STEM Participation Days

Last week, the STEM participation days took place. From 13.09 to 15.09, the Fab Lab team was invited by the district of Siegen-Wittgenstein to the front plaza of the district house. Every year in September, around 1,000 children and teenagers from all types of schools and daycare centers take part in a wide variety of STEM offerings for experimenting, experiencing and discovering. The Fab Lab was part of the various research and discovery stations as an extracurricular learning space.

The team had prepared a workshop on the introduction to 3D printing. A total of six groups of students from the eighth grade upwards from secondary schools and grammar schools took part. A small, mobile Fab Lab was created in a tent for this purpose. We brought a total of six of our eight Prusa 3D printers and ten of our laptops.

First there was a short theoretical introduction to basics, design principles, hazards, modeling and slicing. After a short demonstration part, the pupils were allowed to get hands-on: they could create their own key chains in the free software Tinkercad. Once the model was ready, the students transferred them to the slicer, prepared them for 3D printing, and were then able to print their designs on their own. Of course, we were there to help the students with any questions or problems they might have. For example, pendants with initials and names, or objects such as swords and ping-pong bats were created. The students were allowed to take these home at the end of the workshop.

Despite the rain, the sun was shining inside the tent: we were very happy about the engagement and interest of the students and hope we gave them some understanding of 3D printing!

Open University

On May 14, we were represented with a booth at the Open University at the Lower Castle. In our luggage we had a couple of 3D printers, our robotic arm, as well as our augmented reality sandbox.

Spread over the Lower Castle Square, a lot of institutions and study programs and research projects were represented to introduce themselves. We were very pleased that many of you visited us. Sure, the weather was nice and there was an ice cream truck right next to our tent.

At the booth, visitors were able to learn how to use the 3D printer, and there were many interested visitors who were able to go home with their own printed parts. Our robotic arm, has been blithely demonstrating all day how to 3D scan and digitize objects (to then replicate them with the 3D printers, for example). The augmented reality sandbox was particularly well received. You can interactively change a topography of a map with the sand, build mountains and valleys, and then watch the flow of water on the map with a water and rain simulation. A great way to learn about topography and augmented reality.

GAME NIGHT | VOL. I

Harder. Faster. Pilz

On thirst…thursday, July 7th, 7pm: Sandstr. 26 in Siegen!

Dance, game & drink the night away! Play a round of Mario Kart (Switch & SNES) or Street Fighter 2 (SNES) with (or against) us. Let’s celebrate the end of the semester with plenty of drinks, tasty vegetarian & vegan food and good music.

Everybody welcome! We have food and beer, all for free.
No regristration needed.

Additional opening hours for students

In addition to our opening hours for the Open Lab every Wednesday from 14 p.m. to 20 p.m., this summer term we also have times when the Lab is open specifically for students.
As of now, students can also work in the Fab Lab on Tuesdays and Thursdays during the following times:

Tuesdays from 13 p.m. to 16 p.m.

Thursdays from 14 p.m. to 17 p.m.

These extended opening hours are directed towards students of the University of Siegen in order to offer additional times to work on their projects. Individuals not affiliated with the university are welcome to come to the Open Lab on Wednesdays as usual.

The same recommendations apply here as for the Open Lab:

  • no more than 20 guests in the lab
  • 3G recommended (genesen, geimpft, getestet = recovered, vaccinated, tested)
  • the mask is kindly requested to be worn at all times
    (Exception: drinking and eating in certain areas).
first Open Lab held in April on the 6th of April 2022

Reopening of the Fab Lab

Finally, we are back with good news! The Fab Lab will re-open at the beginning of the summer semester. We are thus happy to announce the date for the next Open Lab:Wednesday, April 06.

However, given the still very high number of corona cases, we have a few recommendations for visitors to the Lab:

Within the Lab we recommend to maintain the3G rule(genesen, geimpft, getestet = recovered, vaccinated, tested). Furthermore, it is recommended to wear a mask at all times. Of course, the mask may be removed for drinking, but we would kindly ask you to put it back on immediately afterwards. For this reason, open drinks (e.g. coffee/tea cups) are currently viewed with caution, as experience has shown that these lead to “Kaffeeklatsch” ­čśë
Instead of eating right at your workplace, we would like to ask you to consume your foodat the open (!) windows in the lobby at Startpunkt to ensure the safety of everyone staying here.

The number of visitors in the Fab Lab is limited to a maximum of 20 guests.

In summary:

  • maximum 20 guests in the lab
  • 3G recommended (genesen, geimpft, getestet = recovered, vaccinated, tested)
  • wearing the mask all the time is kindly requested
    (Exception: drinking and eating in certain areas).
first Open Lab held in April on the 6th of April 2022
View into the Fab Lab

Open Lab temporarily closed

Given the current incidences, we have decided to keep the Fab Lab closed until further notice for the safety of all of us.

Aconcrete date for reopening cannot be set at the moment. As soon as the pandemic situation allows us to safely open the lab again, we will announce this here on the website, via email and social media.

In urgent cases, e.g. for work on a thesis or other projects, please contact us and we will find a solution.

In the view of the anticipated course of the pandemic in the coming weeks, the University of Siegen has adjusted its measures. All buildings of the university will therefore remain closed to the public up to and including 06.02.2022. At this point it is not yet clear what will happen after that.

Regarding the Fab Lab, this means that there will be no Open Lab until at least the 06th of February. Contrary to our previous statement, there will therefore not be an Open Lab on Wednesday, January 19.
We hope that we can see you again on 09.02., but we can’t yet promise this.

Take care of yourselves.

Extension of rotary draw bending to a partially kinematic process with reduced tool surfaces

“If you know plastic, take steel!”

A well-known saying in our steel-dominated region. But how much steel does a production tool really need? This is the question we at the Chair of Forming Technology (UTS) asked ourselves in the DFG project “Extension of Rotat ion Tension Bending to a Partially Kinematic Process with Reduced Tool Surfaces.

Processes and tools

Pipe bends are manufactured in everyday industrial production by means of rotary draw bending. In rotary draw bending, the profile is bent around an internal bending shape. To ensure that the moment required for bending can be applied, the profile is guided through the counterholder on one side. The other end of the profile is clamped to the pivoted bending mold with the clamping jaw.

Schematic representation of the rotational tension bending process (left). Process video (right)

The task in the DFG project was to geometrically resolve and simplify the existing shape-bound tool elements of rotary draw bending.

This enables:

  • Increased flexibility of the forming process
  • economical production of smaller lot sizes
  • individualized products

An area reduction method was used to derive angled contact surfaces instead of the previous fully enclosing tools.

For direct comparison with the conventional design, these novel tools were initially made of tool steel. For direct comparison with the conventional design, these novel tools were initially made of tool steel. Pipes made of stainless steel and brass were examined. The wall thickness was 1 mm and 2 mm.

Deliverables

Compared to conventional tools, the deformation of the tubes is more pronounced and increases with decreasing wall thickness.

Deformation comparison after 90 ┬░ bending: Difference conventional to simplified tools (a). Deviation scan of the manufactured pipe bends (b).

All specimens have a crease on the inner curve in front of the jaw. This can be attributed to the lack of support in the bending mold base, which was also shown in the simulations in a weakened form and represents an acceptable extent of the tolerance feature for the quality.

Can it be one layer more?

Following the positive project results with the reduced tooling, we thought, “If you know plastic, you’ll use plastic!”

So all tool parts were also additively manufactured from polylactide (PLA) at Fab Lab Siegen on 3D printers. The project’s flexibility to bend with reduced tooling surfaces is further enhanced by the additive tooling approach, which allows simplified tooling inserts to be printed on-demand from lower-cost plastic.

From the point of view of the profile, a better / smoother surface is achieved. The wrinkle expression is also in the same order of magnitude. But who wants to have wrinkles? A look at the trowel lying in the inner arch showed that it could not withstand the high load.

Reduced-area tool set made of PLA for rotational tension bending of metal tubes (top)
Deformation comparison: difference between conventional and PLA tools (bottom).

In an adaptation of the tool concept, it was finally possible to bend a tube of comparable quality to that produced with the conventional tools.

The question remains how much profile can be bent with a PLA tool. If you want to answer this, come to us.

Here again a big thank you to the team of Fab Lab Siegen for the support.

Corona

Because there were some questions we would like to clarify under which conditions you can come to the Lab.

We would like to share with you some more detailed info about how to access the Fab Lab. The 3G rule applies, which means whoever is fully vaccinated, recovered or tested negative may visit the lab. However, not all tests are the same. Valid are official PCR tests with a QR code as well as rapid tests from the approved sites (not self-performed tests). University students and employees, for example, can take advantage of the university’s offer of free self-testing through Nov. 30. .
The current regulations for the Fab Lab can be found here.

The Fab Lab opens again – at Reichwald’s corner!

Finally the time has come, from Wednesday, October 13 we open once a week on Wednesdays from 2 to 8 pm. We are very excited to welcome you to the new Lab at Sandstra├če 26, on Reichwald’s corner, and to work (and drink mate) with you again.

The 3G rule applies, which means whoever is vaccinated, recovered or tested negative may come by. However, seating is limited to a maximum of 20 people at any one time. Masks are mandatory throughout the Lab (except at the workplace) and safety distance. Use of the Fab Lab is still free, but as always, everyone brings their own consumables.

It is also important that everyone, including those who have worked in the lab before, must take a safety instruction. Therefore, we are offering additional safety instructions on October 13 at 2 p.m., 4 p.m. and 6 p.m.. After that, there will be regular safety instruction on Wednesdays only at 4 p.m.

As usual, you don’t need to register or pay anything for the visit or the safety briefings.

Tensile Test

If you’ve always wondered what a plastic component from a 3D printer can withstand, you’ve come to the right place. As part of the SmaP research project, we teamed up with the UTS Chair of Forming Technology and literally put our prints to the test (yes, well, maybe more like clamped).

The Attempt

The test we have carried out is the tensile test according to DIN EN ISO 527-1. This DIN standard contains the basic information about the exact execution of the tensile test for plastics.

The Sample

The specimen was dimensioned according to DIN EN ISO 527-2. This standard specifically defines the test conditions for molding and extrusion compounds. In our case, it is an extrusion compound, which is due to the manufacturing process (FDM 3D printers like the ones used extrude liquid plastic into an extrusion compound). Our specimen is a flat specimen of type 1A, this has a rectangular shape with so-called heads for clamping wedges. The width is 10 mm and a thickness of 5 mm.

Test Execution

3 different materials from 2 different printers were tested. 5 samples each were made. Samples of polylactide (PLA) and polyethylene terephthalate (PETG) were printed on one of our Prusa i3 MK3s printers. Furthermore, samples of onyx were produced on the Markforged MarkTwo. Onyx is a nylon with portions of carbon short fibers. For the test, a material sample in standardized form is inserted into a tensile testing machine. This machine stretches the specimen during the test until it breaks or elongation occurs without breakage (looks then like an elongated chewing gum). The specimen is stretched at a standardized speed (1 mm/min). The tensile testing machine continuously pulls the specimen apart during the test. The force that the specimen opposes this imposed strain is meanwhile recorded via the strain. The values in the evaluation can then be determined from the measured data. In the video below, you can see the experimental procedure and the tearing of a sample.

Results

The evaluation contains all essential information about the test and its boundary conditions, as well as a stress-strain diagram, the images of the specimens, and the data on material properties obtained from the test.

PLA

In the stress/strain diagrams of PLA, the range of elastic deformation can be seen in the range of about 0 – 1.8 %, which then stops abruptly when the tensile strength is reached, and changes to plastic deformation. From the area of plastic deformation, approximately between 1.8 and 2%, the quite pronounced part of the necking begins. The material still allows about 1.5% elongation until it finally breaks.

PETG

With PETG, the result cannot be reconstructed quite as nicely as with PLA. Sample PETG_P1, the upper outlier in the diagram, changes from the elastic to the plastic range at about 55 MPa, which then leads to necking at 60 MPa and ends in fracture of the sample at an elongation of 5.1%. The four other specimens behave similarly for the most part and also have only a small area of plastic deformation and pronounced area of necking. Compared to PLA, the elastic range of PETG is more pronounced.

Onyx

The onyx material also has a continuous transition from elastic to plastic deformation, although the region of elastic deformation is difficult to discern. Apparently, this ends at about between 8 and 10 MPa and then turns into a very pronounced part of plastic deformation, which subsequently leads to fracture with only slight necking.

Comparison

In this comparison, all evaluated specimens are summarized in a stress-strain diagram.

Here it can be seen that the specimens made of onyx (black) allow almost twice as much strain until fracture occurs, compared to the specimens made of PETG (red). Compared to the other two materials, the samples made of PLA allow even less elongation and are all already torn at an elongation of ╬Á = 3.4 – 3.8 %. The comparison diagram also shows how much stress the materials can withstand, with PLA being the best performer except for the one outlier (PETG_P1). This is followed by PETG and in third place by the onyx material. Comparing all three materials with each other, it can be seen that PLA allows the least elongation in its elastic deformation range, but also quickly leads to breakage of the specimen after exceeding this range. Therefore, it can be said that PLA is certainly the material with the most brittle behavior. If you now want to realize one of your projects, you can follow these results to some extent, at least as far as tension and elongation are concerned, although the three materials naturally have other strengths and weaknesses.