Appendix B. Sourcing Materials
The first step in planning a CNC project is to find the right materials in your area. Get familiar with local suppliers and make visits to see the range of materials they carry. You can find sheet materials at big box home improvement centers, as well as local architectural material suppliers and lumber yards. Local yards often have a wider selection of sheet materials and offer expertise from an especially knowledgeable staff. Most will deliver the goods that you select and pay for in store.
Tips
- Consider green materials
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As you source plywoods, consider materials that are easier on the environment, you, and your shop. Plywoods and engineered products that come from sustainably managed forests and use clean, low VOC adhesives will usually be labeled accordingly (FSC Certified, for instance). If you are concerned with the embedded energy that comes from transporting heavy lumber products over great distances, look for regionally manufactured products. If cost is an issue, consider the lifecycle of the material itself and how your project will perform over the long term. Spending a bit more for a durable, quality sheet product will ultimately yield the most value in a long-lasting piece of furniture.
- Examine multiple sheets
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When shopping for plywood, examine multiple sheets to find a sheet with a nice grain, minimal camber, and relatively consistent thickness for your project. If you’re working on a project that uses multiple sheets, try to find some consistency across all sheets.
- Always purchase surplus
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Always purchase surplus material for testing and for recutting parts. For your first project, it’s sensible to purchase a second sheet of plywood, or cut a small project and reserve the other half sheet for testing. Surplus material is also useful for creating partial prototypes or in the event that a part is damaged during the cutting, finishing, or assembly process. Having extra material on hand ensures that you can easily cut a replacement part for one that was damaged by human or machine.
Materials We Like
With some research, planning, and practical design decision making, your CNC furniture project should be something that will be used and enjoyed for a very long time. This is a small, but well-researched list of products that balance sustainability, machining performance, and beautiful results:
Plywood and Other Sheet Materials
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Columbia Forest Products PureBond plywoods
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Araucoply sanded panels
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Radiata pine plywood
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ApplePly prefinished and unfinished plywoods
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Koskisen Baltic birch plywood
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Valchromat colored MDF
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Plyboo edge grain bamboo plywood
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Gill Corporation Gillfab 5030 Aluminum/Balsa Panels
Sheet Materials Beyond Plywood
You can make the furniture projects throughout this book using almost any sheet material. You’re really only limited by what your CNC machine can cut, and a few other factors. Materials with dimensional consistency and a high strength-to-weight ratio are particularly well suited for fabricating large-scale furniture projects with a CNC.
You can find greater consistency in dimensionally stable materials like plastics, composite, or metal as well as engineered wood products like OSB or MDF. However, measuring and inspecting any of these materials prior to purchasing ensures that you know exactly what you’re using for a project. The following is a short list of sheet materials that work for fabricating CNC furniture:
Engineered Wood Sheeting (MDF & OSB)
Materials like medium-density fiberboard (MDF) and oriented strand board (OSB) are monolithic, manufactured sheet goods, which offer excellent dimensional consistency. They are sustainably manufactured from industrial wood waste, very easily sourced, and usually quite inexpensive. OSB has plywood’s great strength to weight ratio and machining qualities. MDF, on the other hand, is incredibly heavy for its strength and can prove quite messy when machining.
High-Density Polyethylene (HDPE)
High-density polyethylene (HDPE) is a plastic sheet material with integral color and a solid core. It is waterproof, UV stable, and quite durable, making it suitable for outdoor furniture. It is impact resistant, strong, and easily machined. It is also quite heavy, making it more suitable for smaller projects that don’t require long spans. HDPE is also quite expensive and usually must be special ordered.
Composites
There are a vast array of composite panel products developed for aerospace, transportation, maritime, and other industries. Such panels are either made of solid, integral reinforced resins, or else comprised of two outer skins sandwiching a solid or cellular core material. They are usually expensive and often hard to source in small quantities. However, they are worth mentioning because many are designed with a very high strength-to-weight ratio and are intended for machining, which makes them an interesting and well-suited choice for CNC furniture projects.
Acrylic
Cell cast acrylic comes in a variety of colors and finishes, and is sold under the brand names Plexiglas, Perspex, or Acrylite. Its cost and strength to weight ratio make it ill-suited for full-scale furniture. However, it’s mentioned here as an ideal accessory or scale-prototyping material, which can be either CNC routed or laser cut. Avoid the extruded acrylics, as well as polycarbonates, which are intended for thermoforming rather than machining.