The bristles of a toothbrush are the part that directly contacts the teeth, so the quality of the bristles is of utmost importance. Common bristle materials are nylon filaments and DuPont filaments. Nylon filaments are relatively affordable, have good wear resistance and resilience, and can effectively clean the dirt on the tooth surface. DuPont filaments are the "aristocrats" among bristles. They are softer and more delicate, cause less irritation to the gums, and are especially suitable for people with sensitive gums. When choosing bristles, different diameters and shapes of bristles are also selected according to different needs. For example, some toothbrushes use a combination of thick and thin bristles. The thick bristles are responsible for cleaning the large - scale dirt on the tooth surface, and the thin bristles can penetrate into the tooth gaps to clean the small residues.

• Dryer: PP, ABS, and other plastic materials are prone to absorbing moisture in the air during storage and transportation. If moisture - containing plastic enters the injection molding machine, the produced brush handles may have defects such as air bubbles and deformation, affecting product quality. The function of the dryer is to remove the moisture in the plastic materials and ensure the smooth progress of production. Generally, the drying temperature is set between 80 - 100 degrees Celsius, and the drying time is 2 - 3 hours, which needs to be adjusted according to the actual situation of the plastic materials.

• Feeder: The feeder is responsible for accurately conveying the dried plastic pellets into the injection molding machine. It realizes automated feeding, which not only improves production efficiency but also reduces errors and labor intensity that may be caused by manual operation. Without a feeder, workers would have to pour the raw materials into the injection molding machine bucket by bucket, which is tiring and inefficient. Moreover, the feeder can supply raw materials stably according to the working rhythm of the injection molding machine to ensure the continuity of production.

• Crusher: During the production process, some scraps, unqualified brush handles, or waste materials generated during machine debugging are inevitable. The crusher comes in handy. It can crush these waste materials into small pieces and put them back into production, which is both environmentally friendly and saves raw material costs. This is equivalent to turning "garbage" into "treasure", realizing the recycling of resources and further reducing the production costs of enterprises.

• Color Mixer: If you want to produce toothbrush handles in various colors, you need to use a color mixer. Put the plastic pellets and color powder or masterbatch into the color mixer according to a certain proportion. Through actions such as stirring and tumbling, they are fully and evenly mixed. The mixing proportion and time are crucial. Different proportions will produce different color effects. Generally, the mixing time is about 15 - 30 minutes, which needs to be adjusted according to the actual color requirements and the performance of the color mixer.

• Chiller: The injection molding machine generates a large amount of heat during operation. If it is not cooled in time, it will affect the performance of the machine and the quality of the products. The chiller provides low - temperature circulating water for the cooling system of the injection molding machine to ensure that the injection molding machine operates stably at an appropriate temperature. It's like a "small air conditioner" for the injection molding machine, always keeping the machine "cool" and ensuring the smooth progress of the injection molding process.

• Drying Plastic Pellets: Put the purchased PP or ABS plastic pellets into the dryer and carry out the drying treatment according to the previously mentioned temperature and time. After drying, the plastic pellets should be promptly transferred to a sealed container to prevent them from absorbing moisture in the air again. This step is like giving the plastic pellets a "bath" to remove the "moisture" on them and prepare for subsequent processing.

• Color Mixing (Optional): According to the designed color scheme, put an appropriate amount of color powder or masterbatch together with the dried plastic pellets into the color mixer. Start the color mixer and let them mix fully. During the color - mixing process, you can judge whether the color mixing is uniform by observing the color change of the materials in the color mixer. If the color distribution is uneven, it may cause the toothbrush handle to have color streaks or inconsistent color blocks. Therefore, this color - mixing step must be taken seriously to ensure that each plastic pellet is evenly colored.

• Mold Installation: Install the carefully designed and manufactured toothbrush mold onto the Haijiang injection molding machine. The installation process requires great care. It is necessary to ensure that the mold is firmly installed and in the correct position. The installation accuracy of the mold directly affects the injection molding effect. If the mold is not firmly installed or the position is deviated, it may lead to problems such as flash, inaccurate dimensions, and poor grip of the brush handle. After installation, the mold also needs to be debugged to check whether the mold opens and closes smoothly and whether all components are working properly.

• Parameter Setting: Adjust the various parameters of the injection molding machine according to the characteristics of the plastic material, the structure of the toothbrush mold, and product requirements. These parameters include injection pressure, injection speed, holding pressure, holding time, and cooling time.

• Injection Pressure: Generally, it is between 80 - 150MPa. The injection pressure should be moderate. If the pressure is too low, the plastic material cannot quickly fill the mold cavity, which may lead to problems such as material shortage and incomplete filling of the brush handle. If the pressure is too high, it may cause the mold to be impacted too much, affecting the service life of the mold, and may also lead to problems such as flash and deformation of the brush handle.

• Injection Speed: An appropriate injection speed can ensure that the plastic material evenly fills the mold cavity. If the injection speed is too fast, the plastic material may generate turbulence, resulting in defects such as air bubbles and cavities inside the brush handle. If the injection speed is too slow, it will affect production efficiency and increase production costs.

• Holding Pressure: Usually, it is 60% - 80% of the injection pressure. The role of the holding pressure is to continuously supplement the plastic during the cooling and shrinkage process of the plastic material to prevent the brush handle from having defects such as shrink marks and depressions. The setting of the holding pressure and time needs to be adjusted according to factors such as the thickness and shape of the brush handle.

• Cooling Time: The cooling time depends on the thickness of the brush handle and the cooling efficiency of the mold, generally between 10 - 20 seconds. If the cooling time is too short, the brush handle may be ejected from the mold before it is fully set, and it is easy to deform. If the cooling time is too long, it will reduce production efficiency.

• Injection Molding Process: After everything is ready, start the Haijiang injection molding machine. The dried and color - mixed (if any) plastic pellets are heated and melted in the barrel of the injection molding machine. Then, under high - pressure, they are injected into the mold cavity. In the mold cavity, the plastic material gradually cools and solidifies to form the shape of the brush handle. This process is like casting a spell in the "magic box" of the mold, turning the plastic pellets into the brush handle shape we want.

• Demolding and Deburring: After the injection molding is completed, the mold opens, and the formed brush handle is ejected from the mold. The newly demolded brush handle may have some burrs. These burrs not only affect the appearance but also may scratch the hand. Special deburring tools such as scissors, sandpaper, and trimming machines can be used to remove the burrs on the surface and edges of the brush handle, making the surface of the brush handle smooth and clean.

• Quality Inspection: Conduct a comprehensive quality inspection on the produced brush handles, checking for issues such as cracks, deformations, dimensional deviations, and uneven colors. For unqualified products, they need to be classified and processed. Repairable products are repaired, and non - repairable products are crushed by a crusher and put back into production. Only through strict quality inspection can we ensure that the brush handles flowing into the next process are all qualified and of high quality.

• Traditional Hair - planting: If the traditional hair - planting method is adopted, first, evenly distributed hair - planting holes need to be drilled on the brush handle. Then, bundles of pre - treated bristles are inserted into the hair - planting holes and fixed through glue or hot - melting methods. This method requires manual operation and has a relatively low production efficiency, but it is still a commonly used method for some toothbrushes with high requirements for bristle firmness.

• Injection - molding Implantation: For toothbrushes using the injection - molding implantation method, the bristles are directly molded with the plastic material during the injection - molding process of the brush handle. This method has high production efficiency, and the combination of the bristles and the brush handle is closer, but it requires extremely high precision of the mold, and the design and manufacturing difficulty of the mold is also greater.