Zwick testing our prototypes

Today, Monday the 31st of October, we did a last minute test on our prototype cubes (2 x 2 x 2 cm) with a Zwickmachine: a drawbench that tests materials on their tensile strength. By applying a pressure of 500 N in ~16 seconds on each of the test cubes and measuring the compression, we obtained data of the 5 cubes. Then we compared the data in order to draw a conclusion on which material and pattern will suit the saddle the best. The 5 test cubes:
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The first test cube was a pink cube made of 100% hard material:
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Grafiek1

This cube compressed with 0,159 mm.

The second test cube was a blue cube made of 50% hard material:

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Grafiek2

This cube compressed with 8,045 mm.

The third test cube was a soft cube with a hard spiral pattern in it:
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Grafiek3

This cube compressed with  0,271 mm.

The fourth test cube was a soft cube with a hard circular pattern in it:
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Grafiek4

This cube compressed with  0,399 mm.

The fifth test cube was a soft cube with a 50% hard circular pattern in it:IMG_8467
Grafiek5

This cube compressed with  9,460 mm.

From least to most compressable:
mm                what
0,159             pink cube 100% hard material
0,271             spiral pattern 100% hard material
0,399             circular pattern 100% hard material
8,045             blue cube 50% hard material
9,460             circular pattern 50% hard material

The results were mostly as we expected and with this information we can conclude that a circular pattern consisting of 50% hard material in a soft cube is best to use for suspension. Sadly, we don’t know how this pattern will work on a big scale (we are afraid it will rip easily).

This experiment was conducted on a short notice and we were unable to use the findings in our final saddle. It did give us an idea about all the variables that have to be taken into account when it comes to pressure distribution. Further research is needed to find the best combination of materials and patterns for optimal suspension. For our final saddle we decided to use a mix of hard and soft material (in a circular pattern) because we know from previous prototypes that this allows suspension to happen and is also strong enough to bear a person.

 

Week 5: Heading for the science fair

This is the final week of our project and we still have quite some things to do before we are ready for the science fair. Only half way through the project we discovered and really understood all the possiblities of using reaction diffusion in 3D printing. Since we are almost done, our goal is to lead the way for our successors and to also create some visual and scientific material about reaction diffusion in 3D printing to present next Tuesday.BZ Uitgesneden Mooi

Last week we created a lot of video material of the Belousov-Zhabotinsky reaction. One reaction showed really nice symmetrical spirals that also corresponds with the wanted pressure distribution of the saddle. We decided to use this pattern for our final 3D print. It is shown on the right.

Max has been working with Rhino and Meshmixer for the last two weeks and he created a nice saddle shape which we use to cut out the Avizo files. It is a standard racer bike model but we adapted the 2upside so that if someone sits on the saddle and the cones are pushed down, the surface will be approximitely flat. We printed a small sample of the saddle to get a better understanding of our final product (shown on the right). The blue parts are solid and the transparent parts are flexibel. We are really happy with this first print but there are two problems we noticed:
– the model can break easily if two solid parts are connected by only flexibel material
– there is no suspension if the hard material from different cones is not seperated completely by flexibel material.
Our first conclusion is that we need a plate underneath the 3D print to support the weaker parts of the saddle. We spend Tuesday morning building this part and added a construction that can fix the saddle onto a bicycle. We want to solve the second problem by magnifying the spiral patterns so that the width of the cones is always big enough to seperate the layers.thumbnail_IMG_20161027_134924

We printed a second test model of a sphere. It contains the spiral pattern which we talked about earlier, only this time enlarged. We started testing it and we noticed that there again is very little suspension. This is due to the fact that the hard spiral structure consists of one piece which cannot bend. We want to have a functioning saddle next week so we decided to test some different structures/materials to see if anything works better than our current model. The findings can be found in the research folder.

The rest of our work this week consisted of creating visual material for the science fair and a lot of hours in Rhino and Meshmixer.

Week 4: Reaching the final product

Week 4 was all about conceptualising and perfecting our product idea. On Monday we decided to continue with the bike saddle and we ditched the chair seating and shoe sole ideas (but maybe in the future..?). In the picture shown below (which is of a chair seating instead of a saddle) you can see our thought process:

Pressure, Reaction, Product

 

1. 2D pressure distribution

 

2. Belousov-Zhabotinsky reaction

 

3. 3D printed bicycle saddle

 

 

It starts with the identification of high and low pressure points on the saddle. A lot of research has been done in this field so we decided to use measurements from specialized researchers. The next step is to feed this information to the Belousov-Zhabotinsky reaction. We know from previous weeks that this can be achieved in different ways. Due to time pressure we are forced to use one of the less accurate methods which is controlling the starting point of the reactions by adding solution A in the right proportions. The final shape is then very dependent on nature’s random way of developing a pattern. Hopefully this week we can crack the method a bit more to come up with a shape that fits the pressure distribution well enough.

We film the reaction and create a stack of 2D images that represents the process over time. This information is fed to Avizo and we create a 3D model of the oscillating rings (where the height of the model is the passage of time). Once this has been done, we save it as an STL file and we move on to the next and final step. The pattern has to be measured and scaled to the real size and the the periphery of the saddle has to be cut out. One of the big problems is that Avizo turns the file into a mesh which is really difficult to work with in Rhino. Therefor we are now working with meshmixer software which makes this step a lot easier.thumbnail_IMG_20161026_131959

This week we also printed our first prototype made of two materials. The first thing we learned is the minimal thickness that the Connex3 can print. The blue part of the cilinder is the Belousov-Zhabotinsky reaction printed in hard material. The structure was lost because we scaled it too small. With this experiment we know all the scaling values we have to use for a proper pattern. The transparent part of the cilinder is flexibel material. We noticed that it bends really easily but there is not a lot of supsension when you push it in. We are going to research this further next week.

Interacting with the Belousov-Zhabotinsky reaction

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Today, Thursday the 20th of October, we worked in two groups: Lemin and I worked in the lab and started about 8 reactions and filmed them and Max and Heleen prepared the video footage of the reaction and made 3D-models with it.

We interacted with the reactions in multiple ways:

  • We added more of solution B
  • We added more of solution C
  • We added drops of solution A

When we added more of solution B, we found that the solution in the petridish became very grainy. Because this precipitation made it very difficult to obtain clear footage, we quickly decided to stop the reaction and throw it away.

Adding more of solution C to the reaction slowed the process down a lot. We had to swish the solution for a long time before it turned blue and red and the typical blue rings only started to form after about 10 minutes.

Adding drops of solution A to the reaction formed blue rings in that spot: this is exactly what we had tried to achieve multiple times before. With this information, from now on we can start reactions in every place we want and influence the reaction in such a way that we can make more or less rings appear in the wanted locations. In the pictures below you can see very clearly where we added drops of solution A to the reaction.

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Tuesday the 18th we also did some small experiments. For instance, we wanted to see if the depth of the petridish had any influence on the reaction. We thermoformed a ‘dish’ with multiple bumps with different depths and started a reaction in it. The results were not of any significance, as the solution became too dark to see through and too chaotic. In addition to this, the acid started to bite through the plastic of the dish. In the picture below it is visible that this experiment was not successfull.

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In the table below you can see our other findings:

What did we change? What kind of pattern forms? Why does it work or not? Are we going to use this?
Warmth Too difficult to realize No
Light The difference in warmth has little to no effect on the speed of reaction. No
Touching By touching it one time spirals are formed. By making a line the reaction becomes red without any blue circles. Too difficult to control No
Depth of dish Not visible Can not be filmed as no light travels through the dish. No
Add indicator  The added indicator forms a red drop. It turns blue and red respectively and slowly takes over the underlying pattern. Too much contrast between indicator and underlying pattern. No
Add solution A An oscillating blue pattern starts at the spot A was added. We can decide where a reaction starts. Yes
Add solution B The existing solution is separated by a green/yellow liquid that sticks to the petri dish The reaction stops. No
Adding coloured reaction (with indicator) to see-through reaction (without indicator) The oscillating pattern slowly spreads from the red dot. The contrast is worse than what is normally the case. A small part of the indicator is added to a reaction that has already started. This is already mixed and thus reacts faster with the see-through liquid. Maybe