ABS Injection Parts

ABS injection parts occupy an important position in the electronics industry, machinery industry, transportation, building materials, toy manufacturing and other industries due to their high mechanical strength and good comprehensive performance, especially in the slightly larger box structure and stress Among the components, decorations that require electroplating are inseparable from this plastic.

The main products of Zhongwei Precision Machinery Co., Ltd. are nylon products, plastic products, ABS series, rubber products, etc. Types of injection molding materials that can be processed: polyethylene (PE), polypropylene (PP), nylon (PA, PA6, PA66), polyoxymethylene (POM), ABS, polyurethane (TPU), polyphenylene sulfide (PPS), polystyrene Carbonate (PC), Polyetheretherketone (PEEK), etc.

Product Description

1. Implementation standards: the company strictly implements ISO9001, ISO14001, IATF16949, VDA6.3 certification,

The products have passed the certification of ROHS, FDA EU, etc.

2. Product material standards: ISO, GB, ASTM, SAE, EN, DIN, BS, AMS, JIS, ASME, DMS, TOCT, GB

3. Main processes: plastic injection molding, metal insert injection molding, investment casting, die-casting aluminum,

4. Available materials for injection molding:

Processable nylon products, plastic products, ABS series; injection molding material types: polyethylene (PE), polypropylene (PP), nylon (PA, PA6, PA66), polyoxymethylene (POM), ABS, polyurethane (TPU), poly Phenyl sulfide (PPS), polycarbonate (PC), polyether ether ketone (PEEK) and 3D printing can be customized according to customer requirements.

Production Process

1. ABS plastic drying

ABS plastic is highly hygroscopic and sensitive to moisture. Fully drying and preheating before processing can not only remove pyrotechnic bubbles and silver threads on the surface of the product, but also help plasticize the plastic and reduce stains and ripples on the surface of the product. ABS raw materials control moisture below 0.13%.

The drying conditions before injection molding are as follows: the dry winter section is below 75~80, drying for 2~3 hours; in summer, the rainy day is 80~90, drying for 4~8 hours. If the product must achieve a particularly excellent gloss, or the product itself is complex, the drying time is as long as 8~16h.

The blurring of the product surface due to the presence of a small amount of water vapor is a problem that is easily overlooked. In order to prevent the dry ABS from inhaling moisture in the hopper again, it is best to transform the hopper of the machine into a hot air hopper dryer, but such a hopper must be Enhanced humidity monitoring to prevent material overheating in the event of occasional production interruptions

2. Injection temperature

The relationship between ABS plastic temperature and melt viscosity is different from other non-stereotyped plastics. When the temperature of the melting process rises, the melting will actually decrease slightly, but when it reaches the plasticizing temperature (the temperature range suitable for processing, such as 220~250 ℃), if the temperature continues to rise at will, the thermal decomposition of ABS with low heat resistance will be on the contrary. Will increase the melt viscosity to achieve injection molding

Therefore, the injection temperature of ABS injection parts is higher than that of plastics such as polystyrene, but it cannot have a slow temperature rise range like the latter. For some injection molding machines with poor temperature control, when the production of ABS products reaches a certain amount, yellow or brown caulking particles are often embedded in the products, and it is difficult to use new materials to inject into the sky and other methods to remove emissions.

This is because ABS plastic contains butadiene components, and some plastic particles are firmly attached to the surface that is difficult to clean in the spiral groove at high temperature, which will cause decomposition and carbonization under the action of high temperature for a long time. High temperature operation can cause problems for the ABS, so it is necessary to limit the furnace temperature of the cylinder stages. Of course, according to the type and structure, the applicable furnace temperature of ABS is also different. When the plunger machine is used, the furnace temperature is maintained at 180~230; the screw machine and the furnace temperature are maintained at 160~220. It is especially worth noting that due to the high processing temperature of ABS, it is very sensitive to changes in various process factors. Therefore, the temperature control of the front end of the cylinder and the nozzle part is important. Practice has proved that any small changes in these two parts will be reflected in the product. The greater the temperature change, the more defects such as weld lines, poor gloss, burrs, mold bites, and discoloration will be caused.

3. Injection pressure

Since the viscosity of ABS melt is higher than that of polystyrene and modified polystyrene, a higher injection pressure is used during injection. Of course, not all ABS products have high pressure. For products with small volume, simple structure and large thickness, lower injection pressure can be used.

During the injection process, the pressure in the cavity at the moment when the gate is closed often determines the surface quality of the product and the degree of silver filamentous defects. The pressure is too small, the plastic shrinks greatly, the chance of leaving the cavity surface is large, and the product surface is atomized. If the pressure is too large, the friction between the plastic and the surface of the cavity is strong, and the mold is easy to stick together.

4. Injection speed

ABS material with moderate injection speed effect is better. If the injection speed is too fast, the plastic will be easily scorched, and the gas will be separated out, resulting in defects such as weld lines, poor gloss, and redness of the plastic near the gate. However, when producing thin-walled and complex products, a sufficiently high injection speed must be ensured. Otherwise, it will be difficult to be satisfied.

5. Mold temperature

The forming temperature of ABS is relatively high, and the mold temperature is also relatively high. Generally, the mold temperature is adjusted to 75~85, but when producing products with a large projected area, the fixed mold temperature is required to be 70 to 80, and the movable mold temperature is 50 to 60. When injecting thin-walled plastic parts with large, complex shapes, special consideration should be given to heating the mold. In order to shorten the production cycle and keep the mold temperature relatively stable, after the product is taken out, cold water bath, hot water bath and other mechanical setting methods can be used to compensate for the original time of cooling and setting the mold in the cavity.

6. Material management

When a general injection molding machine injects ABS plastic, its single injection volume only reaches 75% of the standard injection volume. The injection volume should be 50% of the calibrated injection volume to improve product quality and dimensional stability, and to make the surface gloss and color uniform.

Heat-resistant ABS resin molding processing points

General ABS injection parts have insufficient heat resistance. At present, by adding heat-resistant agents such as (-methylstyrene copolymer and N-phenylmaleimide copolymer, a heat distortion temperature (HDT) of 90 has been developed. -120 series of heat resistant ABS resin.

The molecular structure of heat-resistant ABS contains high rigidity benzene ring and n-phenyl group. While improving the heat resistance, the steric hindrance effect of the molecular chain increases, the relaxation speed of the molecular chain decreases, and the product is prone to large internal stress, resulting in product stress. Defects such as cracking, stress whitening, and product brittleness. Therefore, reducing the internal stress of the product is the key to heat-resistant ABS injection molding.

1. Product mold design

The wall thickness of the product is required to be uniform, and the wall thickness difference of the ABS product is controlled within 25% to prevent the local stress concentration from being too large. At the root of weak-strength columns, fillets or stiffeners must be added to prevent column breakage.

In the design of fasteners, the root of the fastener needs to be rounded. The size of the r angle depends on the wall thickness of the product. The ratio of r angle to wall thickness shall not be less than 0.3. As the ratio increases, the internal stress gradually decreases, but the shrinkage of the product surface must also be considered. The design of the cooling channel of the mold should ensure the uniformity of cooling and avoid the internal stress caused by uneven cooling and uneven shrinkage.

2. Material drying

Heat-resistant ABS resin usually absorbs moisture in the air during storage and transportation. Water absorption varies with air humidity, usually between 0.2 and 0.4%. Therefore, it is necessary to sufficiently dry the material so that the moisture content of the material is 0.05% or less, preferably 0.02% or less. Otherwise, surface defects such as splashes and silver streaks may occur. The drying temperature of heat-resistant ABS resin is higher than that of conventional ABS, usually 80-95, and the drying time is 3-4 hours.

3. Forming temperature

The molding temperature is one of the parameters that are particularly noteworthy in the processing of heat-resistant ABS. To ensure that the heat-resistant ABS is fully plasticized, try to use the temperature range above the intermediate value of the molding temperature recommended by the supplier. When the molding temperature is increased, the viscosity of heat-resistant ABS is significantly reduced, the fluidity of the resin is increased, and the flow distance is prolonged, ensuring that the material has sufficient filling capacity.

4. Holding pressure and time

For heat-resistant ABS, whether the holding pressure and time setting are reasonable directly affects the internal stress of the product. The increase of the holding pressure can reduce the molecular gap, reduce the active range of the segment, reduce the melt volume, increase the density, increase the intermolecular force, and improve the shrinkage and internal quality of the product. Minimize the holding pressure in terms of product appearance quality

The dwell time is set based on the time until the gate solidifies as it cools and the screw advances again without applying pressure to the molded product. When the holding time is too long, the material filling is easy to be excessive, the molecular gap becomes smaller, and the internal stress becomes larger; when the holding time is too short, the product is prone to shrinkage and the size is unstable. The setting of the holding pressure time takes the shortest time when the product weight no longer changes as the best holding pressure time.

5. Mold temperature

When molding heat-resistant ABS, a mold temperature machine is used to control the mold temperature. The recommended die temperature is 60-80. The mold temperature is high, the flow is good, the strength of the weld line is high, and the internal stress of the product is small, but the molding cycle is moderately prolonged.

If the mold temperature is lower than the recommendation, the internal stress of the product will be too high, the product performance will be degraded, and undesirable situations such as product embrittlement, threaded hole cracking, and coating cracking may occur.

Post Injection Molding Process

1. Processing equipment: CNC, WEDM, lathe, milling machine, drilling machine, grinder, etc.;

2. Surface treatment: For some products that require subsequent processing, we can provide surface treatment services to achieve the special purpose of customers. At present, we can provide degreasing, polishing, electroplating (gold, silver, nickel, tin, galvanized, etc.), anodizing, electrophoresis and other surface treatment services for precision parts.

Moulds and Inspection Fixtures

1. Mold service life: usually semi-permanent. (except for lost foam)

2. Mold delivery time: 10-25 days, (according to product structure and product size).

3. Tooling and mold maintenance: Zhongwei is responsible for precision parts.

Quality Control

1. Quality control: the defective rate is less than 0.1%.

2. Samples and trial run will be 100% inspected during production and before shipment, sample inspection for mass production according to ISDO standards or customer requirements

3. Testing equipment: automated visual inspection equipment can carry out 100% inspection of products, spectrum analyzer, golden elephant analyzer, three-coordinate measuring machine, hardness testing equipment, tensile testing machine.

Application

ABS injection parts are widely used in automotive, electrical and electronic, office and communication equipment and other fields. Today, in order to meet the special requirements of fire safety in the field of application (especially electronic and electrical products). Among them, the flame retardant technology of PC/ABS alloy has become a research hotspot. However, with the advancement of science and technology, the requirements for the environmental friendliness of materials are getting higher and higher, and the harm caused by traditional halogen-based flame retardants is becoming more and more obvious.

In engineering, ABS is widely used in engineering pipelines. In municipal projects, ABS pipelines can generally be used for pool bottom pipelines of projects with relatively high material requirements.

In addition, ABS plastics are often used in 3D printing, mainly because of the properties of ABS, which are characterized by heat resistance, impact resistance, low temperature resistance, chemical resistance, excellent electrical properties, and product dimensional stability. It is one of the most stable materials in 3D printing materials.

Knowledge points about ABS plastics, in addition to performance and uses, also include the coating process, injection molding process of ABS plastics, and local electroplating of ABS plastics.