A pipette tip is a most commonly used consumable in laboratories. High dimensional accuracy and good concentricity are required. At the same time, the inner wall is required to be smooth without flow marks and the tip without notch and burrs. The precautions for the production process of pipette tips are as follows:
1. Manufacturing environment
Pipette tips are used in molecular detection, in vitro diagnosis, pre-screening and other experiments, so high requirements are put forward for pipette tips for the production environment. Foreign biological contamination on the pipette tip surface will directly affect the results of the analysis. At present, a dust-free workshop Class 100,000 is common to be seen.
2. Choosing equipment
Pipette tips have the characteristics of multiple cavities, deep cavities, thin walls, and fast molding cycles. In terms of equipment selection, they must have high molding efficiency, low failure rate, and long-term stable operation. Therefore, high-speed electric injection molding machines are the best choice. Their characteristics are as follows:
The high-speed electric injection molding machine meets the requirements of precision thin-walled products, reduces the stress formed by the pipette tip in the molding process, and improves the straightness of the pipetting tip.
The mold’s opening and closing speed is fast and the position is accurate, which is more stable for the automatic manipulator to grab the product position.
It has good stability and repeatability. The multi-power system of the motor is controlled by an independent system, and can move at the same time if the mold allows.
3. Matters needing attention
The main defects of pipette tips are lack of materials in the tip, bending, burrs on the tip and mouth, and dimensional stability. Given the above problems, the following points should be paid attention to in the actual production process:
Reasonable injection speeds
If the speed is too fast, the gas will be trapped by the pipette tip and lack glue, and the gas will not be discharged smoothly. If it is too slow, the internal stress of the product will be great, the product will be bent, and the straightness will not be enough. It should be gradually increased while the reasonable observation and selection of mold and product status are considered.
① Select materials with good fluidity to verify the basic parameters, so that the raw materials can be quickly filled, the selection of reasonable pressure and the protection of precision inserts can reduce the probability of poor appearance.
②Reasonable material temperature: raw materials of PP are crystalline materials. If the temperature is too low, the material will crystallize slowly, the appearance of the product will be foggy, opaque, and the product will become brittle. If the temperature is too high, the raw material will be degraded and the strength of the product will decrease.
Reasonable V/P switching
can ensure the relative balance of glue feeding, the product adjustment should start from a short shot and filling gradually. For short shot products, it is necessary to carefully observe the balance and filling eccentricity of the pipette tip. Design a reasonable V/P switch. Avoid situations such as lack of glue, burrs, and insufficient straightness of the pipette tip.
① For the pipetting automatic action, it is necessary to install a negative pressure gauge to monitor the change value of the vacuum, and at the same time set a reasonable vacuum range and linkage with the equipment to achieve the protection of the mold and the auxiliary detection of damage to products during abnormal actions.
② The air volume of the suction fixture plate should be sufficient, and the larger pipe should be selected as much as possible while taking into account the space.
③ The fixture body should be made of plastic plus cushioning structure as much as possible.