Introduction to Casted Materials in CNC Machining(vin tag rivets Owen)

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Computer numerical control (CNC) machining is a manufacturing process that uses programmed computer software to control machine tools. These tools then cut and shape stock material into custom parts and products. CNC machining is commonly used with metals, plastics, wood, foam, and wax. However, casted materials are also frequently machined with CNC.
What are Casted Materials?
Casting is a manufacturing process where liquid material is poured into a mold cavity and allowed to solidify. This results in the formation of a part or product in the shape of the mold. Some of the most common casted materials used in CNC machining include:
- Aluminum - An extremely versatile material, aluminum is lightweight, corrosion-resistant, conductive, and durable. It casts well and is easy to machine.
- Iron - Most commonly cast into gray iron or ductile iron, iron is hard, strong, and inexpensive. It is used for housings, bases, engine blocks, gears, and more.
- Steel - Usually cast into carbon steel or alloy steel, steel offers high strength and hardness. It is commonly used for industrial parts and molds.
- Brass - A copper-zinc alloy, brass is corrosion resistant, machinable, and attractive in appearance. It's used for valves, fittings, gears, and decorative parts.
- Bronze - Containing mostly copper with added tin, bronze offers good corrosion resistance, wear properties, and low friction. It's used for bearings, bushings, and statues.
- Zinc - Zinc has a low melting point and casts easily into intricate shapes. It is then often plated for corrosion protection. Common uses include die cast parts.
Why Machine Casted Parts?
There are several reasons CNC machining is commonly used on casted materials:
- Closer Tolerances - The casting process can only produce relatively crude and imprecise part dimensions. CNC machining is used to bring casted parts to more precise dimensional tolerances and accuracies.
- Improved Surface Finishes - Unmachined casted surfaces are relatively rough. CNC machining is used to improve surface finishes for assembly, function, and appearance.
- Added Holes, Slots and Features - Casting cannot form enclosed holes or internal features. CNC machining adds any required holes, slots, threads, grooves, flats, and intricate contours.
- Component Assembly - CNC machining creates precision mounting surfaces and features used to assemble casted parts into finished products and devices.
- Performance Enhancement - CNC machining can remove excess material to lighten parts. It can also improve strength, balance stresses, and enhance part performance.
The CNC Machining Process for Casted Materials
Preparing casted parts for CNC machining requires careful planning, fixturing, and tooling consideration. Here is an overview of the basic CNC machining process for casted materials:
1. Design Analysis - Engineers analyze casting designs to determine required machining operations and sequences. The goal is to maximize quality and productivity.
2. Fixturing - Castings must be securely fixtured in the CNC machine to avoid movement during cutting. Fixtures prevent vibration and chatter which can break tools. Custom fixtures keep each unique casting in the ideal orientation for machining.
3. Tool Selection - CNC tool selection depends on the material, available machine power, desired surface finish, and features to be machined. Diamond inserts and carbide end mills are common. Tool reach is considered to access necessary surfaces.
4. Rough Machining - The initial roughing cuts remove the bulk of excess material to get close to the final part dimensions. Large depths of cut and feed rates are used for fast metal removal.
5. Semi-Finishing - Intermediate semi-finishing passes bring the part closer to the print specifications using smaller cuts for improved accuracy.
6. Finishing - The final finishing tool paths produce the tight dimensional tolerances and surface finishes called for in the engineering drawings using very light depths of cut.
7. Deburring - Hand or vibratory deburring removes any small burrs, sharp edges, or chips left behind after machining. This improves safety and function.
8. Inspection - Machined castings are thoroughly inspected to verify they meet all print specifications. Additional bench work or re-machining may be required if any features are out of tolerance.
9. Additional Processing - Additional secondary processing such as tapping, threading, plating, heat treating, welding and assembly are often required after CNC machining.
10. Final Verification - Castings undergo final inspection and quality checks before shipment to customers. This validates the machining process produced accurate, high-quality finished components.
Mastering CNC machining for casted materials allows manufacturing shops to expand their services and production capabilities. The pairing of casting and CNC machining combines design freedom and material savings with enhanced precision. Parts can be near net shape casted, with CNC machining providing reliable accuracy and surface quality. Other benefits include faster production, lower scrap rates, and the ability to consolidate assemblies. With careful planning and execution, CNC machining delivers casted parts that meet even the tightest tolerances and most demanding criteria. CNC Milling CNC Machining