10 Principles of Sustainable, Cost-Effective Design: Building a Safer, More Efficient Machine
Manufacturers across many industries are placing increased emphasis on machine designs that support sustainability initiatives and drive economic prosperity. Machines that improve safety, minimize waste, consume less energy and deliver maximum return on investment are critical to the success of any sustainable production program. Building such a machine requires a holistic approach analyzing operational efficiency, safety, functionality, productivity, material use, ease of operation and maintenance.
Following these 10 best-practice design principles machine builders can deliver cost-effective, sustainable machines:
1) Eliminate nonessential mechanical drive components
Simplified machine designs with fewer components run more efficiently and are less expensive to build. Older mechanical power transmission and actuator technologies, such as chain, rack and pinion and worm drives, often stand in the way of more efficient designs. These older devices use components that wear over time and demand frequent maintenance, including lubrication and tensioning.
Machine builders increasingly rely on sophisticated performance and simulation software to help eliminate many of these unnecessary components, including line shafts, and costly pneumatics and hydraulics. With these mechatronic tools, engineers can analyze energy usage, build virtual prototypes and select the best mechanical design to maximize machine performance. This approach results in reduced energy consumption and maintenance costs, and improved uptime and reliability, which together reduce the machine’s total cost of ownership over its useful life.
Machine builders also use direct drive motion technology to improve mechanical efficiencies. The use of this technology creates more reliable, energy-efficient and accurate machines that are less expensive to maintain. For one Rockwell Automation customer, replacing a motor-worm gearbox with a direct drive servo motor helped improve mechanical efficiency from 29 percent to 98 percent. The increased efficiency realized with direct drive technology also allows designers to use smaller servo drives, which in turn, use less energy.
2) Minimize mass of essential mechanical components
After eliminating all nonessential mechanical items, the next step is to minimize the mass of all remaining essential components. The availability of a wider breadth of analytical, modeling and development tools makes this task easier, including the ability to test the machine’s mechanical performance envelope using advanced stress and strain analysis techniques. This allows designers to evaluate potential alternative materials (other than steel) that are lighter and more energy efficient.
These design techniques, popularized by the aerospace industry, minimize the weight of structural components without compromising strength. At the same time, with more complex shapes of structural elements, machine builders can use 3-D computer-aided design and finite element analysis tools, and employ more advanced fabrication equipment to shape and mill contours of structural components. This approach produces a more optimal mechanical design because the structural components represent the critical juncture where waste can be eliminated. Furthermore, it directly reduces the forces required to move the mass of the structure, resulting in the ability to use smaller motors and drives that consume less energy.
3) Substitute fluid power with electric actuation
Wherever possible, machine builders should design machines to use electrical actuation rather than hydraulic and pneumatic systems. Though hydraulic and pneumatic solutions may have slightly lower initial purchase prices, they are typically associated with high “hidden” costs, such as expensive recycling fees for hydraulic fluids and energy costs. Pneumatic systems in particular also can contribute significantly to factory noise levels, increasing hearing hazards and reducing employee comfort. Any opportunity to deploy electrical actuation also will help end users avoid significant energy losses associated with pneumatic air leaks. As end users increasingly seek energy efficiency in their manufacturing, new high-performance electric cylinders offer an ideal alternative.
Electric cylinders combine high speed with high accuracy, repeatability and reliability – and recent electric cylinder technology advances provide improved versatility. Furthermore, their modular design allows them to fit a wide range of machines. Controls for electric cylinders range from simple indexers to more complex programmable multi-axis motion controllers, giving designers more choices and allowing them to better weigh the cost and benefit of each solution.
4) Perform a safety audit after mechanical design, but before control system design
Performing a safety audit before control system design helps engineers chart the course for an effective safety solution, and evaluate and investigate risks early in the development process. This saves critical time and helps machine builders get their equipment to market faster. In addition, the machine’s end users gain optimized production, thanks to an automation system that helps operate machinery and processes in the most efficient way. A safety audit identifies the required safety control system integrity level and helps guide the selection of the overall control architecture to achieve the optimum level of safety.
5) Guard or control access to moving parts
Where hazards cannot be removed through design, machine builders typically will install a fixed physical barrier that protects users from the hazard. When frequent access to the hazardous area is required, non-fixed guards are used, such as removable, swinging or sliding doors. In areas where non-fixed guards are impractical, guarding solutions that monitor the presence of the operator rather than the status of the gate can be used.
While relays and other devices prove effective, many safety applications require a level of programming or more sophisticated safety logic that is best met through a safety controller. Safety controllers offer significant benefits in multistep shutdown or ramp-down sequences, such as transfer line applications, because they provide the necessary logic through software rather than the hard-wired logic of relays. An integrated safety controller is an ideal solution for any application requiring advanced functionality, such as zone control.
With properly designed safety controls and guarding, designers reduce access time, helping make machines safer and more efficient.
6) Use integrated safety systems to reduce control system complexity
The more designers integrate the standard and safety control functions of a system, the better the opportunity to reduce equipment redundancies, and improve productivity and economic factors. This integrated control functionality reduces the number of unique components in use on the factory floor, which in turn, reduces crib inventory costs, as well as maintenance team training requirements. End users also benefit from less waste with fewer parts to maintain and replace throughout the machine life cycle.
In addition, integrated control systems, having broader intelligence regarding machine operation and status, reduce nuisance shutdowns and prolonged restarts, further improving machine efficiency and productivity.
New safe-speed control solutions provide a great example of effective control integration. With safe-speed control, safety input devices, such as guard-locking switches, light curtains and emergency stops, connect directly to the speed-monitoring core of the control solution. This eliminates the need for a separate, dedicated safety controller. Providing use across multiple platforms, safe-speed control solutions help reduce overall system cost and improve flexibility because they allow operators to perform maintenance and other tasks while a machine is in motion. Safe-speed control also helps increase uptime and decrease energy costs because a machine need not be completely shut down and then restarted.
Networking offers another way to integrate safety and standard controls. The introduction of networks to the plant floor brought many benefits to manufacturers, including increased productivity, reduced wiring and installation, improved diagnostics and easier access to plant-floor data. Using an existing network to include safety information extends those same benefits, allowing seamless communication of the complete automation process on one standard network with one set of hardware and wiring.
7) Distribute control and interface devices near point of use
While some control components traditionally were located on the machine, technology advancements make it possible to house entire control systems more closely to the application point. Standard automation components – including controllers, motor starters, drives, sensors, contactors, network media, distribution boxes, I/O and HMI devices – now are designed for on-machine applications.
With an on-machine design approach, machine builders reduce design and installation time, and associated labor costs required to assemble a system. This approach also helps reduce many common machine installation mistakes, since there are fewer wires to run and connections to manually assemble. In fact, some machine builders have seen their total machine teardown and reinstallation time decrease more than 50 percent.
For end users, the compact nature of on-machine controls results in significant plant-floor space savings, helping to reduce overhead, and conserve energy and resources.
8) Develop modular code
Depending on the level of sophistication, programming alone can consume up to 80 percent of a control system’s design budget. To remain competitive, many machine builders employ standardized tools and modular programming concepts designed to speed development and installation, and improve reuse of engineering investments.
An integrated, modular design approach to application development generates and reuses code modules, based on standardized programming methods and models such as ISA-88. Using the same specification document throughout the process helps significantly reduce engineering time and improve the quality and consistency of the machine design.
In addition, having the same program structure, from concept to coding, helps simplify maintenance and troubleshooting. Information is consistent and exactly where the engineer expects it to be. Simplification of the troubleshooting process correlates directly to greater uptime and cost savings. Moreover, when programs possess the same look and feel, customer training is much faster and easier, making problem-solving more intuitive.
9) Make better use of diagnostics
With the ability to embed intelligence-gathering devices into machines without redesign or retooling, machine builders provide customers with self-diagnostic equipment capable of predicting and preventing failures, thereby boosting productivity and reducing repair costs. Moreover, this technology relays the machine condition information back to the machine builder for value-added monitoring and analysis services without compromising existing resources or hindering profitability.
From the end user’s perspective, turning the maintenance function over to the machine builder makes good business sense – it improves machine performance, maximizes capital investments and allows for more cost-efficient use of internal resources. Machines designed with EtherNet/IP connectivity allow remote troubleshooting and thus provide end users with improved diagnostic benefits. The ability to remotely monitor equipment from a distant location helps reduce fuel usage and related emissions, as well as associated travel time and costs of maintenance personnel who otherwise would go to the machine’s location.
10) Design IT connectivity into the machine
Building information-enabled machines capable of connecting into an end user’s IT infrastructure provides them with critical operational insight, including energy efficiency and overall equipment effectiveness (OEE) calculations. This insight, in turn, helps plant managers reduce waste and optimize productivity. A machine’s IT connectivity also helps maximize the benefits of a machine’s track-and-trace capabilities. Using advanced information software, manufacturers track and record relevant data at every step of the process to identify when and where resources were used.
This visibility offers end users a wealth of data for waste reduction and other improvement programs. In addition, these systems also help automate track-and-trace procedures of product genealogy through the full chain of custody. In so doing, these systems help companies comply with regulations, document required data, identify potential product quality issues before they reach the market, and, if necessary, respond to recalls faster and more efficiently.
Thanks to advancements in technology and best practices, machine builders can play an important role in helping companies implement sustainable production practices. By following the above core design principles and leveraging the best of today’s advanced technologies, machine builders can create safer, more cost-effective and reliable equipment.
Steve Ludwig is Programs Manager, Rockwell Automation; and John Pritchard is Product Manager, Rockwell Automation.
This article was provided to Control Engineering for the Oct. 13 Rockwell Automation Safety Custom eNewsletter.