Injection molding process described

Date：2011-12-06 18:03:33

First, the basic principles of injection molding:

The use of plastic injection molding machine heated to a certain temperature, it can melt into the nature of the liquid, the molten liquid with a high-pressure injection into the closed mold cavity, after cooling, the mold after the plastic top of the body receive the required product.

Second, the injection molding of the four elements:

1 plastic mold 2 injection molding machine 3 plastic materials 4. Forming conditions

Third, plastic mold

Most of the formwork using two, three plate mold, there are also some with slide-bit analog lines.

Basic structure: 1. Male mold (the mold) male mold fixing plate, the public mode auxiliary plate, ejector plate, the public template. 2 female mold (upper mold) female template, the mother mold fixing plate, into the apron, positioning ring. 3 constant temperature system cooling. Stable (value) set the mold temperature.

Fourth, the injection molding machine

Mainly by plastics. Injection unit, clamping devices and transmission components; electric drive motor, the motor driven pump, hydraulic pump produces, hydraulic driven piston, piston driven machinery, produce action;

1, according to the injection can be divided into: 1. Horizontal injection molding machine 2 vertical injection molding machine 3 angle injection molding machine 4 multi-color injection molding machine
2, according to the mode-locking can be divided into: 1. Direct pressure injection molding machine 2 crank-type injection molding machine 3. Direct pressure, crank compound
3, by feeding can be divided into: 1 plunger injection molding machine (2) one-way screw injection molding machine 3. Reciprocating screw injection molding machine

4, injection molding machine four systems:

1) Injection system

a. Multi-technology, mixing and corrosion resistance.
b. rate of fire, injection, holding pressure, back pressure, screw speed control section.
c. mixing of the long life of the screw device.
d. barrel interchangeability, automatic cleaning.
e. pump balance and stability.

2) clamping system

a. high-speed, high rigidity.
b. auto mode, change mode device.
c. automatic lubrication system.
d. balance and stability.

3) Hydraulic system

a. All electronic feedback control.
b. the action smooth, high stability, closed.
c. rapid, energy efficiency.
d. hydraulic oil cooling, since the filter system.

4) electronic control system

a. Multi-oriented, with memory, scalability of the microcomputer control.
b. the closed-loop circuit, circuit.
c.SSR (Proportional, Integral, Derivative) temperature control.
d. self-diagnosis. alarm.
e. automatic production quality control records.

5, the existing domestic brand injection molding machines:

1 foreign brands: Barton Demag Mitsubishi Steel Toshiba, etc.;
(2) Hong Kong and Taiwan brands: Zhenxiong full fat FCS Shun Elite Seiki booth, Wei Feng integrated iron one hundred plastic this machine DELHI, etc.;
3 foreign brands: Long Beach Marina starfish Haida Hai too common in Haiti three yuan Ma Yongtai double ace, etc.;

Fifth, the plastic material

Thermosetting plastic and thermoplastic materials can be divided into two kinds: 1. Thermosetting plastic: that can not re-use of plastic, into the final shape of its molecular structure. (2) thermoplastics: refers to the use of plastic can be recycled repeatedly, into crystals (PBT, PA) and amorphous nature (PC, PPO). Crystalline plastic refers to plastic liquid to solid form can be the rule of plastic, its Most molecules by linear or branched chain structure arranged. 3 refers to the use of engineering plastics in mechanical engineering plastic components, long-term use at 100 degrees Celsius, tensile strength of more than 500kg in one square centimeter; flexural strength more than 2400kg in one square centimeter of plastic.

Most plastics are currently used: PP ABS PBT PC PA PPS POM and so on.

1, PP material: (PP polypropylene) is currently the brand most used are:

Taiwan, China Sinopec Zhenhai Refining & Chemical Fiber
South Korea's Hyundai India SEETEC Singapore mytex

Features: light weight, mobility, and colorless. Tasteless, odorless, nontoxic, gloss. Tensile strength heat resistance, and secondary processing performance, with good insulation. Chemical stability; plus on low prices, mainly for bags. toys turnover box. appliances. tube-plate and so on.

Our products are mainly used for electrical enclosure, such as: motor rear cover three small shell around the hood fan, and so after the sun;

General molding conditions: 1. Mold temperature: 20 degrees to 40 degrees 2 drying conditions: 80 degrees for more than 1-2 hours. 3 barrel temperature: 170 degrees to 220 degrees 4 heat distortion temperature: 80 degrees (1.8MPa, 12.7mm). 5 Softening Point: 135 degrees 6. Mold Shrinkage: 0.5% - 0.7% (3.3mm) 7. Tensile yield strength :20-30Mpa;
The modified methods are commonly used: anti-oxidant weather toughening high gloss flame retardant, etc.;

2, ABS material: (propylene clear Butadiene styrene resin). (Acrylonitrile-butadiene-styrene copolymer)

At present, most use of the brand are: Taiwan, China Petrochemical Fiber BASF Korea, Taiwan Chi Mei LG (Ningbo LG) South Korea's Samsung Korea Kumho Chemical

Features: good impact resistance, high strength and rigidity, low temperature, heat-resistant, high gloss, easy to color and secondary processing, surface treatment. Mainly used in cars. Electric. Appliances. Building profiles and so on.

Our products are mainly used for electrical enclosure, such as: electric fans. Cold fan. Drinking. Heater. Ventilators. Yuba and other products around the shell. Stents, etc.;

General molding conditions: 1. Mold temperature: 40 degrees to 60 degrees 2. Drying conditions: 80 degrees for more than 2-4 hours. 3 barrel temperature: 190 degrees to 230 degrees 4 heat distortion temperature: 80 degrees (1.8MPa, 12.7mm). 5 general back pressure :8-15kg / sq mm. 6 Mold Shrinkage: 0.5% - 0.7% (3.3mm)
The modified methods are commonly used: flame-retardant weather toughening alloy;

3, PBT material: (polyethylene terephthalate resin poly butylene terephthalate) Celanese

Most brands do not currently use a fixed, internationally popular brands are: DuPont strange Formosa Plastics DSM General Polyplastics Bayer, etc.;

Characteristics: high wear resistance and rigidity, chemical resistance and strength, weather resistance, dimensional stability, good electrical insulation, enhanced performance, better. Moisture, susceptible to thermal decomposition, mainly for cars. Electric. Appliances. Connectors precision instruments and electronics.

Our products are mainly used for heat-resistant parts: heater's outlet. Building the PTC holder, etc.;

General molding conditions: (according to the proportion of different fiber plus change) 1. Mold temperature: 40 degrees to 60 degrees 2. Drying conditions: 100 degrees to 140 degrees more than 4 hours. 3 barrel temperature: 240 degrees to 270 degrees 4 heat distortion temperature: 210 degrees to 230 degrees (1.8MPa, 12.7mm). 5 Mold Shrinkage: 0.3% - 0.5% (3.2mm) 6. Thermal decomposition temperature: 280 degrees (260 degrees in management can be expected to stay six minutes, otherwise it will decompose, degenerate).

The modified methods are commonly used: toughening flame-retardant;

4, PC material (polycarbonate polycarbonate)

Most brands do not currently use a fixed, internationally popular brands are: Bayer Mitsubishi a strange light Teijin Dow Polyplastics, etc.;

Features: impact resistant high strength, dimensional stability, heat above 130 degrees, with high gloss and transparency, transmission rate can reach 90%, non-toxic. High processing temperatures, forming after the stress, moisture, does not wear. Resistance to fatigue. Mainly used in food containers. CD. Lens. Appliances. Optical instruments.

Our products are mainly used for oil heater, such as: part of the oil heater panel. Drying racks. Electronic oil heater and transparent cover, etc.;

General molding conditions: (according to the proportion of different fiber plus change) 1. Mold temperature: 80 degrees to 100 degrees 2. Drying conditions: 100 degrees to 120 degrees more than 4 hours. 3 barrel temperature: 250 degrees to 300 degrees 4 heat distortion temperature: 130 degrees; 5 mold shrinkage: 0.5% -0.7%

PC materials mobility with increasing temperature is higher, due to temperature regulation in forming a larger proportion of the total.

The modified methods are commonly used: enhanced fire weather and other antioxidants;

5, PA materials (polyamide polyamide), also known as NYLON nylon

Most brands do not currently use a fixed, internationally popular brands are: DuPont Dow Polyplastics Mitsubishi DSM BASF Bayer;

Features: abrasion resistance, fatigue resistance, high water absorption, (enhanced strength) excellent dimensional stability, (for high-precision mechanical objects). Mainly used in cars. Gear the motor. Precision instruments. SMT.IC precision electronic connectors.

Our products are mainly used for heat. Wear-resistant parts, such as: electronic oil heater panel. Castor oil heater, terminal, etc.;

Molding conditions: (according to the proportion of different fiber structure is different change processing) 1. Mold temperature: 80 degrees to 120 degrees 2. Drying conditions: 120 degrees to 140 degrees more than 4 hours. 3 Barrel temperature: 260-310 degrees. Heat distortion temperature: 235 degrees 5. Mold Shrinkage: 0.1% - 0.5%

Equipment requirements:
1 Screw: (L: D = 20:1) standard three sections, with a check ring screws. (Optional closed-nozzle diameter of 3.0mm)
(2) to use corrosion-resistant pipe materials and wear-resistant alloys.
3 insulation panels need to be strengthened on both sides of the template, to avoid the machine heat.
4 material using circular road, male and female mold uniform heat dissipation.
5 Inlet with 0.3mm to 0.5mm diameter pinhole to sneak into the feed.
6 Using 0.02mm-0.04mm depth, 0.5mm-1.0mm Width of the vent, and effective follow-up exhaust.

The modified methods are commonly used: enhanced wear resistant high viscosity, etc.;

6, POM material: (POM polyformaldehyde)

Pioneer is currently no fixed most of the brand used, commonly used in international brands are: DuPont Bao Li Tai-li steel Cologne;

Features: High abrasion resistance, fatigue resistance, excellent dimensional stability, (can be used to require dimensional stability. Wear resistance of mechanical objects) after a serious break down the glare of gas, should pay attention to use of the exhaust. Flame is poor, not acid. Oil, surface treatment is poor, mainly for cars. Gear. Sprayer. Precision electronics.

Our products are mainly used for dimensional stability. Wear-resistant parts, such as: three eccentric peach. Bush, Auchan turntable, etc.;

General molding conditions: 1. Mold temperature: 60 degrees to 80 degrees 2 drying conditions: 80 degrees to 100 degrees 2 hours. 3 Barrel temperature: 170-210 degrees 4. Heat distortion temperature: 90 degrees; 5 mold shrinkage: 0.5% -0.8% 6. Thermal decomposition temperature: 240 degrees (240 degrees in the feed tube can be stuck for 5 minutes, otherwise it will decompose, degenerate).

7, PPS steel material: (polyphenylene sulfide poly phenylene sulfide)

Pioneer is currently no fixed most of the brand used, commonly used in international brands are: Philip Dow strange Polyplastics, etc.;

Features: abrasion resistance, fatigue resistance, high water absorption, self-flame resistance, dimensional stability, excellent (for high-precision mechanical objects) enhanced performance, better, a similar metal sound. Crystalline poor, poor mobility, poor toughness, not color. Corrosive molds and machines, prone to flash. Mainly used in cars. Gear the motor. Precision instruments. SMT.IC precision electronic connectors.

Our products are mainly used for high heat-resistant parts, such as: the PTC heater bracket. Wire frame, etc.;

General molding conditions: (according to the proportion of different fiber structure of the different processing change)

1 mold temperature: 100 degrees to 150 degrees
(2) :120-140-degree dry conditions more than 4 hours.
3 barrel temperature: 270 degrees to 330 degrees
4 heat distortion temperature: 260 degrees (1.8MPa, 12.7mm).
5 Thermal decomposition temperature: 400 degrees (1.8MPa, 12.7mm).
6 Mold Shrinkage: 0.1% - 0.4% (3.3mm)

Equipment requirements:

1 Screw: (L: D = 20:1) standard three sections, with non-return valve screw. (Optional closed-nozzle diameter of 3.0mm)
(2) to use corrosion-resistant pipe materials and wear-resistant alloy double.
3 insulation panels need to be strengthened on both sides of the template, to avoid the machine heat.
4 material using circular road, male and female mold uniform heat dissipation.
5 Inlet with 0.3mm to 0.5mm diameter pinhole to sneak into the feed.
6 Using 0.02mm-0.04mm depth, 0.5mm-1.0mm Width of the vent, and effective follow-up exhaust.
7 should be chrome or mold cavity corresponding surface treatment to reduce the production of gas corrosion.

Six, molding conditions

Molding conditions: speed, pressure, temperature, time, travel, number.

1 injection pressure (time pressure):

In the injection molding of plastic screw top of the unit area pressure;

P = cylinder diameter D0 / screw diameter D1 * hydraulic pressure;

(2) holding pressure (secondary pressure):

Molten material in the cavity to cool, then you must put some pressure to supplement its shrinking part, higher density, then screw on the pressure of plastic called the packing;

3 clamping force: (tonnage)

Clamping of the mold clamping force can exert the greatest;

F = K * P * A (K = 0.4 ~ 0.7, the pressure loss coefficient);

P: maximum pump pressure;
A: Locks template area;
* Set generally no more than 80-100kg / sq cm;

4 Injection volume:

An injection molding cycle, the weight of the plastic into the mold;

5 Injection capacity: grams. Cm3

A screw injection molding machine for a maximum injection stroke the maximum amount that can be shot;

G = 3.14 / 4 * D2 * S * density

D: Diameter of Screw
S: Screw stroke
* The amount of production in a cycle of injection machine should be less than or equal to the maximum injection volume of 80%;

6 Rate of fire:

Screw in the feed-pipe, the unit of time called the rate of fire moving journey;

V = S / T * 100%

S: Screw in feed tube of the trip;
T: screw injection time;

7 back pressure:

Feeding time, back in the opposite direction against the screw, the increase in pressure on the molten plastic;

Back pressure of the role:

1 to improve the mixing effect of molten plastic; (2) increase the temperature of molten plastic; 3 to improve the density of molten plastic; 4 Plastic color to enhance the uniformity;
5 exhaust gas within the molten plastic;

8 Low voltage protection:

Refers to the mold clamping resistance generated when a protective device, which can suppress the foreign body in the mold when the minimization of the damage, reduce the die loss.

It works by clamping the mold from low to high voltage clamping the distance setting a certain time, when the mold clamping in encountered during this period of foreign body, plastic or due to lack of lubrication within the lock is not set to the high pressure switch point, the machine will generate an alert and open mold;

Seven reasons for forming quality improvement analysis:

First, do not shoot full (lack of material)

1 injection pressure is inadequate; 2 holding pressure is inadequate; 3 injection time is inadequate; 4 feeding (accumulator) is inadequate; 5 shot material staging location is too small; 6 injection end position is too small; 7 injection speed not fast enough; 8 nozzle, barrel temperature is not enough; 9 die temperature is not enough; 10 raw materials drying temperature, the lack of time; 11 injection molding cycle is too fast, insufficient warm-up; 12 non-uniform mixing of raw materials; (back pressure lack of speed is not enough) 13. feedstock lack of liquidity; (thin-walled products) 14. mold venting is inadequate; 15 molds feed uneven; 16 cold slug well designed unreasonable; 17 cold discharge port is too small, direction is unreasonable; 18 plastic flow of the cavity is unreasonable; 19 uneven mold cooling; 20. Injection Oil Road, inaccurate, not fast enough; 21 electric system instability, inaccurate; 22 nozzle leak material, there foreign body stuck; 23 barrel wall and screw wear, with the bad;

Second, the flash (flash)

1 injection pressure and too much pressure; 2 clamping pressure is not enough; 3 back pressure is too large; 4 injection and holding pressure time is too long; 5 material storage and cooling time is too long delay; 6 down too long, not fired thermal material; 7 injection pressure. holding pressure too quickly; 8 screw speed too fast, the plastic shear, friction heat; 9 barrel temperature is too high cast; 10 mold temperature is too high, mold uneven cooling chamber; 11 injection stroke debugging unreasonable; 12 holding pressure switching point, end point shot too much; 13 combination of the mold assembly is not tight; 14 mold of a foreign body, lack of transfer mode position; 15. Clamping not parallel, precise; 16 thimble lubrication, lack of maintenance; 17 slide, with the pressure angle pin in place; 18 not pressure cavity inserts in place, hold the mold surface; 19 non-uniform distribution of inlet design reasonable; 20. somewhere in the product design lead to the end wall is too thin and too far; 21 combinations of small inserts irrational, prone to deformation; 22 inserts for the production of wear, deformation, rounded; 23 set components not designed to stability, not hold together, reinforcement; 24 deep cavity exhaust ducts;

Third, the bubble (gas sores)

1 injection, holding pressure is inadequate; (2) back pressure is too small, not enough solid material; 3 injection speed is too fast; 4 storage material too fast; 5 barrel temperature is too high, mold temperature is too low; 6. material drying temperature, the lack of time; 7 shoot back too much; 8 injection molding cycle is too long; (warm-up time increases) 9 inadequate feeding position, the end of injection is too small; 10 before and after the song back position too long; 11 hydraulic machine unstable; 12 barrel, screw compression ratio is not enough; 13 raw materials under the material, uneven mixing; 14 barrel upstream, there are dead; 15 die inlet is too small, the cavity flow not fast enough; 16 cold slug well designed properly, cold material into the cavity; 17 mold cooling properly, mold temperature is too high; 18 design wall thick, uneven internal stress; 19 additive materials properly, easy to decompose precipitation;

Fourth, the silver lines (flow lines)

1 injection pressure is too small; 2 packing too much pressure; 3 back pressure too much pressure; 4 injection speed is too slow, too fast packing; 5 mold temperature, melt temperature is not high enough; 6 injection, dwell too long; 7 debug improper injection stroke, pressure switch point too; 8 material is not drying, too much water; 9 material flow is bad, the viscosity is too high; 10 injection molding machine is not enough Fast, accurate; 11 die inlet is too big or too small; 12 main road, sub-flow channel size is not big enough; 13 the cavity flow direction is unreasonable; 14 mold surface smooth, with oil;

Five, including wind (Burns. Jiao)

1 injection pressure, too fast; 2 much back pressure; 3 screw feeder speed is too fast; 4 barrel temperature is too high; 5 cycle time is too long or too fast; 6 before and after the song back position too long;
7 materials are not dried; 8 good flow of raw materials, sub-feed ratio or dust too; 9 additive unstable, decomposition precipitation; 10 mold venting groove is not deep enough, wide enough follow-up exhaust; 11 flow, feed uneven; 12 mold with tight, clamping force is too large; 13 die dirty, vent by oil, dirt blocking the brine; 14 unreasonable mold design and processing methods, the overall model cavity too; 15 injection molding machine temperature is not stable, accurate; 16 material internal control reflux or dead; 17 nozzle leakage and filling the mouth with the lack of material; 18 screw head (split spindle) unreasonable or broken ; 19 inlet is too small, the cavity flow complex;

Sixth, brittle plastic body

1 injection holding pressure is inadequate; (2) back pressure is too small, not enough solid material; 3 too much back pressure, shear, friction heat increases; 4 firing rate is too slow, not fully crystallized; 5 mold temperature is too high, materials fire, decomposition, deterioration; 6 mold temperature is too low, not fully crystallized; 7 injection, the holding time is inadequate; 8. downtime and cycle time is too long; 9 material storage too long; 10 times expected to add too much or too much dust; 11 material strength, toughness is not enough, the viscosity is not enough; 12 additive unreasonable, or add too much; 13 raw materials has not fully dried; 14 the cavity structure is uneven, too junction far; 15 molds feed uneven, cold material well enough; 16 design wall is too thin, no radiation to help strengthen; 17 injection molding machine temperature instability, precise; 18 material internal control reflux or dead; 19 top of the irrational, plastic body stress increases, resulting in rupture; 20. plastic body post-cooling improper handling, easy to crack.

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