Plastic Material Types
ABS is formed by the copolymer of acrylonitrile A, butadiene B, and styrene S. Each monomer has different characteristics. ABS is a kind of amorphous material. This determines its low-temperature resistance, impact resistance, appearance properties, low creep, good size stability, and easy processability of ABS materials. Moreover, the surface hardness is high and the chemical resistance is good. At the same time, the various properties of ABS can be changed by changing the proportion of the above three components, so ABS engineering plastics have wide-ranging applications. The synthesized ABS can be divided into four types: medium impact type, high impact type, ultra-high impact type, and heat resistant type.
ABS plastic has high hygroscopicity and humidity sensitivity, so it must be dried at 90℃ for at least about 2 hours before molding. And the moisture should be controlled below 0.03%.
The suitable processing temperature of melt adhesive is 190-235℃. The melt viscosity of ABS is medium and needs to be produced at high injection pressure (500~1000bar). The better production effect of ABS plastic by injection is at medium and high speed. The nozzle position of the product is easy to produce air-lines.
The molding temperature of ABS plastic is higher, and the mold temperature should be adjusted at 30-70℃. When producing big size parts, the fixed mold-half temperature is about 5℃ higher than the moving mold-half. The mold temperature affects the product appearance quality, and lower temperature will lead to lower quality appearance.
Polypropylene is a polymer formed by propylene and polymerization. The composition and structure of PP are a kind of crystalline polymer. Among the commonly used plastics, PP is the lightest material, and its density is only 0.90-0.91g/cm³ (less than water). Among the general-purpose plastics, PP has the best heat resistance. With the distortion temperature at 80-110℃, products made of PP can be in 100℃ boiled water. PP has excellent stress cracking resistance and good warping fatigue life.
PP products have the advantages of lightweight, good toughness, good chemical corrosion resistance, and so on. The disadvantages of PP are low dimensional precision, insufficient stiffness, poor weather resistance, easy to be damaged by “copper”, easy to post-shrinkage, easy to aging, brittleness, and warpage after demoulding.
Injection mold process conditions: Drying: if stored properly, drying is not required.
Melting temperature: 220-250℃, no more than 250℃.
Mold temperature: 20-50℃, 40℃ is recommended.
The degree of crystallization is mainly determined by the mold temperature.
Injection pressure: can be as high as 1800bar.
Injection speed: In general, the use of high-speed injection molding can reduce the internal pressure to a minimum.
Polyethylene (PE) is a kind of thermoplastic resin made by ethylene polymerization. PE is inodorous and nontoxic. And it feels like wax, has low-temperature resistance (the lowest temperature can reach at 70℃), good chemical resistance, as well as can endure the corrosion of most acids and alkali (not resistant to oxidation). Indissoluble in general resolvent at normal temperature, it also has excellent electrical insulation, and low water absorption.
PE is a kind of polymer with various structures and properties. It is mainly divided into LDPE, MDPE, HDPE, LLDPE, and properties of ultra-high molecular polyethylene and low molecular polyethylene, and so on.
Injection molding conditions:
The temperature is set as follows: injection nozzle 140-190℃, front section 140-200℃, middle section 130-180℃, screw speed 210-220RPM, mold temperature 10-70℃, material pipe temperature 150-210℃, back pressure 5~10KG, injection pressure 360-500KG / c㎡.
PS (polystyrene plastics) refers to the plastics with a styrene group in the macromolecular chain, including ordinary polystyrene (GPPS), high impact polystyrene (HIPS), expandable polystyrene (EPS) and metallocene polystyrene (SPS) and so on.
General-purpose polystyrene is a thermoplastic resin, which is a glossy, transparent bead or granular solid. The density is 1.04-1.09, the transparency is 88%-92%, and the refractive index is 1.59-1.60. The melting temperature of the product is 150-180℃, the thermal decomposition temperature is 300℃, the thermal deformation temperature is 70-100℃, and the long-term service temperature is 60-80℃.
It is soluble in aromatic hydrocarbons, chlorinated hydrocarbons, aliphatic ketones, and esters. Furthermore, it can withstand the effects of some mineral oils, organic acids, bases, salts, lower alcohols, and their aqueous solutions. The water absorption rate is low, and its mechanical properties and dimensional stability can be maintained in a humid environment. The optical properties are second only to acrylic resins. The electrical performance is excellent, the volume resistivity and surface resistivity are very high, and it is not affected by the change of temperature and humidity, nor by corona discharge.
Its main disadvantages are brittle and easy to crack, low impact strength, poor heat resistance, can not withstand boiling water, and can only be used at lower temperatures and lower load. Besides, it has poor sun resistance and flammability.
In injection molding, the material can be used directly without drying. However, in order to improve the quality of the products, it can be pre-dried in a blast oven at 55-70℃ for 1-2 hours. The specific processing conditions are as follows: barrel temperature about 200℃, mold temperature 60℃ 80℃, injection temperature 170℃-220 ℃, compression ratio 1.6 to 4.0. In order to eliminate the internal stress, the molded products can be treated at 70℃ for 2 hours in an infrared lamp or blast oven.
PC material is a type of widely used engineering plastics, which belongs to non-crystalline plastics. It has good mechanical properties, For example, high impact resistance, high tensile strength, excellent bending strength, low shrinkage, low thermal creep, high dimensional precision, good heat resistance, and low-temperature resistance. It can be used at temperatures ranging from -60 to 120 Celsius. The disadvantages are poor fatigue strength, easy brittleness, low solvent resistance, and poor wear resistance.
PC material has excellent characteristics such as high transmittance, high refractive index, high impact resistance, and dimensional stability. The optical lens made of optical grade polycarbonic acid can be used in cameras, microscopes, telescopes, and optical testing instruments, but also used in film projector lenses, photocopier lenses, infrared auto-focusing projector lenses, and laser beam printer lenses. As well as a variety of prisms, multifaceted mirrors, and many other office equipments and household appliances, its application market is very broad.
The fluidity of plastic is poor, the mold gating system should be thick and short, Cold feed wells will be needed, the gate size should be big, and the mold temperature should be high. The low material temperature will cause a short shot for parts, plastic parts are not glossy, material temperature is too high, easy to overflow edge, plastic parts blistering. When the mold temperature is low, the shrinkage and elongation are small, the impact strength is low, and the bending strength, compression strength, and tensile strength are low. The plastic parts cool slowly when the mold temperature is over 120 Celsius, and the wall of the easily deformable viscous mold parts should not be too thick and uniform to avoid sharp corners and notched materials.
The drying temperature of PC material is 120 Celsius and the time of drying should be over 4 hours. The mold temperature is usually 80 to 120 degrees Celsius. The injection temperature is 280 to 320 degrees Celsius. Slow injection speed and large injection molding pressure should be used in production.
Polyamide is commonly known as nylon, and its main varieties are PA6 and PA66, followed by PA11, PA12, PA610, PA612, PA46, and so on.
Nylon has the excellent mechanical intensity, heat-resistant, low friction ratio, self-lubrication, shake absorption and muffling, oil resistance, weak acid resistance, alkali resistance, and general solvent resistance, good electrical insulation, self-extinguishing, non-toxic, odorless, good weather resistance, and poor dyeing. It has high water absorption, which affects the dimensional stability and electrical properties, but the combination of nylon and glass fiber is very good. The fiber reinforcement can reduce the water absorption of the resin and make it work at high temperatures and high humidity.
Nylon belongs to crystallize plastics material with high melt temperature, narrow melt temperature range, and poor heat-resistant. PA does not soften gradually with the increase of heating temperature but softens in a narrow temperature range close to the melting point. Flow occurs as soon as the temperature is reached. PA is easier to absorb moisture, wet nylon in the molding process, the performance of a sharp drop in viscosity and mixed with bubble products on the surface of silver wire, the mechanical strength of the products decreased, so the material must be dried before processing, it can be dried at 80-110℃ for 6 hours. But please note that PA plastic drying at above 90℃ is easy to cause discoloration.
PA has good fluidity and easy to overflow, so it is suitable to use a self-locking nozzle and to be heated. At the same time, due to the fast condensation rate of the solution, the shortage of products caused by materials blocking nozzles, runners, and gates should be prevented. The mold overflow edge value is 0.03, and the melt viscosity is sensitive to the change of temperature and shear force, but it is more sensitive to temperature. To reduce the melt viscosity, we should start with the barrel temperature. It has a wide range of forming shrinkage, the direction is outstanding, and it is prone to shrinkage, deformation, and so on.
It is a blend of polycarbonate and ABS. On the one hand, it can improve the heat resistance, impact resistance, and tensile strength of ABS; on the other hand, it can reduce the cost and melt viscosity of polycarbonate, improve the processability, and reduce the sensitivity of internal stress and impact strength to the thickness of products. The new varieties of polycarbonate / ABS alloy include flame retardant, glass fiber reinforced, electroplating, UV resistance, and so on. It is mainly used in the automotive industry, computers, photocopiers, and electronic and electrical components. PC/ABS alloy material has been used in automobile decoration parts, lamp housing, and heat-resistant electrical shell.
PC/ABS must be dried before processing. The humidity should be less than 0.04%, and it is recommended that the drying condition is 90mm 110℃ for 2h; the melting temperature should be controlled at about 230m 300℃; the mold temperature should be within 50m 100℃; the injection pressure depends on the plastic parts, and the injection speed is not specifically required, but it is more suitable to be as high as possible.
Chemical and physical properties: ABS+PC has the comprehensive characteristics of both PC and ABS. For example, the easy processing like ABS and the excellent mechanical properties and thermal stability like PC. The ratio of them will affect the thermal stability of ABS+PC materials. The mixed material ABS+PC also shows excellent flow characteristics. The shrinkage is about 0.5%. Characteristic ABS+PC is a kind of modified engineering plastics synthesized by mixing. Among them, PC is polycarbonate, and ABS is the copolymer of acrylonitrile (A), butadiene (B), and phenylephrine (S). This modified plastic has better properties than simple PC and ABS, such as improved impact resistance, heat resistance, hardness, and so on.
Properties of PMMA acrylic plastics:
PMMA acrylic plastics are rigid and transparent materials with a density of 1.19-1.22g/10cm³. The biggest feature of PMMA acrylic plastic is high transparency, light transmittance of 92%, which is the highest value among the plastics, and the ultraviolet transmittance is also up to 75%.
PMMA acrylic plastic has good comprehensive mechanical properties, and its tensile, compressive strength, and bending strength is higher than those of PE, PVC, and PS, but its impact toughness is poor, so it belongs to hard and brittle materials. PMMA has low heat resistance, glass transition temperature at 104℃, melting temperature at 160-200℃, thermal decomposition temperature at 270℃, easy-to-burn, blue flame during combustion, white at the top, and strong flower and fruit smell and rotten vegetable smell at the same time.
PMMA has good dielectric and insulation properties, excellent arc resistance, and atmospheric aging resistance; PMMA has good chemical stability and can resist diluting inorganic acids, intermediate classes, salts, and oils, but it is not resistant to concentrated inorganic salts, hot alkali, ketones, chlorinated hydrocarbons, aromatic hydrocarbons, etc., it will swell and break in alcohols, and has good resistance to ozone and sulfur dioxide gas.
Application of PMMA acrylic plastic: It is widely used in making all kinds of optical glasses, such as lens, prism, reflector, camera lens. And it can make lamps, lighting equipment, instrument dial, dial, and so on. Besides, it can also make aircraft cabin glass, bulletproof glass, optical fiber, etc. Moreover, bright and beautiful products can be made after adding phosphor or pearl powder, which can be widely used in advertising decoration and handicraft production.
PVC (polyvinyl chloride) is one of the most widely used plastics. Usually, various additives are added to improve the properties of PVC materials, such as stabilizers, lubricants, auxiliary processing agents, pigments, reinforcements, and so on.
The softening point of PVC resin is close to the decomposition temperature. It began to decompose at 140℃, but decomposed more rapidly at 170℃. In order to ensure the normal processing of PVC resin, the two most important process indexes are named as decomposition temperature and thermal stability. The so-called decomposition temperature is the temperature at which a large amount of hydrogen chloride is released, and the so-called thermal stability is the time for not releasing a large amount of hydrogen chloride at a certain temperature (usually 190℃). PVC plastics will decompose for a long time at 100℃ unless alkaline stabilizers are added. If the temperature exceeds 180℃, it will decompose quickly.
PVC has the advantages of flame retardancy, high chemical resistance (resistance to concentrated hydrochloric acid, 90% sulfuric acid, 60% nitric acid, and 20% sodium hydroxide), good mechanical strength, and electrical insulation.
Main uses of PVC plastic materials: PVC profiles, PVC pipes, PVC hard materials and plates, PVC general soft products, PVC packaging materials, PVC wallboards and flooring, PVC consumer goods, PVC transparent sheets, etc., PVC plastic materials, PVC plastic materials, PVC plastic materials: PVC profiles, PVC pipes, PVC hard materials and plates, PVC general soft products, PVC packaging materials, PVC wall panels and floors, PVC daily consumer goods, PVC transparent sheets, etc.
Technological conditions of the injection mold. Drying temperature: 80℃ in 2h, material pipe temperature: 160-190℃, mold temperature: 30-60℃, forming shrinkage: 0.1-0.5%. The injection pressure can reach 1500bar and the holding pressure can reach 1000bar. In order to avoid material degradation, appropriate injection speed is required.
POM is paraformaldehyde, and its main properties are high hardness, high steel, and high wear resistance. POM has a low friction coefficient and good geometric stability, so it is especially suitable for manufacturing gears and bearings. POM has the characteristics of high-temperature resistance, so it can also be used in pipeline equipment (pipe valve, pump shell), lawn equipment, and so on.
POM is a kind of ductile and elastic material, which still has good creep properties, geometric stability, and impact resistance even at low temperatures. Due to the high crystallinity and high shrinkage of POM, the highest is 2%-3.5%. Different reinforcement materials have different shrinkage.
POM has a high thermal deformation temperature, the homopolymerization thermal deformation temperature is 136℃, and the copolymerization thermal deformation temperature is 110℃. However, due to the different molecular structures, co-formaldehyde has a higher continuous use temperature. Generally speaking, the long-term use temperature of polyformaldehyde is about 100℃. According to the American UL specification, the long-term heat resistance temperature of POM is 85-105℃. Mechanical properties: because POM is a highly crystalline polymer, it has high elastic modulus, high hardness, and rigidity. It can be used for a long time at -40 to 100℃. Moreover, it can withstand repeated shocks for many times, and the strength does not change much. The strength is not greatly affected by temperature and temperature changes.
Injection molding conditions: POM does not need to dry before injection molding. The melting temperature range is 190-220℃. When the melting temperature is too high, the material will decompose. And during the injection molding process, the holding pressure should be increased to reduce the pressure drop. The screw speed should be suitable, not too high, and the residue should be reduced; the suitable mold temperature is (80mm 100℃), and the product demoulding temperature is relatively high, so pay attention to the protective work when taking out the parts. POM should be processed under the condition of medium injection pressure, medium injection speed, low material temperature, and high mold temperature.
PEEK plastic is a kind of special engineering plastics, which is a macromolecular polymer composed of the aryl group, ketone bond, and an ether bond. It has many properties, such as high-temperature resistance, strong flame retardancy, and excellent chemical stability, so it is often used in construction machinery, aerospace products.
PEEK plastic has the advantages of strong heat resistance and high-temperature resistance. The positive high-temperature resistance of PEEK plastic is 260℃, and the hot deformation temperature is 160℃. If 30% glass fiber is added for modification, the thermal deformation temperature can be increased to 280-300℃.
The electrochemical performance of PEEK plastic is excellent. Even in the high-frequency range, the dielectric index and dielectric loss of 10HZ plastic are small. The data shows that the dielectric point constant is only 3.2 and the dielectric loss is only 0.02 in the environment of PVA.
It has excellent chemical stability, can resist acid and alkali, almost any chemical reagent except concentrated sulfuric acid, and still maintain good stability at high temperature.
It has excellent hydrolysis resistance and can be used for a long time even in the steam environment of 200-250℃.
In addition, PEEK plastics also have excellent flame retardancy, melt fluidity, thermal stability, corrosion, high strength, and easy formability.
PEEK plastics are widely used in the chemical industry, electronic equipment, automobile industry, aerospace, and other fields because of their outstanding high-temperature resistance, heat resistance, strong height, and machinability.
The full name of PPS material is Polyphenylene sulfide. It is famous for its thermal stability and is widely used as special engineering plastics after filling and modification.
PPS is a kind of special high engineering plastics with excellent properties, such as high-temperature resistance, flame retardant, corrosion resistance, weather resistance, dimensional stability, and excellent electrical properties. After modification, PPS is widely used as special engineering plastics, mainly used in the field of electronics and electrical appliances, such as transformer skeleton, high-frequency coil framework, plugs, sockets, junction frames, contactor drum sheets, and various precision parts, etc.
The heat resistance for PPS plastic: Thermal deformation temperature is over 260℃, is currently one of the highest temperatures of thermoplastic engineering plastics, long-term use temperature of 220-240℃, the short-term temperature can reach at 260℃.
Chemical resistance of PPS plastics: At present, we could not find any solvent which can dissolve PPS below 200℃, and it is highly resistant to inorganic acids, bases, and salts.
PPS plastic electrical properties: In the environment of high temperature, high humidity, and high frequency, it has high volume resistivity, surface resistivity, breakdown voltage, low dielectric constant, and dielectric loss angle tangent, so it is an excellent insulating material. After modification, it can also be made into high-strength materials with good electrical conductivity.
PPS plastic mechanical properties: strong rigidity, high surface hardness, excellent creep resistance, and fatigue resistance.
The injection molding conditions: The material is dried at 130-150℃ for 3 hours, the barrel temperature is 280-330℃, the 40%GF+PPS is 300mm, 350℃, the mold temperature is 120-180℃, and the injection pressure is 50-130V MPA, medium injection speed.
It includes SPI A0,A1,A2,A3. The mold is smoothed and then polished with a diamond buff, resulting in parts with a mirror-like finish.
It includes SPI B0, B1, B2, B3. The mold is smoothed with fine-grit sandpaper, resulting in parts with a fine surface finish.
It includes SPI C1, C2, C3. The mold is smoothed using fine stone powder, removing all machining marks.
It includes SPI D1, D2, D3. The mold is first polished with fine stone and then sand-blasting, resulting in a sand-blasting surface.
EDM surface standard based on CHARMILLS VDI-3400. Normally using the CHARMILLS Sparking machines to spark the EDM surface.
Normally The Texturing standard based on MoldTech and YS. It will be done from MoldTech Texturing company and YS Texturing company.
- Medical part 1
- Medical part 2
- Medical part 3
- Medical part 4
- Automotive part 1
- Automotive part 2
- Automotive part 3
- Automotive part 4
- Automotive part 5
- Automotive part 6
- Automotive part 7
- Automotive part 8
- 2K injection molding 1
- 2K injection molding 2
- 2K injection molding 3
- 2K injection molding 4
- Insert molding 1
- Insert molding 2
- Gear 1
- Gear 2
- Optical part 1
- Optical part 2
Kemal Your Professional Injection Molding Partner
Kemal is a professional injection molding manufacturer with over 25 years of experience. There are more than 40 injection molding machines with the injection volume is from 50 tons to 2800 tons, and the maximum injection volume of products is more than 10 KGS.
We have different injection molding machine types, like horizontal injection molding machine, vertical injection molding machine, 2K injection molding machine. To produce medical products and high transparency products, Our company is equipped with a clean room workshop, The whole workshop is equipped with robots, with the aim to realize fully automatic production.
Injection product types：Insert injection molding, Gas assist Injection molding, 2K injection molding, In-Mold Decoration, Micro-injection molding, Thin Wall injection molding, Prototyping Injection molding, Collapsible core Injection molding and Unscrewing Injection Molding, etc.
The injection molding department also has the product secondary processing and product assembly lines. And the secondary processing mainly includes: screen printing, pad printing, painting, ultrasonic welding, electroplating, laser engraving, anodizing, etc.
PLASTIC INJECTION MOLDING: THE ULTIMATE FAQ GUIDE
Kemal is a professional plastic injection molding supplier. We have more than 40 injection molding machines with the injection volume is from 50 tons to 2800 tons, and the maximum injection volume of products is more than 10 KGS. Hope you can get what you want to know about plastic injection molding from this guide.
- What is Plastic Injection Molding?
- How many steps for Plastic Injection Molding?
- Which temperature should we pay attention to during Plastic Injection Molding?
- What types of pressure should be controlled during Plastic Injection Molding?
- What is Cycle Time for Plastic Injection Molding?
- What is Injection Time for Plastic Injection Molding?
- What are the common defects for Plastic Injection Molding parts?
- What are the effects of causing the defects for Plastic Injection Molding parts?
- What is Holding Pressure in Plastic Injection Molding?
- What is Injection Temperature for Plastic Injection Molding?
- What’s the difference between Injection Pressure and Holding Pressure for Plastic Injection Molding?
- What is the Plastic Injection Molding Machine?
- How many types of Plastic Injection Molding Machines?
- What is the advantage of Horizontal Plastic Injection Molding Machine?
- When should we choose Vertical Plastic Injection Molding Machine?
- How to purchase Plastic Injection Molding Machines?
- How many Plastic Injection Molding Machines does Kemal have?
- Why does the deformation happen to the Plastic Injection Molding parts?
- How to improve the deformation of the Plastic Injection Molding parts?
- How to improve the flash of the Plastic Injection Molding parts?
Q1. What is Plastic Injection Molding?
Plastic injection molding is a method of injection and molding. The advantages of plastic injection molding are fast production speed, high efficiency, the operation can be automated, product variety, the shape can be from simple to complex, size can be large or small, and the product size is accurate, the product is easy to be updated, and the shape can be complex. Plastic Injection molding is suitable for mass production and molding processing fields such as products with complex shapes.
Q2. How many steps for Plastic Injection Molding?
The plastic injection molding process can be roughly divided into the following 6 steps:
Mold clamping, injection, pressure keeping, cooling, mold opening, and product removal.
Q3. Which temperature should we pay attention to during Plastic Injection Molding?
During plastic injection molding, we should pay attention to the following 3 temperatures: Barrel temperature, Nozzle temperature, and Mold temperature. The first two temperatures mainly affect the plasticization and flow of plastics, while the latter temperature mainly affects the plastics’ flow and cooling.
Each type of plastic has a different flow temperature. Due to the different sources or grades of the same plastic, the corresponding average molecular weight and molecular weight distribution are also different, which leads to differences in the flow temperature and decomposition temperature. Because the plasticizing process in the machine is different, the cylinder temperature is different accordingly.
Usually, the nozzle temperature is slightly lower than the maximum temperature of the barrel. This is to prevent the “salivation” that may occur in the straight-through nozzle. The temperature of the nozzle should not be too low as well, otherwise, it will cause the premature solidification of the melt and then block the nozzle, or the performance of the product will be affected due to the premature solidification of the material injected into the cavity.
The Mold temperature has a great influence on the internal function and surface quality of the product. The mold temperature determines the crystallinity of the plastic, the size and structure of the product, performance requirements, and other process conditions (like melt temperature, injection speed, and injection pressure, molding cycle, etc.).
Q4. What types of pressure should be controlled during Plastic Injection Molding?
The pressure in the plastic injection molding process includes back pressure and injection pressure and directly affects the plasticization of plastics and product quality.
While using a screw injection machine, the pressure on the top of the screw when the screw rotates and retreats is called back pressure. The size of this pressure can be adjusted by the overflow valve in the hydraulic system. In injection, the size of the plasticizing pressure needs to be changed with the screw design, product quality requirements, and the types of plastics. If these conditions and the screw speed are the same, the temperature of the melt will be higher by increasing the plasticizing pressure, while it will reduce the efficiency of plasticization, increase the reverse flow and leakage, and increase the driving power as well.
In the current production, the injection pressure of almost all injection machines is based on the pressure applied by the plunger or the top of the screw to the plastic. The injection pressure in injection molding is for overcoming the flow resistance of the plastic from the barrel to the cavity, giving the molten material the rate of filling the mold and compact the molten material.
Q5. What is Cycle Time for Plastic Injection Molding?
The time required to complete an injection molding process is called the cycle time. The cycle time directly affects product output and equipment utilization. Therefore, in the production process, the relevant time in the cycle time should be shortened as much as possible under the premise of ensuring quality. In the entire cycle time, the injection time and cooling time are the most important points, because they have a decisive influence on the product quality. The holding time in the injection time is the pressure time for the plastic in the cavity, and it accounts for a large proportion in the entire injection time, generally about 20-120 seconds (extra-thick parts can be as high as 5-10 minutes). The holding time only affects the product size accuracy before the melt at the gate is frozen. The cooling time is mainly determined by the thickness of the product, the thermal and crystalline properties of the plastic, and the mold temperature. The cooling time cannot be too long, because too long cooling time not only reduces the production efficiency, but also causes difficult demolding of complex parts, and even demoulding stress will occur when forced demolding.
Q6. What is Injection Time for Plastic Injection Molding?
For plastic injection molding, injection time refers to the time required for the plastic melt to fill the cavity, excluding the time for mold opening and closing. Although the injection time is short and has a small effect on the molding cycle, the adjustment of the injection time has a great effect on the pressure control of the gate, runner, and cavity. Reasonable injection time is helpful for the ideal filling of the melt, and it is very important for improving the part surface quality and reducing the dimensional tolerance.
The injection time is much lower than the cooling time, about 1/10 to 1/15 of the cooling time. This rule can be used as a basis for predicting the total plastic injection molding time of plastic parts. In the mold flow analysis, only when the melt is completely driven by the screw rotation to fill the cavity, the injection time in the analysis result is equal to the injection time set in the process conditions. If the holding pressure switch of the screw occurs before the cavity is full, the analysis result will be greater than the setting of the process conditions.
Q7. What are the common defects for Plastic Injection Molding parts?
After the plastic part is formed, some defects will occur, which will affect the assembly efficiency or the performance of the overall product. There is a certain difference from the predetermined quality standard (inspection standard), which cannot meet the company’s quality requirements. The following are some common defects of plastic injection molding parts: Color Difference, Short Shots, Warpage / Deformation, Welding Mark, Burr, Flash, Burn Mark, Concave, Bubble, Ejector Mark, and so on.
Q8. What are the effects of causing the defects for Plastic Injection Molding parts?
In the plastic injection molding process, the quality of injection products is affected by factors such as mold design, mold manufacturing, raw material characteristics and resin pretreatment methods, molding processes, injection molding machine parameters, processing environmental conditions, product cooling time, post-processing techniques, etc.
Q9. What is Holding Pressure in Plastic Injection Molding?
At the end of the plastic injection molding process, the screw stops rotating and just moves forward. At this time, the plastic injection molding enters the holding pressure stage. During the holding pressure process, the nozzle of the injection molding machine continuously feeds the cavity to fill the volume vacated by the shrinkage of the part. If the pressure is not maintained after the cavity is filled, the part will shrink by about 25%, especially the ribs will shrink because of excessive shrinkage. Generally, the holding pressure is about 85% of the maximum filling pressure, certainly, it should be determined by the actual situation.
Q10. What is Injection Temperature for Plastic Injection Molding?
Injection temperature is an important factor that affects injection pressure during plastic injection molding. The barrel of the injection molding machine has 5 – 6 heating sections, and each raw material has a corresponding processing temperature (We can make a reference to the raw material data sheet about the injection temperature.). The injection temperature must be within a specified range. If the temperature is too low, the melt will be poorly plasticized, which will affect the quality of the plastic injection molding parts and increase the difficulty of the process; if the temperature is too high, the raw materials are easy to decompose. In the actual plastic injection molding process, the injection temperature is always higher than the barrel temperature, and the higher value is related to the injection rate and the properties of the material, which can be up to 30℃.
Q11. What’s the difference between Injection Pressure and Holding Pressure for Plastic Injection Molding?
The function of injection pressure is to overcome the flow resistance of the melt from the barrel to the cavity, and the melt has a certain rate of filling into the cavity.
The pressure holding is to compact the melt in the cavity, so that the plastic is tightly attached to the mold wall to obtain a precise shape, and the plastic that enters the same part of the cavity at different times and in different directions is melted into a whole.
In the plastic injection molding process, the holding pressure is sometimes equal to the injection pressure, and sometimes it is lower or higher. High pressure can obtain products with higher density, small size shrinkage, and better mechanical properties. However, the residual stress in the product after demolding is relatively large, and the product with strong compression will produce a greater rebound after the pressure is released, which may lead to sticking in the cavity, causing difficulty in demolding, so the pressure should be appropriate.
Q12. What is the Plastic Injection Molding Machine?
Plastic injection molding machine is the main molding equipment that uses plastic molding molds to make plastic products of different kinds of shapes. The working principle of the plastic injection molding machine is similar to the syringe used for injection. It uses the thrust of the screw or plunger to inject the plasticized plastic in the molten state (that is, the viscous state) into the closed mold cavity. It is the process of obtaining products after curing and shaping.
Q13. How many types of Plastic Injection Molding Machines?
In general, there are 3 types of plastic injection molding machines based on external structure. They are Vertical injection molding machine, horizontal injection molding machine, and angle injection molding machine. Among them, horizontal injection molding machine is the most popular one.
Q14. What is the advantage of Horizontal Plastic Injection Molding Machine?
The horizontal plastic injection molding machine is short, so it is easy to be operated and maintained. What’s more, the machine has a low center of gravity, and the installation is relatively stable as well. Besides, the products can automatically fall down after being ejected by gravity, which is quite easy and more convenient to realize fully automated operation. Therefore, it is the best solution to increase production.
Q15. When should we choose Vertical Plastic Injection Molding Machine?
The vertical plastic injection molding machine occupies just a small area, and it is easy to place inserts. Besides, it is convenient to load and unload the plastic injection molds. The materials falling from the hopper can be plasticized more evenly. Vertical plastic injection molding machines are suitable for small plastic injection molding machines. In general, vertical plastic injection molding machines less than 60 grams are more commonly used. Large and medium-sized machines are not suitable and seldom chosen.
Q16. How to purchase Plastic Injection Molding Machines?
The plastic injection molding machine is common machinery for plastic. For operators who use and purchase plastic injection molding machines, firstly they should understand the performance of a good plastic injection molding machine and the aspects that need to be evaluated. Let’s take a look at some tips for purchasing injection molding machines.
1.Technical parameters of the plastic injection molding machine. We should choose the suitable plastic molding machine according to the material, shape, structure, and application fields and specific occasions of injection molded products. Besides, we should also consider the structure, quality, accuracy, number of cavities, runner types, and products’ structure, shape, and size of the mold. Also, we have to think about the production capacity and the automation level.
2.Choosing a supplier who provides excellent after-sales services.
3.To pay attention to the machine model.
4.The machine should be convenient for operation.
5.The machine should be of high automation level, complete and perfect functions, as well as high production efficiency.
6.Energy saving and environmental protection should also be considered when purchasing plastic injection molding machines.
Q17. How many Plastic Injection Molding Machines does Kemal have?
The plastic injection molding machine’s sizes are ranging from 50 to 2800 tons. There are 23 sets of machines for the normal plastic injection molding workshop and 22 sets for the cleanroom injection molding workshop. Furthermore, we have 6 sets of two-shot injection molding (double injection molding) machines. Besides, our largest two-shot injection molding machine size is 1300 tons.
Q18. Why does the deformation happen to the Plastic Injection Molding parts?
There are the following two situations for the deformation of plastic injection molding parts. The first situation is the deformation appears when demolding or immediately after demolding. This is due to the deformation caused by poor curing conditions or poor mold design. The second situation occurs some time after demolding, which is caused by the poor injection pressure conditions set during the plastic injection molding process.
Q19. How to improve the deformation of the Plastic Injection Molding parts?
Here are some tips to improve the deformation of the plastic injection molding parts.
1.Replacement of higher-strength / fiber-reinforced plastics.
2.Replaced with high-release efficiency additive grade material section
1)Check the smoothness of the cooling pipe/calibration rate
2)Increase cooling pipe
3)Increase the smoothness of the lower mold
4)Increase the angle of mold ejection
5)Check/add mold exhaust duct
6)Optimize ejection system
7)Increase mold strength
8)Increase molding ribs
C)Plastic Injection molding machine Parameter
1)Reduce holding pressure
2)Reduce pressure holding time
3)Optimize the transfer pressure point
4)Reduce mold temperature
5)Optimize ejection speed
6)Increase cooling time
Q20. How to improve the flash of the Plastic Injection Molding parts?
Usually, we will improve the flash of the plastic injection molding parts by the following points.
Replace lower flow grade materials.
1) Check mold damage
2) Optimize the ratio of the difference between the mold wall thickness and thinness
3) Change gate location
4) Check/enhance mold structure and strength
C) Injection molding machine parameters
1) Stage optimization of injection pressure
2) Reduce injection pressure
3) Optimize the holding pressure conversion position
4) Reduce holding pressure
5) Reduce injection speed
6) Reduce pressure holding time
7) Reduce injection temperature
8) Reduce mold temperature
9) Increase clamping pressure
10) Replace models with the larger clamping force