HOW CNC MACHINING WORKS
In plastic manufacturing, plastic CNC machining stands out as a versatile method for creating complex parts, assemblies, and prototypes with exacting precision. We delve into the essentials of CNC machining plastics and what you need to know most about the process.
WHAT IS CNC MACHINING?
CNC (Computer Numerical Control) machining plastic falls into a different category from other fabrication processes as it is a subtractive manufacturing process. Here, computer-controlled machines remove plastic material from a solid block, a.k.a "blank" or "workpiece", to create a desired shape. The process itself can involve a number of procedures like milling, turning, and drilling. However, this depends on the component's design. These CNC machines follow precise programmed instructions from CAD (computer aided design) files to craft highly precise and high quality parts.
HOW DOES PLASTIC CNC MACHINING WORK?
STEP 1: DESIGN & PROGRAMMING
CAD Model Creation:
Production start when engineers, designers, and other related persons create a detailed CAD (computer aided design) model of the component they need produced. Within these models, teams need to include all the necessary dimensions and specs to ensure a feasibility & precision. If one measure is off or missing, this can delay a project's completion or deteriorate a component's effectiveness.
CAM Software Loading:
When finalized, an operator imports the current CAD model into a machine's CAM (computer aided manufacturing) software. This software then reads the information to generate toolpaths and creates instructions for the CNC machine itself to follow. These instructions guide the machine's moves and interactions with the plastic material.
STEP 2: SELECTING MATERIALS
When considering the many varieties of plastic available, many struggle with selecting one that will meet the project's needs. As different plastics offer different qualities, teams will need to find the balance between properties and application requirements. They need to consider the following:
What kind of strength does the product actually need?
How much flexibility does it need to have?
How high (or low) of an operational temperature does it need to tolerate?
These are only a few properties teams must consider. We delve much deeper into material selection in our Design Guide.
As a side note, most projects call for one (or a mix) or the following: ABS, polycarbonate, acrylic, nylon, and/or PEEK.
STEP 3: SETTING UP THE MACHINE
With Controlled Fluidics' advanced technology, these machines automatically handle the next steps after proper setup from an experienced human operator. Once set up, the machine will require little to no supervision. If these robots were less advanced, this would require more human intervention and – in turn – elongate production timelines.
However, that is not to say that the machines don't need a hand to get started. An operator places the material in its proper place alongside a machine. Then they will program and test the machine before production begins. This helps to iron out most flaws before establishing a repeatable production process.
STEP 4: THE MACHINING PROCESS
The entire machining process can involve one or more procedures to craft a part. If the component requires complex shapes, slots, holes, and/or contours, generally the machine will mill the blank first to create those features. Using rotary cutters of different lengths and widths, the machine will remove material until completion.
If a component needs to be cylindrical or have cylindrical assets, plastic turning will come into play. The machine will select a stationary cutting tool (or a human operator will set this up on another specialized machine, depending on the case) and will turn or rotate the blank until the necessary features are completed.
Lastly, drilling happens when a component needs precise holes at various angles. Our multi-axis machines can create manifolds with uncommon hole placements without much issue. The machine drills these to the most exacting measurements that can hold the tightest tolerances. It removes a majority of the margin for error when crafting these that a human hand typically does not. With this multiplanar ability, drilling at odd angles presents a much easier and repeatable production process.
STEP 5: POST MACHINING
When the machine completes a cycle, still other procedures may need to happen before a component is ready.
Firstly, through milling, turning, and drilling, these procedures can leave sharp edges or burrs (ridges or rough areas) that need smoothing. The presence of these rough spots can prevent correct assembly, impede expected operation, or can result in system malfunction if/when dislodged through regular use. To mitigate these, manufacturers perform the deburring process to smooth these sections out before further processing.
Secondly, if a customer has chosen to refine the product further after deburring, those finishing processes can begin. This can involve further sanding, polishing, or a coating to enhance surface quality and function.
For more information about those processes and what they entail, we have created a polishing guide here.
BENEFITS OF CNC MACHINING
Each fabrication method – whether that's injection molding, CNC machining, or 3D printing – each has their own sets of advantages. We give the most generalized points here.
PRECISION & ACCURACY
Our CNC machines can meet extremely tight tolerances within microns. This creates repeatable precision for even the most difficult and intricate designs.
REPEATABILITY
CNC machines can produce identical components with great consistency once programmed. This makes it ideal for prototyping and production.
VERSATILITY
Controlled Fluidics works with 30+ different types of plastic, including rare blends and difficult to machine materials. The CNC machines at both our locations are compatible to work with these plastics. Moreover, our engineers have combined decades of experience in designing products and advising customers on best practices based on their industry and application.
SPEED
Machines can produce components quickly and efficiently. This contributes to reducing lead times for most components.
COST EFFECTIVE
For low to medium volume productions, more often than not CNC machining comes out more economical than other fabrication methods because of lower setup costs. For more information about the differences between these fabrication methods, we delve into this deeper both on a separate article about 3D printing and in our Design Guide.
PLASTIC CNC MACHINING APPLICATIONS
Creating prototypes quickly can help teams test fit, form, and function before moving to a higher volume production.
CNC machining can be ideal for creating and producing medical devices. CNC machines offer a high level of precision and can work with materials that have biocompatibility.
Specialized electronics often use CNC machined plastic parts as enclosures, connectors, and other components to have the device function optimally.
Laboratories and related organizations take advantage of the lightweight, durable, and sterilizable properties from CNC machined plastics in their daily operations.
Because of the reliable and stable nature of some plastics, organizations in aerospace utilize these products to advance technology while reducing weight and complexity.
Even the smallest parts can play the biggest role within some assemblies.
FINAL THOUGHTS
Plastic CNC machining is a powerful fabrication method for engineering and product design teams to use. As it offers unmatched precision, flexibility, and efficiency, professionals can better leverage its capabilities to bring innovative designs to life. Whether for prototyping or production, plastic CNC machining marks itself as a cornerstone of modern manufacturing, driving advancements across many industries.