Great Roll Formed Part: noun, a part whose material, tolerances, and roll forming design are executed effectively, on schedule, and at an acceptable cost. A Great Roll Formed Part can easily become part of a reliable supply system.
We’ve shared information that how materials and tolerances are important to make a great roll formerd part. Now we continue with more.
Roll forming design exercise: Draw a continuous line of any shape on a piece of paper.
● As long as the line doesn’t cross itself, the roll forming process can probably produce that shape.
● The potential applications for roll form shapes are only limited by your imagination.
● Do not restrict your thinking when designing your product – always create the best design possible.
● Think in terms of bending the metal into the functional configuration that is really needed.
● IF you have issues with your design, your manufacturer can help you optimize it for the manufacturing process.
Rules of a Great Roll Formed Part
We know, we know. We just told you to get outside of the box, and now we want you to stuff yourself back into it. Actually, these “rules” are more like guidelines to help you maximize efficiency and cost-effectiveness in your design. After all, you’re aiming for a Great Roll Formed Part – a part that is quick and easy to manufacture right out of the gate. If your design requires non-standard processes, shapes, fabrications, etc., your manufacturer will certainly do their best to accommodate it. However, custom tooling and dies can be quite expensive for you, the customer – that’s why we aren’t calling them Great. Keep this in mind before committing to a nontraditional part design.
One thing to think about regarding custom tooling: once you decide to create a set of roll forming tools, incremental changes within that tool set are very affordable. And, you receive the benefits of the additional features for the life of the product. As for the following rules: currently, there are limits to what a roll forming line can do with a coil of sheet metal. If you want to create a design that’s absolutely perfectly optimized for your application (not just optimized for current manufacturing processes), your manufacturer can take that design and make it work with their machinery. Again, these rules are more like guidelines and can be bent or broken when necessary. A Great Roll Formed Part, however, will follow all or most of these rules.
Rule #1: No Extremely Deep or Narrow Channels As much as we all love a tall, leggy u-channel, they can be difficult (read: impossible) to produce on standard machinery. We have a separate service for this type of product, known as MeshTrim. Using this service will greatly decrease the amount you spend on deep, narrow channels, which are still considered a specialty item by other manufacturers. In general, deep and narrow channels require larger diameter forming rolls, which are more expensive to procure. Average size machines do best with a max depth of four inches.
Rule #2: Uniform Thickness Design for a uniform thickness throughout your part, whether you stick with the raw strip stock or fold the material back on itself for increased thickness. Depending on the metal type and profile complexity, we can roll thicknesses of 0.012” to 0.220”.
Rule #3: No Wide, Flat Areas at One Edge Wide shapes with forming work on one edge are unbalanced and prone to waviness. To avoid waves and other warping, add a small leg or offset on the flat edge for greater strength and balance. Small stiffening ribs or hems can make the part flatter and stronger. Roll forming design.
Rule #4: Proper Leg Lengths Short legs can be impossible to roll form in heavier gauge materials due to the lack of leverage. Extremely long legs are difficult to form without specialty equipment. This also applies when hemming or bending material back on itself. There’s a happy middle ground: if you’re worried about your legs being too short, make sure they’re a minimum of 3x material thickness past the tangent point. If you think your legs might be too long, you can make your section wider or open the sidewall at an angle. Roll Forming Design
Rule #5: Proper Pre-Piercing Hole Locations If the hole location of your design is not critical, you should design your pre-piercing pattern to be repetitive without specifying where the holes fall in relation to the end of the part. A partial hole may appear at the end of some parts, and that’s OK. When hole location is critical, place holes at least ½” but less than 4” from the end of the part. This allows for an economical design of the cut off/punch die set. Rol Forming Design
Rule #6: Keep Punched Features Away From Edges Punched features that are too close to the edge of the profile can distort the edge and/or the feature. These should be located at least ½ of the diameter (or width) of the feature away from the edge of the profile.
Rule #7: Max Bend Radii When Possible Tight corners cause cracking in harder materials due to stresses generated in the outer fibers of the bend. Small radii can also increase tool wear and breakage, lessen roll life, and require a mill with greater horsepower. While tighter radii can be accommodated sometimes, none of these things are optimal for roll formers or for your cost. To avoid these issues, allow for a minimum radius of 1-½ to 2 times material thickness.
Rule #8: Symmetrical Design Asymmetrical parts are more prone to twist and other types of distortion in the finished shapes. Designing your part as symmetrically as possible can decrease or eliminate the probability of warping. Many parts cannot be designed symmetrically; Dahlstrom can accommodate these projects in roll tool design and machine setup parameters.
Rule #9: Keep Punched Features Away From Bends Fabrications such as slots, notches, and holes can distort themselves or the part when placed incorrectly. Issues arise when they’re placed too close to (or directly on) the bend line, as well as when they’re placed too close to the edge. To avoid this issue, the edge of the hole or slot should be at least 3x material thickness away from the tangent point of the nearest bend. Note: Harder materials with higher tensile yield will require more distance from the bend line.
Rule #10: Keep Tolerances Loose As mentioned in the tolerances section of this eBook, Great Roll Formed Parts have loose tolerances to reduce part defect rate and keep lead times low. (Don’t worry too much about defective products; Dahlstrom has a field defect level of 1,432 ppm. Six sigma level is 2,700.)
Summary So, what makes a Great Roll Formed Part?
● Readily available materials that are easy to roll form AND fulfill the requirements of your project
● Less strict tolerances allow your manufacturer some freedom in fabrication and bend placement, while maintaining your product standards ● Following the ten design “rules” as closely as possible.
If you want to know more about design accommodations, or you’d like to get your Great Roll Formed Part in the works, feel free to contact us! We are happy to take calls during normal business hours at (021) 67228332. To reach a representative by email, see our contact page.