Factors of Automatic Packaging of Pipette Tips

The determination of the automatic packaging process is affected by many factors. When studying the automatic sorting and packaging process, the shape and material properties of the pipette tip and the box should be considered first, and then the relationship between the incoming position of the tip, the natural position of the tip and the final packaging position should be considered. The shape and material properties of the packaged object will affect the packaging, especially for the feeding system. The more complex the shape is, the greater the probability of being stuck becomes.
 
1.1 Morphological analysis of objects
(1) Characteristics of shapes of the pipette tip
Figure 1 is a schematic diagram of the structure of the 10uL pipette tip, which is mainly composed of the tip body, the rib plate, and the tip interface. The gun head body is conical and is provided with a suction port. The top of the gun head body is provided with a gun tip port for connecting with a pipette, and the gun head body and the interface are integrated. Six vertical ribs are formed on the outer surface of the gun head body, which is convenient for holding the gun head body and placing it on the storage rack. The total length is L, the outer diameter dimension at interface D1, and the outer diameter at the lower step of the rib plate D2. The average size of pipette tips is obtained by measuring a large number of 10uL pipette tips. The dimensions of the pipette tip are 31.6mm (L), 6.0mm (D1), 4.5mm (D2). These external dimensions are the basis for setting the structural parameters of the automatic packaging device. This kind of pipette tip has small sizes and light weights. The structural feature is that the diameter difference between the lower part of the rib plate and D2 forms a certain step.
 

Figure 1 The schematic diagram of the structure of the pipette tip

1. Pipette tip bodies 2. Reinforced plates 3. Pipette tip interface

 
Studying the shape of the pipette tip, the characteristics suitable for automatic discharge are: six vertical ribs are formed on the outer surface of the nozzle body, and there is a 1.5mm outer diameter difference with the lower cone. There is a certain step. The pipette tip is a rotating body with a symmetrical axis, and the orientation along the axis is the most stable. At the same time, the pipette tips are prone to overlap, embedding and twisting. The pipette tips are light, slender and unstable. Power must also be taken into consideration in the packaging process.
 
(2) Characteristics of shapes of the pipette
The pipette tip box corresponding to the 10uL pipette tip is shown in Figure 2. Its main parameters are that the size of the pipette tip box is 120mm×84mm, the number of holes arranged is 96 (8×12) and the distance between adjacent holes is 8.98mm×8.98mm.
 
Features: Just place or insert the pipette tip into the box. There are many holes. Because the distance between the box holes in the tip box is very small, it is easy to miss and mispack when packaging, resulting in a failure. However, the arrangement of the holes is very regular, which is of great reference value for the determination of its automatic packaging. The analysis and comparison of the types of tips and boxes and their respective characteristics are shown in Table 1.
 

Figure 2 Pipette tip boxes
 
Table 2 A comparison of types and characteristics of research subjects

 
1.2 The relationship between the positions of the object
In addition to the characteristics of the shape of the pipette tip, many stacked pipette tips are also influencing factors in the automatic packing of the pipette tips. Generally speaking, the study of the position of an individual includes three aspects, namely, the initial pose (also known as the incoming pose), the natural pose with the highest probability, and the boxed pose.
(1) Three types of postures of the pipette tip
As shown in Figure 3, there are three types of postures of the pipette tip. The incoming position of the pipette tip is scattered and irregular. Although the natural position of distribution is known, there is no correlation between the incoming attitude and the packing attitude of the pipette tip. This requires a special device to realize the conversion of the pipette tip from the incoming position to the boxing position. Here we define standing posture a as posture 1, lying postures b and c as posture 2, and postures d and e as posture 3. The probability of postures 2 and 3 is much higher. Therefore, start from pose 2 or 3 when considering orientation poses of tips. According to the requirement for packing, the final packing pose of the pipette tip is position f.
 

Figure 3 Three poses of the pipette tip
(a) Incoming posture of the pipette tip (b) Natural posture of the pipette tip (c) Packing posture of the pipette tip
 
(2) The position of the pipette tip box
Table 2 shows the relationship between the position of the pipette tip and the box, that is, the relationship between the pipette tip and the box body’s incoming position, the natural position of the large probability distribution, and the position of packaging.
 
Table 2 The analysis of the position of the pipette tip and the box