| 1 | Compare the Complete Unit Price | Pricing transparency | Evaluate the total landed cost, including material, machining, tooling, setup, finishing, inspection, packaging, freight, and applicable taxes. A lower machining rate may not produce the lowest final cost. | Request an itemized quotation with identical drawings, tolerances, material grades, quantities, surface finishes, and delivery terms. | 15% |
| 2 | Check Material and Traceability Controls | Material capability | Common CNC metals include aluminum, stainless steel, carbon steel, tool steel, brass, copper, titanium, and nickel alloys. Material certificates should identify the grade and heat or lot number. | Confirm approved material grades, certificate availability, incoming inspection procedures, and controls against material substitution. | 10% |
| 3 | Measure Prototype Lead Time | Prototype delivery | For a straightforward machined prototype with readily available material, a typical quoted manufacturing window is approximately 5–15 business days, excluding shipping and customer approval delays. | Separate engineering review, programming, material procurement, machining, finishing, inspection, and transit time in the schedule. | 10% |
| 4 | Evaluate Production Capacity | Monthly and peak capacity | Capacity should be expressed in available machine hours, shifts, machine types, and repeatable monthly part quantities—not only the total number of machines. | Ask about current utilization, backup equipment, staffing by shift, capacity during peak periods, and the maximum quantity the supplier can commit to. | 12% |
| 5 | Match Machine Capability to the Part | Equipment and work envelope | Verify axis configuration, spindle capacity, positional accuracy, work envelope, bar-feeding capability, turning diameter, and five-axis access where the design requires it. | Review the machine list and confirm that the supplier can produce the largest dimensions, deepest features, smallest tools, and tightest tolerances on the drawing. | 12% |
| 6 | Review Quality Systems and Inspection | Quality assurance | A documented quality system should control drawing revisions, inspection plans, nonconforming parts, calibration, corrective actions, and final release. Critical dimensions may require CMM inspection. | Request sample inspection reports, calibration records, first-article procedures, process capability data where applicable, and the supplier’s nonconformance response process. | 14% |
| 7 | Confirm Tolerance and Finish Experience | Technical fit | Do not treat general machine accuracy as proof of part-level capability. Tolerance results depend on material, geometry, datum strategy, thermal control, tooling, and inspection method. | Ask for comparable examples, achievable tolerances by feature type, surface roughness capability, geometric tolerance experience, and finishing process controls. | 10% |
| 8 | Compare Finishing and Secondary Processes | One-stop production | Common secondary processes include anodizing, plating, powder coating, passivation, heat treatment, deburring, laser marking, and assembly. Outsourced processes can add schedule and quality risks. | Identify which processes are performed in-house, how subcontractors are controlled, whether color or coating certificates are available, and how finished parts are protected. | 8% |
| 9 | Assess Communication and Engineering Support | Responsiveness and DFM | A capable supplier should identify unclear specifications, unrealistic tolerances, difficult datums, thin walls, deep cavities, and avoidable setup requirements before production begins. | Measure quotation response time, revision control, engineering communication, drawing clarification, design-for-manufacturing feedback, and escalation procedures. | 5% |
| 10 | Verify Delivery Reliability and Scalability | On-time delivery and growth capacity | Evaluate on-time delivery over a documented period, not a single shipment. The supplier should explain how it will scale from prototypes to repeat orders without changing approved materials or processes. | Request historical on-time delivery data, capacity planning methods, safety-stock options, contingency plans, packaging standards, and a written process for handling schedule changes. | 4% |