What is Machinability? Learn How To Enhancing Material Processing Efficiency

Dive into the world of Machinability through our comprehensive blog. Explore the factors influencing material processing, evaluation methods, and comparisons of materials. Learn to enhance Machinability practically and understand its applications in engineering. Stay ahead of future trends and dispel misconceptions. Join us on this insightful journey to efficient material machining.

Table of Contents

What is Machinability?

Machinability is a property that indicates how easily machinable material is to be machined. Soft-getter cutting tools can work at very fast speeds. They reduce tool wear and energy use. This ability improves surface quality and lowers costs. The materials with poor machinability contrast with these. They take more time and cost more. This is because the tools tend to fail more easily. More energy is then spent on the production, leading to higher costs.

The machinability of a material is largely due to hardness, tensile strength, thermal properties and micro-structure, and a number of other factors. These factors influence the process of machining of metal, its result being hard or simple. Engineers focus on machinability and material properties. They select materials that are easy to machine and perform well.

As a result, molds for injection are designed based on highly machinable materials. They often make better products and speed up manufacturing. This shortens production and cuts costs in the long run.

Factors Affecting Machinability

Machinability depends on factors like material hardness, strength, ductility, fracture toughness, and thermal conductivity. For instance, stainless steel, a hard material, causes tool wear during machining. In contrast, aluminum, a softer material, is easily machinable but yields less precise components.

Diverse material properties impact machining performance. Hard materials demand slower cutting speeds and robust tools to avoid wear. Ductility influences chip formation and tool life; brittle materials may cause abrupt tool failure. Thermal conductivity affects heat dissipation during machining, impacting tool life and surface finish.

Proper material selection significantly enhances machinability. Engineers select materials based on project requirements. For precision components, low-hardness, high-machinability materials are preferred. Informed material choices lead to greater efficiency and improved machining quality.

What is Machinability Ratings?

Machinability ratings show how hard materials can be machined. They are a standardized characteristic developed by the American Iron and Steel Institute (AISI). The score comes from the tool life control, speed control, and the reference material’s score (AISI B1112 steel). It gives a 100 to the baseline.

Like the temperature scale (AISI B1112 for Reference material), these scores define the machinability of materials. They range from 100 and up. On the other hand, the harder it is to machine a material, its score falls relatively below the 100% mark. This is shown by the rated machinability of SAE 6061 aluminum. It is 270%, a very high score showing great ease to the machine. In contrast, ASTM Grade 5 titanium rates 17% and can barely be machined.

Machinability can be assessed by examining several key factors:

  • Power Consumption: The energy needed to cut the product plus the energy used during transformation processes.
  • Cutting Tool Life: Addressing the issues of power source, the duration for which this tool can be used before it needs to be replaced again.
  • Surface Finish: Normally, a smooth surface (machined) free from qualitative changes is the target.

These ratings can compare how easy it is to machine different materials. But, they do not include all the details that may affect machining.

Global Machinability Standards and Key Evaluation Metrics

Different countries and regions may have their own standardization organizations and corresponding standards. If you need to find specific Machinability standards documents for a particular country or region, it is best to check the official websites of relevant standardization organizations or government agencies, or seek assistance from local libraries, universities, or professional associations. And below is some common standard.

  • ISO Standards: The International Organization for Standardization (ISO) has published several standards related to Machinability, such as ISO 3685:1993 “Tool life testing with single-point turning tools” and ISO 3002-2:1982 “Geometrical product specifications (GPS) – Surface texture: Profile method – Terms, definitions and surface texture parameters.”
  • American Standards:The American National Standards Institute (ANSI) and the American Society for Testing and Materials (ASTM) have issued various standards related to Machinability, including ASTM A1038-2005 “Standard Test Method for Portable Hardness Testing by the Ultrasonic Contact Impedance Method.”
  • European Standards:The European Committee for Standardization (CEN) has released several standards related to Machinability, such as EN ISO 3685:2016 “Tool-life testing with single-point turning tools.”
  • Japanese Standards:The Japanese Industrial Standards (JIS) have published several standards related to Machinability, such as JIS B 0651:1993 “Test conditions for turning and plain milling metal-cutting tests.”

But the Machinability rate evaluation standards are not a set of official standards, but rather some common measures of material machinability as below.

  • Cutting Force and Power:Measures the force exerted by the material on the cutting tool and the energy required during machining; lower values indicate better Machinability.
  • Cutting Temperature:Evaluates the heat generated during machining; lower cutting temperatures contribute to improved Machinability.
  • Cutting Edge Wear:Observes the degree of wear on the cutting tool’s edge; good Machinability reduces rapid tool wear.
  • Chip Form:Examines the shape and length of chips produced during machining; easy-to-handle and short chips enhance Machinability.
  • Surface Roughness:Measures the smoothness of the machined surface; good Machinability results in better surface quality.
  • Machined Surface Quality:Considers the achieved surface smoothness and accuracy during machining.
  • Machining Precision:Evaluates the accuracy of the dimensions and shape of the workpiece during machining.
  • Tool Life:Studies the lifespan of the cutting tool during machining; better Machinability prolongs tool life.
  • Cutting Force Coefficient Curve: Plots the relationship between cutting force and cutting speed, aiding in understanding material performance at different cutting speeds.
  • Machining Stability:Assesses the stability and consistency of the machining process under various cutting conditions.

These evaluation methods are crucial in material machining. They provide insights into material behavior during machining, enabling appropriate conditions. Understanding cutting performance helps choose suitable tools and parameters. Monitoring Machinability index cutting forces prevents tool breakage. Surface roughness ensures product quality, while tracking Machinability rates cutting temperatures avoids thermal damage.

Machinability Comparison of Common Materials

Comparing the machinability of different materials machinability examples, such as steel, aluminum, copper and alloys reveals significant differences between them. The hardness of steel requires more care in machining than the relatively soft aluminum. Copper is known for its excellent thermal conductivity, but affects machining differently. Alloys have a wide range of properties and their machining rates vary, making material selection critical.

Below is the machinability chart of some common materials, which is an important reference for selecting materials based on their machinability.

MaterialHardness (HRC)Machinability
Steel30-60Fair to Good
Stainless Steel30-60Fair to Good
Cast Iron20-60Fair to Good
Titanium30-48Fair to Good
PlasticsVariesExcellent (Generally)
WoodVariesExcellent (Generally)
Nickel50-70Fair to Good
Zinc30-70Good to Excellent
Bronze60-90Good to Excellent
Magnesium30-55Fair to Good
Tool Steel55-65Fair to Good
Inconel20-45Fair to Good
Tungsten Carbide70-90Poor to Fair
Carbon FiberVariesExcellent (Generally)

Methods to Improve Machinability

Lubricants minimize friction and heat during cutting. Properly selected cutting tools, like carbide tools, enhance efficiency. Optimizing cutting parameters, including feed rate and speed, significantly influences outcomes. For example, a water-based coolant improves Machinability rates.

Implementing these approaches augments efficiency, curbing costs and tool wear. Lubricants reduce friction, extending tool life. Carefully selected cutting tools impact the Machinability index. Optimizing cutting parameters leads to elevated Machinability rates, enhancing productivity and saving expenses.

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