Complete Guide to CNC Acrylic Machining Process
Today’s article will provide insight into CNC acrylic machining that aids us in optical prototyping. CNC acrylic is one of the most common plastics in the current world of manufacturing that rival glass and polycarbonate. This since it finds an array of uses in lots of industries. At Creatingway, we use CNC acrylic machining in all manner of acrylic production. Here are further details as to how we pick the right workpiece, cut, and engrave it through CNC routers. We will also cover what to do after finishing the cutting operations.
Why Do We Carry out CNC Acrylic Machining?
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What Are the Pros of Acrylic Machining?
Acrylic comes with some of the most amazing features which enable its widespread use. Firstly, it is 5x stronger than glass. This strength makes it shatterproof and resistant. In addition, it offers 92% transparency and thus we only lose 8% of the light that traverses it. Meanwhile, window glass offers 83-90% clarity while polycarbonate is only 90% clear. Other than clarity, acrylic does not degrade like other plastics after exposure to UV light for a long time. Some plastics become more brittle while others like PC turns yellow. What can we infer from these properties? Acrylic is basically very durable, clear, and resistant. This makes it ideal for certain uses. We can find it in car lights, ad and shop banners, light tubes as well as emblems. All these uses need a certain level of accuracy and an amazing surface finish. CNC acrylic machining is the ideal solution when working on acrylic.
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What Type of Acrylic Works Better with CNC Machining?
There are two main ways of producing acrylic blanks. They include casting and extrusion. We use extrusion when we want to create sheets while casting when we want any other form. In both cases, the thickness of acrylic varies between 1.5 to 25mm. This variation in thickness makes acrylic ideal for cutting out signs and flat emblems.
Extrusion involves melt mass amounts of acrylic pellets in a special tank. We then process to extrude the molten liquid via a formed hole. This is the extrusion nozzle. Casting acrylic closely resembles the casting of other materials. We pour molten acrylic pellets in a casting form, then allow them to cool before extraction. Cast and extruded blanks behave differently when we subject them to CNC acrylic machining. Extruded blanks have more left-over tension are thus brittle and more likely to break. In addition, they are anisotropic which means it is like CNC machining different materials in the Y and X axes. We thus opt for casting blanks when carrying out CNC acrylic machining.
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How to Fix Acrylic Parts for Machining Operations
Once we pick the blank type, we can proceed to decide the type of acrylic fixing method. There is an array of clamping methods available that vary depending on the blank size. Despite being rigid, we have to take special care when working on acrylic. Our experts opt not to tightly clamp large sheets of acrylic along their entire area. For smaller acrylic sections, we can use simple jigs and vises. We usually tape or glue the longer pieces of acrylic onto the workbench during CNC acrylic machining. Another method involves the use of a vacuum table that is clamping and unclamping sheets.
What Are the Specifics of Acrylic Material Machining?
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Feed-rates
After fixing the acrylic in place, we can proceed to machine the acrylic blank. We subject most acrylic blanks to milling. The machining process of acrylic is similar to machining polycarbonate. The RPM varies between 15,000 to 18,000 RPM. We proceed by using a stable yet aggressive feed-rate. This is ideal to prevent the tool from spending too much time on the workpiece and creating heat through friction. If its feed-rate is too low, chips may fall back into the part and spoil the final surface finish and accuracy.
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Cutting tools
We use special acrylic cutting bits that have flutes. These ensure optimum chip removal and accuracy. Moreover, we have to ensure the drill tip angle is less than that of a standard drill when drilling acrylic. Therefore, when the norm is 120 degrees, we instead use 60 degrees. This also helps in better chip removal. Do not worry if we do not achieve an optically clear surface after this operation. The extra operations to carry out afterward that aid to promote better clarity and quality finish.
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Coolants
We strive to keep the temperature to a minimum in any CNC acrylic machining process. Cooling helps in chip removal as well as lowers the starting temperature.
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CNC Acrylic Engraving
Engraving slightly varies from acrylic machining. We achieve it through milling with a different cutter. We mainly use it when working on aesthetic projects and adverts. Modern CNC methods allow us to engrave even the most complex of designs onto plastic sheets. We can then fill the resulting groove with paint to make it more visible.
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Postprocessing CNC Machined Acrylic
Post-processing involves the use of polishing tools in improving the surface quality. There are also chemical polishing methods that involve the use of a special gas to melt the outer acrylic layer.
If you have any questions or inquiries regarding CNC acrylic machining, then simply contact us. For optically clear acrylic machining needs, Creatingway’s precision plastic machining methods the best outcome.
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