Turning Parameters – How to Choose the Right Ones for Machining

Choosing the right parameters for cutting machining is crucial for the quality of the machined part, tool durability, and process efficiency. Here are the most important parameters to consider.

Cutting speed in CNC turning - arises from the rotation of the workpiece at a specified rotational speed. It should be noted that the speed will not be equal across the entire cross-section of the workpiece being machined. It decreases as it approaches the axis of the part being machined.

What does this mean in practice during turning? If the cutting speed is to remain constant, the rotational speed value must be adjusted according to the change in the turning radius, which depends on:

• Material being machined

• Type of tools

Feed in turning - this is the movement of the tool in the direction of the feed during one rotation of the workpiece, measured in mm per one rotation of the turned part.

The impact of feed on the turning process:

• Surface quality - the larger the feed, the greater the roughness of the machined surface. Large feed rates are used for rough machining, while small ones are used for finishing.

• Cutting forces - an increase in feed leads to increased cutting force.

• Temperature and tool - additional heat source can cause premature tool wear.

• Chip formation - with high feeds, chips are thicker, which may require additional measures.

Selecting the appropriate feed is crucial for optimizing the turning process; balancing quality and production efficiency is key.

Cutting depth is the distance between the unmachined surface and the machined surface, that is, the width of the material removed during one pass of the tool. It is expressed in millimetres (mm). The selection of cutting depth depends on several factors, such as:

Types of machining:

• Rough machining - a cutting depth (2–10 mm) is used to quickly remove material.

• Finishing machining - small cutting depths (0.1–2 mm) are used to achieve precise dimensions and required surface quality.

Type of processed material:

• Materials that require smaller values (e.g., 0.5–3 mm).

• Soft materials that allow for larger values (e.g., 3–10 mm).

Properly setting CNC machining parameters is essential to meeting the dimensional requirements of parts—e.g., too large a feed can degrade surface quality, while too low a feed may necessitate additional tool use. It is important to maintain a balance between efficiency and quality.

Optimal setting of CNC parameters is crucial for the quality and efficiency of the process. It is necessary to adjust cutting speed, feed, and cutting depth to the type of material and to use appropriate tools to achieve optimal results. This is particularly important in production for hydraulics and pneumatics, where precision of dimensions and surface quality (e.g., sealing surfaces) is critical.

Errors in selecting turning parameters can lead to a range of problems affecting the quality of the machined part, tool lifespan, and overall process efficiency. Here are some of the most common mistakes and their consequences:

• Poor surface quality of the machined part.
• Dimensional inaccuracy.
• Rapid tool wear.
• Damage to the tool or workpiece.
• Increased production costs.
• Extended machining time.
• Vibrations and oscillations.

• Follow the recommendations of the tool and machine tool manufacturer.
• Use cutting parameter charts.
• Consider the properties of the material being machined.
• Select parameters for the type of machining.
• Regularly check the condition of tools.
• Use appropriate cooling.
• Perform a trial run to verify the correctness of the parameters.

Selecting the appropriate CNC turning parameters is crucial for achieving optimal machining results. It is worth taking the time to carefully plan the process to avoid errors and their negative consequences.