Introduction to Casted Materials in CNC Machining(whats bronze made of Anna)
- source:NEWRGY CNC Machining
In this article, we will provide an overview of various casted materials commonly used in CNC machining and discuss considerations for machining each type of material. We will also explore the benefits of CNC machining casted components compared to other manufacturing techniques.
Cast iron is arguably the most common cast material used in CNC machining. It offers excellent machinability thanks to its graphitic structure which provides natural lubricity and chip-breaking properties. Gray cast iron in particular is highly suitable and cost-effective for complex, high-volume CNC machined components.
With a carbon content between 2-4%, gray cast iron is relatively soft and easy to cut. It produces discontinuous chips which prevent workpiece buildup and enables higher metal removal rates. The material also absorbs vibration well during machining. Surface finishes down to 10 Ra microinches or less are possible.
Ductile iron contains spherical graphite nodules instead of flakes, making it stronger and more impact resistant than gray cast iron. However, ductile iron is more difficult to machine and requires higher cutting forces. Tool wear is increased compared to gray cast iron.
When machining cast irons, the following recommendations should be considered:
- Use cobalt or carbide tools with positive rake angles
- Maintain low feed rates and high speeds
- Use rigid setups and flooded coolant
- Apply abrasion resistant coatings on tools
Cast aluminum alloys like A356 and 319 are popular for their light weight, corrosion resistance, and easy machinability. The silicon content in the alloys causes the formation of discontinuous chips for efficient chip evacuation. Their low melting point also allows for casting into complex shapes.
Carbide and ceramic tools are recommended for aluminum alloys due to the tendency for work hardening and built-up edge. Coolant should be applied liberally to help regulate temperature. Light depths of cut and lower feed rates are also preferred.
The soft nature of aluminum alloys enables them to be milled rapidly. However, the low rigidity necessitates securing the workpieces firmly during five-axis or multiaxis CNC machining to minimize vibrations and chatter.
Cast tool steels like H13 and P20 are processed via CNC machining into dies, molds, and other tooling used for shaping of plastics, rubbers, composites and metals. Their high hardness and wear resistance allow them to withstand repeated imprinting without losing dimensional accuracy.
Hardened tool steels are extremely abrasive and prone to work hardening. CBN, ceramic and PCD coated carbide tools should be utilized for best tool life. Use high coolant pressure and flow rate to reduce friction and dissipate heat at the cutting interface. Light finishing passes will minimize work hardening effects on the machined surfaces.
Cast austenitic and duplex stainless steels offer excellent corrosion resistance paired with good machinability. However, their low thermal conductivity necessitates proper cooling and lubrication during machining. Built-up edges can also be problematic with sticky chips adhering to the cutting tool.
Positive geometries with ground carbide inserts work well for cast stainless steels. Low feed rates are recommended. Use high pressure coolant directed at the cutting edge for better heat dissipation.
Brass and Bronze
Cast brasses like CDA 836 (naval brass) and bronzes such as CDA 954 (aluminum bronze) are valued for their attractive finish and resistance to wear, galling and corrosion. As copper alloys though, they present some machinability challenges.
Their ductile nature leads to long continuous chips with poor breakability. Brass and bronze also work harden rapidly, causing cutting forces to increase during machining. Use rigid setups and sharp tools with positive rake angles. High coolant pressure can aid chip evacuation and cooling.
Benefits of CNC Machining Casted Materials
- Precision and Accuracy - CNC machining allows casted materials to be shaped to tight tolerances and intricate geometries that would be impossible through manual methods. Parts can be machined identically with a high degree of repeatability.
- Design Flexibility - Complex casted shapes can be further modified via CNC machining. This enables consolidation of parts and innovative designs not feasible with just casting alone. Multi-axis CNC machining opens up even more possibilities.
- Improved Surface Finishes - The optimized cutting parameters and rigid machine tool construction inherent to CNC machining results in far superior surface finishes compared to manual machining of casted materials.
- Cost Effectiveness - Combining casting and CNC machining is economical for medium to high production runs. The near net shape from casting minimizes material waste. CNC machining speeds up secondary processing.
- Automation - CNC machining enables automatic processing of castings with minimal operator intervention. Multiple cast components can even be sequentially machined on pallet systems.
Casting provides an efficient way to produce near net shape components in volume. CNC machining is then leveraged to precision finish these casted materials into final parts. Metals like aluminum, iron and tool steel are commonly machined from castings due to their favorable properties. Considering aspects like tool selection, cutting parameters, rigidity and cooling is key to successfully machining casted materials on CNC machine tools. The pairing of casting and CNC machining delivers high quality finished components quickly and cost effectively. CNC Milling CNC Machining