Nesting refers to the process of looping and iterating on a large raw material in the manufacturing industry, constantly changing and adjusting the placement of parts, arranging cutting patterns, and always finding the best combination to minimize the waste of raw materials.
Nesting can also be called nesting and cutting. It’s an old concept that both carpenters and tailors must consider how to make good use of raw materials and make things out of the least amount of material when doing something.
When an artisan makes a nesting, a common method is to make a paper pattern of the parts in advance, lay them out on raw material, and finally get a solution that the craftsman thinks is the best utilization. This process is nesting, so the English word is Nesting, which means constant change and adjustment, iterating on a large raw material to find the best combination and maximize the saving of raw materials.
In subtractive material manufacturing, nesting is the process of arranging cut parts to minimize raw material waste. It generally refers to the cutting or machining of sheet metal, such as manufacturing parts from sheet metal, steel plates, wood sheets, etc.
There is no need to subtract raw materials in additive manufacturing, there is no need to consider raw material utilization, and material savings do not exist. However, in additive manufacturing, there is the issue of printing efficiency and utilization of effective printing area, which is the specific application of nesting. For example, in a single printing process, multiple parts are nested and combined according to the shape to print as many parts as possible at once.
There are various nesting algorithms. The most common one is the rectangular nesting algorithm, which means that the outer rectangle of the part is chosen to be the part for nesting. When a nesting algorithm is chosen, the basic principles of nesting are specified, such as whether the piece can be rotated, whether it can be turned over, whether the size parts are mixed, etc. Finally, the relatively best solution is obtained. The user can select all nesting algorithms and finally choose the best nesting result based on material utilization.
Because the geometric shape is not limited to special-shaped nesting, a compromise is required regarding calculation effect and time. Although it seems that the impact of the genetic algorithm[1] is good, and the calculation time can be long or short, it is a good choice.
The nesting is done through nesting software, which is generally very expensive for professional nesting software related to factory efficiency. The purpose of nesting software is to minimize scrap. The software can usually read in DXF or IGES design files, and the algorithm determines how the parts should be placed. The software must consider the characteristics of the process, such as laser cutting, tool cutting, plasma, for nesting the data generated by the software is different.
For laser, plasma, and other cutting methods, you also need to consider leading-in and lead-out lines[2] so that you have to avoid hurting the surrounding parts because of the lead lines. For tool cutting, you also need to consider the size of the tool complement[3], whether the need for a common line[4], and other issues.
The software must consider the order of cutting, such as whether the inside is first and then the outside or the outside is first and then the inside, and whether the holes are punched first and then the holes are punched. The software also must consider the textual constraints of the part, such as the orientation of the fibers, the direction of printing, etc. There is also a need, for example, for leather nesting, where there may be defects in the original raw material, and then these areas must be removed during the nesting process to do so.
In short, nesting software should simulate as much as possible the process of natural human artisan thinking and be faster than artisan calculation because efficiency is effective.
Figure 2-32 shows a schematic diagram of the algorithm for a letter-cutting nesting, and Figure 2-32-2 has the best utilization.
Figure 2-32-1
Figure 2-32-2 Schematic diagram of the nesting algorithm
In smart manufacturing applications, the nesting function is usually made into a standard service rather than a separate software in the traditional sense. Users can easily use the nesting service to achieve this. When using nesting services, it is important to note that different processes have different requirements for nesting data. Therefore, it is important to understand the meaning of various parameters to use the nesting data accurately when using intelligent machines to place materials.
As long as manufacturing is involved, we may encounter various nesting problems. First, we must figure out the principle and purpose behind it and then design different algorithms for nesting according to the needs.
Figure 2-33 shows the nesting diagram of the actual smart manufacturing process.
Figure 2-33-1 Wooden chair parts diagram Figure 2-33-2 Diagram of the chair set
[1] a genetic algorithm is a metaheuristic inspired by the process of natural selection that belongs to the larger class of evolutionary algorithms. From https://en.wikipedia.org/wiki/Genetic_algorithm
[2] Lead-in and lead-out lines are used during for the beginning and ending cutting for the best cutting results due to processing reasons.
[3] Tool complement is an offset or shit from center of the tools shaft to the cutters edge along a programmed path.
[4] Common line is used for cutting/netting to improve cutting efficiencies and quality.