When we talk about manufacturing and machining, it’s crucial to differentiate between primary and secondary processes.
Depending on the type of part being manufactured, there are many steps in the process from raw material to finished part. Parts with various surface features or unique shapes often use multiple machines and machining processes.
For example, a CNC machine might cut and form the general shape of the part. Then another machine may form threads on the parts. Then a grinder machine durburrs the part. And after that, the parts are washed and engraved.
Modern CNC machines have advanced capabilities, but they can’t do everything.
Secondary machining processes form the features that weren’t done in the initial machining of the part. This includes things like deburring, engraving, sub-assembly, and surface treatments like anodizing, heat treatment, and powder coating.
These processes form the foundation of the machining world.
It’s where a raw material undergoes substantial transformations to emerge as a product resembling its final form. Think of this as sculpting a rough statue out of a marble block. Here, substantial material is removed, and the basic structure of the part is established. Primary processes include operations like turning, milling, and drilling.
Once the basic form is established, we shift to refining and enhancing.
The secondary processes are like the final touches to the statue, where intricate details are carved, rough edges are smoothed, and the piece is polished to perfection. These operations, which include deburring, engraving, and surface treatments, are crucial for functional efficacy, aesthetics, and safety.
Primary machining processes form the core shape of a component by removing material from raw stock like bar, plate, or castings. Spex utilizes several advanced primary processes, including CNC milling, turning, and Swiss screw machining. Forging and casting are also common methods typically used for parts requiring less precise tolerances.
CNC milling uses computer-controlled rotating cutting tools to remove material from a stationary or moving workpiece. This versatile process is ideal for creating complex shapes, slots, holes, and flat surfaces on block-type or plate-like parts. Spex employs multi-axis CNC milling centers to produce intricate components with high precision and efficiency.
CNC turning involves rotating the workpiece in a lathe while a cutting tool moves linearly along its surface. This process excels at producing cylindrical parts where precise diameters, concentricity, and surface finish are critical. Common examples include shafts, pins, bushings, sleeves, fittings, valve components, and custom fasteners. Modern CNC lathes with live tooling can also perform secondary operations like cross-drilling or milling in the same setup.
Ideal for small, complex, and often long, slender parts, Swiss-style CNC machining feeds the bar stock through a guide bushing past stationary or rotating tools. This provides excellent support right near the cutting zone, enabling very high precision and intricate features on small-diameter components often used in medical, electronics, and instrumentation applications. It's highly efficient for high-volume production of these types of parts.
Designed for high-volume production, multi-spindle machines feature multiple spindles (typically 6 or 8) that allow simultaneous machining operations on several parts at once. As the spindles index, each part undergoes a sequential machining step. This dramatically reduces cycle times compared to single-spindle machines, making it highly cost-effective for large quantities of turned parts like fittings, fasteners, and valve components.
Parts are engraved for a variety of reasons. One of the most common reasons is to keep track of different lot numbers and help identify parts that look similar. Engraving parts can also help identify different metal alloys since they usually look the same.
After parts are machined, we use in-house CNC engravers and laser engravers to add part numbers, lot numbers, AISI numbers, and more to parts.
Deburring is a secondary process used to remove small imperfections from parts. Deburring isn’t always necessary, but sometimes the machining process creates small burrs on parts—especially when there are small slots, threads, or sharp edges.
During the deburring process, a spinning brush, grinding wheel, or belt is used to remove the burrs and smoothen out the part.
A burr is a small protrusion on a part and they’re usually sharp. For certain parts, deburring is a necessary process for parts to function properly and ensure safe handling.
Sub-assembly is a process where two or more separate parts are attached together by the manufacturer. The term “sub-assembly” refers to components that are first assembled together and then integrated into a larger assembled unit. So, a sub-assembly isn’t the final product. Some more complex parts or components are machined as separate parts to speed up the production process, and then assembled.
In some cases, the assembled parts are two different materials, like attaching a rubber o-ring to a metal part.
When sub-assembly operations are outsourced to the manufacturer, it saves time and allows the customer to scale their operations.
Various things can be done to the surface of the part. This includes heat treatment, anodizing, plating, and powder coating. These are usually to add durability to the part.
Different surface treatments are used for different types of parts and use cases. Metals that are more susceptible to rust or scratches are more likely to benefit from surface treatments.
Steel parts are the most common for plating, when a thin layer of zinc, nickel, or chromium is added to the part. Many steel parts are also heat treated, which makes the steel harder and stronger, but also more brittle.
Aluminum parts are often anodized, which adds a thin layer of oxidized aluminum so that its surface is no longer reactive. The layer of oxidation offers protection from scratches and mechanical wear, as well as chemical protection from water and oxygen.
Understanding the timing of a project, especially when lead time is critical, requires a grasp of how secondary processes fit into the overall production timeline:
Integration with Primary Processes: In some cases, secondary processes can be integrated seamlessly with primary ones. For instance, a modern CNC machine might mill a component and then immediately engrave a serial number, all in one go. This reduces additional setup and handling time.
Complexity and Specificity: The more complex or specific the secondary process, the longer it might take. For example, a simple deburring process might add minimal time, while multi-step surface treatments could extend the lead time.
Batch Processing: Some secondary processes, especially those related to finishing, might be done in batches. If your project is part of a larger batch, it could influence the lead time.
Efficiency Enhancements: Many manufacturers, aware of the potential time added by secondary processes, invest in technologies or methodologies to speed these up. For instance, automation and robotics can drastically reduce the time taken for certain secondary operations.
Feedback and Revisions: If there’s a need for adjustments after the secondary processes (maybe a logo isn’t engraved clearly), this can add to the project’s duration. However, regular quality checks reduce these delays.
While secondary processes generally increase lead times, their impact varies based on the project, the processes involved, and the manufacturer’s capabilities. It’s always good to discuss lead time expectations upfront, especially if you’re working on a tight schedule.
Spex has served as a local manufacturer since 1946. We provide a wide range of manufacturing services. If you want to learn more about our precision machining capabilities or secondary machining services, reach out to one of our team members to get a custom quote.
Are there any materials that particularly benefit from secondary processes?
How do I know if my part requires secondary processes?
