Every day, linear actuators in medical devices are making a global impact by saving lives as they continue to advance with our improving technologies. Aside from the versatility of linear actuators being available in many different sizes and force ratings, our technological advancements have also allowed for reliable accuracy and repeatability through micro precision servo actuators. In this article, we will cover the most popular use cases of high-accuracy micro actuators in medical devices and the important specifications to consider.
Important Specifications of Micro Actuators
PA-12 Micro Precision Servo Actuator
Before choosing linear actuators for medical applications, it is important to ensure that their specifications are sufficient to meet all your requirements. The main specifications looked at for micro actuators are:
- Life cycle
- Physical dimensions
- Duty cycle
- Travel speed
- Force rating
- Communication
Lifecycle
All components used for medical devices require high levels of reliability that patients can depend on during medical treatment. Our PA-12-R and PA-12-T Micro Precision Servo Actuators are self-lubricated internally for the life of the unit and require no maintenance when used within their ratings. Generally, the same model actuators with a shorter stroke length and lower force rating will have a longer life cycle when used within their ratings. Choosing the PA-12-R will generally be best for applications that require a longer service life; however, our PA-12-T has a sufficient lifespan for applications with lower usage and prototyping. The PA-12-T also offers similar accuracy and precision while being more affordable than the PA-12-R.
| Model | Lifecycle |
|---|---|
|
1 300 000 |
|
|
94 000 |
|
|
200 000 |
|
|
100 000 |
Physical Dimensions
An actuator’s retracted hole to hole (H2H) dimension is the first crucial measurement when determining its physical requirements. This measurement is the distance from the center of the rear mounting hole to the center of the front mounting hole. It is essential to make sure that this dimension lines up with your application’s rear mounting hole center to the front mounting hole center.
H2H retracted length
Duty Cycle
A duty cycle refers to the ratio of on time to off time, typically expressed as a percentage. For example, if your actuator extends and retracts for 15 seconds, and then spends another 45 seconds at rest before the process repeats, the duty cycle would be expressed as 25%. The percentage displayed is always the ‘on’ time of the actuator.
Travel Speed
For some use cases, there may be a certain range of speeds that your actuator is required to have. To determine your required speed, the stroke length must be divided by the desired amount of time. For example, a stroke length of 2 inches that needs travel in a maximum of 1 second would mean a required speed of at least 2 inches/second. After the minimum speed is confirmed, the next step is to select linear actuators that have a travel speed faster than or equal to the requirement.
Force Rating
Before purchasing micro actuators, we recommend calculating the required force of your application. This is because selecting the right force option is crucial for ensuring smooth operation and long life. An actuator’s dynamic force rating is how much load the actuator can push and pull when the load is applied directly to the shaft. Dynamic force should be selected as something higher than or at least equal to what is required. The static force rating of an actuator is how much load the shaft can hold still when electrical power is shut off. In a circumstance where the actuators are no longer cycling, having a sufficient static force rating will ensure safe operation.
Communication
To achieve their performance, stability, and positional accuracy up to 100um, our PA-12 actuators require users to interface with their internal microcontroller through RS-485 or TTL protocol. For TTL-enabled units such as the PA-12-T, it is possible to communicate via servo pulses. Using a TTL to RS-485 module to communicate with the PA-12-R is required if you were using a controller that does not directly have compatibility with the RS-485 communication protocol.
Both TTL and RS-485 represent standards in serial communications that can be controlled with an Arduino. They provide a framework to develop a set of commands and responses in an 8-bit format that could be used to interface with the onboard microcontroller in our PA-12.
The communication parameters for the serial data connection for both TTL and RS-485 are shown below:
| Item | SPEC |
|---|---|
|
Structure |
Half-Duplex UART |
|
Baud Rate |
576000 |
|
Data Size |
8-bit |
|
Parity |
Non-parity |
|
Stop Bit |
One Bit |
Use Cases
There are many ways to implement micro precision servo actuators into applications in the medical industry. Just to name a few examples, high-accuracy micro actuators have been used to provide linear motion in medical devices such as:
- Precision dentistry equipment
- Fluid injectors
- Microscope positioning
- Healthcare education simulators
- Micro dispensers
- Robot-assisted surgery
- Medical equipment prototypes
- Laser positioning devices
Fluid Injectors
Fluid injectors are devices that require extremely high precision to ensure the rate and volume at which their fluids were being injected at is consistent and accurate. Our TTL/PWM communication provides precise control by allowing users to command our micro precision servo actuators into their desired speed and positions while reading feedback.
Microscope positioning
Linear actuators have gradually been integrated into microscopes for their convenience factor and to improve examination results. Our micro precision servo actuators have the necessary specification for making fine-tuned adjustments on high resolution microscopes. Another way of maximizing results in high resolution microscopy is through the integration of micro precision servo actuators for positioning the sample that was being examined.
Micro Dispensers
Micro dispensers are commonly used in processes involving fluid control such as making medicine. High precision pumps and valves often use high-accuracy micro actuators to control their flow rate and fluid volume. The repeatability and compact size of our micro actuators makes them a perfect fit for the components found in micro dispensers. Our TTL/PWM communication also allows for users to command and adjust our micro precision servo actuators accordingly if there were other variables which needed to be considered such as viscosity, temperature, and other fluid dynamics.
Robot-Assisted Surgery
Certain surgeries require different levels of precision and accuracy depending on the magnitude of the operation. Micro precision servo actuators offer accurate motion control and high reliability for applications such as robot-assisted surgery. This can assist a surgeon in certain operations which required the steady hands found in robots.
Laser Positioning Devices
There are a variety of laser treatments that are rising in popularity for the various health benefits they can offer. Laser positioning devices often need to be adjusted with high levels of precision for the best results possible and to avoid misalignment of the laser beams. The stability and accuracy of our micro precision servo actuators ensure the laser devices can travel and stay in the desired positions during treatment.
In Summary
Micro precision servo actuators such as the PA-12-T and PA-12-R have many different use cases in medical devices as they offer reliable accuracy and repeatability, whether it be for handling fluid flow, driving surgical robots, or positioning medical equipment. Their high performance combined with low maintenance requirements is some of the key reasons micro actuators are popular in the medical industry.
As one of the top suppliers of electric linear actuators, Progressive Automations offers industry-leading flexibility, quality, support, and field experience to meet all your needs. If you have any other questions about what we can offer, please do not hesitate in reaching out to us! We are experts in what we do and want to ensure you find the best solutions for your application.
sales@progressiveautomations.com | 1-800-676-6123