Custom Roll Forming

Pyramid Mouldings' roll forming offers an economical and highly repeatable process with close tolerances on part length, width and cross-section detail. Pyramid facilities can handle roll forming needs for most any industry with over 65 roll machines with 1" to 3" spindle size.

What is Roll Forming?

Shown below is a roll form “flower diagram." It shows how the desired cross section is gradually formed. The material starts as a flat coil or blank and each pair of rolls or pass adds some shape.

 

 

Roll forming is a continuous metal forming process taking sheet, strip or coil stock and bending or forming it to a continuous cross section. The process is performed between successive pairs of rolls that increasingly shape it until the desired section is completed.

The roll forming process can be used to form a wide variety of cross-section profiles. An open profile is most common, but a closed tube-like shape can be created as well. Because the final form is achieved through a series of bends, the part does not require a symmetric cross-section.

 

Advantages of Roll Forming A Metal Part

• The roll forming process allows operations such as punching, notching, and welding to be performed in-line. Labor cost and time for secondary operations are reduced or eliminated, reducing part costs.

• Roll form tooling allows for a high degree of flexibility. A single set of roll form tools will make almost any length of the same cross section. Multiple sets of tools for varying length parts are not required.
  
  
• Roll forming can provide better dimensional control than other competing metal forming processes.
  
  
• Repeatability is inherent in the process, allowing easier assembly of roll formed parts into your finished product, and minimizing problems due
  to "standard" tolerance build up.
  
  
• Roll forming is typically a higher speed process.
  
  
• Roll forming offers customers a superior surface finish. This makes roll forming an excellent option for decorative stainless steel parts or for parts requiring a finish such as anodizing or powder coating. Also, a texture or pattern can be rolled into the surface during forming.
  
  
• Roll forming utilizes material more efficiently than other competing processes.
  
  
• Roll formed shapes can be developed with thinner walls than competing processes.

Roll Forming Techniques

 

There are two common roll forming techniques with variations:

1) Pre-cut or cut-to-length roll forming

• Strips are pre-cut and processed, then fed into the roll former as individual strips. These strips may be cut from a coil or sheet.
  
  
• Processing may include piercing, notching, embossing.
  
  
• Typically used for low-production parts, or parts with certain types of notches.

2) Post-cut roll forming

• Pieces of the cross section are cut to length after forming. This process implies working from a coil of material.
  
  
• Strip can be pierced, notched or further processed before the cutoff operation.
  
  
• Cut-off system moves with the strip and can add other features.

Roll Forming Materials

 

Almost any material that can tolerate bending to a desired radius can be roll formed. The more ductile a material is, the better it will roll form. The roll forming process can handle ferrous, nonferrous, hot rolled, cold rolled, polished, plated or pre-painted metals producing excellent results.

Material Spec Qualification:

• Materials as thin as 0.005" and as thick as 0.1875" can be roll formed.
  
  
• Material pieces as narrow as 1/8 “ and as wide as 72" or more can be roll formed, depending on machine size.
  
  
• Pyramid’s range of materials is
  
  
• .005" to .187" thick
  
  
• .500" to 20.00" wide

Roll Forming Examples From Pyramid Mouldings

#1 Fairing Support Rail - 7835

• .071" G90 HDG
• 20 roll passes on 2" mill
• All holes pre-notched, repeating pattern with multiple lengths
• Parts powder coated black
• Multiple angles in a relatively heavy gauge
• Straightness, twist, bow, flatness of this section is very critical – total indicator reading for flatness

#2 Rear Window Shade Toyota Camry - 7824

• CRS 0.029" thick
• 24 passes
• Pre-notch, part complete off roll machine
• Very difficult section
• Very close tolerances on slots and holes

 

#3 Main Frame For Office Partition - 7864

• 0.056" thick CRS
• Uses 26 pass roll line
• Uses striped pre-painted steel
• Location of striping critical due to welding process
• Difficult roll section due to shape and need to keep section uniform
• Twist, bow and straightness critical
• Tolerances and shape of section critical to customer assembly

Design Considerations

• Bend Radii:

  • Best practice is a one metal thickness inside radius
  • May need slightly larger in high strength steels
  • Sharper corners can be obtained at the expense of tool life
  • Scoring the inside of the strip can help make sharper corners in some cases
    
    

• Deep Sections:

  • Require more passes, larger machines and larger rolls and dies
  • Risk overstressing the edges of the material
  • Typical machines – 100 mm max
    
    

• Short Legs:

  • Three times metal thickness is a good minimum leg length
    
    

• Wide Sections:

  • Apply ribs to offsets to wide panels
  • Helps prevent wrinkles, "oil-canning"
  • Often wide material has appearance issues
    
    

• Cross Section Tolerances:

  • Typically +/- .25 mm to +/- .75 mm
  • Tighter tolerances are achievable: a) different approach to tooling and b) special quality materials
  • Angular tolerances; typically +/- 1 degree
    
    

• Length Tolerances:

  • Influenced by factors, including length of part, speed of rollformer, measuring system, cutoff system and material properties
  • Commonly available: +/- 0.8 mm
  • Special equipment and tolling: +/- 0.25 mm
  • Long parts (3M or more): +/- 3.0 mm and up
    
    

• Straightness:

  • Bow (up or down)
  • Curve (side to side) – 1.0 mm per meter
  • Twist – 1 degree per meter
    
    

• Flare:

  • Typically avoid measuring the cross section within 50 mm or ends
  • Flare can be controlled with special attention