Have you ever wondered how those super-clear displays, illuminated signs, and complex product prototypes are produced with such perfection? You may be surprised to find that the “magic” comes from CNC machining! CNC machining has ushered in a new era in material manipulation, and acrylic is one of its stars.
Acrylic is known for its clarity, but it is also extremely versatile, with the ability to transform from a flat sheet into a complex, beautiful part with the utmost precision.
However, to achieve this, acrylic requires a bit of finesse, and in the case of CNC machining, that comes from utilizing the right tools, techniques, and experience to extract the most from the material without cracking or melting it in the process. The final effects of CNC machining acrylic strike a balance between art and engineering.
Our intention is to provide you with some insight into CNC machining of acrylic parts. We hope to explain why this process works so well, the potential impacts of different (& beautiful) finishes, and the range of real-world applications of CNC machining acrylic, as well as important considerations you should be familiar with to best manage the processes for CNC, and secure accurate and repeatable results.
Why use CNC Machining for Cutting Acrylic?
Selecting the best production method is often the most crucial consideration in manufacturing, and when it comes to acrylic, CNC machining offers numerous benefits. As a manufacturing option, CNC machining has the highest level of precision and is economically advantageous. CNC machining is the most effective method for creating high-value parts for various applications.
Material Compatibility
CNC machining is well-suited for acrylic, largely due to the flexibility of CNC machining control over cutting speed and feed, which is particularly beneficial with acrylic, as it can be easy to create unwanted melting or cracking with incorrect cutting speed and feed.
CNC allows processes to have focused parameters that use as little heat and/or force as possible when processing the material, while still maintaining the best accuracy.
A CNC will cut, engrave detail and finish a polished surface on extruded acrylic or cast acrylic (harder, more stable acrylic) without issue, as it can take the make-up of the acrylic into account to accurately process the material.
Builds High Precision Parts
The most valuable benefit of CNC is being able to produce parts to such high precision; the computer can direct the cutting tool exactly to a pre-programmed specification (like a CAD model) – and at tolerances sometimes as little as a fraction of a millimeter.
This means complex shapes or patterns, as well as complex parts or features that require a perfect match, where paint would usually not be applied and typically have a perfect fit, which is impossible to achieve by hand. This level of dimensional accuracy is crucial not only for parts that fit together as part of an assembly, such as a display case or electronic enclosure.
Increased Rate of Production
Once you have written the design curriculum into the CNC, it is capable of remaking the same item at high speed and with accuracy, over and over. This is beneficial for both single Prototypes (one-offs) and series production (larger quantities). Fully automated systems can operate continuously with minimal oversight.
This produces parts faster than manual methods that require constant attention and increase the risk of mistakes related to fatigue. The speed of automated systems means projects can be produced in a shorter time period, allowing businesses to meet unreasonably tight deadlines and deliver their goods to customers faster.
Minimizes waste
CNC machines are also very efficient with material. The CAM software that runs the CNC machine can automatically lay out parts on a sheet of acrylic with pre-determined cutting paths.
This is achieved using a process called “nesting,” which arranges the shapes as closely as possible to one another, like a complicated jigsaw puzzle, to ensure that the most parts are cut out from a single acrylic sheet.
By nesting, waste is reduced to an absolute minimum! This saves money on raw material costs but, more importantly, it is a more sustainable and environmentally conscious method of manufacturing.
Results in High Repeatability
Because a programmed computer controls every aspect of the machining operation, each part produced is essentially identical to the previous one. Functionally, this repeatability means surface quality and consistency over long runs of parts.
Manual processes introduce variations and inconsistencies; a CNC machine performs the same programming commands the same way every time. This same part is able to provide assurance that the 100th part is just as accurate, which is monumental in regard to branding reputation and product reliability.
Saves on Manufacturing Costs
The cost of buying a CNC machine is high, but the cost savings over time are substantial. Since the manufacturing process is quicker, parts will be made faster. Less waste from material optimization, and there are no raw material costs. Automation capitalizes on and is less reliant on manual labor, meaning lower labor wage costs.
Additionally, CNC machining is capable of machining complicated parts from one setup or routing, often without the need for multiple machines or secondary operations. This streamlines production processes, which saves time and labor costs.
CNC Acrylic Finishes
The final look and feel of a CNC-machined acrylic part can be customized to fit any application. The finish process is just as important as the design and cut. There are a number of popular finish options that can be used to produce a variety of aesthetic and functional results.
Polished Finish
Typically, the goal for a polished acrylic part is when working with clear acrylic. A polished finish restores transparency to acrylic. Once the part has been machined, the cut edges might appear tinted or matte because of imperfections from the cutting tool. Polishing is the act of restoring the edges of the cutting tool.
Polishing can involve flame polishing (taking a hot, pointed flame and passing it over the edge surface with care to melt it to a smooth surface), or vapor polishing (taking the edge and exposing it to a chemical vapor). A polished edge restores the optical quality of the acrylic. The edges will look as clear and glossy as the surface, which has a dramatic impact on display cases, awards, and decorative items.
Matte / Frosted Finish
Sometimes, you don’t want perfect clarity; you want a look that isn’t shiny or see-through. You can get a matte or frosted finish by using certain types of cutting tools that leave a less reflective surface, either after the fact by sandblasting the surface with a fine abrasive, or sometimes even during the machining process. This finish is perfect for privacy screens, lighting diffusers that soften and spread light evenly, and any other use where you want to cut down on reflections and fingerprints.
Machined Finish
The “as-machined” finish is the surface finish that the cutting tool leaves behind right after it finishes cutting. With the right tools, sharp bits, and the best cutting settings, this can be a very smooth and high-quality finish on its own, with only very small, even tool marks showing. This finish is fine for many functional parts where looks aren’t the most important thing. It saves time and money on extra finishing steps like polishing or sanding.
Engraved Finish
CNC machines are great for putting detailed logos, intricate designs, or clear text on acrylic. The machine’s accuracy lets it make engravings that are very sharp and detailed, with a consistent depth. People often use this to make custom signs, awards, and other items that are unique to them. The engraved parts often look frosted, which looks great next to the clear acrylic. This adds a layer of branding and customisation to the part.
Applications for CNC Acrylic Parts
CNC-machined acrylic is used in many different fields and for many different purposes because it is clear, strong, and adaptable. Designers, engineers, and innovators all over the world use it because it can be shaped with great accuracy.
Signage and Displays
This is one of the most common and easy-to-see uses. Acrylic is the best material for everything from the big, lit-up channel letters on a storefront to the classy point-of-sale displays in a store. It looks like glass because it is so clear, but it is much stronger and lighter, making it safer and easier to put up. You can easily engrave it with logos, print on it, or stack it to make amazing 3D effects.
Protective Covers & Enclosures
Acrylic is often used to make protective covers for machinery, electronics, and museum artefacts because it is strong and won’t break. It is easy to see and check what’s inside because it is clear, and it keeps things safe from dust, moisture, and accidental impact. CNC machining makes these enclosures fit perfectly around any object because it is so precise.
Lighting Components
Acrylic is unsurpassed for its light transmission and diffusion properties; therefore, the material is widely used in the lighting sector to make custom lighting fixtures, lightguides for the transmission of light from an LED source across a panel (e.g., in laptop screens), to large-scale architectural lighting pieces. Designers often use a frosted or matte finish to create a soft ambient light or a polished finish to aim light with crystal clarity.
Architectural & Interior Design Elements
Designers love acrylic for its modern and clean feel; architects and interior designers can very easily modify it into virtually any shape. From creating custom furniture like tables and chairs to wall paneling, staircase railings, and room dividers, acrylic is widely used as both a design element and a functional piece.
Being able to CNC cut acrylic into virtually any shape gives architects, interior designers, and furniture designers the freedom to express unique, playful, and breathtaking spaces.
Prototyping & Product Development
When designing a new product, a high-fidelity prototype is an important part of the process in development. CNC machining enables designers to create a high-fidelity prototype in acrylic that looks and feels like the final product, quickly and inexpensively.
CNC machining high-fidelity prototypes is particularly useful for products that have transparent elements, such as consumer electronics, kitchen appliances or even medical devices. Designers can test form, fit and function prior to investing in expensive molding.
Considerations for CNC Machining Acrylic
CNC machining is a great process for working with acrylic, but it can also be challenging. Acrylic requires specific treatment to achieve the best results. Keeping an eye on just a few detail-oriented practices can be the difference between a perfect part and a melted, chipped or cracked piece of plastic.
Choose the Right CNC Cutter
Your cutting tool will make a huge difference in the outcome. For acrylic, use bits specifically designed for plastics. These would typically be solid carbide, single or double-flute bits. The cutting geometry of these bits is designed for making clean shearing cuts in plastic, and, just as importantly, they clear the chips out of the way. If chips do not clear quickly out of the way, they can melt due to friction and stick to either the tool or the workpiece, ruining the surface finish.
Keep an Eye on Cutting Depth and Direction
Don’t get greedy and try to take too much material off in one cut. By taking shallower passes or “step downs”, you place less stress on the acrylic and the cutting tool itself, which greatly reduces chipping or cracking of the acrylic part. Also, note the direction you are cutting in. Using a “climb milling” direction, where the cutter rotates in the same direction as the feed, gives acrylic a better, smoother finish than “conventional milling”.
Using the Right Bits and Ramps
Rather than going straight down with the cutter into the material to start the cut, it is best practice to use a ramping function. Ramping in at a shallow angle allows the cutter to engage gradually, which decreases the resulting cutting forces and reduces the risk of fracturing the material with excessive initial force. Using bits with an “O-flute” configuration is highly recommended for acrylic because the unique-shaped shaped highly polished flute and overall geometry transport chips up and away from the cutting areas.
Use the Right Acrylic Material
Not all acrylic is manufactured in the same way, and the type of acrylic will directly influence how we machine the material. The primary types of acrylic are cast acrylic and extruded acrylic, with cast acrylic generally considered the superior option for machining. Cast acrylic is harder and has a higher melting temperature; therefore, it tends to chip cleanly away, providing a better surface finish in the end. Extruded acrylic is softer and has a lower melting temperature than cast acrylic, thus making it more prone to melting and gumming up the cutting tool. If you are using extruded acrylic, you will need to slow down your cutting speed and feed rate to avoid heat buildup.
Conclusion
CNC machining and acrylic are a perfect pair. This is a powerful process that offers the creative freedom of a myriad of experiences, and technical accuracy and precision. Utilizing CNC machining can produce a wide range of unique products from a simple sheet of plastic, such as signs or critical engineering components. This process has great capabilities for manipulating acrylic and accommodating precision.
By understanding the properties of acrylic and adhering to, or establishing, best practices, selecting the appropriate tooling, controlling cutting variances, and choosing the correct acrylic material, you can optimize your work with acrylic.
The result is not just a part but a great, expertly crafted piece of plastic that fulfills specifications, shows attention to detail in aesthetics, and proves the great capability of the new manufacturing advances.
FAQs
Q: Why are CNC machines suitable for cutting acrylic?
A: CNC cutting machines are a suitable option for acrylic cutting because they are precise manufacturing methods. They provide clean edges and complex shapes with great repeatability, which would be hard to replicate manually, yielding professional-quality parts every time.
Q: How does CNC machining affect the optical clarity of acrylic parts?
A: CNC machining can provide great optical clarity for acrylic components. The cut edge may appear slightly frosted initially, but polishing and other post-processing methods will yield excellent optical clarity, making it suitable for displays and protective covers.
Q: Are CNC machined acrylic parts acceptable for outdoor use?
A: Yes, many acrylic components are suitable for outdoor applications. Certain grades of acrylic are UV light resistant, preventing dulling and degradation, which makes them suitable for outdoor signage, as well as architectural pieces made with CNC.