CNC Machining Services · Dongguan, China

Precision CNC Machining Services in China

SPI manufactures custom metal and plastic parts from prototypes to repeat production. We review geometry, tolerances, material, quantity and inspection requirements before assigning the right process—3-axis or 4-axis milling, 5-axis machining, CNC turning, Swiss or mill-turn.

Quality documentation can be defined with the RFQ, including CMM inspection, dimensional reports, FAI, PPAP, CoC and material certificates where required by the agreed project scope.

ISO 9001 & IATF 16949 Certified Prototype-to-Production Support

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STEP / STP / IGES + 2D PDF accepted · NDA support · Qualified RFQs target an initial response within 24 hours.

Red anodized aluminum bracket manufactured by CNC machining at SPI — **Multi-Axis Aluminum Machining** Actual machined-part evidence for drawing-defined geometry, finishing and dimensional verification.

±0.01 mm Typical general machining tolerance

±0.005 mm Selected CTQ features after engineering review

7–10 Days Typical prototype lead time after confirmation

CMM · FAI · PPAP Project-based inspection and document support

Confirmed Manufacturing Scope

CNC Machining Capabilities at a Glance

Use this capability matrix to confirm process fit, machine range, tolerance scope and inspection support before sending a CNC machining RFQ. Final routing is based on the drawing, geometry, material, quantity, datum strategy and inspection requirements.

SPI CNC machining processes, machine ranges, tolerances and inspection capabilities with RFQ qualification guidance
Capability	SPI Range	RFQ / Engineering Relevance
CNC Process Routes	3-axis and 4-axis milling, 5-axis machining, CNC turning, Swiss and mill-turn	Process selection depends on geometry, feature access, setup strategy and production requirements.
CNC Milling Envelope	Up to 1000 × 800 × 500 mm	Part weight, fixturing, tool access and feature location can reduce the usable machining envelope.
5-Axis Envelope	Up to 750 × 750 × 500 mm	Applied when multi-face access, complex geometry or setup reduction justifies a 5-axis route.
Swiss Bar Capacity	Ø1–32 mm	Intended for suitable small-diameter bar-fed parts and repeatable turned features.
CNC Turning Capacity	Up to Ø1000 mm	Actual feasibility also depends on part length, workholding, rigidity and machining features.
General Machining Tolerance	Typically ±0.01 mm	Applied according to drawing requirements and feature function rather than as a blanket whole-part tolerance.
Reviewed CTQ Features	Down to ±0.005 mm on selected features	Requires review of geometry, datum structure, process stability and the agreed measurement method.
Inspection Support	CMM, optical measurement, surface roughness inspection and functional gauges	Inspection method and reporting depth should be defined during RFQ review for critical features.

Process Routing by Part Geometry

Which CNC Process Fits Your Part?

The right CNC route is determined by feature access, rotational geometry, datum relationships, workholding and production needs. SPI uses the simplest stable process that can manufacture and verify the drawing requirements without adding unnecessary setups.

CNC process selection by part geometry and manufacturing requirement
Process Route	Best Part Fit	Why This Route Fits	Deep Dive
3-Axis CNC Milling	Accessible prismatic geometry Plates, brackets, pockets and housings with features reachable from straightforward orientations.	A strong default when the required faces and datums can be controlled without complex tool access or excessive re-positioning.	3 vs 5 Axis
4-Axis CNC Machining	Rotary or indexed features Parts with side features, cylindrical profiles or geometry distributed around one rotational axis.	Rotation can expose additional features while reducing repeated manual re-clamping and helping maintain positional relationships.	Route by RFQ
5-Axis CNC Machining	Complex multi-face geometry Parts with angled features, difficult access, compound surfaces or critical relationships across multiple faces.	3+2 or simultaneous 5-axis machining can reduce setup changes and improve access, but it is selected only when the geometry and tolerance strategy justify it.	5-Axis Service
CNC Turning / Mill-Turn	Rotational parts Shafts, sleeves, flanges and round bodies with turned diameters plus optional milled features.	Turning controls rotational geometry efficiently, while mill-turn can combine flats, cross-holes and milled features in fewer setups.	Route by RFQ
Swiss CNC Machining	Slender small-diameter parts Pins, connectors, screws and other bar-fed components where support close to the cutting point is beneficial.	Swiss machining is evaluated for suitable slender geometries and repeat production rather than used as a default route for every small turned part.	Swiss Service

Typical Part Fit

Typical Custom CNC Machined Parts

SPI machines prismatic, rotational and multi-feature components in metals and engineering plastics. These examples show typical part geometry rather than fixed capability limits.

Complex aluminum housing manufactured by multi-axis CNC machining — Housings & Structural Parts

Enclosures, brackets and frames with flatness, hole-position and multi-face datum requirements.

Precision CNC turned shafts pins sleeves and bushings — Shafts, Pins & Bushings

Rotational and slender parts where diameter, concentricity, runout, threads and burr condition affect assembly.

CNC machined aluminum heat sink with thin cooling fins — Thermal & Functional Components

Heat sinks, manifolds and interfaces with thin fins, sealing faces, ports or drawing-defined surfaces.

Additional part types

Jigs, Fixtures & Automation Parts Mold Inserts & Tooling Components Engineering Plastic Components

For medical instrument components, precision shafts and device housings requiring project-defined CTQ inspection and traceability, explore our medical CNC machining services .

Material & Finish Scope

CNC Machining Materials and Surface Finishes

SPI machines common metals and engineering plastics and coordinates post-processing where required. Material grade, stock condition, finish and finished-part inspection should be defined together when they can affect CTQ dimensions or assembly fit.

CNC machined aluminum and anodized surface finish samples under inspection — **Finished-Condition Verification** Surface treatment should be reviewed together with drawing tolerances, appearance requirements and final inspection needs.

Common Metals

Al 6061 / 6082 / 7075
SS 303 / 304 / 316 / 316L
17-4PH
4140 / SCM435 / S45C
H13 / SKD / SKH
Ti-6Al-4V
Copper / Brass

Engineering Plastics

POM
PEEK
PEI
PPSU
PTFE
PC
PA
ABS
PMMA

Finishing & Secondary Operations

Anodizing
Passivation
Electroless Nickel
Electroplating
Heat Treatment
Grinding
Bead Blasting
Polishing
Laser Marking
Assembly

Tolerance & Inspection Planning

Tolerances, GD&T and Feature-Level Inspection

Tight CNC tolerances should be assigned to functional features, not applied as one number across an entire part. During RFQ review, SPI aligns drawing datums, machining strategy and the measurement method used for final acceptance.

CMM inspection of a complex CNC machined aluminum frame — **Datum-Based CMM Verification** Complex geometry can be aligned to drawing datums before selected CTQ results are recorded.

Feature-Level Inspection Strategy

CTQ Feature	Main Control Focus	Verification
Flatness	Workholding, machining sequence and stress release	CMM or surface plate
True Position	Datum alignment and feature-to-feature relationship	CMM
Bore Diameter	Tool condition, thermal stability and finishing strategy	Bore gauge or CMM
Runout	Workholding and relationship to the specified datum	Indicator or CMM
Surface Finish	Tooling, machining parameters and post-processing	Roughness tester
Threads	Thread specification and any finish allowance	Thread gauge

Capability boundary: ±0.005 mm may be achievable on selected reviewed CTQ features. ±0.002 mm is reserved for applicable specialized grinding features. Final acceptance is defined by the approved drawing, quotation and agreed inspection method.

Quality Evidence

CNC Quality Documentation and Lot Traceability

Documentation depth should match the project. Prototype orders may need dimensional results and material certification, while first builds or controlled production can require FAI, traceability or customer-defined PPAP evidence.

FAI package with ballooned drawing, measured results, material certificate and CNC machined part — **Drawing-Linked Quality Evidence** Inspection records can be tied to the controlled drawing revision, measured features and identified production lot.

Standard Records

Dimensional results, material certificates and CoC according to the agreed order scope.

FAI Package

Ballooned drawing and first-article results linked to the controlled revision and required characteristics.

PPAP Support

Control plan, MSA, capability evidence or other PPAP elements when defined by the customer and project scope.

Lot Traceability

Material lot, relevant process records, secondary-operation certificates and shipment identification where specified.

Define documentation before production

Include the drawing revision, CTQ list, sample quantity, report format and any customer template with the RFQ. FAI and PPAP deliverables are confirmed in the agreed project scope.

Industry Applications

CNC Machining Across Key Industries

Industry fit depends on part function, material, CTQ features, inspection evidence and production stage—not machine capability alone. The industry pages below show how those requirements affect CNC process and quality planning.

Aerospace

Brackets, housings and precision hardware in aluminum, titanium and other specified alloys.

Datum control · Material traceability

Automotive

EV housings, shafts, powertrain components and production-intent machined parts.

CTQ control · PPAP where required

Medical

Stainless, titanium and engineering-plastic components with burr-sensitive or inspection-critical features.

Feature control · Lot traceability

Electronics

Heat sinks, cold plates, enclosures and hardware with functional interfaces.

Flatness · Burr · Surface condition

Robotics

Joint housings, shafts, reducer components and alignment-sensitive mounts.

Bearing fits · Alignment relationships

RFQ to Production

From CNC RFQ to Finished Parts

A CNC project moves more predictably when geometry, tolerances, material, finish and inspection requirements are aligned before production. SPI uses a controlled five-stage handoff from RFQ review through final shipment.

Submit RFQ Inputs

Send 3D CAD, controlled 2D drawing, material, quantity, finish, CTQ features and required quality documents.
Engineering & DFM Review

Check feature access, datum logic, tolerance feasibility, workholding risk and the intended inspection method.
Confirm Quote & Process Route

Align machining route, secondary operations, inspection scope, approval points and schedule basis before release.
Machine & Verify Initial Parts

Establish tooling and workholding, then verify agreed CTQ features before the remaining batch proceeds.
Inspect, Document & Ship

Complete the agreed inspection records, finishing, packaging and lot identification before shipment.

Multi-face aluminum CNC machining with controlled fixture and datum setup — **Process Route Before Production** Setup, tool access and datum relationships are reviewed against the drawing before the production route is released.

Upload CAD for CNC Review Review the DFM Process

Supplier Confidence

Why Work With SPI for CNC Machining?

SPI combines engineering review, multiple CNC process routes, inspection planning and controlled project handoff to support custom parts from prototype builds through repeat production.

Super-Ingenuity inspection and quality control area in Dongguan — **Drawing-Controlled Manufacturing** Machining, inspection and release records are managed against the agreed drawing revision and project scope.

2018 Established

2,500 m² Dongguan Facility

70 Mold & Machining Team

Engineering Review First

DFM, datum, CTQ and inspection risks are reviewed before the machining route is released.

Process Matched to Part Fit

Milling, turning, Swiss and mill-turn are selected around geometry and production requirements.

Inspection Linked to CTQs

CMM, optical measurement and gauges are assigned according to feature type and agreed acceptance needs.

Controlled Project Handoff

Revision, secondary-process, documentation and shipment requirements remain connected through the order.

Buyer Questions

CNC Machining Service FAQs

Short answers to common RFQ, tolerance, process, lead-time and documentation questions.

CNC Design Guidelines

What is needed for a CNC machining quote?

Send 3D CAD, controlled 2D drawing, material, quantity, finish, CTQs, inspection requirements and delivery location. STEP, STP or IGES plus PDF is preferred.

Which CNC process will SPI use?

SPI selects 3-axis, 4-axis, 5-axis, turning, Swiss or mill-turn according to geometry, feature access, workholding, quantity and tolerance relationships.

What CNC machining tolerances can SPI support?

General machining is typically ±0.01 mm. Selected reviewed CTQs may reach ±0.005 mm; ±0.002 mm is limited to applicable specialized grinding features.

How long does prototype CNC machining take?

Typical prototype lead time is 7–10 business days after requirements are confirmed. Material, complexity, finishing and inspection scope can change the schedule.

What production quantities can SPI support?

SPI supports one-off prototypes, engineering samples and repeat low- to medium-volume CNC production, with routing and inspection adjusted to the project quantity.

Can SPI provide FAI, PPAP and inspection reports?

Yes. Dimensional or CMM reports, FAI, PPAP elements, CoC, material certificates and lot traceability can be provided according to the agreed project scope.

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Send your CAD and controlled drawing for process, CTQ, material, finish, inspection and documentation review before quotation.

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