Design Challenges for 180° Drive Linear Actuators

Design Factors and Challenges for 180° Drive Linear Actuators

In the pursuit of precision linear motion, designers must understand the pivotal factors shaping the design of 180° drive linear actuators, beginning during the development phase of the device. This blog provides a comprehensive overview of the key design factors crucial for optimal performance and the challenges designers may encounter in the development process of 180° drive linear actuators.

Learn more about electric linear actuator systems, including the types of 180° actuator systems and applications that use these systems, here!

Critical Factors for Design Consideration

Force and Speed. When opting for the 180° drive linear actuator, it becomes imperative to establish the necessary force and speed parameters dictated by the application. Various operational scenarios can exist within the application, prompting the consideration of distinct force and speed requisites for each scenario. The drive linear actuator’s load capacity entails two significant variables: static and dynamic. The dynamic load capacity denotes the force applied while the actuator is in motion, whereas the static load capacity refers to the force capacity when the actuator is stationary and holding a load securely in position.

Duty Cycle. The duty cycle is a ratio of the operational time for the drive linear actuator over the total cycle time. The duty cycle will determine the temperature rise of the actuator while in motion, as power is lost through heat. Following duty cycle guidelines helps ensure that the actuator does not overheat the motor and damage the actuator components over its intended life. This requires an understating of the overall time the actuator is working and the time corresponding off time.

Stroke or Travel. The required stroke or travel distance of the application will determine the lead screw specifications as well as influence the choice of the preferred arrangement.

Life or Reliability Target. Using the duty cycle and speed as benchmarks, it's possible to compute the necessary lifespan or reliability objective. This calculation factors into the design and component selection of the mechanism to guarantee the attainment of the desired lifespan or reliability goal.

Captive and Non-Captive Mechanisms. The device design will provide direction for the type of linear motion needed from the direct linear actuator (i.e. captive or non-captive). The decision is critical for the actuator design, so it should be clearly defined at the beginning of the project.

Lead Screw and Nut Selection. Based on the load and speed requirements, the lead screw specifications (primarily diameter and pitch) can be selected. The lead screw must be assessed for factors such as buckling load and critical speed. In some applications, the self-locking attribute of the lead screw proves advantageous for maintaining the position of the load, thus the pitch of the lead screw can be selected accordingly.

The selection of nut material hinges on factors like load, speed, and life/reliability requirements. In instances involving non-captive linear actuators, the nut design is influenced by the specific application details. The nut can either be a standard that is readily available or can be customized per the application specs. There's an option to either adopt standard nuts provided by manufacturers or tailor the selection accordingly. Conversely, captive linear actuators involve nuts with integrated gears.

Bearing Selection. For the output gear stage, the bearing selection needs to be done carefully. If there is excessive axial and radial load, ball bearings should be considered for the design. A combination of ball bearings and sleeve bearings can be considered based on the load, speed and life requirements.

Efficiency. As this linear actuator system involves multiple power-converting mechanical/electromechanical sub-systems, such as the motor, gearbox, lead screw, and nut, consideration needs to be given to each individually, as well as in combination for the system to operate at its optimal level. A safety factor should be used considering the efficiency of each sub-system.

Linear Resolution, Linear Accuracy, and Backlash. The linear resolution depends on the gear ratio, the pitch of the lead screw, and the resolution of the feedback system. The requirements for linear accuracy and backlash should be addressed in the design of the mechanism or the application integration.

Assembly Requirements. Upon finalizing all the major sub-assemblies, it's imperative to also evaluate the assembly process of the components. The choice of assembly techniques, joining methods, mounting features, locating elements, and any specific orientation requirements hold great significance for the design.

Additional considerations should be given to the requirements related to noise and vibration levels, feedback system, weight, size, and environment It's crucial to outline these specifications from the outset, as the design and choice of materials will be guided by these distinctive prerequisites. The factors listed above do not constitute an exhaustive list; there may be other critical factors that arise based on the unique needs and requirements of the specific application.

Challenges During Product Development

The sub-assemblies and components designed for the mechanism are typically sourced from distinct suppliers. Additionally, there are instances where custom sub-assemblies or components must be obtained from suppliers. These circumstances give rise to specific challenges outlined below:

Integration Challenges. Acquiring sub-assemblies and components from various suppliers can introduce integration challenges. Ensuring the seamless compatibility of these diverse components can be a complex task. Close collaboration with multiple suppliers becomes essential to devise an effective integration strategy, ensuing parts are harmoniously integrated to avoid performance issues.

Custom Parts. The necessity for custom parts within a linear actuator can pose a significant challenge. Depending solely on standard parts may result in impractical or non-feasible designs or sub-optimal solutions. The development of custom parts requires additional time, effort, and resources, potentially lengthening project timelines and increasing development complexity.

Unknown Specifications. New applications might not align perfectly with the specifications of standard sub-assemblies or parts. If a supplier lacks clear specifications for the parts, the customer and supplier may need additional testing and problem-solving to bridge specification gaps or mitigate associated risks.

Special Requirements. While standard sub-assemblies or parts might fulfill general-purpose needs, specific applications often require unique attributes such as environmental or force sensors. Addressing these special requirements necessitates collaborating with specialized suppliers who can provide components tailored to these distinct needs.

Design and Testing. The design linear actuator requires actuator-level testing as well as application testing. For the designer, the task of designing, testing, and qualifying the drive linear actuator assembly can be significant.

Conclusion

When designing a linear actuator system, it is crucial to consider several key factors that play pivotal roles in the overall process, including system design, assembly, and testing. Challenges may arise from integrating components sourced from different suppliers, accommodating custom part requirements, dealing with unknown specifications, and addressing specialized needs. Effectively addressing these challenges involves collaborating closely with suppliers and developing custom parts to ensure seamless integration.

The linear actuator development process can have a significant impact on project scope and timelines. The success of the right motion solution design hinges on gaining insights into application requirements, possessing a deep understanding of critical design and development factors for a 180° drive linear actuator, and overcoming the various design and supply chain-related challenges.