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CNC’s changing role in aerospace factory automation

CNC’s changing role in aerospace factory automation
Issue Time:2017-11-07
In automated aerospace assembly, computer numerical controls (CNCs) are better able to address complex interpolated motion than programmable logic controllers (PLCs). CNC technologies are finding increased application in complex airframe alignment tooling, robot control, additive machining, fiber placement and tape laying, and 5-axis machining.

As CNC use grows, manufacturers must integrate them into product lifecycle management (PLM), manufacturing execution systems (MES), and manufacturing operations management (MOM) environments. To optimize production processes, MOM software focuses on efficiency, flexibility, and time-to-market, including:
Integration with order management
Advanced planning, scheduling
Quality management
Tracking and tracing
Supervisory control and data acquisition (SCADA)
Research and development (R&D) management
As CNC technologies and software management tools have grown individually – often counter-productively – challenges have emerged:
Production planning, operational management of a variety of machines
Optimizing performance, flexibility of PLC-, CNC-based production machines
Extracting data for monitoring, putting the right information back into the machines, proper human machine interface (HMI)
Managing operator skill levels on variety of controllers
Maintaining variety of machines, spare parts
One platform, all technologies
Aircraft parts machining and assembly technologies can be standardized using today’s CNC platforms. With system openness, technology can be adapted to fit the machine tool and other production machining technologies – not only for traditional metal cutting, but for composites production. In-cavity fiber molding, composite tape laying, ceramic, and powdered metal additive processes use CNC technology with adaptive modes and high customization for motion control and data transmission.

Using CNC as a single standard for various production technologies enables:
Uniform operation, programming of various machines
Machine data integration on a standard communications platform; consolidated information from various brands of sensors, motion components
Consistent, global programming, operations, maintenance training
The open architecture of advanced CNC comes from standard systems, the virtual numeric control kernel (VNCK) for virtual simulation, and simple language commands on the HMI – all engineered on the control at NC language level. PLCs can be adapted via standard engineering tools, and CNC applications can be supplemented with software tools from third-party suppliers – tool and process monitoring systems, measurement systems, tele-services, and video monitoring systems.

High performance 5-axis machining
To machine complex parts, CNC software can improve performance and precision, since machine kinematics are no longer the sole determinant when machining. The CNC can adjust interpolation of machine axes to integrate with orientation vectors to the workpiece, increasing surface finish quality, optimizing cutting speed, and increasing efficiency.
Workpieces can be programmed in Cartesian coordinates and system-specific cycles, and function macros can automatically calculate machine axis movement.

System integration
Digitalization of industrial processes will eventually encompass every step of product life cycle – design, production planning, engineering, execution, and a network of global services.
Multi-axis machining workflow is typically characterized by the computer-aided design (CAD), computer-aided manufacturing (CAM) CNC process chain. Enhanced CAM with specific post-processing combines realistic machine simulations driven by a VNCK to create a digital twin.
CNC units can be networked to transmit data to the cloud for monitoring and corrective action, tracking back from production output and maintenance alerts on the machine to integration with CAD files and part prototypes. Production of components and assembly of finished aircraft benefit from the controls on the machines. Core elements of a full digital enterprise system begin to emerge from the data generated by the machine controls.

Simulation

Advanced simulation software and virtual production subjects the process chain to a simulative analysis from the CAD/CAM system to the workpiece surface. Instead of repeated testing on an actual machine, programs can be optimized in computer simulation, with the exception of the numerical control program, which is simulated on a real machine.

Virtual production can be performed in three steps:

  • Analysis of the data quality as provided by the part program
  • Execution of the part program by the numerical control (NC) where set-point positions on the NC output are evaluated and velocity can be optimized and controlled
  • Simulation based on characteristic features of position-controlled drives including machine dynamics

Virtual production reduces machining times, improves surface finish, and shortens start-up times for new workpieces.

The mechatronic twin can be run with only a CNC simulator, through Mechatronics Concept Designs (MCD), a Siemens machine design tool. Production times, collision avoidance between spindle and workpiece, tool path optimization, and machine kinematics can be virtualized and evaluated prior to test runs. This simulation can drive the creation of G-code programs on the final machine.

Motors, drives, shafts, slides, cam discs, spindles, etc. are stored with all technical data and animated in the MCDPositions, feeds, and speeds from the central processing unit (CPU) can be transferred to the design engineering computer in the MCD.

The 3D model can be operated like a machine tool via the CNC control. In manual mode, individual axes can be triggered. In production mode, axes can be moved synchronously toward each other via electrical cam discs. Machine functions can be actualized, checked, and optimized.

The digital factory and digital enterprise remain key targets for aerospace, and the power of the CNC on all operational machine motion control, data gathering, and communications levels continue to feed that process, evolving at light speed.