The inconsistency in machinery controls created operation and maintenance inefficiencies at two Boeing plants in the state of Washington. With a control system upgrade, they were able to make the aging machines work like new -- or possibly better -- at a fraction of the cost of purchasing new machines.
The shot peener machines in Boeing's Auburn and Frederickson plants were between 20 and 40 years old, and based on different, aging control technologies and hardware. Some machines used hardwired relay logic, while others had older Programmable Logic Controls (PLCs) and Computer Numerical Controls (CNCs). The inconsistency in machinery controls created operation and maintenance inefficiencies. Parts were becoming obsolete, and maintenance was becoming more expensive. Reliability was an issue. Managers knew that an upgrade was in order.
The aging equipment in question, seven shot peener machines, is used to form and contour the wings and also to harden the wing surfaces of 737, 777, and 767 aircraft. The process involves blasting the aluminum part at high speed with metal shot of different sizes depending on the operation. Larger shot diameters (as large as 0.54 inch) are used for forming and smaller diameters (as small as .028 inch) are used for cold working (i.e., surface hardening). The specialized shot peener machines are quite sizable. The Spanwise Peener machine is 3 1/2 stories high -- large enough to fit the wing skin of a 747 aircraft.
To upgrade the machines, plant managers wanted new control systems that were modern and consistent among all machines. They also wanted human-machine interfaces (HMIs) that would be easier to use and were standardized with operator controls used in other Boeing plants. Standard HMIs make it easier for operators and maintenance personnel to operate the machinery. The commonality of the systems makes operator and maintenance cross-training much more effective and efficient.
For help with this upgrade, Boeing looked to system integrators, Concept Systems Inc. of Albany, Oregon, a CSIA Certified control system integrator company.
The first machine to be upgraded was the Spanwise Shot Peener machine. Used to apply the correct contours to wing parts, this highly specialized piece of equipment was the most challenging to upgrade. It requires precise, synchronized motion and shot delivery. Boeing selected the Spanwise Peener for the first retrofit because the 30-year-old machine was experiencing the most downtime.
Concept Systems engineer Jim Ford was the project manager for the upgrade. At the heart of the upgrade was a Rockwell Automation ControlLogix PAC with Kinetix Motion Control and RSView32 HMI software to provide the operator interface and graphics displays. The original DC motors were replaced with AC servo motors (MPL) that are easier to maintain and operate. New gearboxes were installed as required. New armor plate shrouding was installed to provide better protection of the motor parts and the homing and over-travel switches were also updated, resulting in improved reliability.
"The shot peeners are akin to self-destructing machines," says Franklin French, equipment engineer with Boeing. "There's armor plating in the machine to protect the chamber, but when we opened up the old machine, we found shot inside the wheel motors, ultimately necessitating a replacement of the motors and shrouding."
To help reduce maintenance problems, the new motors were equipped with vibration transducers and resistance temperature detectors (RTDs) to give advance warning of failures, and the HMI was designed to display the temperature and vibration levels, as well as historical trends. The use of coordinated motion made the system operate more smoothly, and from an engineering perspective, it made development simpler. Also, smoother motion optimized accelerations and decelerations, putting less stress on the motors. The use of coordinated motion also ensures all slave axes are synchronized perfectly with the master axis (MTD) to reach their target positions with optimal speed control.
The part parameters for the airplane parts that were run through the Spanwise were originally maintained using Excel spreadsheets. Operators who handled the machinery would enter the parameters and different properties of each respective part during setup of the machine. These parameters would then control shot speed and flow. Programming the new controls for this machine was a challenge given the number of parts, and all of the varying parameters, that needed to be accounted for. Concept's engineers developed a custom Visual Basic, HMI embedded application to read the multiple part program spreadsheets and translate them into machine code for the PLC program and coordinated motion control. The result saves the operator time and reduces the chance of error in manual entry. It also is an increase in efficiency and effectiveness, and one more boost toward increased productivity.
As part of the upgrade, Concept Systems worked with Boeing Cal-Cert group to maintain all existing testing and calibration functions and added many HMI features to simplify the process where possible. In the process of developing the new HMIs, Concept Systems held design reviews with machine operators as well as maintenance personnel, where they discussed what the new operator screens needed to do to make work more efficient. This ensured that the needs of both groups were incorporated into the project requirements. The new HMIs were a tremendous improvement, providing easy access to information for each machine.
To improve the safety of operations, Concept Systems added safety relays, safety door locks and additional emergency stop buttons. Concept used the servo positions (encoders) to measure part positions in the peening chamber, allowing the operator to only interact physically with the machine when the part was in an appropriate position.
Concept Systems was given roughly three weeks of machine access to retrofit the Spanwise Peener. It was critical that the retrofit be accomplished on time in order to minimize downtime. Programming and testing was done in advance, but final site testing was necessary in order to ensure the parts were processed correctly. Within this time, all of the old panels and motors and wiring needed to be removed and the new components installed.
The results? The new system replicates the previous functionality, but with a new, simpler control system. Productivity has increased due to the reduction of downtime made possible by the increased reliability of the new system. Efficiency has increased with control consistency. Communication has improved with the HMI panels, providing easy access to machine functionality and status. This coupled with the fact that the new hardware is well-supported, making access to spares very efficient, has reduced maintenance costs for Boeing and ensures that these benefits will be recognized for years to come.
"The machine is quite reliable now," maintains French. "The peening process doesn't run faster, but the machine downtime has been cut significantly, resulting in an overall increase of 5-7% in productivity of the plant.
"This was my first project with Concept Systems, though other Boeing sites have worked with them on machine upgrades. They seem to have a really robust process for designing and building machines. There are often gray areas in the specification and their process nails these down. I've worked with other integrators but Concept Systems' process is one of the most thorough. And if there was something omitted in the specification, Concept was always willing to work with us."
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