Cutting parameters include cutting speed（Vc）, feed rate（f）, depth of cut（Ap）Rotational speed (n).Cutting speed refers to the relative velocity at the contact line between the cutting tool and the workpiece. Its value directly affects the cutting temperature and tool life. Feed rate (f): The speed at which the tool moves relative to the workpiece. It is measured in millimetres per revolution (mm/rev) or millimetres per minute (mm/min).Depth of cut（Ap):The depth to which the tool enters the material in one pass. It is measured in millimetres (mm).Rotational speed(n): The number of spindle revolutions per minute (rpm). Depends on the cutting speed and tool diameter. How to configure appropriate cutting parameters?

In this article, we will provide a practical guide on how to choose the best CNC machining parameters to achieve excellent results.

Why are cutting parameters so important?

CNC machining is a process that requires precision, knowledge and experience. One of the key factors determining the quality and efficiency of this process is the selection of optimal machining parameters. Incorrect settings can lead to damage to tools, the material being machined, and even the machine.

1. Direct Impact on Part Quality & Accuracy

Surface Finish: Cutting parameters directly determine the final look and feel of the part.

Too High Feed Rate or Wrong Speed: Causes vibrations, chatter, and tearing, leaving a rough, poor-quality surface.

Optimized Parameters: Produce a smooth, clean surface that often requires no additional finishing.

Dimensional Accuracy: Excessive cutting forces (from high feed or depth of cut) can deflect the tool, workpiece, or the machine itself, resulting in a part that is out of tolerance.

2. Direct Impact on Tool Life & Cost

Cutting speed is one of the most important parameters, as it affects tool life, surface quality and process efficiency. Too high a speed can lead to overheating of the tool, and too low a speed can lead to inefficient machining.

Too High Speed: Generates extreme heat, causing the cutting edge to soften, wear out rapidly, or fail catastrophically.

Too Low Speed: Allows the tool to rub instead of cut, causing premature dulling and work hardening of the material.

Optimized Parameters maintain a "sweet spot" temperature, allowing the tool to last for hours instead of minutes, drastically reducing tooling costs.

3. Direct Impact on Productivity & Efficiency

Metal Removal Rate (MRR): This is the volume of material removed per minute. MRR is calculated directly from the cutting parameters (especially feed rate and depth of cut).

Conservative Parameters: Lead to very low MRR, meaning it takes a long time to complete a part.

Aggressive, Optimized Parameters: Maximize MRR, allowing parts to be made faster, increasing throughput and profitability.

4. Direct Impact on Process Stability & Safety

Chatter and Vibration: Unstable parameters cause chatter—a violent vibration that is loud and destructive.

Chatter damages the tool, ruins the part's surface, and can damage the machine spindle.

Tool Failure: A broken tool due to improper parameters is not just a cost issue; it's a safety hazard. Flying tool fragments and the subsequent crash can be dangerous.

5. Impact on Overall Cost

Cutting parameters sit at the center of the manufacturing cost triangle:

Poor parameters increase cost by:

• Increasing Cycle Time (low efficiency).

• Increasing Tooling Cost (short tool life).

• Increasing Scrap/Rework Cost (poor quality)

Understanding the Basic Parameters of CNC Machining（carbide end mill): cast iron, SS, aluminum alloy, steel

Cast Iron:

Rake angle: 5°-10°, Clearance angle: 4°-8°,Inclination angle: 0°-5°,Nose radius: 0.5mm-1mm,Lead angle: 45°-90°

Cutting Parameters:

• Cutting speed(Vc): 110-150 m/min

• Feed rate(fn): 0.1-0.35 mm/rev

• Depth of cut(Ap): To be determined based on specific machining conditions

Stainless Steel:

Rake angle: 10°-15°, Clearance angle: 6°-8°,Inclination angle: 0°-5°,Nose radius: 0.2mm-0.5mm,Lead angle: 45°-90°

Cutting Parameters:

• Cutting speed(Vc): 50-150 m/min

• Feed rate(fn): 0.1-0.4 mm/rev

• Depth of cut(Ap): ≤ 1.5 mm

• 
  

Aluminum Alloy:

Rake angle: 15°-30°, Clearance angle: 10°-20°,Inclination angle: 0°-5°,Nose radius: 0.2mm-0.5mm,Lead angle: 45°-75°

Cutting Parameters:

• Cutting speed(Vc): 300-600 m/min

• Feed rate(f): 0.2-0.8 mm/rev

Steel:

Rake angle: 5°-15°, Clearance angle: 6°-8°,Inclination angle: 0°-5°,Nose radius: 0.2mm-0.5mm,Lead angle: 45°-90°

Cutting Parameters:

• Cutting speed(Vc): 100-300 m/min

• Feed rate(f): 0.1-0.5 mm/rev

• 
  

• 

In practical applications, many factors influence the determination of cutting speed. （carbide end mill cutting speed formula: Vc=π×D×n/1000 ）

01 Workpiece Material

The properties of different workpiece materials, such as hardness, strength, toughness, and thermal conductivity, vary significantly, leading to different requirements for cutting speed. For instance, aluminum alloys, with their low hardness and good thermal conductivity, can be machined at cutting speeds of 300-2000 m/min. In contrast, stainless steel, characterized by high strength, toughness, and poor thermal conductivity, typically requires cutting speeds in the range of 50-200 m/min.

02 Cutting Tool Material

The material of the milling cutter determines its performance characteristics like heat resistance, wear resistance, and hardness, which consequently influence the applicable cutting speed. High-Speed Steel (HSS) cutters, with relatively poor heat resistance, are generally used at cutting speeds of 30-80 m/min. Carbide cutters, offering good heat and wear resistance, can operate at speeds of 100-300 m/min. Ceramic cutters, possessing exceptional heat resistance, enable cutting speeds reaching 500-1000 m/min.

03 Tool Geometry Parameters

Tool geometry parameters, such as rake angle, clearance angle, and lead angle, affect cutting forces, chip evacuation, and heat dissipation. Increasing the rake angle creates a sharper cutting edge, reducing cutting forces and heat, thereby allowing for higher cutting speeds. Reducing the lead angle increases the width of cut and decreases the undeformed chip thickness, altering the cutting forces and heat generation, which in turn influences the selection of an appropriate cutting speed.

04 Cutting Conditions

Feed rate and depth of cut are interrelated with cutting speed. Increasing the feed rate or depth of cut raises the cutting forces and heat generated. To ensure tool life and machining quality, the cutting speed must be reduced accordingly. Conversely, if feed rate or depth of cut is decreased, the cutting speed can be appropriately increased.

05 Tool Wear Condition

As the tool is used, the cutting edge gradually wears, leading to degraded cutting performance. A new tool, with its optimal performance, can utilize higher cutting speeds. Once the tool wears to a certain extent, the cutting speed must be reduced; failure to do so will adversely affect machining quality and tool life.

06 Cooling and Lubrication Conditions

Effective cooling and lubrication carry away cutting heat, lower the temperature of the tool and workpiece, and reduce friction and wear. Employing efficient coolant or lubrication methods enables the maintenance of tool performance and machining quality at higher cutting speeds. Conversely, if cooling and lubrication are inadequate, the cutting speed must be reduced.

Depending on the material and type of machining, the following can be used:

• Liquid cooling:

– Turning and milling of steel, aluminium and cast iron alloys.

– Machining requiring high cutting speeds and precision.

– Deep drilling, where chip evacuation is crucial.

• Air cooling:

– Machining of aluminium, magnesium alloys and composites.

– Operations where the coolant could contaminate the material or cause thermal shock to the cutting edge.

– Milling of thin-walled components where coolant could cause distortion.

• Dry processing:

– Hard turning with ceramic or CBN tools.

– Coolant-sensitive materials (e.g. some composites).

– Dry machining in the aerospace and automotive industries.

07 Machine Tool Performance

The performance of the machine tool, including its power, speed range, rigidity, and stability, impacts the feasible cutting speed. A low-power machine tool cannot provide sufficient drive force to support high cutting speeds. A machine tool with insufficient rigidity is prone to vibration at high cutting speeds, compromising machining accuracy and surface finish, thus necessitating a reduction in cutting speed.

Summary:

Choosing the optimum CNC machining parameters is the key to efficient and precise production. Remember that every material, tool and project requires an individual approach. Using the tips above, you can significantly improve machining quality, extend tool life and increase process efficiency. If in doubt, it is always advisable to consult BAIYANG'S experienced engineer.