Intro to SUB MFG

• • Subtractive Manufacturing, AKA "Machining" is the process of creating a part by removing material from a larger workpiece using precise, computer-controlled tools such as CNC mills, lathes, routers, grinders, EDM machines, etc. The process starts with a solid block, bar, plate, or other raw stock, and material is progressively cut away until the final geometry is achieved.

  • Subtractive manufacturing can produce highly accurate and repeatable components with tight tolerances, fine surface finishes, and a wide variety of geometries, from simple 2D profiles to complex multi-axis shapes. It can be used with almost any machinable material, including metals, plastics, composites, and ceramics.

    • CNC stands for Computer Numerical Control, and means the motion and functions of the machine tool are driven by computer code, typically written in G-code and M-code. This code tells the machine exactly where and how to move cutting tools, change tools, adjust speeds and feeds, and execute other operations to produce the desired part.

• • G-code is a universal, sequential, alphanumeric programming language used by most subtractive manufacturing systems—as well as many additive, robotic, and other automated manufacturing systems. In CNC machining, G-code contains the instructions that tell the machine what to do, when to do it, and how to do it. It controls movements along different axes, spindle speeds, tool changes, coolant activation, and countless other functions.

    • These instructions are executed by the machine’s CNC control—the onboard computer that interprets the code and translates it into precise electrical signals that drive the motors, servos, and actuators. The machine then positions the cutting tool and the workpiece relative to one another with extreme accuracy, often to within a few thousandths (or even millionths) of an inch.

  • Modern CNC systems may also incorporate M-code, which works alongside G-code to control machine-specific functions such as starting/stopping the spindle, activating coolant, opening/closing workholding devices, or initiating automated probing cycles.

    • By automating the positioning and motion of tools, subtractive manufacturing systems eliminate much of the variability found in manual machining, enabling consistent production of complex, high-precision components at scale.

  • Early CNC and NC (Numerical Control) machines of the 1950s–1970s often relied on punched paper tape as the storage and input medium for part programs. These “tape-read” machines used mechanical or optical readers to scan sequences of holes in a strip of paper, with each pattern representing specific commands in the NC language. Editing a program meant physically splicing and re-punching the tape—a slow, manual process.

    • Over time, technology evolved to use magnetic tapes, floppy disks, and RS-232 serial connections for transferring data. This shift allowed programs to be edited digitally and sent directly from a programming station or computer to the machine control, eliminating the need for manual tape handling.

    • Today, modern CNC machines accept part programs from a variety of sources:

      • USB drives and memory cards

      • Direct network connections (Ethernet, Wi-Fi)

      • DNC (Direct Numerical Control) systems for streaming large programs directly to the machine

      • Cloud-based systems for remote program management and transfer

    • Many controls still support legacy RS-232 communication to maintain compatibility with older shop infrastructure, but the trend is toward integrated digital manufacturing systems that seamlessly link CAD/CAM software, CNC controls, and quality assurance tools.

      • This evolution—from physical punched tape to high-speed, networked data transfer—has dramatically increased productivity, flexibility, and reliability, while making it easier for machinists and programmers to manage and update part programs in real time.

History of CNC Machining

• • Subtractive manufacturing can produce highly accurate and repeatable components with tight tolerances, fine surface finishes, and a wide variety of geometries, from simple 2D profiles to complex multi-axis shapes. It can be used with almost any machinable material, including metals, plastics, composites, and ceramics.

    • In modern industry, subtractive manufacturing is used across virtually every sector—aerospace, automotive, medical devices, energy, electronics, and more—to produce everything from precision prototypes to high-volume production parts. It remains a critical technology in manufacturing because it offers unmatched precision, material versatility, and the ability to create components that other processes (such as additive manufacturing) may not be able to produce efficiently or economically.

  • Key advantages include:

    • High Precision & Tight Tolerances – Capable of achieving tolerances within a few microns, making it ideal for components that require extreme accuracy for proper fit and function.

    • Excellent Surface Finish – Can achieve smooth, polished surfaces directly from the machine, reducing or eliminating the need for secondary finishing operations.

    • Material Versatility – Works with a vast range of materials, including those that are difficult or impossible to process with other methods, such as hardened steels, titanium, and certain ceramics.

    • Complex Geometries – Multi-axis machining allows for intricate shapes, undercuts, and features that may not be possible with simpler manufacturing methods.

    • Scalability – Equally effective for one-off custom parts, small-batch runs, and high-volume production.

    • Proven, Mature Technology – Decades of development mean processes, tooling, and quality standards are well understood and widely supported.

    • Integration with Digital Manufacturing – Modern CNC machines can be seamlessly connected to CAD/CAM software, robotics, and quality inspection systems for an efficient digital workflow.

    • Durability & Strength of Components – Parts are cut from solid stock, maintaining full material density and mechanical properties—important for structural and safety-critical applications.

  • Because of these strengths, subtractive manufacturing often complements newer technologies rather than being replaced by them. For example, additive manufacturing may be used to create near-net-shape parts, which are then finished on a CNC machine to achieve final precision and surface quality. This hybrid approach leverages the advantages of both processes to maximize efficiency and part performance.

• • Safety in subtractive manufacturing is critical—not only for the protection of people working around the machine, but also for safeguarding the equipment itself from damage. CNC machines are powerful, precise, and fast-moving systems, and mistakes in programming, setup, or operation can lead to serious injury, costly repairs, or extended downtime.

    • While modern CNC machines are typically enclosed, this enclosure should never be mistaken for complete protection. The machine may be behind doors, but flying chips, broken tools, coolant spray, or even sudden movements can still pose hazards if safety procedures are ignored.

    • Overriding or bypassing a machine’s built-in safety mechanisms for the sake of speed or convenience is never acceptable. Interlocks, guards, door switches, and emergency stop systems exist for a reason: to protect both the operator and the equipment from harm. Disabling these features—whether to check a cut while the spindle is running, to speed up tool changes, or to avoid waiting for a door to unlock—removes a critical layer of protection and exposes everyone in the area to unnecessary risk. In a production environment, seconds saved by defeating a safety system can lead to hours, days, or even weeks lost to injuries, investigations, or repairs. The safest and most professional machinists are those who work with the machine’s safety systems, not against them.

  • One of the most important factors in maintaining a safe machining environment is the accuracy of the program and the correctness of the setup. Every move the machine makes is dictated by the code it is given. If that code contains errors—or if work offsets, tool lengths, or fixturing are not set correctly—the result can be a collision between the tool and the workpiece, a crash into the fixture, or even damage to the spindle itself. Such incidents not only threaten the machine and tooling but can create dangerous situations for the operator.

  • While the most obvious hazards in subtractive manufacturing are immediate—like moving spindles, sharp tooling, or flying chips—there are also long-term health risks that are easier to overlook. Many materials used in machining can create fine dust, mist, or fumes that, over time, may affect respiratory health. Cutting certain alloys, such as beryllium copper or composites containing carbon fibers, produces airborne particles that can be hazardous if inhaled. Even more common materials, like aluminum and steel, can generate fine particulate matter that should be controlled with proper ventilation and extraction systems.

    • Coolants and cutting fluids present another source of potential long-term exposure. While they are essential for reducing heat, improving tool life, and achieving high-quality surface finishes, prolonged skin contact can cause irritation or dermatitis, and breathing in coolant mist can impact lung health. Using mist collectors, wearing gloves where appropriate, and maintaining clean work practices can help minimize these risks.

    • There’s also the matter of noise. CNC machines, especially when roughing heavy cuts or running multiple spindles, can produce sound levels that, over months or years, contribute to hearing loss if proper hearing protection isn’t worn consistently.

    • Recognizing these long-term hazards is just as important as guarding against immediate injury. Good ventilation, mist control, routine housekeeping, proper PPE, and regular equipment maintenance are not just “extra steps”—they are part of building a career in machining that is safe, healthy, and sustainable over decades.