The content of this article provides everything you need to know about J extrusions and their use.
You will learn:
What is a J Extrusion?
The Use of J Extrusions
How J Extrusions are Made
Materials Used to Make J Extrusions
And much more …
Chapter 1: What is a J Extrusion?
J extrusions are extruded trim pieces that have a profile that resembles the letter “J”. They are designed and engineered to create a seamless edge to protect against the effects of water runoff and to provide a professional and aesthetically pleasing finished appearance. The name of J extrusions comes from their shape, which includes a flat bottom that has two curved sides known as legs where one leg is longer than the other to form the letter J. The longer leg is used to attach a J extrusion or J channel to a wall or panel. It can have slots or holes for nailing or screwing a J extrusion to the edge of a structure.
The term J extrusion or J channel, as it is popularly known, covers a wide assortment of specially designed channels that are used for a variety of trimming purposes. The designs of J extrusions are adjusted to meet the special and unique requirements of an application such that they take on the form and configuration of the edge or trim for which they are installed.
J extrusions are made from a variety of materials that can be extruded. The three most common materials are aluminum, steel, and plastic, each of which has the strength and durability to be a protective shield. Since J channels are normally exposed to the weather, they have baked-on coatings of paint, powder, or other types of protective layers.
Chapter 2: Types of J Extrusions
The many different types of J extrusions or J channels are used in many ways and take several different forms with legs having different lengths and variations in the size of the bottoms. For some applications, J extrusions are reconfigured to meet the needs of an application by trimming the legs to enable the J channel to be easily positioned. The three most common forms of J extrusions are without a hem, with a hem, and ones with a long piece that can be screwed or nailed.
Indented J Channel
Indented J Channels have an indented back on their longer leg and are used to hold flat displays or mirrors away from the wall such that air can circulate behind the display or mirror. They are included with deep nose J channels, which can have an indented back for a more secure hold on mirrors and displays. More durable forms of indented J channels are used to hold shower doors since the indentation keeps a shower door securely in the groove of the J channel.
Deep Nose J Channel
Deep nose J channels are designed for irregular wall surfaces and provide secure grip as well as extra protection. They are highly durable and adaptable building materials and are made from various metals with aluminum being the most common due to its corrosion resistance and longevity. Deep nose J channels are a cost-effective solution for wall mountings. Aside from the stability, resilience, and durability of deep nose J channels, they also provide a pleasing aesthetic appearance.
The term deep nose refers to the opening between the legs of a J channel and the width of the bottom. The dimensions are suited for holding mirrors, displays, and panels that have minimal thickness but may be several feet high and wide.
Hemmed J Channels
Hemmed J channels are designed to eliminate sharp metal edges that are found on unhemmed J channels. The hem is placed on the short or long leg of the J shape and involves bending the top edge of the leg over until it is flat against the inner wall of the leg. The process provides a round smooth edge on the top of the leg that will not snag or scratch the surface where the J channel is installed.
Unhemmed J Channels
Unhemmed J channels are the standard version of a J channel with both legs of the channel being straight without any bends or curves. They are the most widely used type of J channel and are the standard for J channels. As with all forms of J channels, unhemmed J channels come in a wide assortment of sizes with the dimensions designed to fit the needs of a specific application. In many cases, which is true of all forms of J extrusions, unhemmed J channels are frequently coated or painted to enhance their strength, durability, longevity, and appearance.
J Channel with Nailer
J channels with nailers are a unique form of J channel that is commonly used when installing a metal roof. The long leg of this form of J channel is extended below the bottom of the J and turned back up to connect with the bottom forming a notch that is similar to a hem. The design makes it possible to slide a flat portion of a metal roof into the formed notch in order to hold it securely. Prior to installing the flat roof panel, the J channel with nailer is nailed or screwed to the roof to form a tight connection.
The few J channels that are described above are a small sampling of the many J extrusions or J channels that are used for construction, manufacturing, and other industrial applications. In every instance, J channels are engineered, adjusted, and configured to fit the requirements of an application. The variety of sizes, types of metals, and other factors makes J channels easy to use and install.
Chapter 3: How J Extrusions are Made
The many forms of J extrusions are manufactured using the extrusion process, which involves a set of steps that are carefully monitored to ensure the quality of the final product. Each process is capable of producing high volumes of J extrusions using any type of material, which vary from plastics to steel. The most used metal for the manufacture of J extrusions is aluminum due aluminum’s many positive properties including its high weight to strength ratio.
J Channel Extrusion
Extrusion is a manufacturing process that has been used since the beginning of the first industrial revolution. The process involves forcing a heated billet of aluminum through a die that has the profile of a J channel. Extrusion can be performed on heated or cold aluminum, which depends on the series of aluminum being used and the requirements of the final product.
Types of Aluminum Used
Aluminum is divided into series that begin with series 1000, which is nearly pure aluminum at 99%, and extends up to the 8000 series that is 90% to 95% aluminum and 5% to 10% alloys. The three-aluminum series that are used the most for manufacturing J channels are series 6063, 6061, and 7075 that have sufficient strength and durability to produce the edges of doors, windows, tables, and machinery. Although several other series of aluminum are used to extrude J channels, these three forms are the most common due to their corrosion resistance, weldability, ability to be cold worked, and acceptance of coatings.
Extrusion Dies
Extrusion dies are circular thick disks that have openings in the shape of the letter J. They are made of H-13 steel that has been heated treated to enable them to withstand the pressure, repetitive use, and heat of the extrusion process. J channel dies are solid dies that produce a single form without any intricate or complex details.
A critical aspect of extrusion dies is the flow rate through the die, which has to be precision controlled. It is essential that every part of the J channel profile be filled, and the aluminum leaves the die at continuous and constant speed. The efficiency of a die is dependent on how well it is designed.
Preparing the Die for Extrusion
Dies for aluminum extrusion of J channels are made from hardened steel and designed using computer assisted design (CAD) software. In many cases, the die does not have to be created and is available in storage. If it is not, then, it is custom machined, which is an expensive and time-consuming process.
Before the die is placed in the extruder, it is heated to 450°C up to 500°C (842°F up to 932°F). The preheating of the die helps extend its life and ensure smooth and even metal flow. The die is placed with all of its components at the end of the barrel of the extruder where the aluminum billet will be forced against it to form the J channels.
Heating the Aluminum Billet
Although aluminum can take several forms, when it is used for extrusion, it is processed in the form of a billet, which is a solid, cylindrical block of aluminum. In order to be able to force the large piece of aluminum through the die, the billet is heated just above its recrystallization point, which softens the billet but does not melt it. The billet becomes malleable enough to be able to be forced through the die but firm enough to keep its shape. The temperature at which the billet is heated varies in accordance with the type of aluminum alloy.
The Cradle or Container
The process of extrusion begins with the placement of the billet in the cradle or container where the force of the ram will move the billet toward the die. The cradle holds the billet as it is pushed toward the extrusion press by the pressure of the ram, a process that is referred to as direct extrusion. The opposite of direct extrusion is indirect extrusion where the billet is held in place, and the die is moved to the billet as it is held in place in the container and supported by a sealing plate. Direct extrusion is the most common form of extrusion and most used.
Prior to the billet being loaded in the container, a release agent is applied to it, which is a form of lubricant or smut that is added to the billet and the ram. The smut prevents the billet, die, and ram from sticking to each other and makes the movement of the billet smoother.
The Pressure of the Ram
The pressure of the ram moves the billet toward the die, which causes the billet to narrow and widen against the walls of the cradle or container. As the ram moves forward, the only place the billet can move is through the die. The pressure and force of the ram heats the die. In order to avoid damage to the die, liquid nitrogen within the die cools it to help preserve its shape and keep it from harm.
Hydraulic force is applied to the ram as it pushes the billet against the die. The amount of force can reach as high as 15000 tons (13607.77 metric tons). The majority of hydraulic presses can apply pressure from 100 tons up to 15000 tons (90.718 metric tons up to 13607.77 metric tons), which varies according to the type of press and how large the produced extrusion is.
Cooling or Quenching
As the J channels exit the die, they are pushed to a water bath that uniformly quenches them, a process that ensures the J channel’s mechanical properties. The exit temperature of J channel extrusions varies depending on the type of aluminum alloy with all 6000 series alloys having an exit temperature between 493.3°C and 512.78°C (920°F and 955°F).
During quenching, the temperature of the J channels is lowered to an ambient level at a slow and controlled rate, which is achieved by forced air or cooling industrial water, with water cooling extrusions at a faster rate creating harder products. The process of cooling has to be meticulously controlled to avoid distorting the J profiles. Controlling the process ensures that the desired properties of the J channels are achieved without any form of structural damage.
Shearing or Cutting
Once the J extrusions have been quenched, they are rolled onto a table and cut to various lengths. Even though the J channels have been quenched, they have not cooled enough and are moved to a cooling table where they remain until they reach room temperature. The length of time the extrusions remain on the cooling table depends on the thickness of the J channels and their dimensions.
Stretching
During the extrusion process, the J extrusions naturally twist due to the pressing and cooling steps of extrusion. The deformations of the J channels necessitates stretching them using specially designed equipment. Stretching begins by attaching the lengths of J channels to grippers on the stretching machine that applies force to elongate the J channels. As with all aspects of extrusion, the temperature during stretching is strictly regulated and controlled.
In order to ensure the success of stretching, the J profiles are heated to soften the metal at a temperature that is not too high and varies with the type of aluminum alloy. The stretch ratio is the length of the profile divided by its original length, a factor that determines the mechanical properties of the J channels and the amount of necessary force.
After the J profile is clamped, it is held in place by a fixed clamp and twisted by a moveable clamp. Various power systems supply the power to shift the position of the moveable clamp. The stretching process affects the shape of the J profile and helps solidify its dimensions.
Finishing Processes
Once J channels have been extruded, they are ready for use. In most cases, especially when they are going to be used as edging, J channels are put through various finishing processes that improve their properties and enhance their appearance. Heat treatments help improve the mechanical properties of J channels such as their tensile strength and yield stress.
Although heat treating of J channels is common, many types of surface finishes are applied to J channels in order to have them comply with their final use. Since the majority of J extrusions are used as edging and support, they have to be painted, coated, sandblasted, and sublimated to make their appearance conform to their placement.
Additionally, various fabrication procedures are performed on J channels to assist in their installation. They are punched, drilled, cut, machined, and pierced such that they can be screwed or nailed. The types of fabrication are in accordance with the method used to attach them.
Chapter 4: Metals Used to Produce J Extrusions
There is a limitless number of metals that can be used to form J extrusions with various grades of aluminum, grades of stainless steel, and carbon steel being the most common. The choice of metal is determined by how the J channels will be used with stronger and sturdier metals being used for heavy load conditions. Metals, such as brass, copper, and aluminum, are used for applications that require a pleasing aesthetic appearance.
Steel
Steel is an ideal metal for the manufacture of J extrusions. It is an all-purpose metal that is used for a wide range of applications and one of the first metals that producers choose when manufacturing J channels for heavy load applications. Steel and its alloys provide high strength, exceptional durability, outstanding resilience, and versatility and adaptability, a factor that makes steel J extrusions useful in several environments and conditions.
Extreme temperatures, stress, and pressure can cause other metals to fail due to expansion. Extruded steel is able to endure such circumstances and maintain its form without failure. Its low cost and high strength make it the perfect metal for high volume production runs and demanding applications.
Stainless Steel
Stainless steel is available in a wide assortment of grades, each of which has properties and characteristics that can be adapted to fit the needs of any type of application. Aside from its corrosion resistance and exceptional mechanical properties, stainless steel has an oxide layer that protects it against the effects of environmental conditions. This aspect of stainless steel makes J extrusions useful in conditions that are hygienic and require protection against bacteria, such as medical facilities and food preparation. Additionally, the shine of most stainless steel grades offers a pleasing appearance.
Although most stainless steel grades can be used in the J extrusion process, series 304, 316, and 430 are most commonly used. They are used to produce 16 ga thin J channels and 11 ga up to 26 ga other J channels. Stainless steel J extrusions are used as trim for corners, backsplashes, and wall panels in a variety of situations.
Aluminum
Of the many metals that are used for forming J extrusions, aluminum is the most commonly used due to its many positive properties and exceptional strength to weight ratio. As with all forms of metals, aluminum is available in several grades with each grade having properties that can meet the requirements of an application. Aluminum can easily be formed and is available as blocks or billets that fit into the extrusion process.
The wide use of aluminum for the manufacture of J extrusions is due to its formability and weldability, which make it possible to shape aluminum on the job in order to adapt a J channel for unique conditions. Although all grades of aluminum can be used for the manufacture of J extrusions, grades 6061, 6063, and 7075, which are the most widely used grades in the world, are the ones chosen to produce most forms of J channels.
Brass
Brass is used to manufacture J extrusions due to its machinability, durability, electrical conductivity, and exceptional corrosion resistance. Since brass is a soft metal, it can easily be cut, drilled, and fabricated to meet the requirements of a J extrusion application. Aside from its positive properties, brass J channels have an excellent appearance and are used for framing mirrors, displays, and pictures.
The properties of brass vary in accordance with how it is alloyed with alpha brass having a copper content of 60% to 70% and a zinc content of 30% to 35%, a combination that makes alpha brass very ductile and easy to shape. Brass with a higher zinc content is stronger and harder, such as beta brass, which makes it ideal for J channel applications that require strength and machinability.
Copper
The main use of copper for the manufacture of J extrusions is due to its aesthetic appearance. It is a ductile metal that is easy to form and shape but does not have the strength for load bearing applications, a factor that limits its use to light weight and decorative applications. Copper is the base metal for the production of brass and bronze, which are stronger and more durable than copper due to their tin and zinc content. The bright red glow of copper is the reason that it is referred to as one of the red metals.
Chapter 5: Uses for J Extrusions
The main use of J extrusions has been as trim for doors, louvers, and windows when vinyl and aluminum siding are being installed. In addition, J extrusions are used as edging for soffits, which cover trusses and rafters. Soffits provide ventilation for roofs to release the build up of heat and prevent insects and contaminants from entering the attic of a structure.
Although the structural use of J extrusions has become their main use, they are also used for decorative purposes for securing mirrors, paintings, pictures, and other forms of displays. J extrusions used for such applications have a pleasing aesthetic appearance and supply support and provide a firm, secure, and tight hold of displayed materials.
Window J Extrusions
Prior to the installation of vinyl or aluminum siding, all windows are trimmed with J channels to hide the cut edges of the siding. The channels are installed such that they overlap to drain rain water. The overlapping and connection between the J channels are created by cutting the bottom of the channels such that they slip into the bottom of the connecting channel. This forms a seal to hide the edges of the siding and secure the windows.
Door J Extrusions
The function of J extrusions around doors is the same as it is for windows with the difference being the size of doors. The main purpose of J channels with doors is to give siding a finished and complete appearance as well as a method for draining the accumulation of rain water. As with most forms of channels, J channels are designed to give a finished and completed appearance. They are installed prior to the installation of siding to hide the rough cuts of the siding and provide a pleasing appearance.
Soffit J Extrusions
J extrusions for soffits are used to hold the soffit in place. They are an alternative to F channels and may be used with F channels to secure a soffit. The flexibility of J channels make it possible to adapt them to the special conditions associated with soffits. The purpose of soffits is to cover open eaves, which expose the rafters or trusses of a structure. Soffits offer a finished appearance, protection for the rafters, cover exposed areas, and fit on the overhang of a building.
During the installation of soffits, J channels are used to hold the soffit in place. They can be used in combinations with F channels, be repurposed to perform like F channels, or be used exclusively as support for soffits. In some cases, they are attached to the fascia boards to hold the soffit. As with F channels, J channels can act as soffit receivers.
Mirror and Display J Extrusions
Unlike their use with doors, windows, and soffits, J extrusions for mirrors support and hold mirrors in place such that they do not vibrate or shift. They also serve the same purpose for signage, panels, and displays. The size of J channels for mirrors and other displays varies in accordance with the thickness and size of the display. Most types of metals can be used for J channels for displays with sturdier and more durable metals used for heavier demanding displays.
Most J extrusions for mirrors are deep nose indented to provide proper support. The indent is designed to hold a mirror or display away from the wall such that air can circulate behind it. Finishes on J channels for displays and mirrors are adjusted to conform with the color of the mirror or display. In many cases, the J channels have finishes that fit the design décor of the room where the display is placed.
Electrical Wiring
J channels are used for organizing, routing, and supporting electrical wiring and cables. They are an enclosed track that allow wires to pass through without being obstructed or blocked by their surroundings. The reason for this use is their durability and ability to withstand harsh and demanding conditions. J channels provide shielding from factors that can damage wires and cables and protect against the effects of heat, weather, and abrasions. The main benefit for the use of J channels for wiring is organization. They help remove wires from being scattered over the floor or hanging from the ceiling.
Chapter 6: Benefits of J Extrusions
The many uses of J extrusions makes them a necessary part of construction projects. They provide a smooth finished appearance for siding and have the ability to securely hold soffits and displays. J extrusions can be reshaped, adjusted, and changed to fit any type of conditions and are made of materials that are long lasting and durable.
Connecting
J extrusions connect the end pieces of siding to provide a finishing touch and smooth even appearance. Their use makes a siding job look complete by hiding rough and jagged edges.
Water Protection
The use of J channels around doors and windows provides a place to catch water and drain it away. Since J channels are securely connected, they make the removal of moisture efficient and easy.
Protection
J extrusions are used to hold soffits in place to protect and hide open eaves. They are installed as receivers to support and hold soffits.
Support
Interior designers make use of J channels for holding displays, mirrors, paintings, pictures, and maps. J channels offer a firm hold and protect the edges of displays from harm. The use of strong durable metals in the manufacture of J channels make it possible for J channels to hold displays that have a heavier load.
Conclusion
J extrusions are made from a wide variety of metals with aluminum being the most commonly used.
The construction industry makes use of J channels as edging for gables and trim around doors and windows.
Since the introduction of J extrusions in the 1950s, their use has rapidly grown as replacements for F channels and Z channels due to their ability to cover edges and corners.
J extrusions come in a wide variety of shapes and are easily adapted to fit unique and unusual conditions. This aspect of their characteristics is what has added to their popularity and wide use.
Although J extrusions can be manufactured by roll forming, the most used method is extrusion, which produces J extrusions with the necessary strength, durability, and resilience that is required for their use.
Related Posts
Aluminum Channels
An aluminum channel is a structurally sound metal component that is made by the extrusion process to produce shapes, forms, and designs for a wide variety of applications. The major benefit of aluminum channels is their weight, which is...
Extruded Aluminium
Extruded aluminum is a continuous piece of aluminum that usually has a constant profile or cross-section throughout its length. It is made by forcing a block of aluminum, called a billet, through a die opening which is smaller than the original cross-sectional area of the billet...
Types of Aluminum Extrusions
Aluminum extrusion, or the extrusion process, owes its beginnings to three men – Joseph Bramah, Thomas Burr, and Alexander Dick. Each of them advanced and perfected the process so that inventors from the industrial revolution could improve it...
Aluminum 1100
Aluminum 1100 is the softest of the aluminum alloys, which makes it easy to shape and form into a wide range of products for industrial and home use. It can be cold and hot worked but is frequently shaped by...
Aluminum Coil
The term "aluminum coil" describes aluminum that has been flattened into sheets where their width is significantly higher than their thickness and then "coiled" into a roll. Stacks of individual aluminum sheets are difficult to...
Aluminum Tubing & Piping
Aluminum piping and tubing is silvery-white, soft, and ductile. The metal belongs to the boron group. Aluminum is the third most abundant element present on earth. Aluminum has low density. When exposed...
Anodized Aluminum
Anodized aluminum is aluminum that has undergone an anodizing process to create an exceptionally durable, corrosion-resistant, and highly aesthetic surface. Anodizing creates a stable aluminum oxide layer fully integrated with...
Metal Channel
A wire brush is an abrasive tool that has stiff bristles made from a variety of rigid materials designed to clean and prepare metal surfaces. The filaments of wire brushes are small diameter pieces of inflexible material that are closely spaced...
Types of Aluminum
Aluminum is the most abundant metal on the Earth’s crust, but it rarely exists as an elemental form. Aluminum and its alloys are valued because of their low density and high strength-to-weight ratio, durability, and corrosion resistance...