Pre-Cut Or Post-Cut Roll Forming Lines? Which Is Better?

Both methods have their advantages, it just depends what's best for your production requirements

Roll forming lines can be configured in two ways to create length-specific formed parts.  One method is pre-cutting, which involves cutting the steel coil before it enters the roll former.  The other method is post-cutting, where a profiled shear cuts the sheet after it is formed.  Both methods have their advantages, and the choice depends on specific factors related to your production requirements.

roll forming machine

With advancements in technology, both pre-cut and post-cut lines have become highly effective and efficient configurations for roll forming.  The integration of servos and closed loop controls has revolutionized post-cut flying shears, providing them with increased speed and accuracy.  Moreover, anti-flare fixtures can now be controlled by servos, allowing a pre-cut line to achieve comparable flare tolerances to a post-cut line.  In fact, some roll forming lines are equipped with both pre-cut and post-cut shears, and with the help of advanced control features, the entry shear can make the final cut of the order, eliminating the scrap that has traditionally been associated with post-cut lines.  This technological progress has truly transformed the roll forming industry, making it more efficient and sustainable than ever before.

Pre-cut shears offer the advantage of being able to handle higher production lines.  Whether the machine accumulates steel in a pit to allow for continuous shearing with minimal downtime or utilizes a rotary shear, production rates can be significantly increased.

Trapezoidal IBR Roofing Sheet Roll forming lines can be set up with multiple configurations to punch and cut off parts in a continuous operation.  For cutting a part to length, the lines can be set up to use a pre-cut die where a single blank runs through the roll mill, or a post-cut die where the profile is cut off after the roll forming process.

When corrugated metal sheet roof panel roll forming producers are making serious decisions about new roll form products, it is critical to consider the best mill configuration to produce the desired product.   

The options involve when to make the cut-off, choosing between roll forming pre-cut material or post-cutting the material.   

With pre-cut material, the strip is cut before entering the roll forming mill, whereas with post-cut material, the strip is cut after the product is shaped through the roll forming mill.   There are advantages and disadvantages to each choice.   

The following points should be helpful in choosing the best option for your roll forming application:

Advantages of a post-cut roll form line:

Increased standing seam roofing panel machine production and less downtime, since material is fed continuously through the roll formerTypically, fewer forming stations are required, since there is no need for the material to self-thread

After a new coil is threaded, the leading edge of the profile does not get deformed

Tooling tends to wear longer between reconditioning, yielding more linear footage

End flare, twist, camber and bow defects are easier to control

Minor mill adjustments are possible with continuously fed material under load in the roll former

Part lengths are not limited by mill specs (i.e. horizontal centers);  if floor space is an issue, the parts can be run directly to the outside of the building

trapezoidal roofing machine

Disadvantages of a post-cut roll form line:

Edge condition from the cut-off die can leave a slight burr and/or distortion with hemmed parts or non-supported areas of a cross-section

More cut-off die inserts are required, when there are many sizes or combinations for a given product

Sometimes it is better to form a pre-cut strip, when there is a severely notched feature in the product

When ridge cap roof panel machine pre-notching is needed, the mill system requires additional capital to add the cut-off press to the system

Double Deck Roof Roll Forming Machine

Advantages of a pre-cut roll form line:

Custom Roll Forming Generally, it is less expensive to utilize an existing electronic feed system already used in the pre-shear, as opposed to adding a second post-cut press at the end of the mill

Hand feeding strips is more economical for low-volume production

Some notch configurations make it easier to run pre-cut strips

Combination roll tooling that forms multiple strip widths does not require shear die changeover

Parts with severe notches or complex cross-sections may not cut well after glazed tile roof roll forming

IBR Trapezoidal Forming Machine

Disadvantages of a pre-cut roll form line:

Strips must self-thread without damage to the lead edges, normally requiring additional forming stations

Lead and trail ends of pre-cut strips are not supported against adjacent roll passes, resulting in straightening issues

Auxiliary guides may be required to control the material as it transitions from pass to pass

Tooling generally experiences more abuse and wear from lead-in edge of profile

End flare condition on exit and lead-in edge can be more prominent on pre-cut parts

Twist, end flare, and bow are harder to minimize, when forming pre-cut parts – especially asymmetrical profiles

Material can jam or double up in production and cause damage to the roll former and tooling

Producing shorter parts has limitations – the profile should be engaged in three forming stations at all times

If Trapezoidal Roof Sheet Machine floor space is a concern, longer parts require a material conveyor between the pre-notch press and the roll former, equal to or greater than the longest part

IBR roofing machine