Press braking and roll forming are both types of metal bending and forming, but though they both fall under the same basic process type, they have little else in common. While both are important, each has distinct advantages and disadvantages, and their appropriate use depends on the end product being fabricated.
What is Roll Forming?
Roll forming is an industrial metal forming process. It makes use of complex equipment for the continuous rolling of sheet metal to bend it into the desired form.
The sheet metal strips go through a set of rolls attached to two stands. Each roll is responsible for performing an increment part until the desired section is achieved. Roll forming is an easy-to-perform process idea for producing complex shapes. It is considered more cost-effective than other sheet metal fabrication techniques.
Types of Roll Forming Machine
There are different types of roll forming machines available, including standardized rolling machines, side-by-side machines, single-duty roll forming machines, double-headed machines, and so on.
What is Press Braking?
Press Braking popularly known as brake forming, it is a metal deformation process, wherein a workpiece aligns along an axis. This can be achieved using a machine pressing tool, called a press brake.
Press Brake is one of the important types of machine pressing tools that clamp the metal piece between a set of dies and a punch for prearranged bending. There are countless benefits of using a press brake. However, it is highly preferred for producing precise bends. Owing to their increasing demand in several industries, it is easy to find them in a variety of specifications and types.
Types of Press Brake Machine
Some of the most common press brake types include pneumatic press brake, mechanical press brake, hydraulic press brake, servo-electric press brake, and so on. Each has its benefits that contribute to its popularity.
Top 8 Features of Press Braking
- Press braking is efficient and cost-effective
- small volumes and with shorter part lengths
- Larger orders get expensive very quickly
- unable to handle longer parts
- brake press is normally easier to set up
- Brake press tooling is normally less expensive than roll forming or stamping
- difficult to provide value-added features like holes or punched shapes during the process
- the force of the die shaping the metal often leaves scrapes on sheet metal
Top 7 Features of Roll Forming
- Works on the continuous coil
- No limit to the length of the bend
- Bends must all be in the same direction
- Profiled lengths are cut to size after forming
- Tooling can be expensive
- The roll forming line needs to be set up by an experienced operator
- Roll forming performs best for projects that require medium to high volumes
Press braking is one of the most common forms of metal bending due to its general cost-effectiveness and efficiency compared to the other available options. Press brakes have a faster, easier setup process, contributing to their comparatively low cost. In general, press breaking is considered the least expensive of the bending processes, and it is an incredibly useful and integral facet of most full-service metal fabrication companies.
The most impressive aspect of roll forming is just how well it handles the shaping and bending of even very long products. While the majority of products can be most cost-effectively and efficiently bent via press brake, there are times when it makes more sense to roll from them instead.
Roll forming also produces an attractive finish without adding an additional finishing step, and secondary processes such as punching can be incorporated directly into the roll forming run instead of being added on as a secondary process.
Top 4 Disadvantages of Press Braking
- Press braking is best for small-to-medium part volumes, so it is usually not a great choice for fabricators specializing in large production runs of a single product. The exception to this rule is when press braking is automated via robots, in which case, even very large production runs are possible.
- Press brakes also cannot make bends for parts longer than a typical bed length. Longer part lengths would generally go through the roll forming or stamping process instead.
- Exceptionally tight tolerances, i.e., those of less than +/-.005, are generally not ideal candidates for press braking.
- Metal items that have undergone the press braking process will not look as immediately “finished” as parts bent in other ways.
Top 3 Disadvantages of Roll Forming
- In fact, roll-forming tooling can only be used for a single product, and not reused in other ways (similar to metal stamping with dedicated tooling), which can add to the overall production cost of some products.
- Roll forming can only form on two sides. This is where secondary processes often become necessary with roll-formed pieces as any forming on the ends must be completed after the rolled part has been cut from the roll.
- The roll forming sometimes results in end flare due to linear stresses if part geometry is not carefully considered, an issue that is not a concern with other types of forming operations, like press braking.
Roll Forming vs Press Braking
For the right applications, roll forming has many advantages over stamping. Roll forming can offer the lowest tooling and maintenance costs with the assurance of quality metal fabrication.
length of a part
The length of a part is one of the most important factors when trying to decide between roll forming and stamping. In most cases, stamping parts longer than 10 inches will have more expensive tooling. A 36” to 48” stamped part may be double or more what roll forming dies would cost. Roll forming tooling, on the other hand, has no restriction on length other than the size of the facility producing the part and the weight-handling capabilities there.
Stamping will get even more expensive if there are multiple lengths of the same profile. To produce parts at multiple lengths, completely separate multiple stamping dies would be required. The more lengths you add, the greater the stamping die cost. With roll forming, no additional tooling is usually required. A simple adjustment can be made on all roll forming machines to produce parts of different lengths, typically using a digitally-controlled computer.
One way stampers attempt to create longer parts is through the secondary assembly. Secondary assembly does reduce the tooling costs, but it increases the labor costs to join the two parts together.
Roll forming can adjust part lengths on the machine on the fly, which is much less labor-intensive.
Stamping short parts is also more labor intensive when including holes, trimming, or complex notching and multiple stamping press stations that may be required then.
Most stamping dies don’t include advanced fabrication options, so a secondary operation is required, which can be conveyorized and automated, also at extra expense and setup cost.
With roll forming, many advanced fabrications, such as holes, trimming, or notching, can all be done inline, reducing secondary fabrication costs, though additional fabrication conveyorizing can also be done in roll forming. For example, as a reduction of allowed end flare, roll forming can produce that; stamping and brake forming do not.
Material, and fabrication processes
Both can handle light-strength steel, such as carbon steel, but when it comes to working with high-strength steel, roll forming has the upper hand.
High-strength steels are very difficult to stamp because of spring back, galling, and scratching. The harder the steel, the more likely the steel will bounce back to its original shape after stamping. Even if stamping is successful in forming high-strength steel, there will be evidence of galling and scratching on the finished shape.
In roll forming, there is a gradual bend as steel moves through each bending pass. This gradual bend reduces spring back, galling, and scratching when high-strength steel is used.