SMC Environmental Protection Trash Can Mold
I. Selection of Mold Materials The material selection for SMC environmental protection trash can molds directly affects the mold's service life, forming accuracy, and the quality of the final product. It is necessary to consider high-temperature resistance, high-pressure resistance, wear...
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Product Introduction
I. Selection of Mold Materials
The material selection for SMC environmental protection trash can molds directly affects the mold's service life, forming accuracy, and the quality of the final product. It is necessary to consider high-temperature resistance, high-pressure resistance, wear resistance, and dimensional stability. Core materials can be classified into three categories based on their functions: mold frame materials, core and cavity materials, and auxiliary accessory materials.
1. Mold Frame Materials
The mainstream choice is to use S50C or P20 steel to build standard mold frames. Among them, the mold frames of Longji are the most widely used in the industry. S50C steel has excellent mechanical processing performance and toughness. After quenching and tempering treatment, it can meet the structural strength requirements of the mold frame and reliably withstand the overall pressure during the molding process. P20 steel has better hardness uniformity and is suitable for medium and large-sized trash can molds with high precision requirements. It can effectively reduce the risk of mold deformation and ensure the stability of the molding process.
2. Core and Cavity Materials
Material selection should be based on the expected service life of the mold and the precision requirements of the product. Pre-hardened steel (P20, P20+Ni) is suitable for small and medium batch production scenarios, with a hardness of HRC30-32, and a mold life of about 200,000 to 300,000 cycles. It has a significant cost-performance advantage and can fully meet the production needs of conventional environmental protection trash cans. Hardened steel (H13, NAK80), after professional heat treatment, can reach a hardness of HRC50-52, with excellent wear resistance and fatigue resistance, and a life of 600,000 to 800,000 cycles. It is suitable for large-scale, high-precision trash can production. Stainless steel (ASSAB Stavax) is specially designed for corrosive environments or high-end products, with a life exceeding 1 million cycles. It can effectively prevent surface rusting of the mold and ensure the integrity of the product appearance.
II. Core Molding Process
1. Pre-molding Preparation
First, conduct a comprehensive quality inspection of the SMC sheet, focusing on confirming core indicators such as the resin paste formula,
fiberglass content, hardness, and material uniformity, to avoid product quality issues caused by material defects from the source.
2. Feeding Process
Calculate the feeding amount precisely based on the volume of the trash can (calculation formula: feeding amount = product volume × 1.8g/cm³), and place the cut sheet in the middle of the mold cavity. For non-symmetric structure trash cans, the feeding point should be optimized to ensure that the material flows simultaneously to the ends of the cavity, ensuring uniform product formation. For deep cavity or complex-structured trash cans, the SMC sheet can be preheated at 100-120°C to improve material fluidity and optimize filling.
3. Pressing and Curing
Control the press to quickly close the mold, and then slowly apply forming pressure after the mold is closed. The conventional pressure is controlled at 3-7MPa. For complex structures or high-precision trash cans, the pressure parameters can be appropriately increased. The forming temperature is set at 120-155°C. For thick-walled trash cans (25-32mm), a medium temperature range of 135-145°C is recommended, and for thin-walled products, it can be increased to 171°C. Through temperature gradient control, internal heat
accumulation in the product can be avoided. The curing time is calculated at 40s/mm. For products over 3mm thick, for every additional 4mm, the curing time is extended by 1 minute to ensure complete curing of the product without bubbles or warping.
III. Comparative Analysis of Mold Types
To highlight the adaptability advantages of SMC environmental protection trash can molds, the following compares them with traditional plastic molds (injection molding, blow molding) and FRP molds from multiple dimensions, providing a reference for production selection:
1. Comparison with Traditional Plastic Molds
|
Comparison dimension |
SMC Environmental Protection Trash Can Mold |
Traditional plastic molds (injection molding / blow molding) |
|
material behavior |
The SMC material is composed of resin and glass fibers. It features high strength, corrosion resistance, and heat resistance. The products are recyclable and fully comply with environmental protection requirements. |
Mostly use thermoplastic materials such as PP and ABS. These materials have relatively low strength and average weather resistance, and their applicable scenarios are limited. |
|
forming process |
Compression molding process is suitable for manufacturing large and complex structural products. It enables one-time curing and molding, with strong molding stability. |
Injection/molding process is more suitable for small and medium-sized, simple-structured products. It has higher batch production efficiency but has limited adaptability. |
|
mold structure |
The structure is relatively complex and requires the design of a cooling water circuit, an exhaust system, and an ejection mechanism. It can withstand high-temperature and high-pressure environments. |
The structure is relatively simple, with the core focusing on the design of the flow channel. It needs to be precisely matched with the parameters of the injection molding machine. |
|
Cost and lifespan |
The material and processing costs are relatively high, but the mold has a long service life (200,000 to 1,000,000 mold cycles), and the cost-effectiveness is outstanding for long-term batch production. |
The initial cost is relatively low, but the mold life is moderate (100,000 to 500,000 mold cycles). The overall cost for long-term production is relatively high. |
|
applicable scene |
Outdoor large-scale environmental protection trash cans, classification trash cans, etc., which have requirements for weather resistance and load-bearing capacity, in such scenarios |
Scenarios where the requirements for strength and weather resistance are relatively low, such as indoor small trash cans |
2. Compared with FRP molds
The FRP molds adopt the hand lay-up molding process, which is highly dependent on manual operation. The quality of the products is easily affected by the skill level of the workers and the production environment, and problems such as delamination and uneven strength often occur. On the other hand, the SMC molds are processed through high-temperature and high-pressure mechanical molding. The products have high density, good uniformity of strength, excellent surface smoothness, and the production efficiency far exceeds the hand lay-up process. In terms of material cost, the price of SMC raw materials is approximately twice that of FRP, but when considering the overall cost including the forming efficiency, product qualification rate, and service life, the long-term usage cost of SMC molds has a more competitive advantage.
IV. Complete processing procedures
The SMC environmental-friendly trash can mold processing strictly follows the "design - processing - treatment - assembly - debugging" full-process specification. Each link requires precise control of accuracy to ensure the overall performance of the mold is stable and reliable. The specific procedures are as follows:
1. Mold design
Based on the size of the trash can, wall thickness, handle layout, and demolding requirements, a three-dimensional model is constructed and the structure design is completed. The core optimization directions include demolding slope, cavity structure, cooling waterway, and exhaust system. Considering the fluidity characteristics of SMC materials, the feeding area is reasonably planned to avoid problems such as poor material flow and air stagnation; at the same time, through simulation analysis, the rigidity, positioning accuracy, and operation rationality of the push-out mechanism are verified to avoid design flaws in advance.
2. Mold frame and cavity processing
The mold frame is processed using S50C/P20 steel, and the shape and mating surfaces are processed using CNC lathes and milling machines. The levelness and verticality of the mold frame are strictly controlled to ensure assembly accuracy. The core and cavity are processed using five-axis machining centers and high-speed milling, etc., for large trash can molds, the five-axis equipment with a worktable surface of 4200X3000mm can handle complex curved surfaces, with a processing accuracy of ±0.005-±0.01mm and a surface roughness of Ra0.8μm, meeting the high-precision requirements of the products.
3. Heat treatment and surface treatment
The core and cavity made of H13 and other hard steel materials undergo quenching and tempering treatment to achieve a hardness of HRC50-52, significantly improving the wear resistance and fatigue resistance of the mold. According to the appearance and usage requirements of the products, the mold surface is polished, textured, or chrome-plated to enhance corrosion resistance and extend the mold service life. At the same time, the cooling waterways are precisely processed to ensure uniform water distribution and constant temperature in the mold cavity, ensuring the consistency of product curing.
4. Component assembly
Assemble DME/HASCO standard push pins, guide columns, positioning pins, etc., precisely adjust the stroke of the push-out mechanism to ensure smooth operation without jamming or deviation. Install heating pipelines and temperature control devices, precisely connect to the press interface, debug the circuit and oil system, and ensure the coordinated operation of all components to meet the forming process parameter requirements.
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