1. Processing companies should first equip each mold with a history card, detailing and statistically analyzing its use, maintenance (lubrication, cleaning, rust prevention), and damage status. This allows them to identify damaged parts and components, the degree of wear, and provides information for problem identification and resolution. It also includes the mold's molding process parameters and the materials used in the product, thus shortening mold trial time and improving production efficiency.
2. Processing companies should test various mold performance parameters while the injection molding machine and mold are running normally, and measure the dimensions of the final molded plastic part. This information determines the current state of the mold, identifying damage to the cavity, core, cooling system, and parting surface. Based on the information provided by the plastic part, the damage condition of the mold and repair measures can be determined.
3. Key components of the mold require close monitoring and inspection: Ejector and guide components ensure the mold's opening and closing motion and the ejection of plastic parts. If any part becomes jammed due to damage, production will stop. Therefore, ejector pins and guide pillars should be regularly lubricated (using the most suitable lubricant), and periodically inspected for deformation and surface damage. Replace any damaged components immediately. After completing a production cycle, apply professional anti-rust oil to the mold's working surfaces, moving parts, and guide components. Special attention should be paid to protecting the bearings of molds with gears and racks, and the spring strength of spring-loaded molds, to ensure they are always in optimal working condition.
As production continues, scale, rust, sludge, and algae easily accumulate in the cooling channels, reducing the cross-section and narrowing the cooling passages. This significantly reduces the heat exchange rate between the coolant and the mold, increasing production costs. Therefore, cleaning the cooling channels is crucial. For hot runner molds, maintaining the heating and control systems is particularly important to prevent production failures. Therefore, after each production cycle, the belt heaters, rod heaters, heating probes, and thermocouples on the mold should be measured with an ohmmeter. If any are damaged, they should be replaced promptly, and the results compared with the mold's history record. Records should be kept to identify problems and take appropriate measures in a timely manner.
4. Pay close attention to mold surface maintenance, as it directly affects the surface quality of the product. The key is to prevent rust. Therefore, selecting a suitable, high-quality, and professional rust-preventive oil is crucial. After the mold completes its production task, different methods should be used to carefully remove injection mold residues depending on the injection molding material. Copper rods, copper wires, and professional mold cleaners can be used to remove residual injection mold and other deposits from the mold, followed by air drying. Do not use hard objects such as iron wire or steel bars for cleaning, as this may scratch the surface. If rust spots are caused by corrosive injection molding, use a grinder to polish the mold and spray with professional rust-preventive oil. Then store the mold in a dry, cool, and dust-free place.
Injection molds are the most important molding equipment in injection molding processing; their quality directly affects the quality of the finished product. Furthermore, since molds account for a significant proportion of the production costs of injection molding companies, their lifespan directly affects the cost of injection molded products. Therefore, improving the quality of injection molds and ensuring proper maintenance to extend their service life is a crucial issue for injection molding companies seeking to reduce costs and increase efficiency.
Injection molding companies often have a wide variety of products and frequent mold replacements. After completing a production cycle, molds are typically stored until the next cycle. However, some companies do not pay enough attention to mold storage, leading to corrosion, decreased surface finish, and other problems during storage. This results in lower product quality, higher scrap rates, and in some cases, molds become unusable, requiring significant investment in new molds and causing substantial waste.
Data shows that usage and maintenance account for 15%–20% of the factors affecting mold lifespan. The lifespan of injection molds can generally reach 800,000 cycles, and some well-maintained molds abroad can even extend this by 2–3 times. However, due to neglect of maintenance, the lifespan of injection molds in domestic companies is relatively short, only about 1/5 to 1/3 of that of foreign companies. The short lifespan of injection molds leads to billions of yuan in wasted steel processing time and energy, as well as losses due to the impact on product quality.
Therefore, the maintenance of injection molds is crucial, specifically as follows:
1. Processing companies should first equip each mold with a history card, meticulously recording and statistically analyzing its usage, maintenance (lubrication, cleaning, rust prevention), and damage status. This allows for the identification of damaged parts and components, the degree of wear, and provides information for problem-solving. It also includes the mold's molding process parameters and the materials used in the product, thus shortening mold trial time and improving production efficiency.
2. Processing companies should test various mold performance parameters while the injection molding machine and mold are operating normally, and measure the dimensions of the final molded plastic part. This information determines the current condition of the mold, identifying damage to the cavity, core, cooling system, and parting surface. Based on the information provided by the plastic part, the damage condition of the mold and repair measures can be determined.
3. Several key mold components require focused monitoring and inspection: Ejector and guide components ensure the mold's opening and closing motion and the ejection of plastic parts. If any part of these components becomes jammed due to damage, production will be halted. Therefore, ejector pins and guide pillars should be regularly lubricated (using the most suitable lubricant), and periodically inspected for deformation and surface damage. Replace any damaged components immediately.
After completing a production cycle, apply a professional anti-rust oil to the mold's working surfaces, moving parts, and guide components. Special attention should be paid to protecting the bearings of molds with gears and racks, and the spring strength of spring-loaded molds, to ensure they remain in optimal working condition.
As production continues, scale, rust, sludge, and algae easily accumulate in the cooling channels, reducing their cross-sectional area and narrowing the cooling passages. This significantly reduces the heat exchange rate between the coolant and the mold, increasing production costs. Therefore, cleaning the cooling channels is crucial. For hot runner molds, maintaining the heating and control systems is particularly important to prevent production failures.
Therefore, after each production cycle, the belt heaters, rod heaters, heating probes, and thermocouples on the mold should be measured with an ohmmeter. If any are damaged, they should be replaced promptly, and the results compared to the mold's history record. Records should be kept to identify problems and take appropriate measures in a timely manner.
4. Surface maintenance of the mold is crucial, as it directly affects the surface quality of the product. Preventing rust is paramount; therefore, selecting a suitable, high-quality, and professional rust-preventive oil is essential. After the mold completes its production task, residual injection molding should be carefully removed using different methods depending on the type of injection molding. Copper rods, copper wires, and professional mold cleaners can be used to remove residual injection molding and other deposits from the mold, followed by air drying.
Do not use hard objects such as iron wire or steel bars for cleaning, as this may scratch the surface. If rust spots are caused by corrosive injection molding, use a grinder to polish the mold and spray with professional rust-preventive oil. Then, store the mold in a dry, cool, and dust-free place.
A well-maintained mold can shorten mold assembly and trial run time, reduce production failures, ensure smooth production operation, guarantee product quality, reduce scrap losses, and lower the company's operating costs and fixed asset investment. At the start of the next production cycle, the company can smoothly produce qualified products. Therefore, for injection molding product processing companies, in the current highly competitive market, well-maintained molds can be a significant advantage.
(1) Single Parting Surface Injection Mold
When opening the mold, the moving mold and the fixed mold separate to remove the plastic part. This is called a single parting surface mold, also known as a double-plate mold. It is the simplest and most basic form of injection mold. It can be designed as a single-cavity injection mold or a multi-cavity injection mold as needed, and is the most widely used type of injection mold.
(2) Double Parting Surface Injection Mold
A double parting surface injection mold has two parting surfaces. Compared to a single parting surface injection mold, it adds a partially movable intermediate plate (also called a movable sprue plate, which houses the sprue, runner, and other parts and components required by the fixed mold) to the fixed mold section. Therefore, it is also called a three-plate (moving plate, intermediate plate, fixed plate) injection mold.
It is commonly used in single-cavity or multi-cavity injection molds with point gate injection. During mold opening, the intermediate plate separates from the fixed platen at a fixed distance on the guide pillars of the fixed mold, allowing the solidified material of the gating system to be removed between the two plates. Double parting surface injection molds have a complex structure, higher manufacturing costs, and difficult component processing; therefore, they are generally not used for molding large or extra-large plastic products.
(3) Injection Mold with Side Parting and Core Pulling Mechanism
When the plastic part has side holes or side recesses, a side-movable core or slider is required for molding. After injection molding, the moving mold first moves downward a certain distance, and then the inclined section of the bent pin fixed to the fixed mold plate forces the slider to move outward. Simultaneously, the ejector rod of the demolding mechanism pushes the ejector plate, causing the plastic part to detach from the core.
(4) Injection molds with movable molding components
Due to certain special structures of the plastic parts, injection molds are required to have movable molding components, such as movable punches, movable dies, movable inserts, movable threaded cores, or rings. These components can be removed from the mold along with the plastic part during demolding and then separated from the part.
(5) Automatic threaded injection molds
For threaded plastic parts, when automatic demolding is required, a rotatable threaded core or ring can be installed on the mold. The opening action, the rotation mechanism of the injection molding machine, or a dedicated transmission device can be used to rotate the threaded core or ring, thereby removing the plastic part.
(6) Runnerless Injection Mold
A runnerless injection mold uses an adiabatic heating method to keep the plastic between the injection nozzle and the cavity in a molten state, so that no solidified material from the gating system is injected when the molded part is removed. The former is called an adiabatic runner injection mold, and the latter is called a hot runner injection mold.
(7) Right-Angle Injection Mold
Right-angle injection molds are only suitable for angle injection molding machines. Unlike other injection molds, the feeding direction of this type of mold is perpendicular to the mold opening and closing direction during molding. Its main runner is located on both sides of the parting surface between the moving and stationary molds, and its cross-sectional area is usually constant, which differs from molds used in other injection molding machines. Replaceable runner inserts can be installed at the ends of the main runner to prevent wear and deformation of the injection nozzle and the main runner inlet.
(8) Injection Mold with Ejection Mechanism on the Stationary Mold
In most injection molds, the ejection mechanism is installed on the moving mold side, which facilitates the operation of the ejection device in the injection molding machine's mold opening and closing system. In actual production, due to the shape limitations of some plastic parts, it is better to leave the plastic parts on the fixed mold side for molding. In order to remove the plastic parts from the mold, a demolding mechanism must be set on the fixed mold side.
