Smart handling of contact lenses in automated manufacturing
The SMARTHANDLE project focuses on developing advanced handling systems for automated manufacturing processes. The project brings together partners specialising in hardware, software, and specific manufacturing needs to innovate and improve automated handling technologies. The authors of this blog participate in the Menicon use case.
Role of the different partners
Within the Menicon use case, DEMCON Industrial Systems and STT Products closely work together. Each of the partners brings in specific knowledge.
STT Products leads the hardware equipment customisation, based on the hardware specifications as defined in collaboration with Menicon. This includes the handling, shaping and transportation of the products. In this, STT Products is supported by the research partners LMS and TECNALIA.
Demcon Industrial Systems focusses on software, digitisation and the application of artificial intelligence. For this, they developed their own standardised machine control platform BRIX. This is the basis of the control software architecture used to control the production cell hardware. In the use case, BRIX is extended towards flexible handling solutions.
Background
Menicon works on automating the production of made-to-order contact lenses, in close collaboration with their development partners DEMCON Industrial Systems and STT Products. As a first step a pilot is defined as the SMARTHANDLE use case. It focusses on the challenges regarding the (smart) complex handling needs at and between the different automated process steps of materials and the end product (contact lenses).
Handling robot and its complexity
The gripper that is being developed is part of the handling robot. It will be used in combination with a commercially purchased robot. The robot and its gripper are controlled by the BRIX machine platform. The robot will handle the loading and unloading of delicate (semi-manufactured) lenses as well as handling the mounting bases and toolholders. The movement of the robot is displayed in this video.
Check the video of the smart handling gripper!
The (repeat) position accuracy of the loading and unloading is bound to set challenging requirements. The set requirements have different challenges that have to be solved along the way. One of these is the (repeat) position accuracy of the robot when loading and unloading the workpiece.
The needed repeat accuracy must be at least ±0.2 mm. The complexity of this is the fact that the frame of reference of the robot is independent from the frame of reference of the heart of the machine. The robot is mounted to the cover cell, while the heart of the machine is a separate assembly within this cell.
To ensure the accuracy of the handling, a two-step docking is designed. The robot will ‘dock’ on a position near the loading/unloading position. This dock resides on the assembly that holds the heart of the machine. The gripper will act as the floating part of the dock, when the robot is docked, the gripper will be accurately positioned in the same frame of reference as the heart of the machine.
Proof-of-Principle
In order to prove the concept above, the most important handling actions are tested in a testing environment. Actions such as loading and unloading workpieces, both docked and undocked, picking and placing tools into the heart of the machine and the docking and undocking itself.
Gripper design
In the light of the set requirements, such as accuracy as well as cycle time, the decision was made to design a combined gripper for handling the different items, raw material, semi-finished workpieces and the toolholder-tool.
An additional requirement for the gripper is that the orientation of the workpieces should be maintained during handling. This orientation is of importance during the operation in the machine.
On top of that, some kind of tactile sensor was needed to gather feedback on the grip on the workpieces to ensure a secure grip and for communicating with the software.
The biggest constraint in designing the gripper is space. The available space within the heart of the machine is very limited, as can be seen in the video. Commercially available grippers meeting the requirements above do not have enough perception capabilities. Therefore, a custom designed gripper is needed.
When docked, the workpiece is accurately positioned for loading and unloading. An additional axis in the heart of the machine enables the machine tool to grab or release the workpiece from the gripper.
A prototype for this gripper was built and indicative conceptual testing indicates that the principle with three fingers allows for good reproducible orientation of the workpiece.
Going forward ..
The next step is to continue searching for options to minimise the volume in space needed by the gripper. This includes diving deeper into incorporating the tactile ability in the fingers, instead of a separate sensor.
Furthermore, extensive testing is needed to optimise the gripper and robot functionality. Further development is needed as well in respect to the requirement of maintaining the correct orientation.