Professionals use CNC machining to shape acrylic for a variety of industrial uses. While it allows for flexible use, acrylic materials frequently break down when compressed or stretched. This means that caution is required when shaping or cutting it. CNC machining is the best tool for acrylic because it works quickly and with precision.
The Advantages Of Acrylic And Why Machining Is Best For It
Acrylic is such a widespread material because of its outstanding properties. First, and most important, it is 5 times stronger than glass. And by stronger, I mean shock-resistant and shatterproof. It is also very transparent. Acrylic has 92% transparency, meaning only 8% of the incoming light is lost when passing through it. To compare, window glass is 83-90% transparent, polycarbonate has 90% transparency. Sure, the difference is small but it is there. Apart from transparency and unlike other plastics, acrylic does not deteriorate after being under UV light for long periods of time. PC, for example, becomes yellow, other plastics become brittle. The same things can be said about corrosion and water resistance.
What do those properties tell us? That acrylic parts are very durable, resistant, and transparent. That makes them perfect for a lot of applications. Car lights, shop and advertisement banners and emblems, light tubes, and others. All of the mentioned applications require the utmost precision and great surface finish. And adding to the fact that Acrylic is quite strong and rigid, acrylic CNC machining is a perfect solution.
CNC Acrylic Operation Types
CNC acrylic operations include:
• Drilling
• Turning
• Milling
• Engraving
Drilling
In CNC acrylic drilling, multi-point drill bits form cylinder-shaped holes in acrylic. With this operation, the machine sends the drill bit through the acrylic perpendicularly. It will then form vertical holes that feature diameters that equal the size of the bit used for the process.
Turning
With CNC acrylic turning, the machining process involves the use of a spinning single-point cutting machine that is designed to eliminate material from a revolving acrylic workpiece. The CNC machine used for this type of job generally feeds the machine in a straight line across the surface of the acrylic.
Milling
In CNC milling acrylic, you’ll be using a spinning multi-point cutting machine to get rid of excess material from the acrylic sheet. When this type of CNC machine is used, it will typically send the workpiece into the cutting machine in the same direction that the machine is already spinning.
Engraving
CNC acrylic engraving is the process of adding a design, symbol, artwork or marking onto an acrylic product. The automated equipment can engrave something quickly and accurately, so it will look identical each time it is done.
Considerations for CNC machining acrylic parts
Choose The Right Cutter
In order to cut acrylic, CNC machine edges must be razor-sharp and strong. This will help prevent acrylic from melting, which negatively affects appearance and functionality. When CNC machining acrylic, stay away from cutters that have been previously used with metal as they will likely have cuts or jagged edges. Smooth, sharp cutter edges can also prevent poor surface finishes.
The material of your cutter is also important. For example, high-speed steel cuts acrylic but doesn’t give a great surface finish. Diamond cutters will give an improved surface finish, but are very expensive. Carbide is often a choice material for CNC cutting acrylic.
For CNC machining acrylic, cutting edge rake angles of 5 degrees and clearance angles of 2 degrees are also recommended.
Choose the suitable acrylic material
Choosing a suitable material is one of the most important things for a correct cutting strategy to create an acrylic piece. So, choose good quality acrylic material and acrylic sheets for your design. It suggests choosing cast acrylic than extruded acrylic as cat acrylic is more clean and easy to cut through during the cutting process. Extruded acrylic can not prove suitable for cutting and get gummy while you cut it.
Different toolings are available for CNC router, such as compression, straight and spiral flutes, and single, twin, and triple flutes. The coating makes the task extremely difficult to complete, but if you select the right tool for your work, it can make a clear distinction between a clean and perfectly smooth cut.
A high-quality router bit is necessary while operating with plastics, and an upward spiral, single flute geometry provides excellent results on acrylic without losing quality. The upward geometry ensures optimal chip extraction and a smooth and consistent finish. Tool selection with the shorter flute length is recommended for best cut quality, and it will be helpful to reduce cutter deflection and chatter.
You must meet an expert who will help you in your tool selection and buying process and determine the suitable material.
Control the cutting speed
It would help control the speed for accurate acrylic CNC cutting. For the precise cutting of the acrylics parts, the spindle speed is recommended to be 18,000 RPM. You can use higher RPM, but it can cause material melting. So, to prevent material from melting, you have to adjust the feed rate at high RPM for the cutting process. Initially, it would help if you used this feed rate for food best cutting. You can set the feed rate on the lower end and multiply the current feed rate to make a new feed rate for your tool.
If you want to get the best results, it is good to divide the cutting process into two small parts, and each part needs to perform with a different tool. You can preserve your finishing tool for a long time, and this action, in turn, enables you to get a high-quality finish. To maintain the highest quality, and if your quality starts to decrease, you should replace your finishing tool regularly.
Coolants
In any kind of CNC acrylic cutting process, keeping the temperature to a minimum is a must. That is why a lot of acrylic sheets are cooled down before machining. It makes for better chip removal and a lower starting temperature. Apart from that, you can use some standard coolants, however, if they have oils, make sure those don’t react with PMMA.
Postprocessing Machined Acrylic
Having achieved the desired precision and form of the acrylic parts, it is always necessary to grind and polish the parts. That is usually done by consecutively applying polishing tools with a smaller grit and a linen towel with polishing paste at last. Apart from that, there are some chemical polishing methods that involve pouring special gas to melt the outer layer of acrylic. And the last but not least are exotic diamond tool single tip milling processes, when a tiny amount of plastic is cut from the surface by a very sharp and durable single-tip mill.
Acrylic CNC Machining Service
Acrylic CNC service is a complex process. However, CNC machining permits greater accuracy and efficiency when forming products from acrylic. This accuracy means less material waste, allowing you to limit the overall cost of a project. At CNC Services China, we provide high-quality CNC machining parts and global delivery. For more information, contact us today.