CNC Acrylic: A Simple Guide to Understanding PMMA Machining

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CNC Acrylic: A Simple Guide to Understanding PMMA Machining

Acrylic is one of the most used clear plastic in CNC systems. This material offers significant advantages over other materials like polycarbonate and glass.

CNC acrylic machining is one of the most prominent processes for acrylic production. Many industries make use of acrylic parts. Therefore, it becomes important to look into its manufacturing processes.

This article offers you a complete guide to CNC acrylic. You will also find the best tips for machining acrylic. Before then, let’s understand what Acrylic is and what makes it important.

What is Acrylic?

Acrylic is a rigid and transparent thermoplastic material. It is also referred to as Polymethyl methacrylate (PMMA). Many industries make use of acrylic as a replacement for glass since it is shatterproof. It is a colorless and clear polymer that can come in different forms. For example, it comes as small granules, pellets, or sheets.

Machinist then uses different thermoplastic processes for acrylic CNC cutting. Such processes include compression molding, extrusion, and injection molding.

Some manufacturers use cell casting for their acrylic CNC design. Acrylic has a very high molecular mass, making it a tough material. It is also 100% recyclable.

Properties of Acrylic

CNC acrylic exhibits qualities that make it work like glass. These qualities include translucence, brilliance, clarity, and transparency. It is one of the most robust materials used in manufacturing. It also has lesser risks of damage. Let’s look at the various properties of acrylic in detail.

Surface Hardness. Acrylic is a lightweight, tough, and durable thermoplastic. Its density ranges from 1.17 g/cm3 to 1.20 g/cm3. When you compare it to other transparent polymers, it has great scratch resistance. Furthermore, acrylic has excellent dimensional stability. This gives it a low water or moisture absorbing capacity.

UV Stability. Acrylic is highly resistant to UV light. Most CNC acrylic designs ensure UV stability. Thus, they are resistant to prolonged sunlight exposure. This property also makes acrylic a great choice for outdoor applications, especially for more open-air exposure.

Transmittance. Acrylic polymer comes with a refractive index of 1.49. This allows it to offer up to 92% of the light passing through it. This light transmittance is higher than that of glass and other plastics. Therefore, it becomes easy to have custom acrylic plastic without losing optical clarity. Also, its environmental stability makes it useful for most outdoor applications.

Chemical Resistance. Aqueous solutions of most laboratory chemicals do not affect acrylics. You can use cleaners, alkalis, detergents, dilute inorganic acids, and others on acrylic. You won’t have to fear damaging the material.

Suitable Processes for PMMA

Acrylic is suitable for processing by a wide variety of machining methods. These include injection molding, plastic extrusion, casting, and several others. Depending on the preferred item design, acrylic fabrication may involve some or all of the following processes.

CNC Machining

PMMA has several enhanced properties that makes it suitable for a wide range of applications. All of these applications need the highest level of precision and surface finish. CNC acrylic machining is the process for fabricating acrylic materials.

a-cnc-machining-process

Being a rigid and strong material, CNC machining is always the perfect solution for acrylics. CNC machining offers great advantages in that it helps to obtain the desired sizes or shapes of materials. That is, you get result that correlates with the input parameters you feed into the acrylic CNC machine. This process has a high degree of accuracy with minimal waste of acrylic involved.

Injection Molding

Just as with other plastics, it is possible to form acrylic into specific shapes. This is done by heating the acrylic. Then, you can put the heated acrylic into a mold where it will cool and harden.

plastic-part-made-from-acrylic-injection-molding

The molding procedure can be injection molding or rotational molding. Injection molding is particularly popular for creating dishware. On the other hand, rotational molding helps to create hollow plastic parts.

Acrylic Extrusion

This process helps acrylic fabricators to improve the processing of their materials. It usually precedes the bonding or lamination stages.

parts-made-from-acrylic-extrusion

Many manufacturers use this process for piping, tubing, and sheeting components. There are two forms of acrylic extrusion in use. They are profile extrusion and sheet extrusion. Both processes have track records of giving the desired results.

Acrylic Welding

This is a binding operation that uses heat to join two or more acrylic pieces together. In this case, there won’t be a need for the use of adhesives, especially when they are not possible options.

cnc-acrylic-welding-operation

The acrylic welding process may include contact welding, high-frequency vibration, spinning, or hot gas emissions.

Compounding (Blending)

While the welding works to bond two acrylic pieces into one, compounding mixes the melted pieces before molding occurs. The purpose of compounding is to develop a product with features of different acrylics. This will ensure that the product meets the desired quality. In many cases, products resulting from this process are often more durable than the raw materials.

Since PMMA is transparent and relatively hard, it can also be employed as a 3D printing material. In this case, it’ll require a slightly higher temperature.

Advantages of Using Acrylic for Your Parts

Acrylic is a popular material, thanks to its outstanding characteristics. These properties tell us that machining acrylic parts are durable, transparent, and resistant. They are also perfect for a wide range of applications. The advantages of acrylic include, but are not limited to, the following:

  • Outstanding weathering and resistance to UV radiation
  • Dimensionally stable
  • Transparent
  • Good rigidity
  • Good abrasion resistance – you can easily polish out surface scratches
  • High gloss and hardness after modification

Applications of CNC Acrylic Parts

Acrylic (PMMA) became popular during the second world war. At the time, it was used to make gun turrets, canopies, windshields, and so on. Several other commercial applications began to come up.

cnc-router-machining-clear-acrylic

They include roofing, automotive headlamps, and more. Today, many industries use a wide variety of acrylic grades. These industries include:

Automotive Industry

Acrylic sheets are used to design car windows, panels, motorcycle windshields, fenders, etc. The colored sheets are perfect choices for different car parts.

These include interior light covers, indicator light covers, and others. Its excellent formability and surface hardness make it a great choice for car manufacturers.

Lighting and Electronics

Acrylics maximize the light-emitting potential of LED lights. Its optical properties and transparency make it great for lamp construction. Furthermore, it has a high light transmission property. Acrylics are scratch-resistant and optically clear. Hence, their extensive use in a wide range of electronic equipment.

Medical and Healthcare

Acrylics are pure and easy-to-clean materials. Therefore, they are useful in making incubators, cabinets, and devices in medical centers. They are also highly compatible with biologics. This makes them excellent choices as fillings for dental cavities.

Architecture and Construction Industry

Most construction works make use of acrylic parts. This is, in part, due to its outstanding UV and impact resistance.

It is a great material for door and window profiles, panels, canopies, façade designs, and more.

Some of the most common products you can make from acrylic sheets include:

  • Glove boxes
  • Displays and signs
  • Lighting fixture lenses
  • Aircraft glazing
  • Desiccators and dry boxes
  • Radiation shields
  • Sinks, knobs, batons, and baths
  • Retail fixtures
  • Windows and glass alternatives
  • Automotive components including fascia panels, steering wheel, and badges

Tips to Get the Best Results from Machining CNC Acrylic

Using acrylic on your CNC system is one of the best decisions you can make for your part. You can carry out a wide variety of works with CNC acrylic. However, there are some tips you should know to ensure successful manufacture.

tips-for-machining-cnc-acrylic

The following tips will help you get a smooth finish from your acrylic CNC cutting.

Tip 1 – Secure Your Material

Machining acrylic is a delicate process that requires careful operations. It is very crucial to secure your acrylic properly to your machine. Not doing this may lead to excess vibration that may ruin the quality of the product.

Tip 2 – Use the Correct Bit

Using wood bit for cutting acrylic on CNC is never the best idea. Always use a bit designed specifically for acrylic cutting.

Tip 3 – Set the Right Feed Rate

Ensure that you use the correct feed rate for your process. This will ensure that you get good clean cuts. You won’t also have to melt your plastic as you’re cutting it.

Tip 4 – Use the Correct Revolution Per Minute (RPM)

The RPM you use has to correlate with the feed rate. The type of acrylic you use will determine your settings. A faster RPM will require you to increase your feed rate. Thus, you can prevent the melting of your material.

Tip 5 – Set the Pass Depth at the Correct Inch

The best pass depth for most materials will be half the diameter of the bit. Some materials need a pass depth of 0.0625” for the best results.

Tip 6 – Cut Direction is Important

Conventional or clockwise direction has a record of producing the best results. This is often best in relation to the direction of the rotating cutter. 

Tip 7 – Don’t Forget the Ramp Feature

When working with CNC acrylic, it is advised to use a ramp. The ramp helps the bit enter your material at the required angle. It will not just plunge straight down. Using a smooth ramp between 1 to 3 inches will give the desired results.

Conclusion

Acrylic is one of the best materials you can work with on CNC systems. There’s a lot you can do with this material. This article has guided you through the various advantages and applications of CNC acrylic. You also now have the best guidelines for machining acrylic. It’s time to get your custom acrylic plastic.

RapidDirect is your go-to company for CNC machining requirements. We are always ready to achieve the best results within a reasonable lead time. With the help of our experienced and knowledgeable engineers, we carry out an effective CNC milling acrylic process.

rapid-direct-cnc-machining-process

We make quality services our priority at RapidDirect. Therefore, you can be sure that you are getting parts with the highest standards. At your request, we provide RoHS material certification. We also carry out full-dimensional and first article inspections. You’ll get all of this at affordable rates.

FAQ – CNC Acrylic

Is Acrylic Better Than Glass?

Acrylic sheets have several advantages over glass and other plastic materials. Their surface hardness is significantly higher while being lightweight. They are also shatter-resistant, and they have high UV stability.

Is It Safe to Use Acrylic?

Acrylic is considered safe, with low hazard possibilities. It does not contain Bisphenol A (BPA) found in many other plastics. Studies show that BPA may have hazardous risks to the health. Since Acrylic is free from BPA, your safety is guaranteed.

Can I Cut Acrylic Using A Router?

You can use a router to cut acrylic for curved or straight cuts. A router with a collar and guide will be best for curved cuts. Cutting acrylic on CNC router requires the use of a specialized bit. It would help if you also cut at a steady rate while keeping the acrylic cool at all times.

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