Custom metal & plastic parts
Pockets, faces, holes and contours. Custom milled metal and plastic parts, from a functional prototype to repeat production.
Bring the drawing. We’ll review cutter access, datums, workholding and critical fits before confirming the manufacturing route.
STEP / STP · IGES · PDF
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01 / THE PROCESS01 / From solid stock to functional geometry
CNC milling uses a rotating cutter to remove material from a clamped workpiece. It creates pockets, slots, mounting faces, bores and three-dimensional contours for housings, plates, brackets and fixtures.
The number of axes is a routing decision. Start with the faces that must relate to each other, the tool approach and the surfaces available for clamping. A simple part may use several setups; an angled feature may justify indexed or multi-axis access.
Review your milling design ↓02 / Milling route selection
Select the simplest practical route that can reach the features, hold the part securely and preserve the relationships defined by the drawing.
01 / FACES & POCKETSA fixed tool orientation suits open pockets, flat faces and holes reached from one direction. Other sides may need the part to be reclamped.
A rotary axis can present additional faces to the cutter. Indexed machining and cutting while rotating are different strategies; confirm the route for the drawing.
Two rotary degrees of freedom can orient the tool toward inclined features or contoured surfaces. Review 3+2 positioning versus simultaneous motion for the actual geometry.
03 / Specifications & acceptance
Use a controlled drawing to identify critical features. Confirm individual tolerances against geometry, material, workholding and measurement requirements.
| Requirement | Specify in the RFQ | Manufacturing implication |
|---|---|---|
| Stock & finished envelope | Overall X/Y/Z, stock condition, deep features and accessible clamping faces. | Travel alone does not establish usable capacity; tools and fixtures also need clearance. |
| Datums & geometric controls | Primary, secondary and tertiary datums; flatness, position and perpendicularity where functional. | Links setup and inspection to the way the part locates in assembly. |
| Pockets, slots & walls | Depths, internal radii, minimum wall sections and any undercuts. | Reveals cutter reach, rigidity and possible special operations. |
| Bores, holes & threads | Diameter limits or fit, hole position, thread standard/pitch and full usable depth; blind or through. | Separates thread engagement from drilling and tool runout space. |
| Surface & edge acceptance | Ra on functional faces, cosmetic zones, edge breaks and burr restrictions at intersections. | Defines sealing, appearance and assembly requirements beyond dimensions. |
| Final condition & records | Dimensions after coating, masked bores, material condition, inspection method and report scope. | Prevents a machined fit from being changed by finishing or heat treatment. |
Resolve drawing notes before cutting. State units, revision and the complete general tolerance standard and class. Identify which dimensions apply after heat treatment or finishing, and how flexible parts should be supported during measurement.
04 / Materials for milled parts
A process-appropriate shortlist for milling. Grade, condition, geometry and required documentation are reviewed for each quote; this list does not indicate stocked inventory.
Housings, plates and fixtures where weight matters. Pocketing and uneven stock removal can release stress in thin sections.
Corrosion-resistant brackets and housings. Grade and condition change machinability, cutting load and finishing choices.
Fixtures, loaded brackets and wear interfaces. Plan machining, heat treatment and final inspection in the right sequence.
Milled conductive blocks, terminals and thermal interfaces. Distinguish the exact alloy and functional surface needs.
Milled guides, insulating fixtures and low-friction components. Check clamping distortion and the conditions used to inspect fits.
Nylon needs moisture-aware dimensional planning; PEEK selection depends on temperature, chemistry and filler content.
Material grades, condition and availability are reviewed for each quotation.
05 / Finishing milled geometry
Finishing follows the function of each face. Map cosmetic zones, mating features and masked areas on the drawing before the route is quoted.
Explore surface finishing ↗Specify functional roughness where needed and acceptable cutter marks on other faces. Define edge breaks and inspect intersecting holes for burrs; “deburr” alone does not define a cosmetic finish.
For aluminum parts, agree texture, color reference and cosmetic zones. Anodizing can change mating dimensions; define masking on bores, threads and electrical contact faces.
Choose a treatment compatible with the alloy and environment. Confirm thickness, coverage and the final acceptance condition; narrow pockets and hidden faces may need special review.
Identify sealing or thermal contact faces separately from visible exterior faces. Agree texture direction and avoid removing material from controlled fits without allowance.
06 / Quality & inspection
For milled parts, agree how bores, mounting faces and pocket features are located from the drawing datums. Confirm access for measurement as well as access for cutting.
Confirm the revision, datum setup, critical bore positions and flatness requirements. Define whether checks apply in the free state or with agreed support for thin parts.
Use an appropriate dimensional method for hole position, face relationships and pocket geometry. Define thread gauging and surface checks separately; a dimensional report does not establish material composition or hardness.
Identify critical features for first-article review and any batch sampling, material records or post-finish reports needed. Confirm document scope and traceability in the quotation.
PROLEAN MFG (SHENZHEN) CO LTD
SGS · CN24/00004900
Certificate dates: 05 Aug 2024–04 Aug 2027, subject to satisfactory surveillance audits. Certification concerns the management system; part acceptance follows the agreed specification.
Explore our quality & inspection approach ↗07 / Milling DFM & cost guidance
These design checks help prepare a useful manufacturing conversation. Final dimensions and process decisions depend on the part’s function and geometry.
Function → feature → process → inspection.
A round end mill leaves a radius in an internal plan-view corner. Give the cutter room to move through the corner; where function permits, a larger radius lets a more rigid tool reach the pocket. If a square mating part must seat, consider a relief feature or review a separate process rather than specifying a zero-radius milled corner.
Review depth together with opening width, corner radius and holder clearance. Long tool overhang reduces rigidity and makes chip evacuation more difficult. Consider a wider opening, shallower pocket or split assembly where function allows; confirm any undercut and special tool access explicitly.
Tall walls and broad thin floors can deflect under cutting and clamping loads. Provide uniform sections and support where possible. Roughing sequence, residual stress and unclamping can affect final flatness, so agree the free-state requirement and inspection support before choosing a route.
Reserve accessible clamping and locating faces. Use assembly function to define primary, secondary and tertiary datums, then identify features whose relationships cross setups. Discuss sacrificial tabs or extra stock before changing the model; reorienting the part does not preserve datum relationships automatically.
Prefer standard hole and thread sizes where function allows. Specify through/blind condition, full usable thread depth, drill depth and any bottom clearance separately. Identify inserts, cross holes and burr-sensitive intersections; avoid demanding full threads to the floor of a blind hole without tool runout space.
Cost follows stock volume removed, tool reach, setups, tight features, finishing, inspection and batch size. Keep tight controls on functional faces, combine accessible features where practical and quote quantity breaks. Mark dimensions after coating and masking needs; a more complex axis route is justified only when the geometry and total process support it.
08 / Parts & applications
Typical milled-part geometries and the requirements they raise. These examples are design references, without customer attribution or application-specific qualification claims.
Relate hole patterns and locating bores to the mounting face. Review flatness after unclamping and access to side features.
Review channel access, sealing lands and intersecting passages. Specify leak or pressure testing separately if required; it is not implied by milling.
Check locating faces, insert positions and the walls left after pocketing. Identify whether the prototype must prove assembly, stiffness or thermal behavior.
For regulated or safety-critical applications, provide the applicable standards, traceability and validation requirements. Project suitability and documentation require specific review.
09 / Prototype to production
Prototype and repeat milling need a controlled revision and an agreed setup plan. Share current quantities, likely repeat demand and any first-article approval gate.
Send CAD and a drawing with datum faces, pocket depths, usable threads, material condition and finish. Include quantities, inspection records and your target date.
Resolve tool reach, clamping access, datum transfer and finish allowances. Confirm price, documentation and manufacturing lead time for the agreed route.
Freeze the revision and acceptance plan. Agree sample or first-article approval, material requirements and any finishing masks before machining starts.
Complete agreed dimensional and surface checks. Protect machined edges and faces in packaging. For repeats, reconfirm revision, stock condition and changed demand.
Ask for pricing at your planned quantities and clarify material documents, inspection scope, packaging, freight and delivery terms. This makes supplier comparisons more useful than a unit price alone.
10 / CNC milling FAQs
Practical answers for engineers,
buyers and manufacturing teams.
Start with feature access and datum relationships. Open pockets and holes in one direction often suit 3-axis work. Rotary indexing can present side faces; 5-axis orientation can help inclined features and contours. Confirm indexed or simultaneous motion, workholding and measurement for the actual part; extra axes do not guarantee one setup.
A rotating end mill leaves an internal corner radius in plan view. If a square component must seat, show the functional clearance and consider a relief. A truly sharp internal profile may require a different operation, subject to geometry and material review.
Depth, a narrow opening and a small corner radius can require a long, slender tool. Reach, chip evacuation, holder clearance and additional finishing passes then become concerns. Widening access or relaxing a nonfunctional radius can be more useful than simply specifying more axes.
Review wall height, unsupported area, clamping loads, material condition and stock removal sequence together. Define flatness and the measurement condition. There is no universal minimum wall thickness or flatness guarantee for every geometry.
State thread standard, size, pitch or class, full usable engagement depth and whether the hole is blind. Distinguish usable thread from drill depth and provide bottom clearance for the chosen tool. Identify inserts and intersecting holes that require specific deburring.
Mark individual fits and geometric controls, with datums and units. Identify which apply after coating or heat treatment and which features need masking. Feasibility depends on the material, feature, setup and measurement method; the drawing and agreed quotation establish acceptance.
Provide STEP/STP or IGES plus a controlled PDF drawing, exact material and condition, finish and inspection scope. Include prototype and repeat quantity breaks. Confirm any first-article review and NDA before sending confidential files via the agreed channel.
Material sourcing, tool access, number of setups, batch size, finishing and inspection all affect the schedule. Share the target date and staged-delivery needs. Quote response time is separate from manufacturing lead time; an order-specific commitment requires review.
