Brief introduction of injection molding and technology
First, the basic principle of injection molding:
The injection molding machine uses the property that plastic can be melted into liquid after being heated to a certain temperature. The melted liquid is injected into a closed mold cavity with high pressure, cooled and molded, and ejected after opening the mold to obtain the required plastic products. Second, the four elements of injection molding:
1. Plastic Mould 2. Injection molding machine 3. Plastic raw materials. Forming condition 3. plastic mould
Most of them use two-plate molds and three-plate molds, and some of them use row molds with sliders.
Basic structure: 1. Punch (lower die), punch fixing plate, punch auxiliary plate, ejector plate and punch template. 2. The master mold (upper mold) master template, master mold fixing plate, glue inlet ring and positioning ring. 3. Cooling of temperature balance system. Stabilize (equalize) the mold temperature. Four. Injection molding machine
It mainly consists of a plasticizing injection device, a clamping device and a transmission mechanism; Electric drive motor, motor drives oil pump, oil pump generates oil pressure, oil pressure drives piston, piston drives machinery, and machinery generates action; 1, which can be divided into:
1. 2 horizontal injection molding machines. Vertical injection molding machine III. Angle injection molding machine 4. 2 sets of multicolor injection molding machines. According to mode locking, it can be divided into:
1. Direct injection molding machine 2. Crankshaft injection molding machine 3. Direct injection and crankshaft compounding 3. According to the feeding methods, it can be divided into:
1. plunger injection molding machine 2. Single screw injection molding machine 3. Reciprocating screw injection molding machine 4. Four systems of injection molding machine: 1. Injection system.
A. multi-stage, mixing-resistant and corrosion-resistant.
B the control of combustion rate, injection, pressure maintenance, back pressure and screw speed is segmented. C. stirring and long-life screw device. Interchangeability and automatic cleaning of material tubes. E. balance and stability of oil pump. 2. Mode locking system
A. high speed and high rigidity.
B. automatic die adjustment and die changing device. Automatic lubrication system. D. balance and stability. 3. Oil pressure system
A. full electronic feedback control.
B. smooth movement, high stability and sealing. C. save energy quickly.
D. hydraulic oil cooling and self-filtering system. 4. Electronic control system
A. multi-level, memory and extensible microcomputer control. B. closed-loop circuit and loop.
C.SSR (proportional, integral and differential) temperature control. D. self-diagnosis. Alarm function.
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E. automatic production quality control and record. 5. Existing brands of domestic injection molding machines: 1. Foreign brands:
Barton Demag Mitsubishi Nippon Steel Dongzhi, etc. 2. Hong Kong and Taiwan brands:
Zhenxiong made every effort to make himself prosperous, and Xinshun exhibited in Taichung Seiki Yilida Comprehensive Weft Fengtie Essence Jin Ri Derun;
3. Foreign brands:
Haitian, Haihai, Xinghai, Taihaotai, Haitian, Sanyuan Universal Double Horse Yongtai Ace, etc.
Verb (abbreviation of verb) Plastic materials Plastic materials can be divided into thermosetting and thermoplastic: 1. Thermosetting plastics: refers to plastics that cannot be reused, and its molecules eventually form the body structure. 2. Thermoplastics: refers to reusable plastics, which can be divided into crystalline (PBT, PA) and amorphous (PC, PPO). Crystalline plastic refers to a plastic liquid that can become regular when it becomes a solid, and most of its molecules are arranged in a linear or branched structure. 3. Engineering plastics Engineering plastics refer to mechanical parts that can be used for a long time at 100 degrees Celsius, and the tensile strength is greater than 500kg per square centimeter; Plastics with bending strength greater than 2400kg/cm2 Most of the plastics currently used are: PP ABS PBT PC PA PPS POM, etc. 1, PP material: (polypropylene polypropylene) At present, most brands used are: China Petrochemical, Taiwan Province Chemical Fiber Zhenhai Refining and Chemical Company, Modern Singapore mytex, and India SEETEC.
Characteristics: light specific gravity, good fluidity, colorless, tasteless, odorless, non-toxic, shiny, high tensile strength, good heat resistance, good secondary processing performance, good insulation and good chemical stability; Plus low price, it is mainly suitable for woven bags, toys, turnover boxes, household appliances, pipes and plates.
The company's products are mainly used for electrical housings, such as: motor back cover, three tubes, front and rear shells, small sun back cover blades, etc.
General molding conditions: 1. Mold temperature: 20 degrees to 40 degrees 2. Drying conditions: 80℃ 1-2 hours or more. 3. Feed pipe temperature: 65438 070℃ to 220℃. Thermal deformation temperature: 80℃ (1.8MPa, 12.7mm). 5. Softening point:1above 35 degrees 6. Mold shrinkage: 0.5%-0.7% (3.3 mm) 7. Tensile yield strength: 20-30 MPa；; The commonly used modification methods are: strengthening, toughening, flame retardant, oxidation resistance, weather resistance and high gloss; 2.ABS material: (acrylonitrile, butadiene, styrene ternary tree.
Fat). (Acrylic-butadiene-styrene copolymer)
At present, most of the brands used are: China Petrochemical, Taiwan Province Chimei, Taiwan Province Chemical Fiber, BASF, South Korea LG (Ningbo LG), South Korea Jinhu Chemical Industry, South Korea Samsung.
Features: Good impact resistance, high strength and rigidity, low temperature resistance, heat resistance, high gloss, easy color matching, secondary processing and surface treatment. Mainly suitable for automobiles, electric power, household appliances, building profiles, etc.
The company's products are mainly used in electrical enclosures, such as electric fans, air coolers, water dispensers, heaters, ventilation fans, yuba and other products, such as front and rear enclosures, brackets, etc.
General molding conditions: 1. Mold temperature: 40℃ to 60℃ 2. Drying conditions: 80℃ for 2-4 hours or more.
3. Feed pipe temperature: 190℃ to 230℃. Thermal deformation temperature: 80℃ (1.8MPa, 12.7mm).
5. General back pressure: 8- 15kg/ mm2. 6. Mold shrinkage: 0.5%-0.7% (3.3 mm) Common modification methods are: strengthening, toughening, flame retardant and weather resistant alloy;
3.PBT material: (polybutylene terephthalate) Most of the brands currently used by Celanese are not fixed. Commonly used brands in the world are: DuPont singular general Polaroid DSM Bayer and so on.
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Features: high wear resistance and rigidity, strong chemical resistance, good weather resistance, good dimensional stability, good electrical insulation, and better performance after reinforcement. Moisture absorption, easy to be decomposed by heat, mainly suitable for automobiles, electric power, household appliances, connectors, precision instruments and electronic products.
The company's products are mainly used for heat-resistant components: heater air outlet, building PTC bracket, etc. General molding conditions: (according to the change of fiber ratio) 1. Mold temperature: 40℃ to 60℃ 2. Drying conditions: 100℃ to 140℃ for more than 4 hours. 3. Feed pipe temperature: 240℃ to 270℃. Thermal deformation temperature: 2 10℃ to 230℃ (1.8MPa, 12.7mm). 5. Mold shrinkage: 0.3%-0.5% (3.2 mm) 6. Thermal decomposition temperature: 280℃ (the feed pipe can stay at 260℃ for 6 minutes, otherwise it will decompose and deteriorate). The commonly used modification methods are: strengthening, toughening and flame retardant; 4.PC material (polycarbonate)
At present, most of the brands used are not fixed, and the commonly used brands in the world are Bayer Singular Mitsubishi Shining Didao Bao Li and so on.
Features: the highest impact strength, stable size, heat resistance above 130 degrees, high gloss and transparency, light transmittance of about 90%, non-toxic. High processing temperature, great stress after molding, moisture absorption, non-wear resistance and fatigue resistance. Mainly suitable for food containers, optical discs, lenses, household appliances, optical instruments, etc.
The company's products are mainly used in oil painting, such as: some oil painting panels, clothes racks, electronic oil painting transparent covers, etc. General molding conditions: (according to the change of fiber ratio) 1. Mold temperature: 80 degrees to 100 degrees 2. Drying conditions: 100℃ to 120℃ for more than 4 hours. 3. Feed pipe temperature: 250 to 300 degrees. 4. Thermal deformation temperature: about 130 degrees; 5. Mold shrinkage: 0.5%-0.7%
The fluidity of PC material increases with the increase of temperature, because temperature regulation accounts for a large proportion in molding. The commonly used modification methods are: enhancing flame retardancy, oxidation resistance and weather resistance; 5.PA material (polyamide) is also called nylon nylon. At present, most brands used are not fixed. Commonly used brands in the world are DuPont, Bao Li, Mitsubishi, DSM, Dow, BASF Bayer, etc.
Features: Wear resistance, fatigue resistance, high water absorption, excellent dimensional stability (high strength after reinforcement), (can be used for high-precision mechanical objects). Mainly suitable for automobiles, gears, motors, precision instruments, precision electronic patches, ic connectors, etc.
The company's products are mainly used for heat-resistant and wear-resistant parts, such as: electronic paint panels, paint casters, terminals, etc.
Molding conditions: (varying according to different structure and fiber ratio) 1. Mold temperature: 80 degrees to 120 degrees 2. Drying conditions: 120℃ to 140℃ for more than 4 hours. 3. Feed pipe temperature: 260 to 3 10℃. 4. Thermal deformation temperature: 235 degrees. 5. Mold shrinkage: 0. 1%-0.5%.
Equipment requirements: 1. Screw: (L:D=20: 1) standard three-stage screw with stop ring. (Optional closed nozzle, diameter 3.0 mm) 2. The feed pipe shall be made of alloy material with corrosion resistance and wear resistance. 3. Both sides of the formwork shall be reinforced with heat insulation boards to avoid the machine from being heated. 4. The circular runner is adopted, and the heat dissipation of the male and female dies is uniform. 5. The feed inlet uses a pinhole with a diameter of 0.3 mm to 0.5 mm to dive into the feed.
6. Use an exhaust hole with a depth of 0.02mm-0.04mm and a width of 0.5mm- 1.0mm to exhaust effectively. The commonly used modification methods are: enhancing wear resistance, heat resistance and high viscosity; 6.POM material: (polyoxymethylene)
At present, most of the brands used by Pioneer Company are not fixed, such as DuPont, Bao Li, Lee Tae, Cologne and so on.
Features: high wear resistance, fatigue resistance, excellent dimensional stability, and serious dazzling gas after decomposition. Pay attention to exhaust when using.
Poor flame retardancy, acid and oil resistance and poor surface treatment, so it should be suitable for automobiles, gears, sprayers and precision electricity.
Purple lamp.
Company products are mainly used for dimensional stability and wear-resistant parts, such as: three-tube eccentric peach, bushing, Auchan turntable, etc.
General molding conditions:
1. Mold temperature: 60 degrees to 80 degrees.
2. Drying conditions: 80℃ to100℃ for more than 2 hours. 3. Material tube temperature: 170 to 2 10 degrees 4. Thermal deformation temperature: about 90 degrees; 5. Mold shrinkage: 0.5%-0.8%
6. Thermal decomposition temperature: 240℃ (at 240℃, the feed pipe can stay for 5 minutes, otherwise it will decompose and deteriorate). 7.PPS steel material: (polyphenylene sulfide)
At present, most of the brands used by Pioneer Company are not fixed, and the commonly used brands in the world are: Philip Pauli Dow Singularity, etc.
Features: Wear resistance, fatigue resistance, high water absorption, high flame retardancy, excellent dimensional stability, (can be used for high-precision mechanical objects) with better performance and metallic sound after reinforcement. Poor crystallinity, poor fluidity, poor toughness, unable to match colors. Easy to corrode molds and machines, and easy to produce burrs.
Mainly suitable for automobiles, gears, motors, precision instruments, precision electronic patches, ic connectors, etc. The company's products are mainly used for high heat-resistant parts, such as PTC bracket of heater, wiring frame, etc.
General molding conditions: (depending on the structure and fiber ratio) 1. Mold temperature: 100 degrees to 150 degrees.
2. Drying conditions: 120- 140℃ for more than 4 hours. 3. Feed pipe temperature: 270℃ to 330℃
4. Thermal deformation temperature: 260 degrees (1.8MPa, 12.7mm). 5. Thermal decomposition temperature: 400 degrees (1.8MPa, 12.7mm). 6. Mold shrinkage: 0. 1%-0.4% (3.3 mm) Equipment requirements:
1. screw: (L:D=20: 1)
Standard three-part with check valve screws. (3.0mm diameter closed nozzle is optional) 2. The feed pipe shall be made of corrosion-resistant and wear-resistant double alloy materials. 3. Both sides of the formwork shall be reinforced with heat insulation boards to avoid the machine from being heated. 4. The circular runner is adopted, and the heat dissipation of the male and female dies is uniform.
5. The feed inlet uses a pinhole with a diameter of 0.3 mm to 0.5 mm to dive into the feed.
6. Use an exhaust hole with a depth of 0.02mm-0.04mm and a width of 0.5mm- 1.0mm to exhaust effectively. 7. Mold cavity should be chrome plated or treated with corresponding surface to reduce gas corrosion in production.
Six, molding conditions
Forming conditions: speed, pressure, temperature, time, stroke and quantity. 1. Injection pressure (primary pressure):
The pressure exerted by the unit area at the top of the screw on the plastic during injection molding; P= cylinder diameter D0/ screw diameter D 1* oil pressure; 2. Maintain pressure (secondary pressure):
When the molten raw material is cooled in the cavity, a certain pressure must be applied to supplement its shrinkage.
Increase the density, then the pressure exerted by the screw on the plastic is called pressure holding; 3. Clamping force: (tonnage)
The maximum clamping force that the mold locking mechanism can exert on the mold; F=K*P*A(K=0.4~0.7, i.e. pressure loss coefficient); P: maximum oil pump pressure; A, locking the template area;
* the set value is generally not more than 80-100 kg/cm2; 4. Injection amount:
The weight of plastic injected into the mold during the injection molding cycle; 5. Injection capacity: gram. cubic centimeter
The maximum amount that the screw of injection molding machine can shoot at the maximum injection stroke; G=3. 14/4*D2*S* density d: screw diameter s: screw stroke.
* The injection quantity of a cycle in production should be less than or equal to 80% of the maximum injection quantity of the machine; 6. Emissivity:
The screw moves in the feed pipe, and the stroke of movement per unit time is called firing rate; V = signal-to-noise ratio * 100%
S: the stroke of the screw in the feed pipe; T: screw injection time; 7. Back pressure:
When feeding, the pressure exerted on the molten plastic is opposite to the screw; The role of back pressure:
1. Improve the mixing effect of molten plastics; 2. Increase the temperature of molten plastic; 3. Increase the density of molten plastic; 4. Improve the uniformity of plastic color; 5. Exhaust the gas in the molten plastic; 8. under-voltage protection:
Refers to a protective device for the resistance when the mold is locked, which can minimize the damage of the mold when it is pressed by foreign objects and reduce the loss of the mold.
Its working principle is that when the distance from low-speed mode locking to high-pressure mode locking is set to a certain value
Occasionally, when the mold encounters foreign matter, plastic or fails to lock the high-voltage switch point within the set time due to insufficient lubrication, the machine will give an alarm and open the mold. Analysis of the reasons for improving molding quality: 1. Incomplete shooting (lack of materials)
1. Insufficient injection pressure; 2. Insufficient holding pressure; 3. Insufficient injection time; 4. Insufficient feeding (storage);
5. The lens section position is too small; 6. The shooting end position is too small; 7. The shooting speed is not fast enough; 8. The temperature of nozzle and feed pipe is not enough; 9. The mold temperature is not enough; 10. Insufficient drying temperature and time for raw materials; 1 1. The injection cycle is too fast and the preheating is insufficient;
12. Uneven mixing of raw materials; (insufficient back pressure, insufficient rotating speed) 13. Insufficient liquidity of raw materials; (The product wall is too thin)
14. Insufficient exhaust of the mold; 15. uneven feeding of the die;
16. The design of cold material well is unreasonable; 17. The cold feed inlet is too small and the direction is unreasonable;