Plastic parts with complex shapes, including holes, are often created using CNC machining. They may start with stock material, or the part may be injection-molded and then further processed with CNC machining. While there are many CNC machining processes, this post will focus on drilling, broaching, and boring.
These three processes are used to create holes in the plastic part. The method used to create the hole depends on its allowable tolerance and function. For example, if it requires threads for fasteners, the method must be compatible with the type and size of threads needed.
Understanding CNC Drilling
Drilling involves creating a hole in the plastic material using a rotational cutting tool – a drill bit. It is the initial step in creating holes for screws, bolts, or other fasteners and is often followed by boring or other finishing processes. Drilling is essential for providing pathways for mechanical fasteners, creating cavities for components, or allowing for the passage of fluids or wires.
Drilling operations in plastic parts can involve a variety of techniques beyond just creating simple holes. Each operation has specific applications and benefits. Here are some common drilling operations and examples of their use in plastic parts:
- Standard Drilling is used to create a straightforward through-hole or blind hole. For example, it can be used to create holes for screws or bolts in plastic enclosures, brackets, or mounts.
- Countersinking creates a conical angled hole for a flathead screw. The hole matches the angle of the screw so that when the screw is fully engaged, it is flush with or below the surface of the part. Countersinking is often used in plastic housings for electronic devices where a smooth, flush surface is desired to avoid interference with other components or aesthetics.
- Counterboring creates a flat-bottomed, cylindrical recess around a hole to accommodate the head of a bolt or screw. This is used in plastic panels or assemblies where socket head cap screws are used, allowing the screw heads to be recessed and sit flush with the part’s surface.
- Spot drilling (center drilling) involves creating a shallow hole to precisely locate the position for further drilling operations. This method is used on plastic parts that require high precision, such as components in medical devices or intricate assemblies where exact hole placement is critical.
- Reaming is used to enlarge an existing hole to achieve a precise diameter with a smooth finish. Plastic components that require tight tolerance holes for shafts or pins will be reamed to ensure a precise fit and smooth operation.
- Tapping is how internal threads in a hole that accommodate a screw or bolt are made. Sometimes, the hole can be drilled and tapped in one setup. Some common applications include plastic components like lids, covers, or connectors that require threaded fasteners for assembly or attachment.
- Step drilling creates a hole with different diameters along its length, often in a single operation. It is used in plastic components that need a stepped hole for different-sized fasteners or components, such as plumbing fittings or modular assemblies.
Benefits of Drilling Plastic Components
Drilling is a fundamental machining process for plastic parts, offering numerous benefits that enhance manufacturing efficiency and product quality. This process is essential for creating precise and accurate holes, which are necessary for fastening, assembly, and functional purposes in various applications. Drilling enables the production of holes with controlled depth and diameter, ensuring compatibility with screws, bolts, and other fasteners. This precision is crucial for maintaining the integrity and alignment of assembled parts, particularly in industries such as electronics, automotive, and consumer products. Additionally, proper drilling techniques minimize the risk of material deformation, chipping, and cracking, preserving the structural integrity of the plastic components. The versatility of drilling allows for the efficient creation of both simple and complex hole patterns, supporting a wide range of design requirements. Overall, drilling is indispensable in achieving reliable, high-quality plastic parts that meet rigorous industry standards.
Understanding CNC Broaching
Broaching is a machining process that involves removing material with a multi-edged tool (broach) to create precise shapes or contours. The cutting edges on the tool are arranged with an offset that determines the depth of the cut per tooth. It is used to produce complex internal or external profiles in plastic parts that are difficult to achieve with other methods. Broaching ensures high accuracy and consistency, which is important for parts that must fit together precisely or function smoothly.
Broaching is used to create internal keyways and splines, complex profiles that require precise geometries, and parts with uniform shapes and dimensions.
Broaches come in various shapes and sizes, including round, spline, standard keyway, and specialty. For even greater versatility, several different methods are often used. Some common methods for broaching include the following:
- Pull broaching is a method in which the workpiece is held stationary, and the broach is pulled through it. It is generally used for internal broaching but can also be used for some surface work.
- Push broaching, as the name implies, involves pushing the broach through the plastic workpiece. It is often used for internal broaching, such as for accurate hole sizing and cutting keyways.
- Surface broaching allows either the broach or the workpiece to remain stationary. It is mainly used for surface finishing operations, but this method can also be used to broach many irregular shapes, including slots and grooves.
Benefits of Broaching
Broaching provides significant advantages for plastic parts, particularly in creating complex internal and external shapes with high precision. This machining process enables the formation of intricate profiles, such as keyways, splines, and custom contours, which are difficult to achieve with other methods. Broaching ensures consistent and accurate cuts, which is vital for parts that need to interlock or fit seamlessly with other components. This precision is crucial for applications in industries like automotive, electronics, and consumer goods, where exact dimensions and flawless finishes are imperative. Moreover, broaching can improve the mechanical performance of plastic parts by producing clean, sharp edges and reducing stress concentrations. This results in components that not only perform better but also have enhanced durability and reliability. Overall, broaching is an essential process for manufacturing high-quality plastic parts with complex geometries and stringent tolerance requirements.
Understanding Boring
Boring is a machining process used to enlarge a hole that has already been drilled or molded. It uses a boring bar fitted with an appropriate cutting insert. In addition to horizontal and vertical boring machines, the process can also be performed on a lathe, mill, or machining center. Depending on the size of the hole needed, several passes may be required to get the desired size.
Boring helps achieve precise diameters (concentricity) and fine finishes. In plastic parts, boring is crucial for achieving tight tolerances and smooth surface finishes, which are essential for the performance and assembly of the final product. It is often used in applications where the initial hole may not be perfectly round or needs to be brought to an exact size.
Benefits of Boring Plastic Components
Boring offers several benefits for plastic parts, enhancing both their precision and functionality. This machining process allows for the enlargement and fine-tuning of pre-existing holes, ensuring tight tolerances and smooth surface finishes that are crucial for high-performance applications. By using boring, manufacturers can achieve exact diameters and superior hole quality, which is essential for components that require precise fits, such as bushings, bearings, and cylindrical features. This precision reduces the risk of misalignment and improves the overall durability and performance of assembled parts. Additionally, boring helps minimize material stresses and avoid issues like cracking or deformation, which can be particularly important in maintaining the structural integrity of plastic components. Boring is an invaluable process in achieving the high standards required in various industries that rely on plastic parts, from automotive to medical devices.
Combining Drilling, Broaching, And Boring Methods
While these methods can be used independently, they are often used together. Combining drilling, boring, and broaching in the manufacturing process of plastic parts can provide increased versatility and greater precision. Initially, drilling is used to create the basic holes in the plastic material, establishing the fundamental pathways required for fasteners or components. Following this, boring can be applied to these pre-drilled holes to enlarge and refine them, ensuring tight tolerances and smooth finishes essential for high-precision applications, such as bushings or alignment features. Additionally, broaching can be employed to add complex internal profiles or keyways to the bored holes, creating intricate shapes and customized contours necessary for interlocking parts or specific mechanical functions. This combined use of drilling, boring, and broaching not only maximizes the dimensional accuracy and surface quality of plastic components but also enhances their structural integrity and performance in complex assemblies. By integrating these methods, manufacturers can produce high-quality, durable plastic parts that meet the stringent requirements of industries like automotive, aerospace, and electronics.
High Precision Machined Plastic Parts with Ensinger
No matter what machining methods are required, Ensinger has the equipment and expertise to deliver extremely tight-tolerance plastic components. Learn more about our CNC machining capabilities. Contact us today.