Yuyao Jinqiu Plastic Mould Co., Ltd.

Injection molding is a widely used manufacturing process for producing plastic parts in large volumes.   Here’s a step-by-step guide to the process, including key critical steps: 1. Design and Material Selection Product Design: Start with a 3D design of the part (using CAD software like Solid Works or Auto，CAD). Plastic Material Choice: Select a polymer based on the part’s requirements (strength, temperature resistance, flexibility, cost, etc.). Common options include: Thermoplastics (most common): PP, PE, ABS, PC, PET. 2. Mold Design and Fabrication The mold is the core of the process, typically made of hardened steel (for high-volume production) Key mold features: Cavities: The hollow shape that forms the part (single or multi-cavity for mass production). Gating system: Channels that deliver molten plastic to the cavity (e.g., sprue, runner, gate). Gates control flow rate and location (e.g., edge gates, sub-gates). Cooling system: Water channels within the mold to cool molten plastic quickly and uniformly (critical for cycle time and part quality). Ejection system: Pins, plates, or sleeves to push the cooled part out of the mold. 3. Preparing the Plastic Material Drying: Many hygroscopic plastics PC, ABS) absorb moisture from the air, which causes bubbles or streaks in the final part. Dry them in a dehumidifying dryer at specific temperatures (e.g., 80–120°C for ABS) for 2–4 hours. Colorants/Additives: Mix in pigments, fillers (glass fiber), or stabilizers (UV resistance) as needed. Pre-com pounded materials (already colored) simplify this step. 4. Injection Molding Machine Setup Injection molding machines consist of an injection unit (melts plastic) and a clamping unit (holds and opens the mold). Setup steps: Mount the mold: Secure the mold halves to the clamping unit (fixed and moving platens). Align carefully to avoid damage. Set temperatures: Heat the barrel (injection unit) in zones to match the plastic’s melting point (e.g., 180–230°C for PP, 230–300°C for ABS). The nozzle (connects to the mold) is also heated. Clamping force: Adjust the clamping unit to apply enough force to keep the mold closed during injection (prevents "flash"—plastic leaking between mold halves). Calculated based on part area and material pressure. 5. The Injection Molding Cycle A single cycle produces one or more parts and includes 4 main stages: a. Plasticizing (Melting) Granular plastic is fed into the barrel via a hopper. A rotating screw pushes the plastic forward, heating it via friction and barrel heaters until it melts into a viscous fluid (melt). The screw retracts slightly to accumulate a measured volume of melt (shot size) at the front of the barrel. b. Injection The screw moves forward rapidly, forcing the molten plastic through the nozzle and into the mold’s gating system, filling the cavity. Key parameters: Injection pressure: Ensures the mold fills completely (varies by material; e.g., 700–1500 bar). Injection speed: Controls how fast the cavity fills (too slow = cold spots; too fast = turbulence/air traps). c.Packing & Holding Once the cavity is full, the screw maintains pressure (holding pressure) to "pack" additional plastic into the mold, compensating for shrinkage as the plastic cools. Reduces sink marks and ensures dimensional accuracy. d. Cooling The mold’s cooling system circulates water to remove heat, solidifying the plastic. e. Ejection After cooling, the clamping unit opens the mold. Ejection pins push the solidified part out of the cavity. The cycle repeats (typically 10–60seconds, depending on part size, structure,weight, performance and so on).    

1、 Analysis of the core causes of poor exhaust emissions Cause category Specific manifestations and mechanisms Typical data/phenomena 1. Design defects in venting system -Insufficient depth of exhaust groove (material decomposition temperature+30 ℃ Carbonized black spots and VOC exceeding standards Appearance scrap rate of 5-8%, loss of RMB 20000 to 40000 Flow mark/fusion mark Melt front temperature difference>15 ℃ Visible flow marks and weakened mechanical properties The cost of secondary processing has increased by ¥ 15000 to ¥ 30000 Extended cycle Filling time increases by more than 0.5s Daily production decreases by 15-20% Annual production capacity loss of ¥ 500000 to ¥ 800000 3、 Systematic solutions and parameter standards 1. Optimization design of exhaust system · Multi stage exhaust structure: · level position Groove depth (mm) Slot width (mm) function Level 1 melt front 0.02-0.03 3-5 Trace gas permeation and discharge level 2 Main channel of parting surface 0.05-0.08 6-8 Concentrated diversion Level 3 Mold periphery 0.15-0.2 10-15 Rapid pressure relief · · Vacuum assisted exhaust technology: · o Vacuum degree ≤ -0.09MPa (absolute pressure ≤ 10kPa) o Response time± 5% >10% for 3 consecutive cycles Infrared thermal imager Local temperature difference>20 ℃ Stop immediately when the temperature exceeds 30 ℃ Gas concentration detector VOC＞50ppm >100ppm triggers alarm · · Preventive maintenance plan: · o Every 50000 cycles: Ultrasonic cleaning of exhaust tank+Three coordinate detection of deformation o Quarterly: Vacuum system sealing test (leakage rate

Injection molding is a complex manufacturing technique in which a special hydraulic or electric equipment melts, injects, and sets plastic into a metal mold to form it. Plastic injection molding is the most common technique for producing components because: Flexibility: Manufacturers may tailor the mold design and plastic-type for each item. This enables the manufacturing of both basic and complicated designs. Efficiency: Once set up, injection molding machines can create huge quantities fast. Electric devices also improve energy efficiency. Consistency: When parameters are tightly managed – the process produces thousands of identical components with consistent quality. Cost-effectiveness: Although the mold is the most expensive, the cost per component is minimal when made in large quantities. Quality: Injection molding can produce – sturdy, detailed, and high-quality – components repeatedly. Because of these advantages – speed, affordability, and quality – injection molding is the preferred method for producing components in a wide range of sectors. So, how does it work? To achieve high-quality plastic products, the injection molding process requires careful control over several variables. Understanding how this process works assists manufacturers in locating dependable producers capable of delivering the required quality and consistency. Step 1: Choosing the proper thermoplastic and mold Before beginning the injection molding process – it is critical to choose the appropriate thermoplastic and mold since they form the finished pieces. Manufacturers must ensure that the plastic and mold function well together – since certain polymers are not suitable for specific mold designs. Each mold consists of two parts – the cavity and the core. The cavity – is a permanent component into which the plastic is injected. And the core – moves into the cavity to produce the final shape. Molds may be designed for single or many pieces. Molds are often built of – steel or aluminum -because of the constant exposure to high pressure and heat. Step 2: Melting and feeding the thermoplastic Injection molding machines may use either – hydraulic or electric power. Most machines consist of- -a hopper, -a long heated barrel with an injection screw within, -a gate at the end of the barrel, and -a mold tool attached to the gate. Step 3: Adding the plastic to the mold When the molten plastic reaches the end of the barrel- -the gate shuts, and the screw returns, -sucking in a predetermined quantity of plastic and increasing pressure for injection. At this time, the two parts of the mold are securely closed under tremendous pressure – known as clamp pressure. Step 4: Waiting and cooling time After the majority of the plastic has been injected into the mold – it is maintained under pressure for a certain period of time, known as – “holding time.” Once the holding period is over – the screw pulls back, relieving the pressure. This permits the plastic to cool and firm in the mold, a process known as – “cooling time.” Step 5: Removal and finishing processes When the holding and cooling durations are complete, and the component has largely formed – ejector pins or plates force it out of the mold. The component then falls into a chamber or onto a conveyor belt at the bottom of the machine. Once everything is done, the components are ready to be packaged and sent to the makers.

In order to ensure the performance and life,the material of the cutter,measuring tools and molds which used in mechanical manufacturing,should have enough hardness should have enough hardness.   Today,I will discuss about the hardness of material with you   Hardness is a measure of material’s ability to resist local deformation,especially plastic deformation,indentation or scratch.Generally,the more hardness of the material,the better its wear resistance,such as gear and other mechanical parts will require a certain hardness to ensure sufficient wear resistance and service life.   Types of hardness     As shown above,there used to be so many types of hardness.I will introduce you to the common and practical indentation hardness test in metal hardness.   Definition of hardness   1. The Brinell Hardness The Brinell hardness(symbol HB) test method,which has become an accepted hardness specification,is one of the first methods to be developed and summarized,and it has contributed to the emergence of other hardness test methods. The principle of Brinell hardness test is: the indenter (steel ball or carbide ball, diameter Dmm) applies the test force F, after the specimen is pressed, the contact area S(mm2) between the ball indenter and the specimen is calculated in the concave diameter d(mm) left by the indenter, and the value obtained by the test force is excluded. When the indenter is a steel ball, the symbol is HBS, and when the cemented carbide ball is HBW. k is a constant (1/g= 1/9.80665 = 0.102). 2. The Vickers hardness Vickers hardness (symbol HV) is the most widely used test method that can be tested with any test force, especially in the field of small hardness below 9.807N. The Vickers hardness is the value obtained by dividing the test force F(N) by the contact area S(mm2) between the standard plate and the indenter, calculated based on the diagonal length d(mm, the average length in both directions) of the indentation formed on the standard plate by the indenter (tetragonal coned diamond, relative surface Angle =136˚) at the test force F(N). k is a constant (1/g=1/9.80665) 3. The knoop hardness The Knoop hardness (symbol HK), as shown in the following formula, is calculated by dividing the test force by the indentation projection area A (mm2) based on the longer diagonal length d (mm) of the indentation formed on the standard sheet at the test force F by pressing the long diamond indenter with relative side angles of 172˚30' and 130˚. Knoop hardness can also be measured by replacing the Vickers indenter of a microhardness tester with Knoop indenter. 4. The Rockwell hardness The Rockwell hardness (symbol HR) or Rockwell surface hardness is measured by applying a preload force to the standard sheet using a diamond indenter (tip cone Angle: 120˚, tip radius: 0.2mm) or a spherical indenter (steel ball or carbide ball), then applying a test force and restoring the preload force. This hardness value is derived from the hardness formula, which is expressed as the difference between the indentation depth h(μm) between the preloaded force and the test force. The Rockwell hardness test uses a preload force of 98.07N, and the Rockwell surface hardness test uses a preload force of 29.42N. The specific symbol provided in combination with the indenter type, test force, and hardness formula is called a scale. The Japanese Industrial Standards (JIS) define various related hardness scales.   HR(Diamond indenter, Rockwell hardness)=100-h/0.002 h:mm HR(Ball indenter, Rockwell hardness)=130-h/0.002 h:mm HR(Diamond/ball indenter, surface Rockwell hardness)=100-h/0.001 h:mm     Hardness testing machines are widely used because they are simple and quick to operate and can be tested directly on the surface of raw materials or parts. Hardness Selection Guide Selection guide for hardness testing methods for your reference: Material Micro Vickers hardness (Knoop hardness) Tiny surface material properties Vickers hardness Rockwell hardness Surface Rockwell Brinell Hardness Shore hardness (HS) Shore hardness(HA/HC/HD) Leeb hardness IC chips ● ●               Tungsten carbide, ceramics (cutting tools)   ▲ ● ●     ●     Iron & Steel Materials (Heat Treatment Materials) ● ▲ ● ● ●   ●   ● Non-metallic materials ● ▲ ● ● ● ●       Plastic   ▲   ●           grinding wheel       ●           Castings               ●   Rubber, sponge           ●           shape Micro Vickers hardness (Knoop hardness) Tiny surface material properties Vickers hardness Rockwell hardness Surface Rockwell Brinell Hardness Shore hardness (HS) Shore hardness(HA/HC/HD) Leeb hardness Sheet metal (safety razor, metal foil) ● ● ●   ●         Sheet metal (safety razor, metal foil) ● ●               Small parts, needle-shaped parts (clocks, watches, sewing machines) ● ▲               Large-format specimens (structures)             ● ● ● Microstructure of metallic materials (phase hardness of multilayer alloys) ● ●               plastic plates ▲ ▲   ●   ●       Sponge, rubber sheet           ●           Inspection, judgment Micro Vickers hardness (Knoop hardness) Tiny surface material properties Vickers hardness Rockwell hardness Surface Rockwell Brinell Hardness Shore hardness (HS) Shore hardness(HA/HC/HD) Leeb hardness The strength and properties of the material ● ● ● ● ● ● ▲ ● ● Heat treatment process ●   ● ● ●   ▲   ▲ Carburizing hardening layer thickness ●   ●             Decarburization layer thickness ●   ●   ●         Flame and high-frequency quenching hardening layer thickness ●   ● ●           Hardenability test     ● ●           The maximum hardness of the welded part     ●             The hardness of the welded metal     ● ●           High-temperature hardness (high-temperature characteristics, hot workability)     ●             Fracture toughness (ceramic) ●   ●               Hardness selection conversion Knoop to Vickers conversion Based on the fact that objects with the same hardness have equal resistance to the two types of Knoop Vickers indenters, the stress of the two types of Vickers Knoop indenters under load is deduced respectively, and then according to σHK=σHV, HV=0.968HK is obtained. This formula is measured under low load, and the error is relatively large. In addition, when the hardness value is greater than HV900, the error of this formula is very large, and the reference value is lost. After derivation and correction, the conversion formula of Knoop hardness and Vickers hardness is proposed. Verified by actual data, the maximum relative conversion error of the formula is 0.75%, which has high reference value. Conversion of Rockwell to Vickers To Hans· The Qvarnstorm conversion formula proposed by Qvarnstorm is modified to obtain the conversion formula of Rockwell hardness to Vickers hardness: This formula is converted with the standard data of ferrous metal hardness published in China, and its HRC error is basically within the range of ±0.4HRC, its maximum error is only 0.9HRC, and the maximum calculated HV error is ±15HV. According to the stress σHRC=σHV of different indenters, the formula is obtained by analyzing the relationship curve between Rockwell hardness and Vickers hardness indentation depth. This formula is compared with the national standard experimental conversion value, and the error between the calculation result of the conversion formula and the standard experimental value is ±0.1HRC. According to the actual experimental data, the conversion of Rockwell hardness to Vickers hardness is discussed by linear regression, and the formula is obtained: This formula has a small range of use and a large error, but it is easy to calculate and can be used when the accuracy is not high. Conversion of Rockwell to Brinell hardness The relationship between Brinell indentation and Rockwell indentation depth was analyzed, and the conversion formula was obtained according to the stress σHRC=σHB of the indenter. The error between the calculated results and the standard experimental values is ±0.1HRC. According to the actual experimental data, the formula was obtained by linear regression method. The formula error is large, and the range of use is small, but the calculation is simple, and it can be used when the accuracy is not high. Conversion of Brinell to Vickers The relationship between Brinell hardness and Vickers hardness is also based on σHB=σHV. The conversion result of this formula is compared with the conversion value of the national standard, and the conversion error is ±2HV. Knoop to Rockwell conversion Because the corresponding curves of Knoop and Rockwell are similar to parabolas, the approximate conversion formula is derived from the curves. This formula is accurate and can be used as a reference.