Is surface treatment always included in CNC machining quotes?
How quotes are typically structured
In most professional workflows, surface treatment is not automatically included in CNC machining quotes unless it is clearly specified in the RFQ or drawing. A standard quotation typically covers material procurement, programming, machining, basic deburring, and dimensional inspection, based on an agreed-upon CNC machining service process. Any additional coating, corrosion protection, color, or cosmetic requirement must be defined to avoid mismatched expectations.
When RFQs only state “CNC part” without surface specifications, suppliers generally assume an as machined surface finish: tool marks within a functional Ra range, cleaned and deburred, but without anodizing, plating, or painting. If end-use, environment, or branding requires more, it should be built into the quote from the beginning.
When surface treatment is integrated or quoted separately
Surface treatment is often quoted as a distinct process step because it affects routing, lead time, dimensional control, and quality documentation. For example, precision housings or manifolds undergo an efficient CNC milling service and CNC turning service, with prototypes validated through CNC machining prototyping. Once geometry is confirmed, production batches under a low volume manufacturing service can incorporate defined finishing steps, each costed and controlled.
In cases where corrosion resistance or appearance is critical, the anodized, plated, or coated condition must be explicitly specified. For aluminum parts, specifying an CNC aluminum anodizing service directly influences process flow and inspection dimensions, as coating thickness has to be accounted for in machining allowances.
Material, application, and why clarity matters
Whether finishing is included also depends on the material and sector. Many functional components in Aluminum 6061 for indoor use operate satisfactorily with an as-machined or clear anodized condition; stainless parts in Stainless Steel SUS304 or Stainless Steel SUS316L may only require cleaning or passivation. High-temperature or aggressive media applications, such as those using Inconel 718 or engineered plastics like ABS, may require different handling, but not necessarily decorative coatings.
In Automotive, coated, anodized, or plated states are often part of the drawing and thus included in the formal quote and control plan. In project-based Industrial Equipment, customers sometimes separate machining and finishing between different vendors, so quotes reflect machining only. In regulated Medical Device applications, surface condition is tightly defined (passivation, polishing, cleanliness), and must be explicitly included, validated, and documented.
To avoid misunderstandings and unexpected surcharges, define the required final surface condition, environment, and critical cosmetic zones in the RFQ. A clear scope enables your machining partner to provide an accurate quote and select the optimal process chain from the outset.
