How Brass is Made and Machined with CNC(anodizing Franklin)

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Brass is a metal alloy made up of copper and zinc. The proportions of copper and zinc can vary to create different types of brass with unique properties. Brass is highly malleable, durable, and corrosion resistant, making it a popular material for musical instruments, plumbing fixtures, gears, ammunition casings, and decorative items. Understanding how brass is made and machined using computer numerical control (CNC) provides insights into this versatile metal.
Making Brass
Brass production starts by melting and mixing pure copper and zinc metals. The percentage of copper versus zinc determines the type of brass. Common brass alloys include:
- Yellow brass - 67% copper, 33% zinc
- Red brass - 85% copper, 15% zinc
- Naval brass - 60% copper, 39% zinc, 1% tin
- Aluminum brass - 77% copper, 2% aluminum, 21% zinc
Melting is performed in a furnace at around 900-940°C. Once the metals are fully liquefied, they are combined and stirred to produce a homogeneous mixture. The molten brass can then be cast into ingots or other shapes.
After cooling, the brass ingots are reheated and hot worked through processes like rolling, extrusion, or forging to create brass sheets, tubes, rods or more complex shapes. Annealing may be performed periodically during hot working to soften and re-work the brass as it hardens. The final microstructure and mechanical properties are controlled through the alloy composition, hot working, and heat treatment.
Machining Brass with CNC
Once the raw brass stock is fabricated, it can be machined into parts and products. Modern CNC machining centers are commonly used for precision brass machining. CNC machining utilizes computerized controls to automate the machining process.
CNC milling is performed on brass parts to cut and shape them to specifications. In CNC milling, the brass stock is fixtured on the machine bed while rotating end mills make passes across the surface to remove material. Features like pockets, slots, chamfers, and contours can be produced via programmed milling toolpaths.
CNC turning is used to machine rotationally symmetric brass parts. The brass stock is held horizontally in the chuck of a CNC lathe. As the part rotates, single point cutting tools make axial and radial cuts to shape the exterior and interior features. Common operations include facing, boring, grooving, parting, threading, and profiling.
CNC machining offers several benefits for brass parts:
- High precision and tolerances down to +/- 0.005 in or less
- Faster production compared to manual machining
- Ability to machine complex 3D contours and shapes
- Minimal setup time between jobs
- Automated unattended operation
However, CNC does require specialized programming knowledge and upfront costs for equipment. The programs are generated using CAD models and CAM software. A skilled machinist is needed to oversee the CNC equipment and verify quality.
Brass Machining Tips
Here are some tips when machining brass on a CNC machine:
- Use sharp carbide end mills and inserts. HSS tools will wear quickly in brass.
- Take light depths of cut and faster feeds/speeds. Brass cuts easily so avoid overly aggressive parameters.
- Use compressed air to blow away chips during operation. Brass produces long stringy chips that can recut the surface.
- Apply cutting fluid/oil to reduce friction and prevent chips from sticking.
- Avoid using coolant washout as it can stain and corrode brass.
- Watch for work hardening. Annealing between operations may be needed for extensive machining.
- Use higher spindle RPMs than steel (up to 10,000 RPM on small tools). Brass requires faster speeds.
- Account for brass thermal expansion. Tight pockets may need allowance for expansion.
With the right techniques, CNC machining can produce highly accurate and aesthetic brass components to meet design specifications. Brass remains a popular choice for both form and function across many industries due to its unique combination of material properties. CNC Milling