How to reduce bad smell and energy consumption during plastic injection moulding process?

Time:2019-05-29 08:52:21 / Popularity: / Source:

Nowadays, moulding products can be seen everywhere in daily life or in the field of production and circulation. Moulding products refer to products which are plasticized and melted by injection moulding machine, injected into cavity of molding, cooled by cooling, melted and solidified, molded by injection moulding machine. These plastic products are inseparable from injection moulding. As a branch of plastics processing industry, injection moulding technology is the fastest growing production process for all plastic processing technologies due to its ability to form complex shapes in a fast, batch, and low cost manner. For knowledge of injection moulding, many people may not know too much. Let's take a look at how to reduce bad smell and energy consumption during plastic injection moulding process? What should we pay attention to during plastic injection moulding process?
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How to reduce bad smell during plastic injection moulding process?

  • Using a more pure resin
In many plastics, especially in plastics such as polyvinyl chloride, styrene, polyethyl acetate and acrylates, residual traces of monomers can produce unpleasant odors. Resins with very small monomer residues can eliminate those odor. If you use a resin that is odorless itself, it also has a good effect. For example, DuPont plastic parts processing plant has developed a new grade of acetal copolymer that emits very small amounts of odor during plastic injection moulding process.
  • Change additive
1. Catalyst tertiary amine used in production of polyurethane foam often brings a strong odor and also fogging on inner window of automobile. Solution to this problem is to find alternatives to these amines. One of measures is to use polyhydroxy compounds, which are not only components of polyurethane molecular chain, but also have catalytic activity. Some polyols can even replace half of tertiary amine catalyst, and resulting product emits a much weaker odor.
2. Phenol stabilizers used in PVC extrusion or calendering are often replaced by low-odor zinc stabilizers. Heat stabilizer tin stannate is also commonly used in automotive PVC products due to its low odor and low atomization properties. Plant extract oils such as erucic acid and oleic acid are much less odorous than amine lubricants (for polyolefin and styrenic food packaging materials) made from animal extract oils.
  • Adding adsorbent
If polymer is filled with a small amount of zeolite (an aluminosilicate adsorbent), it can remove odor of material. Zeolite has a large number of crystal cavities. These cavities can capture small molecules of odorous molecules. Adsorbents have been successfully applied to polyolefin extruded pipes, injection and extrusion blow molded containers, insulation packaging materials, extruded outer packaging materials and sealing polymers. Molecular adsorption powders can also be added to plastics as moisture absorbers. In addition to moisture, these vapors can also contribute to smell of moulding products.

How to reduce energy consumption in injection moulding

For an injection moulding moulds manufacturer, energy consumption of plastic injection moulding process accounts for about 60%, so effectively reducing energy consumption of injection moulding machine is an important way to save energy in injection moulding moulds manufacturer. With continuous improvement of energy-saving technology of injection moulding machine itself, reducing overall energy consumption of injection moulding moulds manufacturer requires comprehensive consideration from aspects of production management, processing technology and materials, and production workshop support.
  • Production workshop
Layout of production workshop focuses on two aspects: under conditions of production demand, optimize layout according to production process, and meet requirements of flexible application under specific production conditions.
1. Power supply has an appropriate margin while satisfying power required for stable production, so that power consumption is too large due to excessive power consumption.
2. Construct an efficient cooling water circulation facility and equip cooling water system with an effective insulation and insulation system.
3. Optimize overall production layout of workshop. Many productions have successive processes, and reasonable work station coordination can reduce time and energy consumption required for turnover and improve production efficiency.
4. Consider the most effective small units for separate control of lighting and other plant equipment.
5, Regular maintenance of workshop equipment, to avoid damage to public facilities, affecting normal operation of production, resulting in increased energy consumption.
6. It is recommended to use a dust-free workshop when conditions permit, and do 5S work in the workshop to prevent dust from harming mechanical precision parts.
  • Injection moulding machine
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Injection moulding machine is a large energy consumer in injection moulding moulds manufacturer, and energy consumption mainly comes from motor and heating.
1. Select appropriate injection moulding machine according to characteristics of product. “cut blocks with razor” type of injection moulding often means a lot of energy waste.
2. Select all-electric and hybrid injection moulding machine, which has excellent energy-saving effect and can save energy by 20-80%.
3, Using new heating technology, such as electromagnetic induction heating, infrared heating, etc., can achieve 20-70% heating and energy saving.
4. Use effective insulation and insulation measures for heating and cooling systems to reduce heat and cold losses.
5. Maintain good lubrication of transmission components of equipment and reduce energy consumption caused by increased friction or unstable operation of equipment.
6. Use low-compression hydraulic oil to reduce waste of working energy in hydraulic system.
7, Using parallel motion, multi-cavity injection moulding, multi-component injection moulding and other processing technologies can significantly save energy.
8. Traditional mechanical hydraulic injection moulding machine also has a variety of energy-saving driving systems, which replaces traditional quantitative pump mechanical hydraulic injection moulding machine with remarkable energy-saving effect.
9. Regularly maintain heating and cooling pipelines to ensure that there are no impurities and scales inside pipelines, and achieve heating and cooling efficiency of design.
10. Ensure that injection moulding machine is in good working condition. Unstable processing can result in defective products and increase energy consumption.
11, Ensure that equipment used is suitable for products processed, such as PVC processing often requires use of special screws. Mold structure and mold conditions often have a significant impact on injection moulding cycle and processing energy consumption.
1. Reasonable plastic injection mould design, including runner design, gate form, number of cavities, heating and cooling water channels, all help to reduce energy consumption.
2, Use of hot runner mold, not only can save materials, reduce material recovery energy consumption, plastic injection moulding process itself also has significant energy-saving effects.
3, Profiling fast cooling and fast hot mold can significantly save processing energy and achieve better surface quality.
4, Ensure that each cavity is balanced filling, help to shorten molding cycle, ensure product quality stability, and have excellent energy-saving effects.
5. Using CAE-assisted design technology for plastic injection mould design, mold flow analysis and simulation, can reduce energy consumption of mold debugging and multiple mold repair for injection moulding moulds manufacturer.
6. Under premise of ensuring quality of product, use of lower clamping force to form, help to extend life of custom plastic injection molding, which is conducive to rapid filling of mold and helps energy saving.
7. Do a good job of mold maintenance to ensure effective heating and cooling waterway conditions.
  • Peripheral equipment
1. Select auxiliary equipment with suitable capabilities to meet work requirements without excessive margin.
2, Do a good job of equipment maintenance, to ensure that equipment is in normal working condition. Auxiliary equipment that is not working properly may cause unstable production or even poor quality of parts, resulting in increased energy consumption.
3. Optimize cooperation and operation sequence between host and peripheral devices.
4. Optimize mutual position of peripheral equipment with production equipment, and let peripheral equipment be closer to host as much as possible without affecting operating conditions.
5. Many auxiliary equipment manufacturers provide on-demand energy-saving systems that can achieve significant energy savings.
6. Use fast die change equipment to reduce waiting time required to switch products during production.
  • Materials
Energy consumption of different materials processing is different. At the same time, poor management of materials or improper management of recycled materials will increase production energy consumption.
1. Under premise of satisfying performance of product, material with lower processing energy consumption should be preferred.
2. Under condition of satisfying performance and cost optimization, high-flow material is preferred.
3. Note that materials from different suppliers may have different process conditions.
4, Material drying treatment. It is best to use immediately after drying, to avoid material damp and waste of energy after drying.
5, Do a good job of material preservation, to prevent material from mixing impurities or foreign matter, and ultimately cause product defects.
6. Some products are allowed to add certain recycled materials, but attention should be paid to preservation and cleanliness of recycled materials to avoid bad parts due to unclean materials.
  • Processing technology
custom plastic injection molding
1. Under premise of satisfying performance of product, the shortest molding cycle is used.
2. If there is no special factor, try to use processing technology recommended by injection moulding moulds manufacturer for processing.
3. For all specific products and custom plastic injection molding, save all stable equipment and process parameters, and shorten adjustment time of next replacement production.
4. Optimize process, using a lower clamping force, a shorter cooling time and a dwell time.
  • Adopt new plastic injection molding technology
1. Adopt auxiliary plastic injection molding technology, such as gas assist, liquid assist, steam assist, micro foam plastic injection molding technology.
2. Adopt a unitized molding scheme to reduce intermediate links.
3, Using in-mold welding, in-mold spraying, in-mold assembly, in-mold decoration and other new technologies.
4. Adopt new low-pressure plastic injection molding technology to shorten molding cycle and reduce melt temperature.
5. Adopt energy regeneration system.
  • Production management
1. Producing high-quality products at one time and reducing non-performing rate is the biggest energy saving.
2. Maintenance and energy consumption of entire production system is closely related. This involves not only mainframe, but also surrounding and factory equipment. For example, if workshop changeover crane fails, it is necessary to change custom plastic injection molding manually, which will inevitably prolong waiting time of equipment and increase energy consumption.
3. Equipped with workshop energy consumption monitoring system to facilitate purposeful implementation of energy analysis and improvement.
4. When equipment is shut down for maintenance, not only maintenance contents and items of equipment itself, but also condition of connection between equipment and other systems, and performance of work.
5. Regularly compare with industry benchmarks to see if there is room for further improvement.
6. Establish reliable contracts and cooperative relationships with suppliers, which is beneficial to enterprise energy conservation management.
  • Staffing
1. Machine personnel must carry out systematic operation training.
2. Machine personnel should carry out simple equipment maintenance training.
3. Close cooperation between frontline production personnel in various departments.

Plastic injection moulding process

Processing of moulding products is an extremely complicated process, and if you don’t pay attention, you will make mistakes and cause moulding products to be scrapped. Complete plastic injection moulding process includes stages of feeding, plasticizing, filling, holding, backflow, cooling and demoulding, each stage must be strictly regulated and controlled.
First: Feeding, adding granular or powdered plastic to hopper of injection moulding machine, and bringing with plunger and screw into barrel for heating.
Second: Plasticization: After molding plastic is heated, compacted and mixed in the barrel of injection moulding machine, it is transformed into a continuous homogenized melt by loose powdery particles or granular solid materials.
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Third: Filling: Plasticized plastic melt enters and fills mold cavity through a nozzle and mold casting system under a certain pressure and speed by action of plunger or screw of injection moulding machine. This stage is called filling.
Fourth: Pressure retention: After filling is completed, melt still maintains pressure to feed material under push of plunger or screw, so that melt in cylinder continues to enter cavity to supplement shrinkage of plastic in cavity. Pressing time should be appropriate, and excessive holding time tends to cause internal stress in injection moulded parts, causing warpage or cracking of injection moulded parts.
Fifth: Backflow: After pressure is maintained, pressure of melt in cavity behind plunger or screw is released. At this time, melt pressure in cavity will be higher than pressure in front of gate. If gate is not frozen at this time, phenomenon that melt in cavity flows back through casting system occurs, which causes injection moulded parts to have defects such as shrinkage, deformation, and loose texture. If gate is frozen when injection pressure is withdrawn, backflow phenomenon will not occur, and it can be seen whether backflow occurs and is related to dwell time.
Sixth: Cooling: Cooling process of injection moulded parts in custom plastic injection molding refers to whole process from which plastic melt at the gate is completely frozen to which injection moulded parts are pushed out from cavity. At this stage, feeding or backflow is not continued, and plastic in cavity continues to cool, harden and set.
Seventh: Demoulding: After injection moulded parts are cooled and custom plastic injection molding can be opened, plastic injection moulded parts are pushed out of mold under action of pushing mechanism.

What should I pay attention to during plastic injection moulding process?

1, Different raw materials, temperature required in plastic injection moulding process is also different. If temperature is too high or too low, it will have a bad influence on processing of raw materials, which will adversely affect final product. For example, if temperature is too low, color of liquid raw material will produce some abnormal conditions; if it is too high, product will have a burr phenomenon after production, and product quality will not meet requirements.
2. In plastic injection moulding process, you need to pay attention to controlling cooling time. Specific time required depends on specific conditions of processed products. Plastic injection moulding process has a greater impact on brightness of product, so it is necessary to pay more attention.
3, In plastic injection moulding process also need to pay attention to control speed inside casting channel, if it is too fast, there will be burrs and it will lead to filling and saturating. If it is too slow, it will shrink and it will break easily. Therefore when pouring, we must pay attention to control of its processing speed, so that quality of produced products meet required requirements.

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