Profile Extrusion Equipment
Profiles may consist of a single material or multiple materials. Single material profiles may include things like 4 foot diameter sewer pipe or drinking straws. Though the size of the extruder and the length of the line will vary greatly, the process is basically the same. In this case a single material is fed into a single extruder and through the forming die.
Co-Extrusion
If two or more materials are required to make the product, a co-extrusion process is used. For instance, if the drinking straw has 2 colors of stripes on it, a total of 3 extruders are used and each one feeds a material into a central co-extrusion die. Other examples are applying a weather resistant cap-stock onto a base that is not weather resistant, or adding flexible barbs to a rigid frame member, or various other combinations. Obviously, another extruder is needed for each additional material that is combined.
No matter how what size or how many extruders are used, they are combined with additional pieces of equipment to form the
extrusion line. The equipment employed after the extrusion exits the actual extruder is referred to as “downstream” equipment.
Downstream equipment is generally divided into three categories:
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Equipment for Cooling - The part must be cooled in a way that ensures the desired shape is maintained.
The cooling equipment must be able to accept tooling that will hold the different parts to be made on the line.- Air Rack
- Cooling Tank
- Vacuum Tank
- Sizing Table
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Puller - A puller is needed to pull the material away from the die as it is being extruded and pull it through the cooling tooling and equipment.
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Handling - some equipment is needed to handle the part after it comes through the puller.
- Cutter
- Saw
- Takeoff Conveyor
- Winder
Cooling Equipment
Air Cooling
The use of air to cool parts is rarely used anymore because it is so inefficient. However, because it is inefficient, it gives the operator time to shape the part with inexpensive tooling for parts that are very complex and the volume does not justify the costly tooling needed to make the part with a water tank. The Air Rack is a simple frame, usually with cooling fans, and simple plates and fixtures to mount jigs and fingers to push on the part and hold it in the desired shape.
Cooling Tank
The Cooling Tank allows for the circulation of water over the part as it is pulled through the tank. Some type of support is usually mounted inside the tank to hold the part while it is being cooled by the water. The water is either sprayed on the part from multiple directions to help the uniformity of the cooling or the tank is flooded with water so that the part is immersed in the water as it passes through the tank. If the tank is flooded, some provision must be made for the water that leaks around the part as it enters and exits the tank. Spray tanks generally offer more efficient cooling with the added cost and maintenance of the spray nozzles. Commonly, more than one cooling tank is used in any given extrusion line to ensure that the part is cooled sufficiently and maintains dimensional stability once it leaves the last tank in the line. The cooling section of an extrusion line may extend out to 160 feet or more.
Sizing or Calibration Table
A Sizing or Calibration Table is a piece of equipment with vacuum pumps and water circulation and a system to mount dry calibrationor other special tooling when needed for very complex parts thatrequire tight tolerances. This type of equipment is commonly usedfor window profiles and other profiles that require tight control of complex shapes.
Puller
The Puller is a key component of the balance between the push of the extruder and pulling the part through the cooling and shaping stage. Speed control is critical, but so is the grip of the part so that it doesn’t slip. The puller will generally use two opposing belts made from either rubber or polyurethane to grip the part. Larger pullers that require greater grip will normally use cleats made from rubber or polyurethane.
Cutter
Small parts can be cut with the use of a sharp blade that passes through the part with high speed and high torque. Cutters are available that allow for the part to pass through and the blade is controlled by one of several methods to cut “on demand” so parts can be cut to practically any length.
Saw
Larger and more solid parts require a saw to cut them to length. Saws can be made in a variety of configurations but generally they are mounted in a table below where the part passes. Then on demand when the part is to be cut the saw and blade is raised up through the part. Since the part is moving, it is necessary for the table top and saw to move with the part as the blade goes up through the part and back down to a neutral position. Grips of some type are actuated during the cut to hold the part to the table and keep it stable during the cut.
Take Off Conveyor
It is typical to have some type of conveyor to take the parts after they are cut by the saw or cutter to where they are packaged. Otherwise, since the parts are no longer being pushed or pulled, they would back up at the cutter or saw and cause problems. This is generally a very simple conveyor that is running slightly faster than the line speed of the part.
