Preform mold manufacturing process
一. Design stage
1. Product analysis and demand confirmation
2. Mold design planning
二. Material preparation stage
1. Mold material selection
2. Material procurement and inspection
三. Parts processing stage
1. Rough processing
2. Finishing
3. Electrodischarge machining
四. Heat treatment stage
1. Quenching and tempering
2. Nitriding treatment
五. Surface treatment stage
1. Polishing treatment
2. Coating treatment
六. Mold assembly stage
1. Parts cleaning and inspection
2. Mold assembly process
七. Debugging and mold trial stage
1. Mold debugging
2. Mold trial process
八. Acceptance and delivery stage
1. Mold acceptance
2. Mold delivery
Our preform mold manufacturing process is professional and complete, providing you with the best service, welcome to contact us!
一. Design stage
1. Product analysis and demand confirmation
Before manufacturing the preform mold, the preform product must be analyzed in detail. This includes understanding the purpose of the preform, such as for beverage bottles, cosmetic bottles or pharmaceutical bottles. Preforms for different purposes vary greatly in terms of dimensional accuracy, hygiene standards, and appearance requirements. For example, pharmaceutical preforms have extremely high requirements for dimensional accuracy and hygiene, while beverage preforms may pay more attention to appearance and cost control.
Communicate with customers to confirm the specific size, shape, weight, material and other key parameters of the preform. At the same time, the production batch must be clarified, because the batch size will affect the structural design and manufacturing process selection of the mold. If it is large-scale production, the durability and production efficiency of the mold are more important; if it is small-scale production, the cost control and flexibility of the mold may be the priority factors.
2. Mold design planning
Based on the product analysis results, carry out the overall design of the mold. Determine the basic structure of the mold, such as single cavity or multi-cavity. Single-cavity molds have a simple structure and are suitable for small-batch, high-precision preform production; multi-cavity molds can improve production efficiency and are suitable for large-scale production, but the mold structure is complex and difficult to design and manufacture.
Design the cooling system and consider the layout, shape and size of the cooling channel. The design of the cooling channel should ensure that all parts of the preform can be cooled evenly to avoid deformation or internal stress caused by uneven cooling. For example, for slender preforms, it may be necessary to design a spiral cooling channel inside the core to improve cooling efficiency.
Plan the demoulding mechanism and select a suitable demoulding method, such as push rod demoulding, push plate demoulding or pneumatic demoulding. The design of the demoulding mechanism should ensure that the preform can be demoulded smoothly while avoiding damage to the preform. For example, for preforms with complex internal structures, special demoulding devices may be required to prevent the preform from breaking during demoulding.
Design the gate and runner system. The gate position should be determined according to the shape and wall thickness of the preform, and try to choose the thicker part of the preform to ensure that the plastic melt can evenly fill the cavity. The flow channel system should be designed to enable the plastic melt to flow smoothly into each cavity, and the balance of the flow channel should be considered to ensure that the filling of each cavity is consistent.
Complete the detailed drawing design of the mold, including two-dimensional drawings and three-dimensional models. Two-dimensional drawings are used to guide the processing of mold parts, and three-dimensional models can be used for virtual assembly and interference inspection to find problems in the design in advance, such as collisions between parts, unreasonable wall thickness, etc.
二. Material preparation stage
1. Mold material selection
According to the design requirements and use environment of the mold, select the appropriate mold material. For the core and cavity parts of the preform mold, it is necessary to select materials with high hardness, high strength and good wear resistance. For example, P20 steel is a commonly used pre-hardened plastic mold steel with good processing performance and comprehensive mechanical properties, which is suitable for most preform molds.
If the mold needs to have good corrosion resistance, such as for the production of plastic preforms containing corrosive additives, stainless steel materials such as S136 steel can be used. This steel contains a high proportion of chromium, which can form a dense oxide film on the surface and effectively resist corrosion.
For other parts of the mold, such as templates, guide columns, etc., the corresponding materials can be selected according to their functional requirements. For example, the guide column needs to have high hardness and wear resistance, and high-quality carbon steel or alloy steel can be selected and surface quenched.
2. Material procurement and inspection
Purchase according to the selected material specifications and quantities. During the procurement process, reliable suppliers should be selected to ensure that the quality of the materials meets the requirements. The quality certificate of the materials and other relevant documents should be complete, including data such as the chemical composition and mechanical properties of the materials.
After the materials are purchased, they should be inspected. The inspection content includes whether the size of the material meets the requirements and whether there are defects on the surface, such as cracks, sand holes, etc. For steel, hardness testing and metallographic analysis can also be performed to ensure that the hardness and organizational structure of the material meet the standards. If it is found that the material does not meet the requirements, it is necessary to communicate with the supplier in time for replacement.
三. Parts processing stage
1. Rough processing
First, the main parts of the mold, such as the core, cavity and template, are rough processed. The purpose of rough processing is to remove most of the material excess so that the shape and size of the parts are close to the final requirements. During rough machining, larger cutting amounts, such as larger cutting depth and feed rate, are usually used to improve machining efficiency.
For parts with simple shapes, such as flat templates, ordinary milling machines can be used for machining. For parts with complex three-dimensional shapes, such as cores and cavities, CNC machining centers are generally used for machining. CNC machining centers can accurately machine complex surfaces and contours according to pre-programmed programs. In the rough machining stage, it is important to reserve appropriate machining allowances for subsequent finishing, generally around 0.5 - 1mm.
2. Finishing
Finishing is to further improve the dimensional accuracy and surface quality of parts on the basis of rough machining. The cutting amount for finishing is relatively small, the cutting depth is generally around 0.05 - 0.2mm, and the feed rate is also small to obtain better surface roughness.
For the core and cavity of the mold, high-speed cutting technology is usually used for finishing. High-speed cutting can reduce cutting force, improve machining accuracy, and obtain better surface quality. For example, using a ball-end milling cutter to finish the cavity surface can make the roughness of the cavity surface reach about Ra0.8 - Ra1.6μm.
Finishing also includes the detection and adjustment of the dimensional accuracy of the parts. During the processing, measuring tools such as calipers, micrometers, and three-dimensional coordinate measuring instruments should be used to measure the dimensions of the parts in real time to ensure that the dimensions of the parts meet the design requirements. If dimensional deviations are found, the processing parameters should be adjusted in time or compensation processing should be performed.
3. Electrodischarge machining
For some mold parts with complex shapes, such as parts with deep grooves, narrow slits or sharp corners, it is difficult to meet the requirements using conventional mechanical processing methods. At this time, electrodischarge machining is required. Electrodischarge machining uses the high temperature generated by the pulse discharge between the electrode and the workpiece to etch the workpiece material.
In the manufacture of preform molds, for example, the bottle mouth of the preform is processed. Since there is a fine thread structure inside the bottle mouth, these complex shapes can be accurately processed using electrodischarge machining. First, an electrode that matches the shape of the bottle mouth must be made, and then the EDM machine is used to etch away the material on the workpiece to form the shape of the bottle mouth. The surface of the part after EDM generally needs to be polished to reduce the surface roughness.
四. Heat treatment stage
1. Quenching and tempering
In order to improve the hardness and wear resistance of mold parts, some key parts, such as cores and cavities, need to be quenched and tempered. Quenching is a heat treatment process that heats the parts above the critical temperature, keeps them warm for a certain period of time, and then cools them rapidly. Quenching can make the parts have high hardness, but the parts after quenching will produce large internal stress, which can easily cause the parts to deform or even crack.
Tempering is a heat treatment process that is carried out immediately after quenching. Its purpose is to eliminate quenching internal stress, stabilize the structure and size of the parts, and adjust the balance between the hardness and toughness of the parts. For example, for mold parts made of P20 steel, the quenching temperature is generally around 820-860℃, and the tempering temperature is around 550-650℃, which can make the hardness of the parts reach around HRC30-35, while having good toughness.
2. Nitriding treatment
Nitriding treatment is a surface strengthening treatment process that can form a nitride layer with high hardness, good wear resistance and strong corrosion resistance on the surface of mold parts. For bottle embryo molds, nitriding treatment can effectively improve the service life of the mold.
During the nitriding process, the mold parts are placed in a nitriding furnace, and under certain temperature and atmosphere conditions, nitrogen atoms penetrate into the surface of the parts to form a nitride layer. The thickness of the nitride layer is generally around 0.02-0.05mm, and the surface hardness can reach around HV900-HV1200. The surface of the parts after nitriding treatment has good wear resistance and corrosion resistance, and can resist the erosion and corrosion of the plastic melt.
五. Surface treatment stage
1. Polishing treatment
The surface quality of the preform mold directly affects the appearance of the preform. Polishing the core and cavity surface of the mold can make the surface of the preform smooth and improve the quality and appearance grade of the preform. The degree of polishing depends on the specific requirements of the preform. For some preforms with extremely high appearance requirements, such as cosmetic preforms, the roughness of the mold surface may reach about Ra0.2 - Ra0.4μm.
Polishing processes include rough polishing, medium polishing and fine polishing. Rough polishing generally uses tools such as grinding wheels and sandpaper to remove processing marks and minor defects on the surface of parts. Medium polishing uses materials such as abrasive paste to further refine the surface roughness. Fine polishing uses special polishing agents and polishing tools, such as wool wheels, polishing cloths, etc., to make the surface reach the required finish. During the polishing process, care should be taken to avoid affecting the dimensional accuracy of the parts.
2. Coating treatment
In order to improve the performance of the mold, the mold surface can also be coated. The coating can play a variety of roles such as improving wear resistance, corrosion resistance, and demolding performance. For example, titanium nitride coating is used. This coating has the characteristics of high hardness and low friction coefficient. It can effectively reduce the adhesion of plastic melt on the mold surface and improve demolding performance.
There are many methods for coating treatment, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD). PVD coating has the advantages of uniform coating, strong adhesion, and small thermal impact on mold parts. When coating, it is necessary to ensure that the surface cleaning and pretreatment of mold parts meet the requirements to ensure the quality and performance of the coating.
六. Mold assembly stage
1. Parts cleaning and inspection
Before assembly, all mold parts should be cleaned to remove impurities such as oil, iron filings, etc. on the surface of the parts. After cleaning, the parts should be inspected again to check whether the dimensional accuracy, shape accuracy and surface quality of the parts meet the requirements. If the parts are found to be defective or do not meet the requirements, they should be repaired or replaced in time.
For some high-precision parts, such as cores and cavities, precision measuring tools such as three-coordinate measuring machines should be used for inspection to ensure that the size and shape deviations of the parts are within the allowable range.
2. Mold assembly process
According to the mold assembly drawing, first assemble the template. Position the fixed template and the movable template through the guide column and guide sleeve to ensure the relative position accuracy between the templates. The guide column and the guide sleeve should be matched accurately, and the gap should be appropriate, generally around 0.02-0.05mm, to ensure smooth opening and closing of the mold.
Install demoulding mechanisms, such as push rods, push plates, etc. The installation of the push rod should ensure that its position and length are accurate, and the fit between the push rod and the core should be appropriate to avoid jamming during demoulding. The installation of the push plate should ensure that it can smoothly push the preform to demold.
Install the cooling system, connect the cooling pipe, and check whether the cooling pipe is unobstructed and whether there is any water leakage. The cooling pipe should be well sealed, generally sealed with sealant or sealing gasket.
Install the gate and runner system to ensure that the connection between the gate and the cavity is tight, and the size and shape of the runner meet the design requirements. During the installation process, be careful to avoid foreign matter entering the runner to avoid affecting the flow of the plastic melt.
七. Debugging and mold trial stage
1. Mold debugging
After the mold is assembled, it is necessary to debug. First, check whether the opening and closing of the mold is smooth and whether the guide mechanism is working properly. Through manual mold opening and closing operations, observe the movement of various parts of the mold, such as whether the demolding mechanism can demold normally and whether the cooling system circulates normally.
Check the electrical control system of the mold to ensure that the control circuits of the heating device, cooling device, demolding device, etc. are working properly. For molds with automation functions, such as automatic opening and closing, automatic demolding, etc., program debugging should be carried out to ensure the accuracy and reliability of automated operations.
2. Mold trial process
After qualified debugging, mold trial is carried out. Add plastic raw materials to the injection molding machine and perform injection molding according to predetermined process parameters, such as injection pressure, injection speed, holding time, cooling time, etc. During the mold trial process, observe the flow of plastic melt in the mold cavity, such as whether there is stagnation, jetting, etc.
Observe the molding quality of the bottle embryo and check whether the size accuracy, shape accuracy, surface quality, etc. of the bottle embryo meet the requirements. If the preform is found to have defects, such as dimensional deviation, bubbles, weld marks, etc., the mold should be adjusted. The adjustments may include gate position and size, cooling channel layout, demoulding mechanism parameters, etc. After multiple mold trials and adjustments, qualified preforms are produced.
八. Acceptance and delivery stage
1. Mold acceptance
When the mold trial is successful and the preforms that meet the requirements are produced, the mold should be accepted. The acceptance content includes the appearance quality, dimensional accuracy, performance indicators, etc. of the mold. The appearance of the mold should be neat and tidy, without obvious damage and defects. The dimensional accuracy should meet the requirements of the design drawings, and the key dimensions of the mold should be tested by measuring tools such as three-coordinate measuring machines.
Performance indicators include the production efficiency, demoulding performance, cooling effect, etc. of the mold. For example, the production cycle of the mold should meet the design requirements, the demoulding process should be smooth, and the cooling uniformity of the preform should be good. During the acceptance process, a detailed acceptance report should be provided to record the results of the acceptance and the problems found.
2. Mold delivery
After the mold is accepted, the mold will be delivered to the customer. At the same time, the customer should be provided with the mold's instruction manual, maintenance manual, spare parts list and other related documents. The instruction manual should provide detailed information on the mold's operating methods, process parameters, precautions, etc. The maintenance manual should include common mold failures and troubleshooting methods, maintenance points, etc. The spare parts list should list the model, quantity and other information of the mold's wearing parts and spare parts so that customers can perform maintenance and repairs during use.
Foshan Heyan Precision Mold Technology Co., Ltd.'s main business is preform molds, bottle blowing molds, bottle cap molds and other products. It has a strong engineering, R&D, technology, and sales team, advanced processing equipment and rich project experience. If you want to know more or have special needs, please call 13318345050, WeChat ID.pet bottle mold
