How to choose milling materials? Comprehensive answers from basics to industry applications

Introduction: Milling materials – a central cornerstone of modern manufacturing

In high-end manufacturing fields such as aerospace, medical devices, and mold processing, the choice of "milling material" directly determines product accuracy, processing efficiency, and production costs. Have you ever chosen the wrong material and caused your tool to wear out too quickly? Confused about how to set milling parameters for different materials? This article will help you thoroughly understand the key knowledge of milling materials and solve the core problems in actual processing with popular language + professional cases from basic attributes to the forefront of the industry.

1. Basic material attributes and classification: the first step in selecting the right material

1.1 Metal Milling Materials: The "Workhorse" of Industrial Manufacturing

Metal milling materials are currently the most widely used category, and the common types and characteristics are as follows:

Real case: When processing titanium alloy blades in an aviation parts factory, due to the high strength and low thermal conductivity of the material, ordinary parameters were used in the early stage, resulting in a tool wear rate of 20% per hour. Subsequently, by adjusting the process (more on this below), the wear rate was reduced to less than 5%.

1.2 Non-metallic milling materials: a "new force" for innovative applications

Non-metallic milling materials are rapidly emerging in emerging fields due to their unique properties:

• Engineering plastics (such as PEEK, nylon): wear-resistant, insulating, suitable for electronic equipment shells, pay attention to temperature control during milling to prevent deformation;
• Composite materials (such as carbon fiber reinforced resin): high specific strength, light weight, is a key material in aerospace, but the fiber is easy to crack and has extremely high requirements for tools;
• Wood: Traditional non-metallic materials, often used in furniture manufacturing, milling should pay attention to the grain direction to avoid burrs.

1.3 Material hardness, strength and machinability

Material hardness and strength are the core indicators affecting milling difficulty: the higher the hardness, the greater the cutting resistance; The higher the strength, the more prone the material to elastic deformation. The machinability rating is a common industry standard, mainly based on cutting force, tool wear speed, surface roughness and other indicators (such as level 1 is the most difficult to machine, level 5 is the easiest to machine).

1.4 Heat treatment state: the key to changing the processing properties of materials

The heat treatment state of the material directly affects the milling effect:

• Annealing treatment: reduce the hardness of the material, improve the machinability, suitable for stainless steel, mold steel and other difficult-to-machine materials;
• Quenching treatment: to improve the strength and hardness of the material, more wear-resistant tools and higher cutting speed should be selected during milling;
• Case: A mold factory processes hardened Cr12MoV mold steel (hardness HRC60+), and unannealed direct milling leads to tool chipping, and the processing efficiency is increased by 3 times after annealing (hardness HRC25-30).

2. Milling process and parameter optimization: core techniques to improve efficiency

2.1 Cutting speed and feed: controlling the "rhythm" of machining

Cutting speed and feed are the core parameters of milling, which need to be precisely matched according to the material properties:

• Cutting speed: refers to the linear speed of the cutting edge of the tool relative to the material (unit: m/min), too high can easily lead to tool overheating, too low is inefficient;
• Feed rate: refers to the feed distance (unit: mm/r or mm/z) of the tool per revolution or each tooth, too large is easy to produce burrs, and too small is poor surface roughness.

Practical Reference Table: Recommended milling parameters for common materials

2.2 Milling Force vs. Tool Load: Balancing efficiency with longevity

Milling force is the force of the tool on the material during machining, and its magnitude is directly related to the hardness of the material and cutting parameters. Excessive tool loads can accelerate wear and even cause tool breakage. Solving Tips:

1. Layered milling: splitting the depth of cutting to reduce the load on a single cut;
2. Optimize tool paths: Avoid vertical downing, employing spiral or ramp downing.

2.3 Coolant and Lubrication Strategy: The "Cooling Artifact" of Processing

Coolant and lubrication strategies directly impact machining quality and tool life:

• Wet milling: using emulsion or cutting oil, good cooling effect, suitable for difficult materials such as stainless steel and titanium alloy, which can reduce tool wear by more than 30%;
• Dry milling: no coolant, environmentally friendly and low cost, suitable for aluminum alloy, wood and other easy-to-cut materials, but the cutting speed needs to be controlled;
• Case: When processing aluminum alloy cylinder blocks, an auto parts factory uses dry milling (cutting speed 400m/min), with a surface roughness of Ra0.8μm to meet product requirements.

2.4 High-speed milling parameters: Pursue ultimate efficiency

High-speed milling (cutting speeds 2-5 times higher than conventional) can significantly improve efficiency, but it needs to be met:

1. Material adaptation: preferentially used for easy-to-cut materials such as aluminum alloys and engineering plastics;
2. Equipment requirements: good rigidity of the machine tool, high spindle speed (≥10000r/min);
3. Parameter points: Reduce feed rate (conventional 50%-70%), increase cutting speed, use special high-speed tools.

3. Tool selection and matching: the "sharp weapon" of precision machining

3.1 Tool Material: The core that determines the tool's performance

Common tool materials and applicable scenarios:

• High-speed steel: good toughness, low price, suitable for wood, mild steel and other easy-to-cut materials, machinability rating of 4 or above materials;
• Cemented carbide: high hardness, strong wear resistance, suitable for stainless steel, aluminum alloy, etc., is the most widely used tool material at present;
• Ceramic tools: High temperature resistance, extremely high hardness, suitable for difficult materials such as titanium alloys and superalloys (machinability rating below level 2).

3.2 Tool geometry: the key to affecting the machining effect

The number of edges, helix angles, and coatings in the tool geometry need to be selected in a targeted manner:

• Number of blades: 2-3 flutes for rough milling (large chip removal space), 4-6 flutes for fine milling (good surface quality);
• Helix angle: 30°-45° for aluminum alloy (to reduce sticky knife), 45°-60° for stainless steel (to increase the cutting edge length);
• Coatings: TiN coating (universal), TiAlN coating (high temperature resistance, suitable for high-speed milling), DLC coating (friction reduction, suitable for plastics).

3.3 Special tools: to meet special machining needs

• Rough milling cutter: sharp cutting edge, large chip discharge groove, suitable for removing a large amount of margin, such as mold steel roughing;
• Precision milling cutter: with a large number of cutting edges and high precision, suitable for surface finishing, such as medical device parts;
• Profiling mills: Shaped to fit the contours of the workpiece, suitable for complex surface machining, such as aerospace blades.

3.4 Tool wear and life: the key to controlling costs

The main causes of tool wear are: high material hardness, improper cutting parameters, and insufficient lubrication. Tips for Extending Life:

1. Regularly check the cutting edge of the tool and replace it in time when the wear exceeds 0.2mm;
2. Adopt tool life management system to preset life according to processing materials and parameters;
3. Case study: A mold factory improved tool life from 50 pieces/bar to 150 pieces/handle by optimizing tool-material matching (Cr12MoV mold steel + TiAlN-coated carbide tool), reducing the cost per piece by 20%.

3.5 Tool-Material Matching Principles: Core Logic

1. Hardness matching: tool hardness ≥ material hardness + 3HRC;
2. Complementary performance: choose hydrophobic coated tools for easy-to-stick knife materials (such as aluminum alloys), and choose high-toughness tools for high-strength materials (such as titanium alloys);
3. Efficiency priority: choose high-wear resistance tools for mass production, and general-purpose tools for small-batch processing.

4. Industry applications and special materials: expand the boundaries of processing

4.1 Milling for Aerospace Materials: Challenges and Breakthroughs

Milling difficulties for aerospace materials (superalloys, carbon fiber):

• Superalloys (such as Inconel 718): High temperature resistance, high hardness, machinability rating of 1.5, prone to edge accumulation during cutting;
• Solution: Using ceramic tool + wet milling, cutting speed 80-100m/min, feed rate 0.1mm/z;
• Data support: An aviation factory adopted this scheme to increase the processing efficiency of superalloy blades by 40%, and the surface roughness reached Ra0.4μm.

4.2 Die Steel Milling: Balancing Precision and Efficiency

Milling requirements for mold steels (e.g., Cr12MoV, H13):

• Accuracy: dimensional tolerance ±0.005mm, surface roughness Ra≤0.8μm;
• Key points of the process: annealing first, rough milling and then aging treatment, and high-speed milling for fine milling;
• Case study: A mold factory processes H13 mold steel, reducing the scrap rate from 5% to 1% through the "rough milling-aging-finishing" process.

4.3 Milling of medical device materials: safety first

Special requirements for medical device materials (cobalt-chromium alloys, biocompatible materials):

• Biocompatibility: avoid contamination during processing, and the tool needs to be sterile;
• Accuracy requirements: orthopedic implant size tolerance ±0.003mm;
• Material properties: Cobalt-chromium alloy has high hardness (HRC35-40), and ceramic tools + dry milling are required.

4.4 Strategies for difficult-to-process materials: Overcome core problems

Milling strategies for difficult-to-machine materials (machinability rating ≤ level 2):

1. Pretreatment: annealing and softening treatment to reduce hardness;
2. Tool upgrade: PCD (polycrystalline diamond) or CBN (cubic boron nitride) tools;
3. Process optimization: Low-temperature cutting (-50°C~-100°C) is used to reduce tool wear.

4.5 New material processing trends: future directions

• Lightweight materials: carbon fiber, magnesium alloy and other applications have expanded, and the chipping resistance of tools is more required;
• Functional materials: shape memory alloys, ceramic matrix composites, which need to develop special milling technology;
• Industry data: The demand for milling lightweight materials in the aerospace sector is expected to grow by 35% in 2025 (source: China Machinery Industry Federation).

5. Yigu Technology's view

The essence of the selection and application of milling materials is the precise matching of material properties, process parameters and tool performance. In the context of the transformation of the manufacturing industry to high-end and intelligence, enterprises need to jump out of "empiricism" and optimize solutions based on data and cases. Yigu Technology suggests: Give priority to the "material-tool-parameter" integrated solution to predict machining problems in advance through simulation; At the same time, we will pay attention to the development of new materials and new tools, and transform technological innovation into core competitiveness. In the future, milling will pay more attention to efficiency, environmental protection and precision, and mastering the core knowledge of materials is the key to the company's foothold.

6. FAQ

1. Q: How to solve the problem of easy knife sticking when milling aluminum alloy?

A: TiAlN or DLC coated tools are used to increase the cutting speed (300-500m/min), and dry milling or kerosene is used as coolant to reduce the feed rate (0.2-0.3mm/z).

2. Q: What tool is most suitable for difficult materials (such as titanium alloys)?

A: Ceramic tools or PCD tools are preferred, with TiAlN coating, using low speed (50-80m/min), small feed (0.05-0.2mm/z), and layered milling process.

3. Q: How to choose between dry and wet milling?

Answer: easy-to-cut materials (aluminum alloy, wood) are selected for dry milling (environmentally friendly and efficient); Selective wet milling for difficult-to-machine materials (stainless steel, titanium alloy) (cooling and lubrication, extending tool life).

4. Q: How can I tell if a tool needs to be replaced?

Answer: When the roughness of the machining surface deteriorates (such as Ra>1.6μm), the dimensional tolerance exceeds, the tool edge cracks or the wear exceeds 0.2mm, the tool needs to be replaced in time.

5. Q: What are the core process points of die steel milling?

Answer: Annealing treatment (reducing hardness) first, rough milling followed by aging treatment (eliminating internal stress), high-speed milling (cutting speed 150-200m/min), and 4-6 flute finish milling cutters are selected.