The project started off with the creation of several objectives. These objectives have shaped the contents of the project in several major ways which will be described further below. but first a general review of the workflow during the project.
The objective to create a torque resistant material:
With the connex pinter we could make use of printing more materials in one print. Using this fact the main focus of the tests was to make the finger move more human by making it torque resistant. After some trial and error the added shape of a double helix in the design seemed to be the most effective of all the tests.
The objective to create a more humanoid feeling:
Because of the fact that the project had to be based of the pneumatic technique that was also used in the original project it was rather hard to create a humanoid feeling. specially with the added boundaries the connex printer added with material properties restrictions. because of all those problems the creation of a humanoid form was scrapped in favor of the functionability of the gripper.
Multi-material printing has a great potential to improve soft robotics in functionality and interaction. Due to the composition of the materials, functional components can be create in one print with unique material characteristics. Although it is warranted that one should be careful with the use of the materials as for example the materials from the Object500 Connex are very brittle and can break quite easily. The removal of support material can be quite an issue, however water soluble support material is in attendance and should ease the development of soft robotics with multi-material printing and enable the designer to print even more complex geometries.
After all the simulations and drawings it was time to print and test. This is the design which we have previously tested in CATIA. The bending motion is even better than expected, thus the model can be considered a success. Nonetheless we discovered that the material is very weak and the finger already broke apart. The next model will be reinforced at, what we discovered to be, critical points.
Video take of an applied pressure test to the first finger model
Today, the first model of a gripper-finger was made in Rhinoceros and sent to the Objet500 Connex printer (1). The model is visible in the figure below. This printed model is used to test the initial behavior of the material and air chambers.
The model of the gripper-finger was printed later that day. However, while removing the support material one bellow broke immediately, making it already unable to function. Thereby we had issues to completely remove the support material on the inside of the finger in the air-chambers.
Therefore the following was concluded from this first prototype:
- The thickness of the finger is to small. It broke too quickly. So for the next model a thickness of 2 mm will be applied (instead of 1mm).
- Also the finger was to flexible. It could not stand straight on its own. For a next prototype we will have to make the material less flexible. That means the material for the next prototype will be a combination of 70% ridged and 30% soft material, instead of 60%/40%.
- Lastly, we need to think of a way to successfully remove the support material inside the finger. First ideas are to add a ridged cylinder in the whole length of the finger which can be pulled out after printing. This will ensure that there is space to erode support material. Secondly, a one way valve at the top of the finger could be added, so water can flow through the whole finger and clean all the air chambers, but prevent the air from leaking when in use.
For the next prototype these findings will be used to improve the gripper-finger.
Rhino model of the printed finger.
The print from the Rhino model. Although it looked good on first sight, there it is more difficult to make a working finger than we thought. For example one bellow broke immediately when it was cleaned (broken bellow is shown in the last two pictures).
(1) Stratasys, http://www.stratasys.com/3d-printers/design-series/connex-systems/
Hi and welcome on our weblog!
We are Victor, Joost, Yasmine and Marc and will be doing a project in Soft robotics as part of our minor Advanced Prototyping for the next few weeks.
Our task is to help Rob Scharff in his research in flexible 3D printing in combination with pneumatic sensors.
The Connex printer at IDE now offers the possibility to print combinations of rigid and flexible materials.
It creates a lot of new opportunities to enrich the functionality of 3D-printed soft robots which is something we have to explore.
During the upcoming four weeks we will be posting our research process and prototypes on this weblog.
Marc van Almkerk, Victor Gutgesell, Joost Remmerswaal, Yasmin Koers