In extrusion, thermoplastics are melted to a viscous mass in a screw and then pressed into shape through a shaping die.
Machine parameters for the success with Effect pigments
Masturbates or compounds are usually used to color the molten mass with effect pigments. For a satisfactory result in plastic extrusion with effect pigments, a balanced ratio must be maintained between the mixture energy and pigments which are as undamaged as possible. Excessive shear from mixing sections or inappropriate screws or filters destroy effect pigments and dramatically decrease the pearl luster effect.
The orientation of the pigments is a requirement for an even effect. This has to be ensured in the process through an corresponding engineering and design of the machinery.
Special possibilities in Co-extrusion
Co-extrusion is used to combine different materials or the same materials in different colors or effects. The two materials are combined into one flow in the co-extrusion die. If an effect pigments is used in the surface layer, it is possible to increase the effect strength and by the same time saving cost due to a thin layer and the perfect orientation of the effect pigment on the visible surface However, it must be taken into account that, due to the much thinner co-extrusion layer, a higher concentration of effect pigment must be used than in solid layers in regular extrusion – this could mean up to ten percent in the plastic, depending on the layer thickness and desired effect. Less pigment is needed when the entire layer mass is colored.
The inner layer in co-extrusion usually uses high coverage. It is also called the substrate layer because of its much higher layer thickness. Functional materials can be used in this, such as to improve the barrier or other properties, or internal recycling materials can be used to save raw materials and boost waste reduction and economy. Effect pigments are seldom used in this layer.
This technique can be used in all extrusion processes, including extrusion blow molding.
Extrusion is the most important process where a billet is pushed and / or drawn by way of die for creating rod, or pipe in a specific shape. This process is also used to develop vinyl (PVC), aluminum & other profiles / components that are used to produce windows and doors. The extrusion process is carried out with the assistance of various Extrusions Machinery such as Extruder, PP / TQ Film Plant, Extrusion Lamination Plant, Synthetic String Plant, and others. There are mainly two types of extrusions processes, hot extrusion and cold extrusion.
In the Hot Extrusion Process, different products are manufactured using various materials that are also called Extrusion Materials. Mainly, the extrusion materials that are used include Aluminium, and Copper along with their alloys. Some of the other quality extrusion materials that are extruded using hot extrusion process are as follows:
- Refractory Alloys
Similarly, in the Cold Extrusion Process various products are developed from a range of materials. Some of the major Extrusion Materials include:
- Aluminum Alloys
Depending on your requirements, you can choose different extrusion materials for developing an array of products. The selected material must have the capability of being extruded into the designed profile. The extrusion material specifications may or may not match the design requirements as desired by you, but if the material has low melt strength and low melt stiffness, then it may be possible to extrude it in the design geometry. Hence, it is very important to select the proper extrusion materials. Some of the good extrusion materials are as follows:
- Acrylonitrile Butadiene Styrene (ABS)
- Polycarbonate (PC)
- Polyester (PETG)
- Polyethylene (High Density-HDPE, Low Density-LDPE)
- Polypropylene (PP)
- Polystyrene (General Purpose-GPPS, High Impact-HIPS)
- Polyvinyl Chloride (Rigid-RPVC, Flexible-FPVC)
During the selection of the extrusion materials, you must consider some of the important attributes related to them such as:
Hydrostatic drives are presently used in many demanding applications. At least three types of output performance are commonly available.
Variable Power, Variable torque transmissions: are based on a variable displacement pump supplying a variable displacement motor. These transmissions provide a combination of constant torque and constant power. These units are the most adjustable, most flexible and most expensive.
Constant Power, Constant variable torque transmissions: are based on a variable displacement pump supplying fluid to a fixed displacement motor under constant load. Speed is controlled by varying pump delivery. This is considered the best general-purpose drive, with wide speed range and simple controls.
Constant Power Variable Torque: transmission are based on a variable displacement pump with a power limited , driving a fixed displacement motor. Th main strength of this transmission is the efficiency.
- Step-less adjustment of speed, torque and power,
- Smooth and controllable acceleration,
- Ability to be stalled without damage
- Easy controllability.
|DC drive system has been in use for nearly a century now, with the first drive ever to be developed being claimed to be operated on direct current. DC drive is the speed control system of the DC motors. The basic DC drive control system helps in starting, stopping, changing the direction and speed of the motor. The DC drive system which has only two main component, a converter and a regulator, is simpler is operation to the AC drive and is ideal in many operations. Another advantage is that the DC drive can be retrofitted with existing DC motors.
Speed of a DC motor is directly propotionae depends on the armature voltage and field current, the DC drives helps in controlling both the two currents. Motor Speed is primarily determined by Applied Armature Voltage.Motor Torque is controlled by Armature Current (amperes). Understanding these two concepts of DC motors provides the key to understanding total drive performance.Types of DC drives:
There are several types of DC drives available with various speed controls. Some of them being:
Brushless DC Drives: A drive that is frequently being used, a brushless drive does not contain a brush. The motor contains permanent magnets, the size of the magnets determine the horse power capabilities of the motor.
|One of the most sought after device when stable speed is required, AC drive refers to the device used to control the speed of an AC motor. AC drives converts the AC power into an adjustable frequency, adjustable voltage output for controlling motor operation. Changing the frequency is the primary function of an AC drive.
The AC motor consist of two part – a stationary part called the stator and a rotational part called the rotor. The shaft part of the rotor extends outside the motor and connects the equipment to be rotated. AC drives and motors and drives are getting increasingly used with the use of the modern PMW technology solution. The two AC drive systems used on extruders are the adjustable transmission ratio drive and the adjustable frequency drive.
Mechanical Adjustable Speed Drive: They are of belt, chain, wooden block and traction type. These drives are rarely used nowadays because it is maintenance intensive and provides only limited speed control. Mechanical adjustable speed drives are rarely used nowadays because they are maintenance intensive, have limited speed control, etc.
The adjustable transmission ratio drive: can have either mechanical adjustable speed drive or an electric friction clutch drive.
Adjustable Frequency Drive: An AC squirrel caste induction motor is connected to a solid-state power supply for providing an adjustable frequency to the AC Motor. The AC squirrel cage induction motor has several advantages in terms of low price, simplicity, low maintenance, compact construction,etc. The cost of the adjustable frequency drive is mostly determined by the solid-state power supply.
Eddy Current Drive: In the extrusion industry the eddy current drive has been widely applied in the past. The continuing popularity of the drive is due to the simplicity of the drive. An eddy current drive consist of a fixed speed AC motor driving a steel drum. Inside the drum the wire is wound round a rotor. By controlling the speed of the rotor, the rotor speed can be varied. Due to the simplicity of the operation eddy currents are widely used.
AC motors continue to be the most moving equipment for fixed speed requirements of industry. Their basic simplicity, dependability and ruggedness make AC motors the natural choice for the vast majority of industrial drive applications.
Warm extrusion is generally done when it is required to acquire a proper balance of all the requisite forces, final extrusion properties, and ductility. This process is carried out with the assistance of skilled and knowledgeable personnel, who use innovative techniques and best quality Extrusion Machines to create the required parts or objects. By using Warm Extrusions Equipments, the extrusion ratio may become very high but the best part is that it still produces high quality extrusions parts. The extrusion ratio can be easily defined as the beginning cross-sectional area divided by the final extrusion’s cross-sectional area.
The hollow cavities present in the extruded aluminum or other extruded material cannot be developed with the use of simple flat extrusion die, as there is no way to provide the support to the die center barrier. Alternatively, the die takes the shape of that of a block having depth, starting with such shape profile which provides the support to the center section. Then, internally the die shape morphs along its length and takes the final shape, with back of the die providing support to the suspended center pieces.
Warm extrusion process is carried out above the room temperature, but below the material’s recrystallization temperature. Generally, the temperature ranges from 800 to 1800 °F (424 to 975 °C).A brief of the extrusion technology or the extrusion process is as follows:
- The stock material is heated
- The heated material is loaded into the container in the press
- Dummy block is placed behind it. Here the ram presses onto the material and pushes it out of the die
- Then, the extrusion is stretched to straighten it
- For better properties, it may be heat treated or cold worked
One of the products that is formed by using warm extrusion is Aluminum Extruded Tubing. It is a hollow linear aluminum product, which is cylindrical in most cases. But, aluminum rectangular tubing and aluminum square tubing is also developed for various specialty applications like building supplies and aluminum downspouts. Extruded Aluminum Tubings are formed when the aluminum is extruded through a die. Aluminum Extruding Tubing is used in various applications such as:
- Mining equipment
- Hardware joints
- Fluid and gas transport
- Light building frames
- Structural applications
- Lighting fixtures
- Light poles
- Heat transfer & heat shield applications.