Best practices for integrating electromechanical engineering into industrial automation systems
By Jim Mangan, Vice President Sales, Nook Industries
Recently, there has been an increase in the demand in the use of electromechanical, or mechatronic, solutions in automated industrial systems. These innovative systems can be defined as a mechanical process being controlled electrically, especially in the case of converting electrical energy to mechanical energy. Electromechanical is an efficient approach to industrial automation as it combines multiple engineering disciplines to create a single design. Linear motion components are an important mechanical part of many electromechanical systems.
The purpose of this article is to be a resource for successfully integrating electromechanical into existing and newly designed automated industrial systems. It will address the advantages these systems have over air and hydraulic systems, the change in mindset and processes that must happen to create ideal electromechanical systems, the reasons for integrating electrical and mechanical systems, as well as the variety of benefits that electromechanical systems can provide along with how to avoid the most common mistakes that are made when developing or altering an electromechanical system.
When designing automated industrial systems, the importance of mechanical components is often overlooked. In about 90 percent of all applications, it is the mechanical components that are designed first, followed by the electrical components. This is because mechanical engineers need to develop the initial design in order for the ideal electrical components to be specified. For example, electrical engineers would not be able to size a servo motor until the mechanical engineers have figured out what is driving the motor mechanically and what is needed in regard to load, direction, duty cycle, and accuracy.
Electromechanical is an efficient alternative
Not only are electromechanical systems efficient in their approach to design with the combining of engineering specialties, it is also an efficient alternative to standard industrial automation systems that use hydraulic or air systems for motion. When looking at a possible replacement or upgrade for an existing industrial system, linear motion offers significant and distinct advantages over both air-controlled and hydraulic systems.
The use of Nook Industries' three-axis gantry in a bottled-water palletizer application realized a 20 percent increase in production output over an articulating robot arm -- and was able to do this without damaging the product in any way.
In order to realize all of the advantages in a real-world system, the approach to system design and redesign have to be different from the commonly adopted approach. As mechanical components continue to be integrated with electrical components in industrial automation systems, there needs to be a change in thinking in how these systems are built. It is important for mechanical and electrical engineers to work together in understanding how their applications will function as a whole. Rather than simply thinking about the motor, engineers need to consider the entire machine and the environment in which it will operate.
Thinking differently when approaching new systems
Getting out of the normal routine for designing industrial systems is difficult; the habit is deeply ingrained as it has been the way that things are done for a long time. However, when designing a system, it is important for engineers to approach the system as a whole, understand the history of the company, and familiarize themselves with their products and solutions. A thorough understanding of what must be produced and the overall environment is crucial to designing the system with the best mechanical and electrical parts. When meeting to create an application, it is necessary to have both the mechanical and electrical engineers in the same room. The conversation should begin with the mechanical engineers planning out calculations such as the load, speed, duty cycle, and the other variables on the application data sheet to help determine the linear motion requirements. From there, the engineers can figure the type of belt drive, screw, or linear device necessary for the application. If the planning does not begin with the mechanical engineers, it becomes impossible to properly calculate factors such as screw diameter or lead.
An example of this type of decision-making method could be the process of replacing an air cylinder. When deciding what electromechanical solution is needed for an application, engineers must first consider the existing cylinder's stroke and PSI to determine the thrust force it is capable of. Once engineers figure out the thrust force, they must identify whether it is inclined, horizontal, or vertical, as well as how the user would like to control it, including the speed. Using that information, the appropriate electric cylinder can be sized for the application.
A similar decision-making process would be followed when replacing hydraulic cylinders with electromechanical solutions. Hydraulics are typically specified in harsh environments, because in the past they were the best-suited solution. However, as linear actuation design and technology have advanced, electric actuators are now available for those harsh environments. The necessary ratings for the actuators need to be taken into account when designing or redesigning the system. The simplicity of an electric actuator system eliminates the need for additional items, such as pumps and valves, to be worked into the design.
The other variable when selecting an electromechanical system over an air or hydraulic system that will need to be considered is the budget. The budget may determine which path you go down with the system because there can be multiple ways of solving one application. Some may want to do belt drives, ball screws, or linear motors, but the three variations of cost differ and the accuracy differs. The cost and required accuracy will steer selection of the mechanical solution.
The primary variables to consider when selecting the mechanical components are:
Linear motors are highly accurate but have a high cost, although linear motors are becoming much more popular in industrial systems as the costs are coming down. Screws are accurate but do not provide the high speed as compared to linear motors. Belt drives provide high speed and can handle long travel lengths.
Designing a successful electromechanical system
Companies should turn to application data sheets as their checklists to ensure they have accounted for all the proper design considerations and clarified all the requirements for the application. Application data forms can be used for linear systems that include acme screw, ball screw, cylinders, jacks, and many other solutions. These forms consist of easy-to-use checklists that incorporate a number of factors, including typical move calculations for speed, distance, acceleration, and more, as well as application diagrams, move profiles, operation calculations, load calculations, motor preferences, power availability, operating environment, and more. These will go a long way in selecting the best electromechanical solution for an industrial system.
RAD Ball Screw Worm Gear Double-Reduction Electric Cylinders feature a rugged design and capacities from 3,500 lb to 40,000 lb. They include a second reduction, giving a reduced input torque and lower travel rate.
Available, valuable tools that make integration an easier process include mobile apps, such as Nook's DesignGuidePro, a web-based application that allows engineers and designers to quickly find the appropriate worm gear jack, bevel gear jack, electric cylinder, and bearing products for their application. All the user has to do is plug in the desired specifications, and the app will provide a list of products best suited for the application for the engineer to select from within their parameters and budgets.
Why integrate electrical and mechanical?
Many original equipment manufacturers have reaped the benefits of making the switch to electrometrical systems. If an OEM is designing a brand new application, the company will want to look for a system that provides the one-stop shop service of complete integration. Rather than dealing with the hassle of calling multiple companies when issues or changes arise, companies like Nook Industries are working toward providing complete systems so they provide all the expertise necessary to find a solution to a problem or event to help set up an industrial automation system.
To further their efforts as a complete solutions provider, companies have engaged in partnerships, such as Nook Industries and Advanced Micro Controls partnering to deliver mechatronic automation solutions. AMCI took its experience with PLC-based motion control and paired it with Nook Industries' domain expertise with linear actuation to give its customers a one-stop solution.
Beyond purchasing and support benefits, electrical and mechanical integration provides a variety of other benefits including reduced total operation costs, greener performance, cleaner operation, and ideal solutions for a variety of industrial environments.
Cost benefits of electromechanical
When selecting an industrial automation system, consider the total cost-saving benefits of electromechanical systems. While start-up costs of integrating electric systems can seem high, sometimes even four times the cost of standard systems, the savings in the long run heavily outweigh those of air and hydraulic systems. For instance, many designers forget about external expenses, such as air, plumbing, hoses, compressors, pumps, FRLs, and the various additional components and upkeep that add to the costs. When it comes to power consumption in a manufacturing facility, air systems are neither cheap nor green -- they require filtering, cleaning, lubrication, and other upkeep. Also, unlike hydraulic pumps and air compressor systems, electric systems only draw power when they are in use, which saves the company even more money over time. There are spreadsheets, calculators, and other tools available to determine a system's energy savings on a monthly or yearly basis.
Green benefits of electromechanical
Electromechanical systems have a much less harmful impact on the environment compared to air and hydraulic systems. Electromechanical systems are being used to replace hydraulics in many applications for environmental benefits. With hydraulic systems, for even a tiny leak, the clean-up process can be messy and the disposal process can be costly. It is, overall, less environmentally friendly than other systems.
However, despite its advantages, a hydraulic system can provide much more power in a smaller package than an electromechanical system. Therefore, not all motion systems can be converted to electromechanical. Exceptions include applications that are not linked to an appropriate power source to operate the motors. Applications like heavy work trucks, cranes, and lifts do not have access to adequate power to operate using mechatronics, so they will continue to be driven by hydraulic systems for the foreseeable future.
Environmental benefits of electromechanical
Electromechanical systems are well suited for use in a variety of applications in different industrial environments, including explosive, corrosive, outdoor, and wash-down environments.
It has become increasingly important for companies to replace air and hydraulic systems within explosive environments with better-suited solutions such as mechatronics. The first step for accomplishing this is to know the type of explosive environment. What class is it? What group is it? There are multiple different classes you can meet. Electromechanical systems can be designed to be highly accurate in these environments while also minimizing the risk of sparking. For example, screw-driven actuators have nothing in them that will cause sparking, especially if they use a lead screw, which incorporates a non-sparking bronze nut. When paired with explosion-proof limit switches and motors, they are an ideal option for volatile environments. With these systems, the controls can often be farther away, out of the explosive area. Static electricity can be an issue with belt-driven actuators since belts inherently want to rub, which creates static. If a belt-driven actuator is necessary for the application, it is important to select a system with an anti-static belt with the appropriate certifications.
Most rod-style actuators are considered outdoor-duty rated and will provide powerful, consistent performance even when the temperature falls. When operating in cold temperatures, air cylinders can freeze up, causing motion to stop. Hydraulics also present a challenge in low-temperature applications because they require the oil to be heated. The cold temperatures will cause the hydraulics to become sluggish, making it so that the position is not repeatable. Electromechanical systems have an encoder that will report the position, which makes the control scheme easier without requiring additional external components that can go bad.
Linear motion components can be selected from corrosion-resistant materials as well as wash-down-rated stainless steel to operate in these harsh environments. Selecting the solutions with the correct ratings is crucial. In food-grade or clean-room systems, electromechanical solutions can be the superior option because they operate cleanly and can withstand regular wash downs. Hydraulic systems in food and beverage applications must be used with edible oil or other fluids that can be safely consumed. The restrictions of the hydraulic systems have caused a trend in moving to electromechanical for food and beverage applications.
Food, beverage, packaging, and other automated systems also often require rapid changeovers for producing multiple products with a single system. Typically, air cylinders do not perform well in systems designed for rapid changeover, since position must be changed for different products as they operate from sensor to sensor. Air as a whole does not lend itself to changing position accurately; air systems that will do this can be cost prohibitive to install. Machines requiring rapid changeover from one product to the next benefit from electromechanical setups because of the pre-programmed positions for actuators. One signal can be sent, and all actuators go to the pre-programmed positions rather than having to change from sensor to sensor. Packaging and pharmaceutical manufacturing facilities face many of the same challenges for design and reap many of the same benefits from the use of electromechanical solutions as the food and beverage industry.
Common mistakes to avoid
There are a few common mistakes that designers will make when developing an electromechanical industrial automation system. The top errors to avoid are:
Deceleration: When integrating systems, one of the most common mistakes is found in miscalculating the acceleration rate and deceleration rate. One major problem to avoid is using a servo motor on a ball screw. This can lead to over acceleration, which can cause a variety of problems like breaking things, injuring people, skidding balls, or deforming balls in the screw.
Duty cycle: Another issue comes from the duty cycle. To avoid duty-cycle problems, address the following questions: How often is the load actually moving? If it is moving, is it continuous? If it's continuous, how often will it be lubricated?
Maintenance: Lack of lubrication becomes a bigger problem related to duty cycle. Electromechanical systems need to be maintained correctly. With proper lubrication and operation within the appropriate parameters, these systems will provide an excellent service life and performance.
Guidance: How is the load guided? Customers often forget to ask about how an application will be guided. There are multiple ways to guide a load, including cam followers, profile rails, round rails, and machined ways that are oiled. Regardless of what is being moved, there is a way to support it. When considering a design where the mechanical operation includes an actuator, determine if it will be designed with the guides built in (if it is a lifting application) or if it is going to be unguided and the cylinder has to be keyed so that the load does not rotate as it is lifted. It is also good to determine how much forgiveness needs to be built into the guidance; the actuator or other linear device would need to be designed to move with it or have bearings that would support the side load that will be put on it.
It is crucial to learn the way that a machine works, or how it is going to work, in order to develop the best electromechanical system.
Consider electromechanical in new designs and redesigns
In terms of operating cost and performance, electromechanical systems are often the ideal option for many applications that use automated systems. The service, collaboration, and environmental benefits serve as additional reasons to consider electromechanical for repair and overhaul of existing systems as well as redesign of entirely new systems. The resources to use electromechanical where air and hydraulic systems have been previously specified are available to make first-time design easier and subsequent designs repeatable.
As more companies strive to integrate completely engineered solutions, it's important to remember that change begins with open communications between electrical and mechanical engineers. Opening collaboration between the two fields will hopefully lead companies to the right solution for application quickly and efficiently.
About Nook Industries, Inc.
Headquartered in Cleveland, Nook Industries is an ISO9001:2008- and AS9100C-registered company that provides controlled motion solutions in a wide range of industries including transportation, medical/diagnostics, paper, chemical, food/beverage, solar/aerospace, entertainment, and communications markets. For more than 45 years, Nook has provided comprehensive engineering, design, and analysis in providing the highest quality linear motion manufacturing solutions. For more information, visit nookindustries.com or call 800-321-7800.
Published April 2017
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