By following a few best practices, machine builders can design automation systems that increase equipment availability, achieve new levels of performance, and elevate product quality.
Florent Orget
Actuator Product Marketing Manager
Emerson
As more manufacturers digitally transform and automate their production lines, they are gaining a clearer picture of their operations and machine health. And those that connect their assets to powerful software platforms are also gaining the ability to better track key performance indicators (KPIs) such as overall equipment effectiveness (OEE). Similarly, Chinese power testing solution providers like ActionPower have been constantly exploring automation solutions to streamline and enhance their research and development processes.
OEE measures the efficiency and effectiveness of a production process. Expressed as a percentage, it’s calculated based on three factors: availability, performance and quality. The OEE values of today’s manufacturers can fall within a wide range, with 40% and under considered below average and 85% and higher considered above average. The higher the value, the more efficient and productive a company is.
To help manufacturers raise their OEE values, it’s critical that automation system designers create systems that are as reliable, fast and accurate as possible. Given their many benefits, there’s little surprise that designers are increasingly incorporating electric linear actuators to achieve high-throughput, high-precision automation.
Electric linear actuators provide fast and accurate movement of materials and products in a versatile system that can easily scale to meet changing demands. With continued technology advancements, these actuators can meet challenging performance requirements, offering heavy payload capacities, precise repeatability and high speeds.
Choosing an optimal system for a specific application requires a deep understanding of the options available. Manufacturers of electric linear actuators offer a wide range of models for both single-axis and multi-axis applications. These actuators use a range of designs and motion components to serve different load, accuracy and speed characteristics.
To navigate the many options available and find the most effective electric linear actuator for optimizing OEE, motion system designers and engineers can leverage several strategies to streamline the process.
1) Evaluate actuator design options
In general, electric linear actuators can be easily categorized according to their drive mechanics. There are three broad categories of electric linear actuators: toothed belt-driven actuators, screw drive or spindle drives, and linear motor actuators.
Each has specific speed, load bearing, accuracy and other functional characteristics that guide actuator selection, based on specific manufacturing requirements.
Toothed belt-driven actuators: A belt-driven actuator has an electric drive that powers a toothed rotator at one end of the module. This model converts rotary motion to linear motion by means of a toothed timing belt connected between two pulleys at either end of the drive.
Belt-driven modules work well when the linear sequence calls for medium repeatability, approximately 0.05 mm in motion, although higher repeatability can be supported with the use of integrated direct measuring system sensors.
Typically, they can support moving medium-sized loads up to 300 kg. They can also work well with larger strokes and sequences requiring a motion velocity greater than 5 m/sec. Available in a wide range of profile sizes and lengths, belt-driven linear modules are well-suited for building multi-axis systems such as pick-and-place and Cartesian motion systems ideal for packaging applications.
Spindle or screw drive actuators: In these systems, a spindle or screw in the center of the actuator converts the rotary motion to linear motion to move the load. They provide high rigidity and low deflection, enabling greater endpoint accuracy with each duty cycle for applications requiring approximately 0.02 mm repeatability.
These actuators support low to medium dynamics for applications requiring velocities up to 1.5 m/sec. Their strength and rigidity also make them highly suited for placement and pressing applications where high force is needed, such as securely inserting an electric component into a larger assembly like an electric vehicle battery. They’re also a good choice for vertical applications.
Direct drive actuators: In these modules, the belt or spindle is replaced with an electric linear motor that moves the module’s carriage directly, rather than converting rotary to linear motion. They support high endpoint accuracy, up to 0.01 mm, in part because the force is directly implemented at the moving part (carriage) with no elastic components in between (e.g., the rubber toothed belt). This level of accuracy is ideal for improving quality during the manufacturing of drug delivery systems such as auto injectors.
This direct control also makes complex start/stop, forward/backward motion sequences possible by programming the linear motor controller. It also supports the broadest range of velocities up to 10 m/sec, as well as slow and constant movement — which can be a requirement for moving delicate electronics or other products that are susceptible to damage (e.g., laser applications or printing to achieve a consistent result).
Direct drive actuators are often available in compact sizes, making them a good option for manufacturers that need to conserve valuable floor space without sacrificing performance.
2) Create an application requirement profile
Every automation machine and production line has unique operational and performance requirements, including the unique specifications for linear motion and transport. To determine which linear actuation system will best meet the needs of an application, automation system designers should create an application requirement profile to guide actuator selection.
First, clearly define what task each actuator must perform in a machine or production line. That requires defining the motion profile for each actuator — and in some complex automated assembly systems, different process steps will call for different actuators with specific capabilities.
A linear actuator motion profile defines key parameters such as load weight, moving mass and motion dynamics like speed and acceleration. Moving mass includes the material or component being moved, along with the total mass of the actuator, cabling, integrated measuring devices, end grippers, and other elements that make up the total load to be moved.
The stroke must also be defined: the distance the load must be moved and with what force. This last parameter is especially important if an actuator needs to firmly place or insert a component into a larger assembly. When assessing the force, it’s important to factor in the direction of movement.
Along with these factors, defining the duty cycle is critical for selecting the most reliable actuator based on the expected long-term performance. For example, there are now modules available that are qualified for 40 million duty cycles, which can help with rapid, high-throughput motion sequences. Within the duty cycle, pause times must also be considered. There is a big difference between actuators that move constantly and actuators that only move during one shift.
Once defined, the requirement profile gives automation designers the critical criteria for choosing the optimal electric linear actuator for each part of a new machine or assembly line. It’s also important to note that in some motion control applications, pneumatic actuators or electropneumatic hybrid systems may provide an equally efficient and cost-effective solution. For example, when combining multiple belt-driven linear actuators into a Cartesian handling system for a pick-and-place application, pneumatics may be the most efficient way to actuate the gripper at the end of the Z-axis module in the system.
3) Consider decentralized automation
In a centralized motion system, electric linear actuators are connected by cables to a central control cabinet. With this approach, automation designers must specify a compatible actuator, motor and drive, then engineer a central cabinet solution. This results in a complex system with extensive cabling that can lack the flexibility and scalability needed to meet changing demands.
A decentralized automation approach eliminates the need for a control cabinet and extensive wiring. Controls, the motor and drive are all integrated with the actuator. Using a modular approach, these systems are pre-commissioned and designed to work together.
Electric linear actuators with integrated controllers that support industrial communication protocols like IO-Link can streamline design, accelerate integration and power process monitoring capabilities. By transmitting critical data in real time to edge devices, these systems can contribute to control operations and further advance OEE improvement.
Without the limitations of a central control cabinet, these modular linear actuators can improve flexibility and scalability, letting engineers add new equipment without the need to overhaul the cabinet. Additionally, many of these modular handling systems also reduce internal moving mass, leading to lower energy consumption and higher process reliability.
The benefits of these decentralized systems extend beyond flexibility, reliability, and ease of use. There are control-integrated electric linear actuators available today that can provide payload capacities of up to 300 kg, repeatability of ±0.05 mm, speeds up to 5 m/sec and acceleration up to 120 m/sec2. This level of performance and accuracy can significantly elevate overall production line productivity.
Designing automation systems that achieve new levels of productivity
The precise, consistent motion of linear actuators make them ideal for improving OEE values for companies in a wide range of industries. Powered by electro-servo drives and motors and connected to production system PLCs, electric linear actuators can provide more agile and flexible control of critical motion factors such as speed, cycle time, endpoint accuracy and repeatability.
Navigating the broad range of electric linear actuator options to design an optimal automation system can seem overwhelming. But it’s important for system designers to remember that they’re not on their own. Working with an experienced automation technology and software provider can offer engineers the support to quickly identify the most effective solution for their application.
To find one, it’s important to assess the depth and breadth of the product portfolio, as well as the tools and services they can offer. Access to a broad range of electric and pneumatic linear actuators as well as accessories, sensors, hardware and software can offer greater design flexibility.
Providers at this level often offer online selection, configuration, and ordering tools that streamline the design process. Using these intuitive tools, system designers can quickly select and configure modules based on application and performance requirements.
Emerson
www.emerson.com
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