# Roll of Material Calculation

Our current procedure for obtaining the partial quantity of  rolled materials are based solely on visual approximation of the employees. These materials are issued and used for specific products and the unused materials are returned to our stockroom after all the proper transactions are performed. In order to increase the accuracy of the approximation of rolled materials, I came up with a formula of calculating the length of rolled materials.

Calculations shown below can also be used for many types of rolled material such as rolled carpet or roll of paper. Company-wise, it can also be used to calculate the partial length of SRP, left/right split tape, membrane, center glass, shim, laminate, blank and printed foil. For this example, the shim material for Main Body equipment is used.  Note that variations of the linear length due to stretching and compaction of material are ignored.

Initial data are recorded as shown below:

• Core Diameter: 8.20 mm
• Outside Diameter: 19.60 mm
• Length: 430 ft.

The area of a rectangle can be calculated by multiplying its length times its width. For this example, the width will be the thickness of our shim material.

• Area(rectangle) = Length * Thickness—> A = L T

The area of a circle can be calculated as shown below.

• Area(circle) = Pi * Radius^2 —> A = pi * R^2

The area of the rolled(shaded) material can be calculated by calculating the area of the whole circle minus the area of the core circle as shown below.

• A = pi * Ro^2 – pi * Rc^2

Substituting the Area of the rectangle into the area of the rolled material leads to the following equation.

• L*T = pi * Ro^2 – pi * Rc^2

Thickness of Material Calculation

The formula above can now be simplified to give the thickness of material given the outside radius, core radius, and the length of material.

• T = ( pi * (Ro^2 – Rc^2) ) / L

to be continued…. About Editorial Staff