How does different surface finishing treatments affect the total cost of custom parts?
Quick AnswerSurface finishing adds 5-50% to the base CNC machining cost. As-machined: 0% added cost. Bead blasting: 2-5%. Anodizing Type II: 5-10%. Powder coating: 8-15%. Zinc/nickel plating: 10-20%. Electropolishing: 15-30%. Hand polishing/buffing: 20-40%. Hard coat anodizing (Type III): 15-25%. Chrome plating: 25-50%. Higher quantities reduce per-unit finishing cost significantly. SOMI provides transparent cost breakdowns showing finishing costs separately.Cost by Finishing TypeBead blasting: $2-15 per part. Setup cost: minimal. Suitable for all quantities. Anodizing Type II: $5-30 per part, $50-200 minimum batch charge. Color adds $2-10. Quantity discount: 30-50% at 1,000+ parts. Powder coating: $8-40 per part, $100-300 minimum. Color changes add setup. Best for 100+ parts. Electropolishing: $5-50 per part. Minimum $100-200. Batch process, so cost per part decreases significantly at higher quantities.Hidden Cost FactorsPart size: Larger parts cost more to finish due to more material, longer processing time, and larger tanks/fixtures needed. Geometry complexity: Parts with deep internal cavities, blind holes, and complex internal features may require specialized fixturing or manual touch-up. Tape/plugging: Areas that must remain uncoated (conductive surfaces, sealing surfaces) require masking -- adding $2-20 per part. Quality level: Cosmetic vs functional specifications affect cost. A Class A automotive finish costs 50-100% more than a standard industrial finish.Cost Savings StrategiesDesign parts with the finish in mind: avoid sharp corners that cause coating buildup, specify minimum shelf life if appearance is critical, and combine parts of the same finish in a single batch. Using the same supplier for both machining and finishing eliminates packaging, shipping, and handling costs between processes, typically saving 10-20% of total finishing cost.Why Choose SOMI Custom PartsAt SOMI Custom Parts, we manage finishing in-house or through closely integrated partner facilities, eliminating the cost and risk of shipping parts between separate suppliers. Our quoting system provides detailed finishing cost breakdowns and recommends cost-saving alternatives. For example, if your design specifies electropolishing, our engineers may suggest whether bead blasting would achieve the required appearance at 50% lower cost.Case StudyA client specified electropolishing for 500 CNC-machined 316L stainless steel parts at a quoted finishing cost of $12 each. SOMI's engineers reviewed the application and determined that passivation + bead blasting would achieve the same corrosion resistance and appearance at $4 each -- saving $4,000 on the order. The client approved the alternative, and the parts passed all functional requirements.Industry DataFinishing costs represent an average of 15-25% of total CNC part cost (NAMRC Machining Survey, 2025). Companies that integrate finishing with machining through a single supplier report an average 18% reduction in total part cost and 30% shorter lead times compared to using separate finishing vendors (MFG Monthly, 2025).Related QuestionsWhat surface finishing options are available for CNC parts?What surface treatments are used in sheet metal?What is anodizing?What is electropolishing?