Application case of integrated lead screw motor in medical syringe‌

With the advancement of precision and intelligent medical equipment, syringes, as key devices for drug delivery, place higher demands on motion control accuracy, reliability, and responsiveness. Traditional motors are prone to positioning deviation and insufficient stability in micro-dosing scenarios. Integrated stepper servo motors, with their high-precision positioning and closed-loop control capabilities, are becoming an ideal drive solution for medical syringes.

1. Device Overview

• Device Name: Medical Syringe

• Core Component: Integrated lead-screw stepper servo motor (Model: STM3548B-485-M-1ZB-6.35-1.27-L180-Y)

Features:

• Supports homing and contour positioning modes to ensure repeatable positioning accuracy;

• Compact design accommodates space constraints in medical equipment;

• A single motor per device meets the requirements of high integration.

2. Application Solutions

(1) Motion Control Design

• Mode Switching Logic: Upon startup, the device first enters the home return mode, confirming the zero position via a sensor, and then automatically switches to the contour position mode for precise displacement.

• Control Optimization: Integrated communication between the motor and controller provides real-time position data feedback to avoid cumulative errors.

(2) System Integration

• The motor directly drives the syringe plunger, eliminating intermediate transmission components and improving efficiency and reliability.

• A 485 communication interface enables data exchange with a host computer, supporting remote parameter adjustment and status monitoring.

3. Application Products

• Product Model: STM3548B-485-M-1ZB-6.35-1.27-L180-Y

• Technical Parameters:

  • Step Angle Accuracy: ±5 arc minutes;

  • Communication Interface: RS-485;

  • Rated Torque: 1.27 N·m;

  • Shaft Length: 180 mm

4. Problem and Solution

Challenge: During the commissioning process, the customer incorrectly used the origin return mode, resulting in the device being unable to locate the zero point, affecting injection accuracy.

Root Cause:

• Incorrect configuration of the zero return mode parameters;

• Improper sensor wiring prevented the zero position signal from being triggered.

Solution:

1. Standardized Operational Procedures:

   • Forced origin return after power-up, confirming the zero position with the sensor before switching to position mode;

   • Verified the wiring scheme to ensure signal transmission stability.

2. Technical Optimization:

   • Added zero position verification logic to the control program to prevent invalid displacement;

   • Provided a graphical debugging tool to help customers monitor motor status in real time.

5. Summary

The integrated stepper servo motor significantly improved the accuracy and operational stability of medical syringes through high-precision positioning and intelligent mode switching. In this case, the solution to the zero point loss issue demonstrates the importance of closed-loop control and standardized processes. In the future, this technology can be further expanded to applications such as microinjection pumps and automated dispensing equipment, contributing to the intelligent upgrade of medical equipment.