Nesting

From Wikipedia, the free encyclopedia

This article is about the manufacturing process. For building or having a nest, see nest and Nesting, Shetland.
For computer-related nesting, see nesting (computing).

Nesting refers to the process of efficiently manufacturing parts from flat raw material.

Image 1: Simple rectangular nesting
Image 1: Simple rectangular nesting
Image 2: Improved Nesting with rotated parts
Image 2: Improved Nesting with rotated parts
Image 3: Minimizing waste by mixing different parts
Image 3: Minimizing waste by mixing different parts

Companies manufacturing parts from flat raw material such as sheet metal use a variety of technologies to perform this task. The sheet metal nesting for flat sheets and nesting for coils are different algorithms. Material may be cut using off-line blanking dies, lasers, plasma, punches, shear blades, ultrasonic knives and even water jet cutters.

In order to minimize the amount of scrap raw material produced by this process, companies use nesting software. The software analyses the parts (shapes) to be produced at a particular time.

Using proprietary algorithms, it then determines how to lay these parts out in such a way as to produce the required quantities of parts, while minimizing the amount of raw material wasted.

A number of off the shelf nesting software address the optimization needs. While some cater to only rectangular nesting others also offer profile or shape nesting where the parts required can be any odd shape and not just rectangles. These irregular parts can be created using popular CAD tools. Most of the profile nesting software can read IGES or DXF profile files automatically, a few of them work with builtin convertors.

An important consideration in shape nesting is to verify that the software in question actually performs true profile nesting and not just block nesting. In block nesting an imaginary rectangle is drawn around the shape and then the rectangles are laid side-by side which actually is not profile nesting. There still remains a scope for waste reduction

Nesting software must take into account the limitations and features of the machining technology in use, such as:

  • Machining cannot take place where the raw material is clamped into place;
  • Some machines can access only half of the material at a particular time; the machine automatically flips the sheet over to allow the remaining half to be accessed;
  • When punching, the width of the punch tool must be considered;
  • Shearing may be permitted only in certain areas of the sheet due to limitations of the machinery;
  • A laser can cut parts at any rotation; a punch can only do so at right angles;

Nesting software may also have to take into account material characteristics, such as:

  • Defects on material that must be discarded;
  • Different quality areas that must match corresponding quality levels required for different parts;
  • Direction contraints, that may come from a printed pattern or from fiber direction;

Many machine manufacturers offer their own custom nesting software designed to offer ease of use and take full advantage of the features of their specific machines.

If a fabricator operates machines from more than one vendor, they may prefer to use an off-the-shelf nesting package from a third-party vendor. They then have the potential to run jobs on any available machine, and their staff should not have to learn several different software packages.

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