Injection Molding Screw
Why Choose Us
Rich Experience
Kotler has been engaged in the plastic machinery industry for more than 10 years, specializing in the production of plastic molding, wear-resistant and corrosion-resistant screw tubes for extruders, and special components.
Wide Product Range
Mainly used in the production of connectors, connectors, automotive precision components, optics, mobile phones, computers, precision gears, medical, special wires, plastics involving high temperature, high pressure, high corrosion, high wear PEEK, PPSU, LCP, PA46, PA66, PA4T, metal powder, neodymium iron boron, stainless steel powder, thermosetting BMC, bakelite, liquid silicone, optical PC, PMMA, etc.
Professional Technical Team
Kotler has an excellent team of professional design, R&D, manufacturing, sales and fast after-sales support, especially the designers who are proficient in the characteristics of various plastic raw materials, molding processes, molds and the characteristics of famous brand molding machines around the world. From customer consultation to design, quotation, manufacturing, installation and commissioning, we provide customers with one-on-one services!
Reliable Product Quality
Screw materials are purchased from Japan and Europe to ensure quality. We have independently developed HIP hot isostatic pressing sintered components and special centrifugal casting bimetallic barrels. the products of Kotler have passed ISO9001 quality management system certification.
The screw is a critical component of an injection molding machine. Its functions include transporting, compacting, melting, stirring, and applying pressure to plastics. All of this is accomplished through the rotation of the screw within the barrel. As the screw rotates, the plastic generates friction and mutual movement against the inner wall of the barrel, the bottom surface of the screw groove, the screw edge advancement surface, and between the plastic and itself.
Uniform Melt Preparation The screw’s design, with its helical flights and varying depths, helps efficiently melt, mix, and homogenize the plastic material as it is transported through the barrel. This results in a more consistent and uniform melt, which is essential for producing high-quality injection-molded parts.
Precise Metering and Shot Size Control The screw’s ability to measure and deliver a precise amount of molten material (shot size) ensures consistent part weight and dimensional accuracy. This precise metering capability allows for better control over the injection process and final part quality.
Increased Productivity The screw’s continuous rotation and metering function allow for faster cycle times and higher production rates compared to alternative mechanisms, such as plunger-style injection units.
Versatility Injection molding screws can be designed and optimized for different types of plastic materials, processing conditions, and part geometries, making them versatile for a wide range of applications.
Improved Melt Quality The screw’s ability to generate shear and heat the material effectively can improve melt quality, reducing defects such as voids, burn marks, and flow lines in the final parts.
Enhanced Mixing and Compounding
The screw’s design, with its various mixing and compression sections, allows for effective blending and compounding of additives, fillers, or reinforcements into the plastic material.
Reduced Energy Consumption
The efficient melting and metering capabilities of the screw can help reduce the overall energy required for the injection molding process compared to alternative methods.
Easier Maintenance and Replacement
Injection molding screws are relatively straightforward to maintain, service, and replace when necessary, making them a practical and cost-effective component of the injection molding system.
Types of Injection Molding Screws
General-Purpose Screws
General-purpose screws are suitable for a wide range of applications without specific requirements. They are versatile and handle various molding materials and techniques. Their design enhances performance across many injection molding projects, offering flexibility in handling different types of plastics such as polypropylene, ABS, polyethylene, and polycarbonate. These screws are ideal for facilities and industries that need adaptability for frequently changing production materials.
Barrier Screws
Barrier screws are designed for challenging plastic resins that require superior mixing. They feature a barrier flight positioned between the metering and feed sections of the screw, which improves resin mixing and prevents premature melting of the plastic. This design enhances melt homogeneity, making it suitable for complex mixing and melting processes.
Mixing Screws
Mixing screws focus on achieving accurate color blending and mixing of additives in plastic materials. Their design includes grooves and flight configurations that ensure thorough incorporation of color blends and additives, resulting in improved quality consistency of the final parts.
Feeding Section of Plastic Raw Materials The feeding section is where unmelted plastic is introduced and conveyed through the screw’s grooves toward the nozzle. As the screw rotates, the plastic densifies and advances due to increased friction between the plastic and the inner surface of the barrel, or reduced friction between the plastic and the screw surface. Good feeding effectiveness is achieved when the plastic slides smoothly on the screw.
Melt Plasticizing and Pressurizing Section This section transitions from the deep feed section to the shallower metering section. The main functions include melting, compaction, and pressure accumulation. Melting occurs primarily in this section due to frictional heating and less efficient conductive heating, transforming compacted particles into molten plastic without air bubbles.
Plastic Injection Screw Metering Section The metering section impacts the accuracy of plastic injection. It ensures a precise volume of plastic is delivered, maintaining uniform pressure and melt temperature. This section also handles melting of stubborn particles, melt refinement, and maintains constant pressure for accurate injection.
Designs and Functions of Injection Molding Screws
Screw Head Surface
The surface of the screw head must be smooth, with no right-angled or acute corners, to prevent material accumulation and ensure smooth material flow. Sharp corners can lead to cracking and material yellowing.
End Faces of the Apron
The design of the apron’s end faces is crucial. Flat joint surfaces can lead to reduced service life and material accumulation. An inclined surface, typically around 30 degrees, is preferred to minimize accumulation and enhance durability.
Movable Clearance of the Apron
The clearance between the apron and the screw should be appropriate for the materials processed. Too much or too little clearance can lead to instability and improper material discharge.
Threaded Part Hardness
The threaded part of the screw head should not be excessively hard, as high hardness can reduce thread strength. Proper heat treatment and nitriding are essential for maintaining thread integrity.
Why Does the Injection Molding Screw Slip?
Influence of Injection Molding Process Parameters
Low temperatures in the back section of the barrel can cause screw slippage. The material must reach a critical temperature to form a molten film layer; insufficient residence time can lead to incomplete melting and screw slippage.
Impact of Equipment
Screw and barrel wear can also cause slippage. Worn areas can prevent effective material movement. If wear is suspected, inspect and repair or replace the screw and barrel as needed. The compression ratio is crucial for uniform plasticization.
Material Uniformity
Poorly shaped pellets or inconsistent material can affect feed consistency and cause screw slippage. Uniform pellets reduce free volume and improve melting and movement. Hygroscopic materials like nylon may also cause slippage if moisture is present.
How To Reduce Wear Of Injection Molding Screws
Screws operate under high temperature, pressure, mechanical torque, and friction. To reduce wear:
1. Control barrel temperature to match the ideal processing range for the plastic.
2. Avoid excessive friction by ensuring proper melting and even material distribution.
- Fully preheat the injection molding machine before use.
- Match the screw to the material, especially for corrosive or hard materials.
- Clean and replace stable materials after using corrosive materials.
- Use high material temperatures, low screw speeds, and low back pressure for glass fiber materials.
- Avoid using the lower temperature limits for production to prevent excessive wear.
- Close the blanking port and clean the barrel if the machine is shut down for over half an hour.
- Prevent foreign matter from damaging the screw and barrel.
- Avoid screw idling and slipping.
- Clean the barrel when switching materials.
- Avoid mixing incompatible materials to prevent reactions and accidents.
- Check for damage to the rubber screw’s check ring seat if discoloration occurs.
Get Better Mixing From Your Injection Molding Screw
Operators using a standard, general-purpose screw may increase back pressure for better mixing, but this can result in higher melt temperatures and longer recovery times. Instead, consider screws designed for improved mixing, which handle resin dynamics more effectively. Reduce back pressure to the minimum required for machine operation to achieve better mixing with faster recovery and lower melt temperatures.
Three Internal Signs Your Injection Molding Screw Is Worn And Needs To Be Replaced
Burrs on Screw Flights Burrs may appear on the trailing side of the flight due to high compressive forces and angular motion, leading to surface damage.
Polished or Rounded Flight Corners Wear from particles and abrasion can erode the screw material, leading to rounded or polished corners.
Leakage Flow During Operation Increased radial clearance between the screw flights and barrel wall can cause leakage flow, reducing throughput and increasing melt temperature, which may lead to higher RPMs and energy consumption.
Our Factory
Suzhou Kotler Precision Machinery Co., Ltd is located in the city of Suzhou, "where there is a paradise above and Suzhou and Hangzhou below." Kotler is located in the southwest of Suzhou city, west of the Taihu scenic area 2 km, south of Dongshan scenic area, north of Suzhou ring expressway 1 km, and east of Suzhou central elevated road. It is an important manufacturing base in east China with convenient transportation. The superior transportation position is an important reason for setting up the factory.
Our Certifications
Ultimate FAQ Guide to Injection Molding Screw
We're well-known as one of the leading injection molding screw manufacturers and suppliers in China. Welcome to buy high quality injection molding screw in stock here and get quotation from our factory. Contact us for customized service.
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