"J" Aluminum Extrusion
The extrusion process is capable of producing a wide range of configurations and shapes that are used to produce various industrial and commercial products. The use of aluminum extrusions takes several forms from ones that are designed for ornamental purposes to ones that are used for structural support. The types of aluminum used to produce aluminum extrusions are in the 6000 and 7000 series, which contain magnesium and silicon as alloying materials.
Quick links to J Aluminum Extrusion Information
A Special Type of Aluminum Extrusion – "J" Extrusions
A very common type of aluminum extrusion is a J extrusion that has a long side with a bottom portion that is twisted or curled to take the form of the letter J. The purpose of J aluminum extrusions is to close or seal the edges of structures and materials in order to protect the interior of a structure from water runoff and provide a finished pleasing appearance.
One of the types of extrusions commonly produced by the extrusion process is channels, which take several forms and have several appearances. The shared feature of all channels is a U shape that is the channel portion of the extrusion. J extrusions fall into the group of channels due to their curved or bent portion at the bottom of their extended long side. J extrusions are more popularly known as J channels, since channels are used as trim, coverings, and protective edging.
Types of J Extrusions
As with all forms of channels, the terms J extrusion or J channel covers a wide range of forms, shapes, and designs that are classified as J channels. Each of the different varieties is designed for a specific function, which can be decorative and ornamental or pragmatic and necessary. The variations in the types of channels is created by adjustments to the extrusion die from which the channels are made and can include indentations, holes, grooves, and other features.
J-Cap
J-caps are used as borders around doors, panels, mirrors, and signs. The term J-cap is a general reference for all types of J extrusions, moldings, edge trims, or J channels. They are available in all of the different forms of J extrusions and are widely used in construction projects for concealing and covering edges. The short side of the channel portion of a J extrusion or J-cap is normally exposed to the elements while the longer side of the J is used to securely attach the J-cap to a wall or panel. The list of names of J-caps includes J moldings, J channels, or J edge trims. In architectural parlance, J-caps are referred to as drip caps or edging.
Hemmed J Extrusions
In most cases, J extrusions have straight blunt edges that are similar to an unformed piece of aluminum. This particular shape can interfere with the installation of a J channel due to its sharp edge. Hemmed J extrusions are designed to overcome the challenges associated with the blunt edges of typical J channels. The form of a hemmed J extrusion is exactly the same as that of all other forms of J channels with one slight adjustment, which is bending or crimping of the top of the short portion of the J form. The process for adding the hem to a J channel requires an extra step to the manufacturing process but offers protection when the J channel is installed.
Nailer J Extrusions
Although it is common for J extrusions to come without holes for screws and nails, there are certain forms that come with nail holes added for the convenience of installation. The reason that J extrusions come without holes is to allow installers to adjust the placement of a J extrusion to match the configuration of where the J extrusion will be placed. As with hemmed J extrusions, the addition of holes to J extrusions is an extra step in the manufacturing process. The configuration of nail holes takes several different forms depending on the requirements of the application for which the J channel is being used.
Deep Nose J Extrusions
The term deep nose J extrusion tends to be misleading in that it can garner several different types of visualizations that are mostly incorrect. J channels do not have any portion that resembles any type of nose. Deep nose refers to the channel portion of a J extrusion, which is the opening between the long side of the channel and the short side of the channel. With deep nose J extrusions, the distance between the two long portions is small, around 5/16" (8 mm), a space that is large enough to fit the edge of a mirror or wall hanging.
The development of deep nose J extrusions was to adjust J extrusions to fit irregular wall surfaces and provide room for applications such as light weight mirrors and foam mountings. Deep nose J channels are ideal for the inset and drop method of installation using the deep bar on top and shallow channel on the bottom. One of the necessary features of deep nose J extrusions is their finish, which has to match the décor of the room where the deep nose J extrusion is installed. Deep nose J channels are construction items and decorative accent pieces.
Indented J Extrusions
Indented J channels are an unusual form of J extrusion that can be combined with deep nose J channels as an extra measure for gripping a surface. The differentiating factor in regard to indented J extrusions compared to other forms of J extrusions is the configuration of the long portion of the J shape, which has a grip-like shape or indentation that makes the long portion protrude toward the short portion. The indented back is designed to move what the J channel is holding away from the wall against which it is placed. This configuration allows for air to circulate behind the held object, preventing moisture and condensation from accumulating, which can damage the surface of a mirror or art piece.
How J Extrusions are Made
The extrusion process is one of the more popular manufacturing methods for the production of various forms of aluminum, plastic, and other materials. In essence, it is an uncomplicated process that involves heating a large piece of material and forcing it through a die or profile that has the shape of the desired components. The key portions of an extruder are the barrel that contains the piece of material, a ram that forces the material along the barrel, and the die or profile that has the shape and form of the desired part, which would be in the shape of the letter J for J extrusions.
With aluminum extrusion, a lump of aluminum, referred to as a billet, is placed in the barrel of the extruder. As the billet is pushed along the barrel, it is heated such that the aluminum softens and becomes soft and ductile. The movement of the ram at one of the barrel against the billet increases the pressure applied to the billet as it is forced through the J channel profile, which exits the extruder as a long piece of aluminum in the form of the letter J. The movement of the long aluminum J channel continues along a trough until it reaches a predetermined length and is cut.
Although the long piece of J channel is completed and somewhat cool, it is taken to another location where the cooling process is allowed to continue. This may take several hours or a day depending on the parameters of the J channels design. Once completely cooled, J channels are cut to transportable usable lengths and shipped.