The main function of the feeding device is to add material particles or dry powder to the die hole in the turntable, and then complete the film forming by the rotation of the turntable and the pressing of the die. Among the many indicators of tablets, the difference in tablet weight is a very important parameter. In addition to the express provisions of the Pharmacopoeia, many pharmaceutical companies have established their own stricter internal control standards.
In the double laminating machine manufactured by IMA, the C52 sheet weight control unit (industrial PC) can be used to control the difference in sheet weight. Of course, the factors affecting the difference in tablet weight are not only the self-quality of the tablet filling mechanism, the turret jumping, but also the die size. In addition to the processing accuracy factors such as deviation, the stability of the filling amount of the forced feeding device plays a very important role in the weight difference of the tablet. Therefore, the structure and operation of the forced feeding device are studied and analyzed to understand and grasp the influence of the filling amount. Factors and control of the weight difference of the tablets are very important.
1 The influence of the structure of the forced feeding device on the material filling stability The structure of the forced feeding device mainly includes three parts:
(1) The power transmission part is used to convert the one-way rotation of the output shaft of the speed regulating motor into the reverse rotation of the stirring wheel, that is, the relative rotation of the two impellers scrapes the material discharged from the hopper into the die hole of the turntable.
(2) The fixed part, the function of which is to position the forced feed mixing wheel on the main body, and the turntable has reliable and precise matching requirements, and the gap is within a few lines.
(3) The agitating wheel and the chamber portion, which is the part of the forced feeding device that directly affects the material filling stability. When designing the mixing wheel and the material chamber, the design principle is 2: to ensure the fluidity of the material and not to change the original state of the material.
In order to ensure the fluidity of the material, the outer dimensions of the mixing wheel and the inner dimensions of the material cavity should have a proper ratio. The design should pay attention to: (1) the diameter of the mixing wheel should not be too small, otherwise it will not function as a sufficient scraping material; (2) The mixing diameter wheel should not be too large, so there should be a certain space in the material cavity to ensure the sufficient fluidity of the material; (3) The structure and shape of the mixing wheel itself can fully scrape the material.
When designing the forced feeding device, it is necessary to ensure that the material has good fluidity, because the pharmaceutical company in the pressing of the tablet, the ratio of each material is carried out according to the technical regulations, while ensuring the ingredients of the raw materials and the ingredients of the auxiliary materials. To ensure the compressibility of the material, such as bulk density, moisture content, particle size, fluidity, etc., if the original state of the material is changed, then the parameters of the tablet disintegration degree, friability, and hardness will be affected. In order to ensure that the original state of the material does not change, the designer can design the mixing wheel according to its shape and size (can be tested in the laboratory), and the user can choose according to different materials.
2 The disc valve of the feed hopper device controls the lower part of the disc valve of the material flow feed hopper device and the forced feed device, and the flow rate is controlled by the hopper butterfly valve. The greater the demand for material filling, the greater the amount of material flowing from the hopper to the forced feeding device; the smaller the demand for material filling, the smaller the amount of flow from the hopper to the forced feeder. It is worth noting that in order to minimize the time that the material stays in the chamber, that is, to speed up the material circulation rate, the hopper flow should be reasonably controlled, rather than opening the flow to the large size. This is because the longer the material stays in the chamber, the more its original state will be changed, and the more difficult it is to meet the requirements for the disintegration and friability of the pressed tablets, so the material is reasonably controlled. Flow rate, speeding up the flow of material in the chamber is an important point to note when using a forced feeding system.
3 The influence of the rotation speed of the mixing wheel on the filling stability The rotation speed of the mixing wheel is set by the frequency conversion motor under the control of the frequency converter. After the structural design of the forced feeding device is shaped, the rotation speed of the stirring wheel is stable to the filling of the material. Sex needs to be explored in actual production commissioning to find a suitable critical speed. Suppose a limit condition, such as zero rotation speed of the mixing wheel, the material obviously cannot flow sufficiently; the rotation speed of the mixing wheel is very high, the height is up to the limit, the mixing wheel is like a rotating cylinder, then the material can not flow sufficiently, so the rotation speed of the stirring wheel There should be a reasonable range. There are two basis for determining the speed range of the mixing wheel:
(1) According to the characteristics of the material, if the fluidity of the material is good, the speed range of the stirring wheel can be adjusted according to the setting range of the specification. If the material flowability is poor, the setting of the stirring wheel speed should be slightly higher or according to the specific blanking situation; if the material flowability is extremely poor (for example, the material cannot fall freely from the hopper), then the auxiliary blanking device should be designed. For filling, the design of the auxiliary blanking device can only be designed separately according to the customer's materials and its different requirements. The rotational speed of the dispensing impeller should be set according to the specific blanking situation.
(2) According to the rotation speed of the turntable, the rotation speed is high, the output is large, the rotation speed of the stirring wheel is also high; the rotation speed is low, and the filling amount is required to be small, the rotation speed of the stirring wheel can be reduced. Under the premise of satisfying the above requirements, the rotation speed of the mixing wheel should be lower to minimize the influence on the material.
4 material density, moisture content, particle size uniformity, etc. affecting the density of the material, moisture content and uniformity of particle size will affect its fluidity and compressibility. Pharmaceutical companies need to fully consider when formulating materials. This, otherwise, may make a wrong judgment when there is a reason for the instability of the tablet weight difference.
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