Samson's Design Considerations
There is almost no limit to the shapes roll forming can create, meaning that it can be used to create parts for an almost limitless variety of applications. When designing a part for roll forming, focus on creating the shape you need, not the shapes that you think we might be limited to creating. Even if your shape exceeds our capabilities, it can more than likely be produced by combining two or more shapes.
The roll forming process can be used to produce high-quality products. By its very nature, roll forming permits close tolerances for either heavy- or light-gauge material, allowing for the forming of parts with uniform shapes and dimensions with fine details. Finished shapes, including those made using pre-coated materials, often have a clean appearance with no die marks.
Here is What Designers Should Consider When Designing a Part For Roll Forming
Because roll formed shapes have uniform cross sections, they are easily bent. When rings or segments of rings are required, shapes can be curved to a uniform radius at the rolling machine without wrinkles and without disturbing a prefinished surface.
Helices are also possible. Please consider your material’s elongation when designing parts with rings to help eliminate wrinkles and fractures. Usually, the more elongation a material has, the easier it is to bend. Where curves are not a constant radius, the uniformity of roll formed shapes makes them ideal for stretching or tangent bending.
Pre-piercing is the fabrication of a series or a pattern of holes in the flat strip before forming and can be done in one continuous operation together with roll forming to help save on production costs. With repetitive piercings, like wallboard plaster bead or shelf posts, a small die can be used, which will minimize the piercing tool cost when forming a pre-pierced part.
Post-piercing is piercing that is done in the line after the part is formed. If piercing, notching, or tabbing is required at either or both ends of the part, keep the pattern of holes and notches close to the ends of the part, so that these operations do not repeat throughout the full length of the part. Often, this process is less expensive and more desirable than pre-piercing because post-piercing allows for better dimensional accuracy from the end of the part.
Welding dimples, projections, tabs, stops, and raised areas can be formed while the parts are being rolled to improve accuracy in the finished part while saving on manufacturing costs.
Almost any material that can be obtained in coils can be roll formed. The material should be as ductile as the design strength of the finished product will allow; this allows for a crisp design, sharp corners, and easy bending. When high-strength alloy steels, heat-resistant steels, titanium and other alloys are used, the bend radii specified by the mill should be followed. In many circumstances, the bend radius can be reduced.
- The shape should not be designed features that are too deep for the rollers. Shape depth should generally be under 4 inches.
- Since the raw stock is sheet metal, the part should be designed to have uniform thickness throughout. However, thickness may be increased by folding the material to double thickness if needed.
- If wide, flat areas are required at the edge of a part, you should consider using small stiffening ribs in your design. The part will stay flatter and be much stronger.
- When planning a leg, as with an angle or a channel, the length of the leg should not be less than three times the thickness of the material. This also applies when hemming or bending the material back on itself.
- When planning pre-piercing where the location of the holes is not critical, design the pattern to be repetitive without specifying the location of the beginning of the pattern from the end of the part.
- When the pre-piercing pattern is critical and not repetitive within the part, try to design it to be less than 6 feet long.
- If a piercing pattern is used which requires holes in a specific area relative to the end of the part, try to keep it more than 1/2 inch (but within 4 inches) from the end of the part.
