Metal Moulding

Chapter 1: Principle of Metal Moulding

This chapter will explain metal moulding and roll forming, including metal mouldings created from roll forming. It will also discuss the metal moulding process.

What are Metal Mouldings and Roll Forming?

Roll forming is a gradual process of bending a flat sheet of metal to obtain a longitudinal and uniform profile by processing it through a set of mated tool dies. The process is carried out until a uniform shape is obtained.

Thus, roll forming can be used to create metal mouldings by using large machinery to gradually bend flat sheet metal into long, uniform profiles. This is accomplished by passing the sheet metal through a number of matched tool dies.

Compared to alternative forming services, roll forming may have greater tooling costs. However, roll forming enables more in-line manufacturing, medium to large runs, and higher output. Roll forming results in extremely tight tolerances and aesthetic finish. This is because of the more progressive forming sequence. Any shape, no matter how intricate, may be created using the technique by adding tooling. No length restrictions exist because the material is passed through while coiling. When done in large quantities, roll shaping is more economical. It can produce high-strength steels while supporting ductility and permits in-line fabrication at reduced labor cost.

The roll forming process has only a few clear drawbacks; for example, small quantities and orders are more expensive compared to certain other metal forming operations like press brake forming. Although tooling might be expensive, long-term labor cost savings can balance tooling expenditures on a per-piece basis. The roll forming line must be set up by a qualified operator. End flare, a problem where one end of the component flares outwards, results from linear stresses in roll forming. However, there are several methods to address it based on part design. The projects that need medium to high quantities, precise tolerances, and an appealing look are best suited for roll forming.

Chapter 2: Architectural Metal Mouldings

This chapter will discuss architectural metal moldings and how metal moldings from roll forming are made.

How Roll Formed Metal Mouldings are Made

The manufacturing method known as roll forming is used to create metal moldings; it uses large machinery to gradually bend flat sheet metal into a long, uniform profile. This is done by passing it through a number of matched tool dies. Next, an uncoiling/straightening mechanism is used to unwind a big coil of sheet metal into a pair of mated roll dies. In order to smoothly and synchronously pull/push the material through the machine and ultimately make metal moldings, each set of roll dies is operated by its own system of gears.

Imagine these mated dies as a railway wheel and a track. They are designed to fit one inside the other flawlessly while leaving space between them for the metal to slide through. With each set, the metal is progressively bent closer to the desired shape. More die sets are needed to pass the metal through complex geometries than through simpler profiles. Typically, a roll form mill will have 10-30+ pairs of roller die supports.

The reason why bending in only one motion may not be sufficient is that force is used to change the physical structure of flat metal when bent. This force stresses the metal, which must subsequently be released in another way across the entire workpiece by twisting, curling, etc. This force should be gradually applied and controlled. Thus, the metal is gradually "massaged" into its final shape during roll forming, thereby managing the direction where the stresses are released. By doing this, the workpiece almost perfectly adapts to its new shape.

The metal is sliced into distinct pieces in one of two ways after passing through the forming dies. For one, it may pass through a cutoff mechanism created especially for the final moulding profile, which precisely measures the pieces and creates clean ends. However, the metal is roughly pinched or smashed if there isn't a cutoff created for the shape. After being sawed off, the moulding is deburred as a follow-up procedure to provide secure, smooth edges. The completed moulding is then released onto a run-out table so that it may be packaged safely for storage or shipping.

Such operations and processes are excellently done by companies such as https://www.dahlstromrollform.com/.

Use of Drawbench Machine in Roll Forming

An uncoiler and matched sets of roll dies are still useful in a drawbench machine, but they do not have individual power sources. Instead, the metal ribbon's leading edge is clamped using a huge clamp connected to a chain drive. The clamp draws the metal through the roll dies, moving away from the coil after turning on the chain drive. When no more material is left, the chain drive is halted so that the finished product can be cut using a hacksaw or a pair of big metal snips. For each length of moulding needed for the project, the clamp is reset, and the procedure is repeated.

The currently available drawbench tool sets are fairly simple, only including 4-8 sets of rolling dies. As a result, a lot of forming stresses are applied quickly. Consequently, the "completed" product frequently comes out twisted and bent several ways. In such cases, a different machine known as a stretcher is used to insert the moulding. By forcing the moulding in opposite directions, the stretcher reduces stress on the metal and returns the moulding to its initial straightness.

Few (if any) firms still use the drawbench, which is one of the original types of roll forming save for Dahlstrom. Dahlstrom invented roll-formed metal mouldings in the early 1900s; hence, a large portion of the moulding equipment was initially created for this specific procedure.

Chapter 3: Decorative Metal Mouldings

For over 110 years, companies like Dahlstrom have been the go-to source for aesthetic metal moldings, casings, chair rails, and other interior design trim. Dahlstrom moldings were widely used in early 20th-century design for decorative interior designs like doors, transoms, and sidelights. As a result, generations of architects who have contributed to some of the most recognizable structures in history are familiar with the name Dahlstrom on a global scale.

Categories of Decorative Metal Mouldings

Five main categories of decorative metal moulding have been adopted to strengthen and coat other metals. The main types are rusted steel moulding, sublimation moulding techniques, bronze and copper moulding techniques, galvanized steel, and stainless steel.

Rusted Steel

Rusted steel is a metal moulding technique introduced a few years ago by trend-seeking designers. The objective is to decorate a metal to make it look more attractive and be used in high-class stylish applications. Designers intentionally accelerate a given metal’s rust to obtain the desired effect. The process takes skill and a considerable number of resources.

Firstly, the steel, iron, or metal to be rusted is placed in a container or bucket. Next, distilled white vinegar is poured inside the container to completely immerse the metal object. The white vinegar can also be sprayed onto the metal and left in humid conditions. The soaked metal is left in the solution for over an hour before draining or wiping away the vinegar. A mixture of heated peroxide is added on top of the metal object. The peroxide starts to bubble on the metal, and rust is formed to decorate the metal.

Sublimation

In this type of moulding, the metal is submerged in a container of molten metal. This process is done to give metals a stylish appeal. The coating substance is first heated until it melts. The metal to be coated is then carefully dipped into the molten substance and allowed to cool. Additional designs and patterning can be done before the coating completely solidifies, including custom designing and brandings.

Bronze and Copper

Bronze and copper mouldings are other preferences for decorative metal moulding. A typical example is the Statue of Liberty, which was coated with a copper lining and, over time, reacted with oxygen and moisture to form a greenish appearance. Industrially, metals are coated with a lining of bronze or copper. Other oxidants can later decorate the lining to form an attractive color.

Galvanized Steel

Galvanized steel is yet another type of molding that can be used. Galvanization is a process whereby a protective zinc coating is added to iron or steel to prevent it from rusting. The zinc is first molten until it is completely liquified. The metal to be coated is then dipped in the bath of molten zinc, leaving a perfect finish to the iron or steel surface.

Stainless Steel

Stainless steel is a shiny, reflective, and attractive metal formed from the decorative moulding of steel. The moulding is done in the process of purifying iron ore. Some raw materials involved are nickel, chromium, silicon, and molybdenum. The raw materials are added step by step to obtain an attractively decorated metal mould that can be used in numerous applications.

Considerations of Metal Moulding Design

Metal moulding designs should be made while considering the following:

Metal Moulding Shape

The product's shape is the first consideration of a metal mould design. If the product is generally round, centrifugal moulding is probably the most suitable metal moulding process. However, investment casting or sand casting is the most suitable method if the part's shape is not round and its geometry has complex features like internal ribs or passageways.

Metal Moulding Size

For many sizes, sand molding is more available than investment molding. However, if a product is less than 1200 pounds (544 kg), the level of detail and overall geometry must be considered to choose between investment molding and sand molding.

Solidification modeling software is used to support the casting quality. This software simulates the flow of molten metal into metal molds and analyzes the solidification predicted during the cooling of the mold. This model ensures a compliant part by supporting the mold design.

Dimensional Tolerance

This refers to the deviation permissible from the desired measurements of the molding. Investment molding generally achieves tighter tolerances than other metal molding methods.

Surface Finish

Surface finish refers to the texture of the part’s external surface after metal molding and is measured using the root mean square. Generally, investment molding has a finer root mean square range than sand molding. This, in turn, results in a reduced need for machining. Sand castings can also be machined to achieve a fine surface finish, but this involves additional costs and lead time.

Chapter 4: Types of Roll Formed & Metal Moulded Parts

The different types of roll formed and metal molded parts include:

Metal Channels (Brass, Stainless, Aluminum & Steel Channels)

Channels are the roll-formed metal parts that are used and sought most frequently. With existing tooling for U-Channels, J-Channels, several C-Channels, and Hat Channels, Johnson Bros. is ranked first in the nation. They produce all kinds of metal channels, such as steel, stainless steel, and aluminum. Johnson Bros. has created approximately 250 distinct U-channels and J-channels in recent years, ranging in size from 0.060" O.D. wide to 19" O.D. wide.

Some U and J channels feature legs bent over or under 90°, uneven, or both. Even certain U & J Channels are available without edge burrs and with Hemmed Legs for added strength. The most popular type of channel is U & J channels with equal legs bent to 90°, and this form of channel has the most often used tooling in typical inventory.

Types of Metal Channels

Channels can refer to a large variety of metal profiles with various shapes, but the most common types of channels are classified as follows:

• U-Channels and J-Channels
• Open Seam Square & Rectangular Channels with Return Flanges C-Channel, Cees & Box Channel Tubing & Tubes

• Channel with Outward Flanges, Hats, and Hat Channels
• Inward Flanged, Strut Channels, and C-Channels
• Z-Channels and other oddly shaped metal profiles

Metals of every kind are used to create channels, although stainless steel, steel, and aluminum are the most prevalent.

Profiles, Sections, Shapes & Metal Mouldings

Unusual cross-sections and forms can adopt an endless variety of shapes because of the many tooling prints accessible in the industry. It is impossible to single out a particular industry as its main user because roll formed profiles, moldings, and shapes are used by most sectors.

Johnson Bros Metal Forming has tooling for well over 300 distinct parts in this area. These can be either for which they already have currently usable tooling or for which they have private tooling belonging to a client and not necessarily open to the public. In contrast to channels, tooling in this category is often unchangeable; hence, it is uncommon to use tooling from one part to the next. Existing tooling can be slightly modified, and features like hemmed edges can be applied with little to no additional die costs. Their machines typically accept pieces with a maximum height of 3" and a maximum width of 15", but smaller parts are frequently used.

How Profiles, Sections, Shapes & Metal Mouldings are Made

Metal molding is typically manufactured from thinner materials than profiles and special shapes. In many cases, decorative metal is also used to make moldings. Although profiles can be made of thinner metals, they are typically used for more structural purposes. The word "Special Shapes" refers to both metal profiles and moldings. Although prevalent, structural shapes can also be slim and aesthetically pleasing.

Pre-punching and post-punching are widely used in pre-punch presses for profiles, moldings, and other shapes. For companies like Johnson Bros Metal Forming, the cutoff procedure involves precision cutting-to-length, end fabrication, and other fabrication regarded as a component of the pre-punch operation. In addition, gag punching is done during the cutoff operation to provide tighter tolerances than possible with pre-punching and to account for uneven holes and other fabrication irregularities. During the roll forming process, the pre-punched fabrications' surrounding areas may be stretched, leading to distortion.

A major reason for post-punching is to avoid distortion. However, pre-punching is frequently utilized when post-punching cannot create the necessary fabrication or when post-punching becomes an expensive alternative. Along with gag punching, pre-punching can use a wide range of fabrications and patterns. Johnson Bros Metal Forming can accommodate lengths from 4 to 40 feet (1.2 to 12.2 m). In their flying pre- and post-press operations, accelerators with servo drives and die boosts provide high speed and precision. With the aid of these devices, items that are incredibly thin and made of foil can also be cut to size.

Multiple pre- or post-presses can be employed, and press controllers offer numerous fabrications and designs using the same die. The flying die presses are typically mechanical, hydraulic, and pneumatic from the best manufacturers. A preventative maintenance plan can be used to keep roll forming equipment up to date, and many of them have DC and High-Speed drive systems. Many of the best roll forming machine manufacturers produce them, including Dahlstrom, Yoder, and Tishken.

V-Shapes, Angles, and Angle Irons

The most fundamental of all roll formed profiles are metal angles. The necessary tooling is easy to use and cheap to put up. Hemmed legs can also be fitted with present tooling on thinner materials. Most angles have equal legs; however, L-shaped angles or angles with unequal legs can be custom-made. Vee's are angles that bend at an angle greater than 90°. In addition, there are angles where the legs are left more exposed than at a 90° bend. The most typical angle bend is a 90° bend.

Johnson Brothers is skilled at forming angles to precise completed and arbitrary lengths at a low cost and rapid rate. On the hydraulic and pneumatic presses, cutoff die boosters and accelerators are used to achieve this. Johnson Brothers specialize in creating angles with unbalanced legs that are either thinner or of the same width as hot-rolled mill angles, extrusions, or angle irons but are not available in those forms. It is worth noting that roll formed angles have a bigger outer corner radius and a sharper inside corner radius. This is unlike hot rolled mill angles, which have a tighter outer corner and a wide inside corner.

Roll Formed Tubing (Rectangular, Square, Round, and Special Shapes)

Roll-formed metal tubes and tubing are created for sophisticated and highly specialized end uses. These are not just typical, everyday grades of tubing. This tubing is sometimes created to reduce costs, such as when pre-finishing is used instead of post-finishing. Other instances include:

• Roll formed tubing is used for normally accessible thinner walls.
• Costly secondary fabrications can be avoided with in-line fabrications, such as holes, embossing, slots, perforating, embossing, end fabrication, cut-to-length, and others.
• Roll formed tubing is useful when the tube has dimensional features such as open seams, hemmed seams, flanged seams, and finned seams that would need costly additional labor.
• It can also be used for processes done in-line, such as inserting materials and molding, applying double-sided tape, and cladding one material over another. In other cases, the best and perhaps the only way to get the practical design outcome desired is to use roll-formed tubing.

Roll formed tubing is not intended as a replacement for the most popular types of tubing, such as extrusion, welded seam metal, seamless metal, and drawn metal tubing. Instead, roll formed tubing must have an inexpensive design capability or be used in a less costly design process since it is fundamentally different from conventional classes of tubing.

Open Seam Tubes

This tube is frequently found in square, round, and rectangular shapes and is also offered in uniquely shaped tubing. Its square and rectangle tubing forms are also known as purlins, cees, box channels, and C-channels. It can be readily pre-finished and is frequently pre-fabricated in line with perforations, slots, holes, and other features like cut-to-length and end fabrication. Most standard and many non-standard sizes have existing tooling; nonetheless, modifying or creating new equipment may be necessary.

A precise aperture or gap is required to make room for an insert in the cutoff die. This will facilitate the clean cut in order to get the most cost-effective clean cuts without pre-notching.

Lock Joint and Lock Seam Tubes

The most typical shapes for this kind of tubing are round, square, and hex tubing, which are typically pre-finished. It is a very advantageous form of tubing to reduce costs in a design because of its capacity for thin walls and pre-finishing. It can easily be produced in-line with the following processes: perforating, embossing, cut-to-length, and holes. Using the flying cutoff die for end fabrication includes:

• Crimp cutting gives a somewhat tighter fit into an opening (such as a plastic orifice) without catching on end cut burrs or end flare.
• Swaging allows for different thicknesses of fit between one tube's end and another tube's end, mapping out potential ground penetration.
• When pre-punching is used, extruded holes and dimple-free ends are produced. It is also possible to apply double-sided tape, in-line and insert molds, wire, and many other insert materials into the tube's grooves as needed.

Lock seam ends are typically cut with a minor tapered dimple for maximum production speed. The dimple is a point of the blade imprint as it penetrates. Pre-punch operations can be incorporated for a slower, slightly costlier in-line dimple-free cutting process with high volumes. Low volume production allows for the provision of hand de-dimpling plugs or secondary fabrication of de-dimpling. Secondary roll edge deburring is an option if preferred over in-line crimp cutting for clean, bigger roll edge end deburring. Tubing can also undergo additional secondary fabrication as needed.

Finned and Flanged Seam Tubes

While a finned seam often refers to external flanges, a flanged seam can refer to both inner and exterior flanges. The seam may have flanges or fins on one or both sides. The variables, tolerances, capabilities, and applications of open seam tubing also apply to this material. The inclusion of the flanges to the open seam tube makes it much stronger. Thus, in its square and rectangular shape, inward flange seam can also be termed strut and framing channels and is utilized in structural applications.

When a tube needs to go against the edge of another product, finned seam and externally flanged tubing are particularly useful. Customers occasionally join the fins using welding, either before or after installation. In addition to serving as framing, rails, tracks, guides, stiffeners, slides, channels, etc., it is an excellent design for a polished structural or decorative edge. Flanged seam tubing can be decorative, lightweight, and effective when employed for sliding curtain tracks and other applications. There is already tooling available for popular sizes, but additional tooling might be needed. Modifications to roll die tooling are typically not an option.

Hemmed Seam Tubes

Open and split seam tubes with hems require a protected burr-free edge. It is frequently used for rails, slides, or tracks that must have some material slide into them when built. These components are typically pre-finished or decorative with strength characteristics. Many thicknesses have hem-producing tooling already in place, especially the thinner ones. Similar clearances, characteristics, capabilities, and applications as with open seam tubing are possible.

Split Seam Tubing

Split seam tubing is particularly attractive when a welded seam or seamless tube will function just similarly. However, the size, thickness, and volume may make it difficult to buy it from welded seam, drawn, or other seamless tube suppliers. It's worth noting that this tube won't have the same torque strength as that of a tube with a welded seam or one that is seamless. But to compensate for this, the width and temper can be enhanced. It is a relatively affordable style to utilize with pre-finished and decorative metal treatments when strength is not a concern.

Existing split seam tooling is widely available, especially for round sizes. However, rectangular, square, and unique hollow profiles are less common. Additionally, split seam round tubes are employed for inner compression bushings and sleeves, as well as curtain and drapery rods. These tubes need to go through a pre-punch operation to be cut cleanly. Otherwise, they come with dimples that may be larger than those on lock seam tubes. Unless volumes are high, clean cuts typically necessitate new tooling costs.

Flexible Duct, Round, Corrugated, and Spiral Tubing

This particular type of tubing is made differently than other tubes. In reality, it is first created as a straight profile or molding shape before being bent into a ring shape. Next, the molding ring or profile's edges are inline-locked together, yielding a corrugated or flexible tube or pipe. Although little recognized, the technology has been used for over a century to create culvert pipes. It is now utilized mostly for high voltage applications, HVAC ducting, and other functions. It is made from stainless steel, aluminum, copper, and galvanized steel. Although heavy-duty applications can have walls up to 0.75" thick, the thinner wall thickness categories are more typical.

Chapter 5: Applications of Roll Formed Metal Mouldings

This chapter will discuss the applications of roll formed metal moldings.

Applications of Roll Formed Metal Mouldings

The applications of the different roll formed metal moldings include:

Metal Channels (Brass, Stainless Steel, Aluminum, & Steel Channels) Applications

Channels are employed in practically every industry with variations of channel terms like in:

• Railings
• Reinforcements
• Rims
• Framing and frames
• Rings and clamps
• Purlins
• Standards
• Cladding
• Subgirts
• Girts
• Covers
• Inserts
• Decoration
• Tracks
• Trim
• Holders
• Brackets
• Slides
• Posts
• Supports
• Stiffeners

V-Shapes, Angles, and Angle Irons

Angles are used in various industries, often for framing. Other applications include:

• Posts
• Bars
• Rails
• Hangers
• Flanges
• Frames
• Reinforcements
• Supports
• Trim
• Brackets
• Stiffeners
• Collars

Open Seam Tubes Applications

Open seam tubes are commonly used for:

• Tracks
• Guides
• Slides
• Inserts
• Supports
• Brackets
• Holders
• Railings
• Covers
• Framing
• Poles
• Cladding
• Wireways
• Troughs
• Bushings
• Sleeves

Lock Joint and Lock Seam Tubes

Some of the applications of lock joints and lock seams include:

• Reinforcements and stiffeners
• Car top rack rails
• Poles
• Shade, map, and screen rollers
• Posts
• Indoor and outdoor clothes dryers
• Towel bars
• Coat and garment hangers
• Shower rods,
• Curtain and drapery rails
• Indoor lamp tubing and poles
• Snack tray legs
• Perforated and expanded metal
• Flagpoles
• Easel legs

Conclusion

Using a set of matched tool dies, a flat sheet of metal is gradually bent during the roll forming process to create a longitudinal profile. The procedure is continued until a consistent shape is attained. Thus, by gradually bending flat sheet metal into long, consistent profiles using big machinery, roll forming can be used to produce metal mouldings. To achieve this, the sheet metal is sent through a series of matched tool dies.

Roll forming may require more expensive tooling than other forming methods; however, it offers greater in-line production, larger runs, and higher output. Roll shaping produces beautiful finishes with incredibly tight tolerances. The more progressive developing sequence is the reason for this. By including tooling, any shape—no matter how complex—can be produced using the process. Because the material is passed through while being coiled, there are no length constraints. Roll shaping is more cost-effective when done in big volumes. High-strength steels may be produced while maintaining ductility, allowing in-line production at a lower labor cost.