The screw metering system of the Vial powder filling machine: How to ensure filling accuracy?
In the pharmaceutical, biological reagent, and medical beauty powder filling industries, the filling accuracy of Vials is the lifeline of product quality, directly related to medication safety and GMP compliance. The screw metering system, as the most mainstream high-precision metering method for powder filling at present, its precision control capability determines the core value of the equipment. Many enterprises encounter problems such as large dose deviations and unstable batches during production. The root cause lies in not mastering the core control logic of screw metering. Today, based on the design experience of the HONSIMBA single-head powder filling machine, we will analyze the key technologies for ensuring filling accuracy through screw metering.
Firstly, customized screw body design is the foundation of precision. The screw is not a universal part. Different materials have greatly varying fluidity, density, and particle size, requiring matching exclusive screw parameters. HONSIMBA, considering the small-dose filling characteristics of Vials, adopts precise equal-distance and equal-depth screws, with the lead and pitch optimized through fluid mechanics simulation to ensure uniform and stable discharge volume per revolution; the screws are made of 316L hygienic-grade stainless steel, with an inner wall mirror-polished Ra ≤ 0.8 μm, without burrs or dead corners, to avoid material adhesion and residue. For special materials such as traditional Chinese medicine powder and freeze-dried powder, we will also customize variable lead screws to solve the problems of material bridging and uneven discharge, reducing measurement errors from the source.
Secondly, high-precision servo drive system is the core of precision. Ordinary stepper motors have open-loop control and are prone to skipping steps or stalling, resulting in dose deviations. HONSIMBA filling machines use imported servo motors + planetary reducers to achieve closed-loop precise control, with screw rotation angle accuracy reaching ±0.01°, capable of precisely controlling the rotation angle and speed of the screw to ensure consistent discharge volume each time. The system can automatically calculate the screw rotation speed based on the filling dose, supporting a wide range of dose adjustment from 0.1g to 10g, with the filling error controlled within ±5% within GMP's strict requirements.
Thirdly, stable control of material state is the precision guarantee. Powder materials are prone to moisture absorption, stratification, and bridging, and fluctuations in material state will directly affect measurement accuracy. In the hopper design, we adopt a low-speed anti-bridging stirring device, which can adjust the stirring speed according to the material characteristics to prevent material agglomeration and stratification; the hopper is designed in a sealed manner, isolating external moisture to avoid material moisture absorption and agglomeration. At the discharge port, a gradually constricted design is adopted, combined with a flexible sealing structure, to ensure continuous and uniform material entry into the screw metering chamber, eliminating the phenomenon of material interruption or spillage.
Fourthly, control of powder leakage and residual is the precision supplement. During the filling process, powder leakage and screw residue can lead to a lower actual filling volume. HONSIMBA filling machines adopt a drip-proof filling needle design, with the screw precisely retracting after filling to cut off the material flow, avoiding tail material dripping; the connection between the screw and the hopper uses food-grade silicone rubber sealing to prevent material leakage. After each production, the screw, hopper, and other components in contact with the material can be quickly disassembled and cleaned, without residual dead corners, ensuring the consistency of measurement between batches.
Finally, regular calibration and maintenance are the key to the continuous stability of precision. During equipment operation, screw wear and parameter drift can affect precision. Our equipment has an automatic calibration function that can quickly complete dose calibration; it is also recommended that enterprises conduct a precision check once a month and inspect the wear of the screws once a quarter to replace easily worn parts in a timely manner.
The precision control of Vial powder filling is a systematic project throughout the design, manufacturing, and use process. HONSIMBA always takes GMP standards as the core, integrating precision control into every detail to help enterprises achieve stable and compliant production and safeguard the quality bottom line of each bottle.