Low-Volume CNC Machining: How to Control Costs?

1. Design Optimization and Process Simplification: Cut Invalid Costs from the Source

• Precision Grading and Tolerance Relaxation: Distinguish precision requirements based on part usage—The geometric tolerance of test parts can be relaxed to 1.5-2 times the mass production standard (e.g., mass production requires ±0.005mm, while small-batch can be set to ±0.01mm), and the surface roughness Ra value can be relaxed from ≤0.8μm to ≤1.6μm. Only key mating surfaces retain high precision, which can reduce processing time by 30% . A automotive R&D center shortened the processing cycle of 80 chassis test parts from 12 days to 7 days through this method.
• Structure Simplification and DFM Principles: Adhere to the "Design for Manufacturability (DFM)" concept, communicate with customers to optimize part structures—for example, changing deep holes (depth > 5 times the diameter) to shallow holes + stepped structures to reduce tool wear in deep hole drilling (the cost of deep hole drilling tools is 4-5 times that of ordinary drills); replacing sharp corners with rounded corners to avoid the use of special tools. A medical device manufacturer reduced the tool cost of 30 biopsy forceps parts by 50% through structural optimization .
• Process Merging and Path Optimization: Use CAM technology to plan optimal machining paths, reduce machine idle travel, and integrate multiple independent processes—for instance, completing milling + drilling in one clamping instead of changing fixtures multiple times. When a new energy parts factory processed 100 motor end caps, process merging shortened the unit processing time from 45 minutes to 28 minutes .

2. Refined Material Management: Reduce Core Cost Loss

• Precise Procurement and Specification Adaptation: Select raw materials with "nearest specifications" based on part size—for example, when processing 15mm×15mm parts, prioritize 16mm×16mm plates over 20mm×20mm plates. An electronic parts factory increased material utilization rate from 38% to 65% through specification adaptation. At the same time, adopt the "joint procurement" model, collaborating with small-batch customers in the same industry to purchase special materials together, reducing the purchase unit price by 10%-15% .
• Rational Use of Alternative Materials: Use low-cost materials for non-critical parts—for example, replacing 7075 aluminum alloy with 6061 aluminum alloy (30% lower cost) and 316L stainless steel with 304 stainless steel (25% lower cost). Special materials are only used when corrosion resistance and high strength are required. When an automotive R&D company customized 50 chassis test parts, switching to alternative materials reduced material costs from 18,000 RMB to 11,000 RMB while meeting test requirements .
• Scrap Classification and Secondary Utilization: Classify and store scraps generated from CNC machining by material (aluminum alloy, stainless steel, titanium alloy, etc.). Small scraps are used to process small parts (such as screws and gaskets), and large scraps are entrusted to third parties for re-forging into plates. A precision machinery factory reduced monthly material procurement costs by 12,000 RMB through scrap reuse .

3. Equipment and Working Hour Optimization: Improve Output per Unit Time

• Precise Equipment Selection: Prioritize general equipment with multi-process capabilities (such as 3-axis vertical machining centers) and avoid specialized equipment (such as 5-axis machining centers)—the debugging time of specialized equipment is 2-3 times that of general equipment, and the hourly rate is 50% higher. When a parts factory processed 120 gear blanks, using 3-axis machines instead of 5-axis machines reduced working hour costs by 40% .
• Standardization of Debugging Processes: Develop "debugging templates for low-volume orders," presetting tool parameters, fixture positioning points, and coordinate systems for parts of the same type (such as flanges and brackets). A machinery factory shortened the debugging time for orders with less than 50 units from 2 hours to 40 minutes through standardized debugging .
• Centralized Production Scheduling: Concentrate production of small-batch orders with the same material and process (such as processing aluminum alloy parts every Wednesday) to reduce equipment changeover times. A medical parts factory increased monthly effective equipment processing time from 120 hours to 180 hours through scheduling optimization, reducing unit working hour costs by 25% .

4. Supply Chain and Management Optimization: Reduce Hidden Costs

• Local Integration of Supply Chain Resources: Prioritize cooperation with local or nearby (within 300 kilometers) material suppliers and heat treatment manufacturers to reduce transportation time and costs (long-distance transportation costs are 2-3 times higher than short-distance). A precision parts factory reduced monthly transportation costs from 5,000 RMB to 1,800 RMB after choosing a local heat treatment plant .
• Process Simplification and Quality Prediction: Establish a "fast communication channel for small orders" with customers, using simple 3D models instead of complex 2D drawings, and confirming acceptance standards in writing in advance to avoid later rework (rework costs often account for over 15% of small-batch orders). At the same time, use CAM systems to simulate the machining process and predict potential quality issues, reducing the scrap rate .
• Flexible Quotation and Cooperation Models: Adopt "tiered quotations" for long-term small-batch customers (e.g., 8% price reduction if annual cumulative orders exceed 500,000 RMB), charge a reasonable "process preparation fee" for one-time small orders to cover debugging costs, and negotiate to shorten the payment cycle (e.g., 30% advance payment + 70% payment upon delivery) to reduce capital occupation costs. After a medical device company cooperated with a local manufacturer, both parties reduced costs by 8%-12% .

Why Can These Methods Effectively Control Costs?