AP projects 2015
To find the best possible recipe for the 3D printing we decided to conduct more experiments, changing the different variables to see what works best. We closely documented these experiments for more understanding and reference.
- Create a fibrous lupine-based product with 30% less Alginate.
This might create a product that has a higher fluidity, making it better suitable to extrude from a syringe or even a needle.
- Instead of adding CaCl2 try adding CaSO4.
The instructions mentioned that both salts might work, we want to try to see if it is as effective.
- Experiment with different salt concentrations.
The salt solution is a key factor in solidifying the fibrous lupine-based product, perhaps using a higher concentration solution could create a sample with more structure and, or strength.
- Less Alginate
Instead of mixing 20g lupine with 10g Alginate, we used 7gr. The rest of the preparation were standard procedure, so the only difference was the Alginate. This resulted in a mixture that, as expected, had a higher fluidity and was less of a gelatin fluid. It also was a lot smoother and had fewer chunks.
We even managed to extrude it through a 0.5mm needle, creating the possibility to extrude very accurately. An extra benefit is that the salt solution can reach deeper into the product, creating an extruded line that is almost 100% solid, as can be seen below.
In the rest of the experiments we continued to use the solution with 7 gr Alginate, partly to reduce waste, and partly for convenience.
- CaSO4 instead of CaCl2
As can be seen in the picture down-right, the calcium-sulphate solution looks milky white, instead of the clear look we got with the calcium-chloride solution. To get an equivalent molar amount of CaSO4, we dissolved (111/136*5,4) = 4,4 grams in 135 mL of water. We tested this solution on a couple of extruded lines of the product mentioned in experiment 1, by dripping it on the product with a syringe. For comparison, we did the same with the calcium-chloride solution, on a different extruded line. Immediately it became apparent that the calcium-sulphate solution was a lot less effective than the calcium-chloride solution. The strands of Lupine product were still very fluid, and hardly had any bonding, in comparison to the strands we exposed to the calcium-chloride, which were bonded nicely, and had a certain strength.
- Different salt concentrations
To indefinitely rule out the use of the CaSO4 solution, we tried creating a highe
r concentrated solution. For this, we added another 5 grams of CaSO4 to the solution we already had, making it a solution with a concentration of approximately 9.4 gr / 135 mL. Apparently doing this
crossed the maximum solubility boundary, as a lot of the salt could not dissolve. We tried the solution on a new strand of the product, and the effectiveness hardly improved.
After ruling out the CaSO4 solution, it was time to experiment with different concentrations of the CaCl2 solution. We did this by adding, consecutively, a factor 0.5, 1, 2, 3 and 4 of the original 5.4 grams, to (5 times) 135 mL of water. After creating the different solutions, we created 5 different strands of the product. These strands where then used to drip the solutions on, giving us 5 different strands to test and compare. To test the strands, we used the criterion Strength. We measured the strength of the 5 strands using a digital force meter. Because the strands had a varying thickness, we tested the each of the 5 strengths in three different thicknesses (as they all showed a thick, medium thick, and a thin part).
Remark: Because the strands had a slightly different thickness, the measurements might be slightly inaccurate.
A table showing the strength’s for each thickness of the 5 different strands:
|Concentration [gr/135 mL]||2,7||5,4||10,8||16,2||21,6|
|Strength Thick [N]||0,5||1,6||2||2||2|
|Strength Medium [N]||0,9||0,6||1,2||1,8||1,7|
The following graph represents the data noted in the table above:
Less Alginate seems to be a good choice for further use, as it has a more fluid and less gelatin structure, it is more suitable to be extruded out of a smaller hole.
CaSO4 can be ruled out as a solution to solidify the product with, because it has been proven to be a lot less effective than CaCl2.
A higher concentration definitely seems to be a good choice for solidifying the product. The chart shows that there is a certain inaccuracy because of the varying strand thickness. Nevertheless, a trend can be deducted showing that a higher concentration results in a higher strength of the strands. What can also be concluded from the chart is that it is very likely that there is a maximum concentration that has an optimal result. Judging from the three categories (thick, medium and thin) it might be best to use a factor 3, or a concentration of 16,2 gr/135 mL in the solution.