CNC Nesting: All About This CNC Cutting Method

Nesting is a method for arranging parts to minimize cutting time and material waste. Imagine using the outline of your hands to cut out parts. Hold them side by side and look at the space they fill. Now interlace your fingers and watch how the space shrinks. That’s nesting, a while the idea seems simple, the algorithms needed to figure it out have been around for around 80 years.

Nesting started with the “rucksack problem”: determining how to pack the most odd-sized objects into a fixed space. Think about packing for a long trip when you can only bring one piece of carry-on luggage, or a shipping clerk at Amazon trying to find the smallest box that holds your order.

Nesting algorithms can also solve the “best fit” problem. Imagine trying to figure out how to cut a group of random length pieces out of fixed-length boards, bars, or extrusions to minimize waste. Extend this to high-volume manufacturing, and the need for nesting tools becomes evident.

Overall Greater Efficiency

Nesting can do more than just juggle objects on a 2D layout. Different tools allow you to minimize travel movements of a hot end or CNC cutter, share a common cut line across multiple parts to eliminate skeletons, and cram multiple parts into the working volume of a 3D printer. Expensive tools and skilled laborers help make nesting critical to production efficiency and cost savings.

If you work with subtractive CNC (routers, milling machines, laser cutters, waterjet, or plasma cutters), you’ll benefit from 2D nesting, especially if your workflow supports SVG files. Additive manufacturing, such as 3D printing can also benefit, but at the cost of a much higher learning curve and more complicated software.

The simplest nesting packages draw an imaginary box around each object, juggling these rectangles to minimize waste. More elaborate solutions offer profile or shape nesting, embedded parts, and taking into account odd shapes and subtle opportunities to fit them together.

The highest-end tools add priority (cut the most important parts first), shared edges (one cut line for multiple parts), and travel time minimization. After all, a cutter that isn’t cutting isn’t making you money.

Another important concept is static versus dynamic nesting. Static nesting software fits a specific set of objects into the smallest space. Dynamic nesting picks and chooses from a list of potential parts depending on the size and shape of the raw material.

When Does Nesting Happen

Nesting fits into the workflow between design and machining. Once you’re satisfied with your part diagrams, feed them to the nesting software, which rearranges everything into a tighter and tighter formation. You tell the software how long to optimize and the nesting algorithms arrange and rearrange, calculating the total material needed after each pass. The pass with the least material is saved and handed back to your workflow for CAM conversion to G-code.

Different nesting CNC tools may require SVG, DXF, DWG, IGES, or DSTV files. It’s wise to validate input and output formats with the software vendor.

Below are a few common and popular nesting software options:

• TruNest: TruNest from Autodesk offers industrial workflow support at a price. It handles multi-user workflows, a pre-processor that confirms an object drawing can be nested, customized interfaces, order scheduling, and many other features valuable to large design and production facilities.
• Deepnest: Deepnest is another open-source nesting product, in this case optimized for laser, plasma, and water jet cutters. It runs on Windows, Mac, and Linux. It reads DXF, SVG, and CDR files, and writes to DXF or SVG. It offers cut line merging and part-in-part layouts to maximize material use and minimize cutting time.

• SVGnest: SVGnest is free open-source software available for download from GitHub. Described as a browser-based vector nesting tool, the software claims to work for arbitrary containers and concave edge cases and performs on-par with existing commercial software. It’s limited to SVG inputs and outputs.
• D4 Nest: D4 Nest brings true nesting to 3D printing. The company claims the software can arrange 3D models in a given space to minimize the total height and limit size to machine capacity. It offers a free trial and monthly subscriptions at the individual, service bureau, and OEM level.

Nesting brings two important benefits to CNC operations: It reduces waste and saves time. Tools include open-source, simple file import/export workflows to multi-user large scale production tools.

Keep in mind that 3D nesting is a far more complex problem, especially when supports, sintering shrinkage, bridging limits, and other technical limitations are taken into account. There are many more 2D options, especially at the hobbyist and limited production level.

We’ve explained how the tools work and a little about their workflow requirements. With open-source options at the cost of a download, there’s no risk to trying some nesting in your next project. Have fun and good luck!

(Lead image source: cncdynamics.co.uk)