Advancements in Plastics Machining Techniques: Enhancing Precision and Efficiency

Published on May 27, 2024

Many manufacturers prefer machining over molding for various plastic parts and products. Machining plastics typically provide better precision for precision components than molding. Moreover, machining is often a more cost-effective choice because creating molds can be expensive and time-consuming. Although machining may not suit all plastics or applications, it’s often a more economical option for medium to low-production runs of plastic parts and products.

Precision & Efficiency with Modern Plastics Machining Methods

Modern methods for plastics machining rely on the material used for fabrication to ensure precision and efficiency. Machining is most effective for rigid plastics, similar to metal machining. Opt for plastics resistant to distortion like acrylics, fiber-reinforced thermosets, glass-reinforced nylon, and PEEK for better machining results.

Advantages of plastic machining over other methods include:

  • Allows fabrication of larger plastic workpieces
  • Can produce thicker walls
  • Lower energy requirements
  • More cost-effective low-to-mid-volume production runs
  • No expensive molds needed
  • Offcuts of plastic workpieces can be recycled
  • Prototypes can be made without committing to specific tooling
  • Shorter lead times

There are many methods – both modern and vintage – for fabricating plastics. Machining can use CNC (computer numerical control) technology, laser cutting, or waterjet cutting to achieve tight tolerances for complex plastic components and products. Machining with CNC equipment allows multiple tool types that are programmed to follow specific pathways to carve out complex plastic components. Cutting methods using lasers offer fewer possibilities for materials due to the heat they generate, especially when it comes to thermoset plastics; machining with lasers also uses computerized and automated methods for fabricating. Machining plastics with waterjets involves pressurized water mixed with abrasives that slice through tougher materials, a technique often used for trimming fiber-reinforced thermosets as it doesn’t produce heat.

CNC Plastics Machining

CNC machining is a subtractive process that uses tools to cut solid pieces from a block of material to shape a workpiece into a product or part. While normally associated with metals, this machining method is becoming more popular when fabricating plastics. Machining with CNC technology can produce parts with greater precision and tighter tolerances than can be achieved with processes like injection molding of plastics. CNC machining also offers a wider range of materials from which to choose than other machining methods, which continue to advance.

Advantages of modern CNC plastics machining methods include: 

  • Advanced controls: Advanced controllers allow greater flexibility in programming, offering more options for customized programming rules, subroutines, or parameters. Additionally, more intuitive interfaces make CNC machines easier to operate. At the same time, network connectivity and cloud access allow for robust data storage and analytics capabilities that can be used to optimize production.
  • Automation: CNC machines can be integrated into production systems in a way that wasn’t possible even a decade ago, with automation continuing to develop that allows collaboration between automatic tool loaders and pallet changers with robots. All this allows for less supervision, allowing for lights-out facilities that can manufacture parts and products without operators even onsite.
  • Processing: Developments in processing power for CNC machines’ CPUs (central processing units) has brought faster production rates through their higher capacity for memory storage and more rapid transmission of data. CNC technology can now process enormous amounts of data to run complicated programs that control toolpaths and allow work on multiple axes simultaneously.
  • Precision: Today’s CNC machines make components from plastics with incredible precision. Machining components and automated control systems for CNC equipment have developed over time, allowing part designers to tweak designs to increase precision by augmenting material rigidity and bearing performance while reducing vibrations during processing.
  • Multiple axes: Capabilities allowing CNC machining of plastics on multiple planes simultaneously have reduced production times while retaining superior accuracy. With 5-axis CNC machines, it’s possible to automate the fabrication of many complex components without repositioning them, saving time and money.

With advanced controls, increased automation, more processing power, greater precision, and the ability to work on multiple axes, it’s no wonder that more plastic products and parts are made via CNC machining. Plastics also continue to evolve along with CNC technology, allowing manufacturers greater choice in their materials.

CNC Plastics Machining: Industries & Applications 

When it comes to plastics, machining with CNC technology has many applications across multiple industries.

These include: 

  • Aerospace: Corrosion and impact resistance are two of the most important properties for the aerospace industry that can be engineered into plastics; machining these durable yet lightweight materials into structural components results in better overall performance for aircraft and spacecraft. 
  • Agriculture: Drainage and irrigation solutions often use CNC machined plastics; machining plastic is also done for various agricultural components, including tools, planters, and greenhouses.
  • Automotive: Using plastics, CNC machining is employed to manufacture dashboards, door handles, linings, and other interior components; additionally, exterior parts like bumpers, engine covers, and housing for automotive electronics can also be made via CNC machining. 
  • Electronics: Due to their lighter weight and ruggedness, anything from home appliances to smartphones will contain machined plastics; machining with CNC technology offers electronic goods greater consistency that also ensures longer-lasting products.
  • Food processing: CNC technology is often used for manufacturing storage containers made from food-grade plastics; machining impact-resistant plastics into carrying trays also provides an efficient means for transporting food products.
  • Healthcare: Due to the biocompatibility, durability, lighter weight, non-permeability, resistance to sterilizing agents, and other properties of medical-grade plastics, machining with CNC technology is useful for making medical implants like pacemakers, components for equipment to monitor vitals, and other medical devices. 
  • Mining: Components for conveyors, gears, sheaves, slurry piping, and other machinery used in mining operations are often made from CNC-machined plastics.
  • Oil and gas: Containers and seals used for extraction and storage of petroleum and natural gas are used due to the chemical resistance provided by many machined plastics.

The use of CNC machining for plastic fabrication of parts and products goes well beyond even these industries and applications.

Machining Plastics with Laser Cutters

The first laser cutter was developed by Bell Laboratories in the mid-1960s, though its applications and features were initially limited to the cutting of thin sheets of steel. These laser cutters have since developed into fiber lasers that rely instead on a solid medium rather than carbon dioxide as the original Bell prototype. Today’s laser cutters more precise and energy efficient, as well as faster.

Lasers work by creating electrical flows similar to those generated by fluorescent tube lighting. A laser cutter concentrates light through a lens before focusing it towards the cutting surface. The laser beam essentially causes material to evaporate. Originally used for drilling holes and cutting metals for specific applications, laser cutting is now used more widely for machining plastics.   

Advancements in laser cutting of plastics include:

  • Automation: Artificial intelligence (AI), along with AI’s sibling science machine learning and robotics, have driven the use of automation in integrated production systems.
  • Integration: Today’s laser cutters are largely integrated into automated systems with real-time monitoring capabilities that allow instant adjustments to production.
  • Portability: Less bulky than lasers based on carbon dioxide, some of today’s laser cutters are made small enough to be held by hand.   
  • Precision: The accuracy of fiber laser cutters has made them useful in producing complex components with intricate designs, which are useful for various medical and electrical applications.
  • Sustainability: The energy efficiency of fiber lasers has made them an important tool for sustainable parts production.

These modern advances in laser technology have made them suitable for certain applications involving fabrication of plastics. Machining with lasers often provides greater convenience, efficiency and versatility, while also making parts production more sustainable.

Laser Cutting: Plastics Machining in Industries & Applications

Employed by many industries due to their lower cost and speed when performing precision machining operations, modern laser cutters have become more widely used due to modern technological developments.

Common industries and applications for plastics machined via laser cutters include: 

  • Agriculture: Many intricately designed and flat components for heavy farm equipment like planting machines, fertilizing apparatus and tanks for bulk storage require joining or welding, for which laser cutting is ideal; a specific method known as tube laser cutting that involves making holes and slots in tubing is often used for fabricating structural elements for agricultural machinery and equipment.
  • Art: Able to produce detailed imagery onto plastics, machining techniques using laser cutters often are used for engraving inlays or complex components within artwork.
  • Automotive: For vehicular components made from plastics, machining with laser cutters offers a means to maintain high production rates while not compromising on precision or consistency.
  • Defense: Composites made from Kevlar-based materials used in military body armor often use laser cutting due to its difficulty in processing.
  • Electronics: Composites used for printed circuit boards are often made from plastics; specialized methods using laser cutters control fracturing while drilling holes or engraving information into these delicate components.
  • Furniture: For furniture that incorporates plastics, machining with laser cutters allows for engravings on or fabrication of components.
  • Parts manufacturing: Because of the high initial cost of investment, laser cutting lends itself to use by contract manufacturers who make parts, subcomponents and whole assemblies for other companies.

Though the heat they emit limits the types of plastics, machining with lasers offers definite benefits for certain applications.

Machining Plastics with Waterjet Cutting Tools

With waterjet cutting for plastics, machining is done via a high-pressure stream of water mixed with an abrasive. Waterjet cutting offers manufacturers a very versatile method for cutting that produces less waste than other techniques for machining plastics. As it produces no chips, dust or gas, unlike other cutting methods, it’s also more friendly environmentally. Many manufacturers implement this technology due to its cost-effectiveness for precision machining. The development of this technology is still in its infancy, however, as cutting-edge technology enables it to do more.

Recent developments in waterjet cutting for plastics includes improvements in: 

  • Abrasives: With abrasives typically made from garnet between 150 to 50 mesh (89 to 297) microns, plastics can now be machined via waterjets only 3 to 4 inches (76.2 to 101.6 mm) from the nozzle’s tip. New developments in waterjet technology allows abrasive material to travel more directly to the cutting head, with efficient recycling of garnet to keep sufficient abrasive material in the stream cutting away at the workpiece.
  • Accuracy: Past waterjets were considered substandard to other machining methods as they couldn’t meet tight tolerances. However, engineering nozzle advancements now allow waterjet cutters to achieve a precision of 0.0005 inches (12.7 microns). Additionally, a revolution in waterjet technology allows these cutters to perform similarly to 5-axis CNC machines to work on five different axes simultaneously.
  • Directed pressure: Previously, waterjet cutting of plastics had a problem with directing the solution of water and abrasive material without the waterjet’s tubing flexing, which would lead to variations in tolerances. New developments in waterjet cutting include combining swivels with high-pressure tubing to prevent this flexing and better direct the pressurized water.
  • Integrated processes: Like other manufacturing processes for making products or parts from plastics, machining with waterjets is increasingly using high-tech solutions to integrate their systems. This includes the use of smart technology that allows for remote monitoring and control of processes like barcode reading, dispensing abrasive solution, drilling, marking, and tapping, along with automated loading and unloading of components.  
  • Sensors: These days, 5-axis programming of waterjets allows plastic workpieces to remain in a static position. This is largely due to sensors that allow operators to prevent crashes and make adjustments during the fabrication process.

Waterjet cutting technology continues to develop. Though not unlikely to completely replace other processes, it’s found its niche in the machining of plastics and other materials.

Waterjet Cutting: Industries & Applications for Machined Plastics

With plastics, machining with waterjet rather than CNC technology is becoming increasingly common across many industries.

Plastic machining via waterjet includes the following industries and applications: 

  • Advertising: Advertisers in the display industry often use plastics, machining materials like acrylic glass with waterjets to make aesthetically pleasing displays, signs, and other advertising materials.
  • Aerospace: Often machining plastics like ABS or PC (polycarbonate), the aerospace sector uses such materials for fabricating lightweight components.
  • Automotive: Waterjets are used to machine plastics like PVC (polyvinyl chloride) and PUR (polyurethane) for the automotive sector to make dashboards, door panels, and interior trim.
  • Electronics: Waterjet cutters are used to machine plastics like ABS and PC for covers and housings in electronic devices, as well as for electrical insulation.
  • Packaging: For PET (polyethylene terephthalate), PP (polypropylene), and other customized plastics, machining via waterjet helps meet specifications for the food industry.

As waterjet cutting for plastics continues to advance, new applications are likely in the near future.

Benefits of PlasticMachining 

There are numerous benefits that plastics machining offers over other methods of fabrication. It can create more complex components without the high costs associated with producing molds for the injection molding process. Machining plastics can also offer shorter lead times, making it better for manufacturing prototypes and for trial production runs. When comparing metals to plastics, machining of the latter allows for the addition of properties that allows critical parts to better withstand acids, bases, exposure to radiation, high heat and other hazards.

In many cases, machined plastic parts are superior to their metal counterparts. With the unique properties of plastics, machinery can be made with components that are more reliable and require less maintenance, reducing the chance of unplanned downtime and increasing productivity. Typically, machined plastics also have lower coefficients of friction so generate less heat when operating. Besides CNC machining, laser cutting and waterjet cutting, there are other plastics machining methods that continue to evolve.

Other Plastics Machining Methods

There are numerous other machining methods that can be used with plastics. Machining techniques often use more modern tools to shape plastic components and products, though many of these processes have been around for decades, or in some cases even centuries.

Other methods for plastics machining include: 

  • Hot-knife cutting: This is considered a lower-tech means to achieve the same result as laser cutting, using a heated knife or similar element; hot-knife “machining” of plastics is typically used for soft plastics like polystyrene.
  • Milling: This process dates back to the latter part of the 18th century and milling can still be done by hand with manual rotary cutters, but the technique has since become automated and an integral part of the CNC machining process.
  • Punching: With this process of machining plastics, sheets of malleable materials are punched out into shapes, which can be done by hand but is more often done via CNC machining. 
  • Sawing: Using manual or mechanical tools to cut and separate plastics, machining with saws has also increasingly become automated.
  • Turning: Also having become an integral part of the CNC machining process, this is a technique for creating curves or circles in workpieces is now seldom done without automation.
  • Ultrasonic cutting: Using high-frequency vibrations, this modern technique for plastics machining involves a sonic tool and abrasive particles to remove layers of material; used on more fragile plastics, machining is automated and operated via computer similarly to CNC technology.

Many of the above have become automated and incorporated into more modern and automated plastics machining techniques. 

Best Plastics for Machining

The best plastics for machining largely depend on the polymer’s properties most needed for the application. With a tensile strength of 21 thousand pounds per square inch (about 1476 kg per cm²), PAI (polyamide-imide) is one of the stronger plastics; machining PAI via CNC technology is easier due to this high strength. For certain applications, cost may be the chief factor; PE (polyethylene) is both known for its machining properties and lower cost, so is often used for applications like making consumer goods, gears, and wear strips.

Also known as acetal, POM (polyacetal and polyoxymethylene) is a commonly used engineered thermoplastic for CNC machining due to its good dimensional stability and stiffness, along with its superior strength; POM is used for parts for motor vehicles, industrial machinery, and electronics. Among the hardest plastics, machining PEEK (Polyether Ether Ketone) is difficult; however, PEEK’s high chemical and thermal resistance make it an excellent choice for the aerospace and healthcare sectors. Offering both strength and durability, ABS (Acrylonitrile Butadiene Styrene) is often used for prototypes made from plastics; excellent machining properties make ABS one of the easiest plastics to machine.

As development continues with various composites and engineered plastics, machining can use CNC machines, laser cutters, waterjets, and other technologies to form workpieces into parts and products. Keeping abreast of newly engineered plastics and machining methods for working with them requires a partner like Spaulding Composites, Inc. In the composite business for over a century and a half, our company manufactures engineered thermoset composite materials, along with machined components made from them. To learn more about our capabilities, contact one of Spaulding’s representatives today.