Coil-fed processing: 4 quick formulas for production planning

Coil fed processing is a simple and effective way to introduce lean production concepts in sheet metal fabrication: in line production, continuous process, reduced WIP and minimum waste.

Four quick formulas help production planning, and answer these simple questions:

- How to calculate coil length from inner diameter, outer diameter and thickness?

- How to calculate the running time for a metal coil?

- How to calculate coil length from weight, material type, width and thickness?

- How to calculate coil weight from width, outer and inner diameter?

This article will show how these formulas are obtained, to provide tools that can be easily adapted to new materials and conditions.

Follow the links and discover more on roll forming lines and coil fed punching and laser cutting systems.

Defining a metal coil?

First of all, let’s determine which are the basic information defining a metal coil.



The coil internal diameter (ID measured in [mm]) depends on the type of re-coiler of the slitting line. Most common bore sizes are 508mm, but also 406 and 610mm are used.

The coil outer diameter (OD measured in [mm]) depends on the capacity of the service center. It must be also checked with the geometrical characteristics of the uncoiler where the metal coil will be processed.

In the following calculations, the thickness (T, measured in [mm]) of the metal coil means the total thickness - including paint if present. In case of coated coils, the thickness of the paint can be between 0,03mm and 0,08mm: note that some producers of coated coils, indicate only the metal thickness on the coil labels. The paint thickness can slightly influence the results of the formulas.

The coil width (W measured in [mm]) is the transversal dimension of the coil, and together with the previous information it allows the calculation of the coil length (L measured in [m]), which is an important data to calculate the quantities that will be produced with one coil.

The material type is important to define the density of the metal (D, measured in [kg/dm^3]). Here are some references for the most common materials:

- Carbon steel, Galvanized steel and Aluzinc: 7,85 kg/dm^3
- Stainless steel: 8 kg/dm^3
- Aluminum: 2,71 kg/dm^3
- Lead: 11,3 kg/dm^3

Having the geometry of the coil defined, it is easy to calculate the metal coil weight (measured in [kg]).


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