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/