Although the term “linear actuator” can be defined broadly as any mechanical device that converts energy into controlled, straight-line motion, the definition narrows in the context of devices used for medical treatment and biomedical/chemical research.
5 Steps to Designing Linear Actuators for Medical Devices
Although the term “linear actuator” can be defined broadly as any mechanical device that converts energy into controlled, straight-line motion, the definition narrows in the context of devices used for medical treatment and biomedical/chemical research. For these types of linear motion applications, which require smooth motion, efficiency, accuracy, precision, and prolonged continuous or high-speed movement, the term refers to a new generation of precision-engineered lead screws, acme screws, and linear motion mechanisms, like those manufactured by Helix Linear Technologies.
Medical applications range from simple tasks to more sophisticated challenges that require greater force, speed, and control. The hospital bed adjustment mechanism is an example of a simple actuator application, while syringe pumps (small infusion pumps that are used to gradually administer intravenous medications to patients or control the administration of small amounts of fluids as part of laboratory research) are more complex.
The specific type and size of actuator that a design engineer needs depends on the nature of the application. The innumerable combination of stroke sizes, speeds, voltage, and types of these actuators are seemingly endless. Follow these five steps to design the right actuator for your medical device needs.
Step One – Basic Specifications
Understanding the basic specifications for the load, actuator, power, and control required by your application is critical. Your first step toward selecting the right actuator and weeding out unsuitable solutions is to determine:
- Energy source – How will you drive your actuator? Will your power come from an electric motor, pneumatic, hydraulic, mechanical, or piezoelectric source?
- Force requirements – How much force is necessary for your application and in what direction will the load need to move?
- Speed – How fast will your actuator need to move?
- Distance – How far does your actuator need to travel? In other words, what is the stroke length?
- Duty cycle – How frequently will the actuator operate and how much time will elapse between strokes.
- Environmental factors – What are the environmental factors (e.g., temperature variations, moisture, vibration, etc.) that will affect operation?
Step Two – Evaluating Options
Once you’ve researched the basic specifications of your application, you’ll need to evaluate the various application- and actuator-specific options and how they apply to your situation.
- How will you mount the actuator within the device?
- Does the application require manual operation as a safety precaution?
- Are you working with limited space and need to fit a specific actuator footprint?
- If you are using an electric motor, what type and at what voltage?
- Does the application require feedback in terms of speed force and/or position?
Step Three – Assessing Power Needs
The next step is to perform an assessment of your mechanical and electrical power needs. Once you know the force that your application needs you will be able to calculate the amount of electrical power required to generate the mechanical power that you need.
Step Four – What’s the Duty Cycle?
The next step of establishing the duty-cycle factor is very important. You may have decided upon an actuator that seems suitable through all of the previous steps but it may ultimately fail because the duty-cycle limits are exceeded. The duty cycle indicates how often the actuator will operate and the amount of time that elapses between strokes. This is a key contributing factor to heat generation and dissipation in a linear motion system. The component with the lowest allowable temperature establishes the duty-cycle limit for the entire system.
Step Five – Balancing Efficiency with Life Expectancy
The last step in selecting the right actuator for your application is to strike a balance between the device’s life expectancy and efficiency. Having both wear out at the same time is preferable to replacing the actuator, which can be challenging in many medical applications.
Helix Linear Actuators Drive Medical Device Applications
Helix Linear Technologies has the knowledgeable, experienced professionals that can help you progress through these steps as well as a complete line of advanced precision-engineered lead screws, Acme screws, and linear actuators for your medical device applications.
To learn more about Helix linear actuators for medical device applications, download a copy of the newest Helix catalog: