in it: hearts. If you touch one of the hearts, or the oak leaf next to it, you suddenly hear voices. Text passages that match the object touched resound softly and wonderfully recited from the case and make you want to listen to the story.

A story is told here with multimedia and attention to detail

Jenny and Simon took on the presentation of the work and built the suitcase. Wired inside is a touch board from Bare Conductive® that is connected via conductive yarn to things that are historically significant and, in some cases, 3D printed. Touching the thread closes the circuit and the text passages stored on the chip and previously recorded with virtuosity are played.

Literature as a haptic experience

All this was first presented in Bad Säckingen at “Kunst trifft Handwerk,” an annual outdoor event at the picturesque Trompeterschlößchen, where Germany and Switzerland bundled streams of tourists before the pandemic moved in. The title of the event also fits perfectly with this haptic project, which combines literary effusion with gifted tinkering. Currently on display at Fab Lab Siegen.

“Garbage – Environment – Design” – With Art Against Littering

As part of the cooperation project “Garbage – Environment – Design“, Sarah and Marios, two of our students, travelled to Palestine last year in September. The two-week project, organised by the Goethe-Institut in Ramallah, was intended to counteract the throwaway culture in public spaces from Europe that prevails there and to build a bridge between consumption and art. For this purpose, approaches of “upcycling” should be used, which make something new out of something old.

Two students each from Germany, France and Palestine were involved in the intercultural project and designed the exhibition and built matching exhibits in a workshop. During the ten-day stay on site, prototypes were to be produced collaboratively from everyday objects through upcycling in order to draw attention to everyday environmental problems. The project benefited from the input of other Palestinian and international experts from the fields of design, art, education and architecture.

The material such as pallets, Yton stones and plastic bottles were picked up directly from the street and were only a part of the countless resources used.
An example of the effective use of materials are the hanging gardens consisting of two green bottle walls planted with mint, which were set up to welcome exhibition visitors at the main entrance of the Goethe Institute. The results were exhibited in the Franco-German cultural area for intercultural discussion and experimentation.


In addition, during the students’ visit to Palestine, the action day “Art and Consumption” took place, in which the residents were to actively and collectively clear a piece of land of rubbish and litter.

The aim of the project was to communicate civil rights, but above all civic duties, and to mobilise local young people in particular to take on civic responsibility. Among others, the project was carried out in cooperation with Vecbox, the first Palestinian Makerspace, who brought local expertise.

Sarah and Marios were already able to draw on experience gained in the West Bank through the Yallah cooperation and exchange project in April last year, as well as through the come_IN project.

Project: 3D Copy Shop A Wooden Codel Was Created from a Plaster Face Cast

A Contribution from Eri

  • A photo series was created from a plaster face mask.
  • A point cloud from the photo series was created with Linux/Colmap.
  • The points were cleaned up and processed with Meshlab
  • The milling paths were generated with Pycam.
  • The toolpath files were created with a tool developed in-house.


simplified so that the GCode can be run with the Fablab CNC software as well as NCcad.

Face1_Punkte
  • The workpiece: a 1 1⁄2 year old, dried piece of end-grain wood, pre-drilled for “spaxing” onto the sacrificial plate.
  • Cutter: 6 mm cylinder for “roughing” and 6 mm spherical head for “finishing”.
Face2_Tools
Face3

About The Manufacturing Process

The feed rate for milling could be increased significantly. The cutter length was not sufficiently taken into account during the creation. This is how the saying of the day came about: “One more delivery is possible”. Before any collisions occurred, it was stopped. After remodelling and x-times finishing (Proxxon), the following emerged:

Face4
Face5
Face7

This project was kindly supported by the University of Siegen. Many thanks for this, especially to Daniel for his collaboration and Helga for text drafting and layout.

Remark:
Only a very slow Linux notebook (Ubu 19.04) is available on site. (possibly faster with SSD or cloud computing ??)
Network access for updates planned.
Friday afternoons are aggravating and not so well suited for such projects with public traffic and the limited time of the staff.
Other spax screws are missing or have not been found.
The cutter selection is limited.
Unsolved : Chatter marks.

Aya – a Selfmade 3D Printer

Aya – that’s a 3D printer that students of the Human-Computer Interaction master’s program produced in the winter semester 2015/2016 as part of the “3D Printing” seminar.

At the beginning of the seminar, the students were first familiarized with the basics of digital fabrication: What manufacturing processes are there, what materials can be used for printing, what are the possible application potentials? They also learned more about the individual steps of 3D printing: from modeling, to slicing (the “translation” of a 3D model into instructions for the printer), to the printing itself. For the subsequent project work, four students decided to devote themselves to building their own 3D printer.

The project participants used a kit as a basis, which already contained most of the parts needed for construction. All blueprints as well as the control software are available open source and so the students first built the printer according to the distributor’s template. However, they quickly discovered that not everything was working properly. So they decided to print some housing parts themselves using a different 3D printer in the Fab Lab and made other changes to improve print quality, such as adjusting the holder for the consumable. This was followed by a longer calibration phase, because the automatic support systems, which the printer actually has for this, unfortunately didn’t work quite as well as expected.

The students spent an entire semester working on the printer, which they named Aya (after a Japanese movie character). Aya is a Delta Robot 3D printer whose distinctive feature is its design: The three-axis system, which differs from conventional printers with linear axis systems, enables fast, precise printing. In addition to smaller test prints, the first larger prints such as an owl or a vase have already been made. Initial test runs indicate that Aya can print at a fabulous speed of up to 300-350 mm/second.

Even though the study project has now been completed, the students want to continue working on optimizing the 3D printer. For example, the installation of the control electronics or the stabilization of the base frame is being considered here to make Aya more transportable. There are also plans to test Aya with other materials such as ABS – the plastic used to make Lego bricks, for example – because so far only PLA, an environmentally friendly plastic based on (corn) starch, has been used as a material.

The students themselves learned a lot about 3D printing during the seminar and by building Aya. On Technology Day, the printer was presented and used for the first time in front of a broad public.

Aya in full size:

Zeit.Raum – Making Siegen come alive

The interdisciplinary research project ZEIT.RAUM Siegen is being carried out in close cooperation with citizens and aims to make the city of Siegen experience and understand its space and history in a collaborative way using innovative technology. ZEIT.RAUM is designed to facilitate collaboration and exchange between all interested parties – from academics and students to schoolchildren and amateur historians – about the city’s history, present and future. This opens up new forms of knowledge generation and transfer.

The project consists of two interlinked components: A touchable table-sized city model for interaction, produced using various digital fabrication processes and exhibited in the Siegerland Museum. Built-in sensors enable an interactive experience of the city and its history, which also stimulates individual memories. The second central element of the project is the Stadtwiki, a collaborative digital platform on Siegen’s city history, which is being developed by and for citizens. In addition to collecting information, it also serves as a forum to discuss the meaning of the data collected. Places of remembrance are identified, processed and reflected upon. All components of the project should be designed in such a way that they are easily accessible, understandable and easy to use for all interested parties.

One of the first test prints for the interactive city model

The role of the Fab Lab

We at Fab Lab are also involved in the project on several levels, especially in the creation of the interactive city model. The existing virtual 3D model of the city of Siegen, which was created by Prof. Jarosch, serves as the data basis for this. The topography is milled out of a large plate in the Lab. Which material is best suited for this is currently being tested. The true-to-the-original buildings of the city installed on it, on the other hand, are printed with the 3D printers in the Fab Lab. The sensor technology that will later be installed in the city model, which should be as user-friendly as possible, is also being developed in our lab. Several students are also involved in the project, working on individual components of the project within the framework of qualification theses.

Paper prototype for the interaction concept of the city model

Current developments

Currently, students are working on the design of the interaction concept and have, among other things, created a paper prototype of the city model. Likewise, the first prototypes for the city model have already been successfully printed and the sensor technology extensively tested. The model is printed with conductive filament so that the sensors can later be built directly into the city model. As part of this initial technical work, a developer board (see cover picture) was also created on which the following were installed: Arduino-Leonardo, Raspberry Pi 2, CAP1188-Breakout, 3D-printed touch sensor and 3D-printed matrix.

Test of the sensor technology to be installed in the city model

During one of our last project meetings, a first model of the Nikolaikirche – probably the best known landmark of the city of Siegen – was already printed. It took our Ultimaker a whole three hours to make the 1:9000 scale model.
Here you can see the result:

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Other project partners

In addition to the Fab Lab, the University of Siegen also involves the Chair of Didactics of History headed by Prof. Dr. Bärbel Kuhn, the Chair of Practical Geodesy and Geoinformation headed by Prof. Dr. Monika Jarosch and the Chair of Computer Supported Group Work headed by Prof. Dr. Volkmar Pipek. The realisation was made possible by the support of the university and the Friends and Patrons of the Siegerlandmuseum, who see the project as an investment in the future of the Siegerlandmuseum. The Siegerland Museum is to be strengthened by ZEIT.RAUM in its role for cooperative and inclusive historical work in and with the region.

We will of course keep you informed about further developments of the project in and around the Lab.