Self-corrective process control in patch-based fiber lay-up
Composites manufacturing experienced notable advancements in automation technology in recent years; however, the level of process control – and subsequently quality control – for fiber layup is still far behind that seen with other materials. For today’s advanced technologies like AFP, visual in-process inspection of input material is only now being implemented. Self- corrective measures in response to non-spec input material are difficult to put in place. Placement accuracy has to be individually checked. Composites manufacturers are in search for automation solutions that incorporate intelligent process control to ensure part quality and availability of the production System.
Patch-based fiber lay-up enables exactly that: a new level of self-corrective process control through the discretization of the process, dividing it into individual placements of patches. This is the core principle of the Fiber Patch Placement (FPP) technology: by placing the fibers additively by robots in appropriately-sized patches, each patch can be individually controlled.
Fiber Patch Placement systems of Cevotec feature advanced process monitoring and control capabilities, divided into three main functional groups. The first of these groups is responsible for active, in-process quality control using self-correcting algorithms and is composed of two vision inspection units. The first unit identifies the quality of each patch that is cut by determining if the patch dimensions are correct and if there are any fiber defects, such as gaps and waviness. Patches conforming to predefined, quantitative quality thresholds are further processed while non-conforming patches are discarded. The second vision inspection unit identifies the relative position of the patch on the placement gripper once picked up. Any deviations from the robot coordinate system in position and orientation are detected and the placement coordinates are adjusted on the fly before the patch is placed. In combination, the in-process quality control system ensures that only 100% in-spec raw material is being precisely placed on its intended position.
The second functional group of process monitoring is responsible for predictive maintenance. Tension sensors in the main driving belt of the feeding module let the operator know ahead of time when maintenance is needed. Similarly, force-torque sensors between the gripper and the arm of the placement robot can calculate the elasticity module of the gripper foam and identify when the gripper is reaching the end if its useful life. This predictive control ensures sufficient time to schedule maintenance with least impact on production.
The third functional group collects relevant data on key process parameters. Data such as cutting device temperature, patch temperature, cell temperature, cell humidity, deposition pressure, etc. is collected for every patch placed. Analysis of this data enables key insights into process reliability and repeatability. Correlating the data with actual layup quality enables engineers to set and adjust process parameters in real-time – and ultimately ensure part quality by controlling process parameters.
These advanced process control features largely become possible through the discretization of the fiber lay-up process. Fiber Patch Placement technology therefore enables manufacturers to improve not only their part quality, but also equipment reliability & availability.
Cevotec enables manufacturers to build complex ﬁber composites in high volume and quality – by smart process automation based on Fiber Patch Placement technology. With SAMBA Series, Cevotec offers a customizable ﬁber lay-up automation platform for challenging 3D geometries and multi-material laminates with complex ﬁber orientation. ARTIST STUDIO is the associated CAE software for generating patch-based ﬁber laminates and automated robot programming. Along with development services that include FE-based modeling and simulation, Cevotec offers the entire process chain from digital design to ﬁnal ﬁber product.