There are several ways to curl or spread the lip on the cylindrical part. For example, this can be done using a press or orbital molding machine. However, the problem with these processes (especially the first one) is that they require a lot of force.
This is not ideal for thin-walled parts or parts made from less ductile materials. For these applications, a third method emerges: profiling.
Like orbital and radial forming, rolling is a non-impact process of cold forming of metal. However, instead of forming a post head or rivet, this process creates a curl or edge on the edge or rim of a hollow cylindrical piece. This can be done to secure one component (such as a bearing or cap) inside another component, or simply to treat the end of a metal tube to make it safer, improve its appearance, or make it easier to insert the tube. into the middle of the metal tube. other part.
In orbital and radial forming, the head is formed using a hammer head attached to a rotating spindle, which simultaneously exerts a downward force on the workpiece. When profiling, several rollers are used instead of nozzles. The head rotates at 300 to 600 rpm, and each pass of the roller gently pushes and smoothes the material into a seamless, durable shape. In comparison, track forming operations are typically run at 1200 rpm.
”Orbital and radial modes are really better for solid rivets. It’s better for tubular components,” said Tim Lauritzen, product applications engineer at BalTec Corp.
The rollers cross the workpiece along a precise line of contact, gradually shaping the material into the desired shape. This process takes approximately 1 to 6 seconds.
“[Molding time] depends on the material, how far it needs to be moved and what geometry the material needs to form,” said Brian Wright, vice president of sales at Orbitform Group. “You have to consider the wall thickness and the tensile strength of the pipe.”
The roll can be formed from top to bottom, bottom to top or sideways. The only requirement is to provide sufficient space for the tools.
This process can produce a variety of materials, including brass, copper, cast aluminum, mild steel, high carbon steel, and stainless steel.
“Cast aluminum is a good material for roll forming because wear can occur during forming,” says Lauritzen. “Sometimes it is necessary to lubricate parts to minimize wear. In fact, we have developed a system that lubricates the rollers as they shape the material.”
Roll forming can be used to form walls that are 0.03 to 0.12 inches thick. The diameter of the tubes varies from 0.5 to 18 inches. “Most applications are between 1 and 6 inches in diameter,” Wright says.
Because of the additional torque component, roll forming requires 20% less downward force to form a curl or edge than a crimper. Therefore, this process is suitable for fragile materials such as cast aluminum and sensitive components such as sensors.
“If you were to use a press to form the tube assembly, you would need about five times as much force as if you were to use roll forming,” says Wright. “Higher forces significantly increase the risk of pipe expansion or bending, so tools are now becoming more complex and expensive.
There are two types of roller heads: static roller heads and articulated heads. Static headers are the most common. It has vertically oriented scroll wheels in a preset position. The forming force is applied vertically to the workpiece.
In contrast, a pivot head has horizontally oriented rollers mounted on pins that move synchronously, like the chuck jaws of a drill press. The fingers move the roller radially into the molded workpiece while simultaneously applying a clamping load to the assembly. This type of head is useful if parts of the assembly protrude above the center hole.
“This type applies force from the outside in,” Wright explains. “You can crimp inward or create things like O-ring grooves or undercuts. The drive head simply moves the tool up and down along the Z axis.”
The pivot roller forming process is commonly used to prepare pipes for bearing installation. “This process is used to create a groove on the outside of the part and a corresponding ridge on the inside of the part that acts as a rigid stop for the bearing,” Wright explains. “Then, once the bearing is in, you shape the end of the tube to secure the bearing. In the past, manufacturers had to cut a shoulder into the tube as a rigid stop.”
When equipped with an additional set of vertically adjustable internal rollers, the swivel joint can form both the outer and inner diameter of the workpiece.
Whether static or articulated, each roller and roller head assembly is custom manufactured for a specific application. However, the roller head is easily replaced. In fact, the same basic machine can perform rail forming and rolling. And like orbital and radial forming, roll forming can be performed as a stand-alone semi-automated process or integrated into a fully automated assembly system.
The rollers are made from hardened tool steel and typically range from 1 to 1.5 inches in diameter, Lauritzen said. The number of rollers on the head depends on the thickness and material of the part, as well as the amount of force applied. The most commonly used is a three-roller one. Small parts may require only two rollers, while very large parts may require six.
“It depends on the application, depending on the size and diameter of the part and how much you want to move the material,” Wright said.
“Ninety-five percent of the applications are pneumatic,” Wright said. “If you need high precision or clean room work, you need electrical systems.”
In some cases, pressure pads may be built into the system to apply pre-load to the component prior to molding. In some cases, a linear variable differential transformer can be built into the clamping pad to measure the stack height of the component before assembly as a quality check.
The key variables in this process are axial force, radial force (in the case of articulated roller forming), torque, rotation speed, time and displacement. These settings will vary depending on the part size, material, and bond strength requirements. Like pressing, orbital and radial forming operations, forming systems can be equipped to measure force and displacement over time.
Equipment suppliers can provide guidance on optimal parameters as well as guidance on designing part preform geometry. The goal is for the material to follow the path of least resistance. Material movement should not exceed the distance necessary to secure the connection.
In the automotive industry, this method is used to assemble solenoid valves, sensor housings, cam followers, ball joints, shock absorbers, filters, oil pumps, water pumps, vacuum pumps, hydraulic valves, tie rods, airbag assemblies, steering columns, and antistatic shock absorbers Block the brake manifold.
“We recently worked on an application where we formed a chrome cap over a threaded insert to assemble a high-quality nut,” says Lauritzen.
An automotive supplier uses roll forming to secure bearings inside a cast aluminum water pump housing. The company uses retaining rings to secure the bearings. Rolling creates a stronger joint and saves the cost of the ring, as well as the time and expense of grooving the ring.
In the medical device industry, profiling is used to make prosthetic joints and catheter tips. In the electrical industry, profiling is used to assemble meters, sockets, capacitors and batteries. Aerospace assemblers use roll forming to produce bearings and poppet valves. The technology is even used to make camp stove brackets, table saw breakers, and pipe fittings.
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Post time: Sep-09-2023