The fully automatic powder tablet press is an automated equipment that uses an electromechanical integration system to achieve automatic quantitative filling of powder materials, precise pressure molding, automatic demolding and collection of finished products. It is widely used in fields such as pharmaceuticals, ceramics, electronics, and new materials (such as preparing tablets, ceramic substrates, battery electrodes, etc.). Its working principle revolves around the core process of "feeding → quantitative → pressurization → demolding → waste cleaning", and through the coordinated operation of mechanical structure and electrical control system, efficient and stable powder forming is achieved.
1、 Core workflow and principle breakdown
The operation of the fully automatic powder tablet press is centered around the continuous rotation of the turntable (or mold group), coupled with the coordinated action of multiple workstations, to complete the transformation of powder from a "loose state" to a "dense formed body". It can be divided into six key steps:
1. Automatic feeding system: achieve uniform powder conveying
The core of the feeding system is to stably and uniformly transport the powder to be pressed to the "quantitative mechanism", avoiding powder bridging (agglomeration) or uneven feeding that may cause weight deviation of the formed body.
Common feeding methods:
① Vibration feeding: The bottom of the hopper is equipped with a vibrator, which uses high-frequency vibration to loosen the powder and slide it out along the feeding channel;
② Spiral feeding: The powder is forcibly pushed to the quantitative area through the rotation of the spiral rod (suitable for powders with high viscosity or poor flowability);
③ Gravity feeding: using the powder's own gravity to feed, combined with a stirring blade to prevent powder stratification in the hopper (suitable for powders with good fluidity).
Key function: Ensure that the powder in the silo is always in a "waiting state", providing a stable source of materials for subsequent quantitative processes.
2. Quantitative filling: precise control of the weight of the molded body (core precision link)
Quantification is the key to determining the quality (weight, density uniformity) of the molded body. Through the combination of a "quantitative ring+punch", a fixed volume of powder is accurately cut and filled into the mold cavity.
Working Principle:
When the turntable drives the lower punch to rotate to the "filling station", the lower punch moves downward and forms a fixed volume "measuring space" with the mold cavity;
The feeding system transports the powder to the measuring space, and the excess powder is scraped flat along the surface of the mold by a "scraper plate" to ensure that the powder volume in each cavity is completely consistent (volume quantification method, converting weight through powder loose density);
Some high-precision equipment will be equipped with a "weight feedback adjustment system": the weight of the molded body is detected in real time through sensors. If the deviation exceeds the threshold (such as ± 0.5%), the system will automatically adjust the descent depth of the punch (change the volume of the measuring space) to achieve dynamic weight compensation.
3. Preloading and exhaust: reduce defects in the molded body
For powders with high air content or loose structure (such as traditional Chinese medicine powder and activated carbon powder), direct high-pressure pressing can easily produce defects such as bubbles and cracking. Therefore, the air in the powder needs to be discharged through the "pre pressing station" first.
Working Principle:
The quantified mold rotates with the turntable to the "pre pressing station", and the upper pre pressing punch lightly presses the powder downwards (usually at a pressure of 10% -30% of the final pressure). The air between the powder particles is discharged from the exhaust hole of the mold cavity; After pre pressing, the powder becomes initially dense, laying the foundation for final pressing molding.
Note: Some small tablet presses or low demand scenarios can omit this step and directly enter the final pressing stage.
4. Final pressing: Core pressing process (powder densification)
Final pressing is a key step in compressing loose powder into a molded body with a fixed shape, density, and strength, relying on the collaborative pressing of the "upper main punch+lower main punch".
Working Principle:
The pre pressed mold is rotated to the "final pressing station", at which point the lower punch has been raised to the "forming position" through the cam mechanism (with a fixed height at the bottom of the mold cavity);
The upper main punch moves rapidly downwards under the drive of a high-pressure oil cylinder (or precision cam), applying a set pressure to the powder in the mold cavity (the pressure range can be from a few kN to several hundred kN, adjusted according to the hardness requirements of the molded body);
Under high pressure, the gaps between particles in the powder are compressed, and a dense molded body is formed through van der Waals forces, mechanical interlocking, or the action of a small amount of binder (if added);
After pressurization, maintain a certain "holding time" (usually 0.1-2 seconds) to ensure uniform density of the molded body and avoid rebound and cracking after demolding.
5. Automatic demolding: separation of molded body and mold
Demoulding is the process of removing the pressed molded body from the mold cavity, avoiding damage or deformation of the molded body, and relying on the "upward movement of the lower punch" to achieve it.
Working Principle:
After final pressing, the mold rotates to the "demolding station", and the lower punch moves upward under the push of the cam or top rod, pushing the formed body out of the mold cavity to the upper surface of the mold; At this point, the formed body has detached from the inner wall of the mold cavity and is waiting for subsequent collection.
6. Finished product collection and waste cleaning: achieving automated closed-loop
The molded body after demolding is sent to the finished product hopper through a "feeding plate" or "conveyor belt", and the equipment performs a simple cleaning of the mold to complete a single cycle.
Key action:
The feeding plate scrapes the molded body from the surface of the turntable into the finished product channel to prevent the molded body from continuing to rotate with the turntable;
Some equipment is equipped with "mold cleaning brushes" or "blowing devices" to remove residual powder debris from the mold cavity and prevent affecting the accuracy of the next filling.
2、 Core Drive and Control System: Ensuring Automation and Accuracy
The "automation" and "high precision" of the fully automatic powder tablet press rely on the collaboration of two major systems:
1. Mechanical drive system
Power source: The main power is usually provided by servo motors, which convert the rotational motion into the up and down linear motion of the punch through mechanisms such as reducers, camshafts, and connecting rods (servo motors can achieve precise adjustment of speed and pressure, adapting to different powder characteristics).
Key components:
① Cam mechanism: controls the movement trajectory (up, down, stop) of the upper/lower punch at different workstations, which is the core to ensure the timing coordination of each link;
② High pressure oil cylinder: used for pressure output in the final pressure stage (hydraulic driven tablet press), which can achieve stepless pressure adjustment;
③ Rotary table: carries multiple sets of molds (commonly 10-40 stations), and achieves parallel operation of multiple stations through continuous rotation, greatly improving production efficiency (such as a 40 station tablet press, the rotary table can produce 40 molded bodies per rotation).
2. Electrical control system
Core components: PLC (Programmable Logic Controller)+touch screen+sensors (pressure sensor, weight sensor, position sensor).
Control logic:
The operator sets parameters (filling amount, pre pressure, final pressure, holding time, turntable speed, etc.) through the touch screen;
PLC controls the action timing of actuating components such as servo motors, oil cylinders, solenoid valves, etc. according to preset programs;
Sensors provide real-time feedback on pressure, molded body weight, punch position, and other data. If any abnormalities occur (such as excessive pressure or weight deviation), the system immediately triggers an alarm and shuts down to avoid equipment damage or the production of non-conforming products.