Pre-Machining Preparation Stage

 Drawing Analysis and Process Planning

• First, interpret the part drawings to clarify key dimensions (such as diameter, length, tolerance), geometric tolerances (such as roundness, coaxiality), surface roughness requirements, and the application scenarios of the parts (such as load-bearing and wear-resistant requirements).
• Develop a process route based on the material (steel, aluminum, copper, plastic, etc.), determine the machining sequence (e.g., rough turning first, then finish turning), select equipment (conventional lathes, CNC lathes), tool types (external turning tools, internal hole tools, thread tools, etc.), and cutting parameters (rotational speed, feed rate, depth of cut).

 Raw Material Preparation and Pre-Treatment

• Raw material selection: Choose the form of raw materials (such as round bars, forgings, castings) according to the size and performance requirements of the parts, ensuring that the size of the raw material is slightly larger than that of the finished product (with machining allowance reserved).
• Pre-treatment process: For metal raw materials, if there are internal stresses (such as forgings and castings), heat treatment processes like annealing and normalizing are required to avoid deformation after machining. For raw materials with oxide scales and rust on the surface, cleaning methods such as grinding and pickling are needed to ensure machining precision.

 Equipment and Tool Debugging

• Check the precision of the lathe (such as spindle runout, guideway parallelism) to ensure the equipment is in normal working condition. Install and calibrate the tools, and adjust the tool angles (such as rake angle, relief angle) according to the process requirements to ensure smooth cutting.
• For CNC lathes, it is necessary to write the machining program and conduct a simulated operation to verify the correctness of the program logic and avoid collision accidents.

Core Machining Stage (Lathe Machining)

 Clamping and Positioning

• Select the clamping method according to the part structure: For shaft parts, three-jaw chucks, four-jaw chucks, or centers are commonly used for positioning; for sleeve parts and disc parts, chucks combined with pressure plates can be used for fixing. Ensure firm clamping without damaging the surface of the raw material, and keep the positioning datum consistent with the machining datum.

 Rough Turning

• The purpose is to quickly remove most of the excess material from the raw material, make it close to the basic shape of the part, and reserve a finish turning allowance of 0.5-2mm.
• The main machining contents include turning key surfaces such as the outer circle, inner hole, and end face, removing obvious burrs and excess protrusions, and laying the foundation for finish turning. During this stage, the cutting speed and feed rate can be appropriately increased to prioritize machining efficiency.

 Semi-Finish Turning and Intermediate Treatment (Optional)

• For parts with high precision requirements, semi-finish turning is required after rough turning to further refine the dimensional precision and reserve a finish turning allowance of 0.1-0.5mm, reducing the cutting load during finish turning.
• If significant stress is generated during the part machining process, stress-relief heat treatment should be conducted at this stage to avoid deformation during subsequent machining or use.

 Finish Turning

• Perform machining in accordance with the final dimensional and precision requirements specified in the drawings. Strictly control the cutting parameters (reduce rotational speed, decrease feed rate) to ensure that the dimensional tolerance, geometric tolerance, and surface roughness meet the standards.
• For special structures (such as threads, grooves, conical surfaces), it is necessary to replace the corresponding tools for specialized machining. For example, use thread tools to turn external or internal threads, and use grooving tools to machine annular grooves.

Subsequent Finishing and Inspection Stage

 Auxiliary Machining (Optional)

• If the part requires higher surface quality, grinding (such as cylindrical grinding, internal hole grinding) and polishing processes can be carried out after finish turning to further reduce the surface roughness (e.g., reaching below Ra0.8).
• Some parts require subsequent processes such as hole machining (drilling, reaming, boring) and tapping to complete structural features that cannot be processed by lathes.

 Heat Treatment (Optional)

• For parts that need to improve hardness and strength (such as gear shafts, wear-resistant sleeves), heat treatment processes like quenching and tempering are required after machining to ensure that the mechanical properties meet the standards. If deformation occurs after heat treatment, re-finishing grinding is needed for correction.

 Surface Treatment

• Conduct surface protection treatment according to application requirements. Common methods include galvanizing, chrome plating (for rust prevention), blackening (to improve wear resistance), and anodizing (for aluminum alloy parts) to extend the service life of the parts.

Quality Inspection

• Dimensional inspection: Use tools such as calipers, micrometers, dial indicators, and projectors to check whether the key dimensions and geometric tolerances meet the requirements of the drawings.
• Surface quality inspection: Visually inspect or use a roughness tester to check the surface finish, and identify defects such as burrs and scratches.
• Performance inspection: For parts with special performance requirements, conduct hardness tests, tensile tests, etc., to ensure they meet the application standards.

 Packaging and Warehousing

• Clean and rust-proof the qualified finished products, select appropriate packaging methods (such as bubble film, cartons, special tooling) according to the size and precision requirements of the parts to avoid damage during transportation, and finally classify and store them in the warehouse.

 Key Precautions

1. During the machining process, timely clean the chips to prevent them from wrapping around the tools or scratching the surface of the workpieces.
2. Regularly check the wear of the tools and replace them in a timely manner to prevent the decline of machining precision due to tool wear.
3. For batch-produced parts, batch machining can only be carried out after the first part passes the inspection, and sampling inspection should be conducted during the process to ensure product consistency.