Find the Right Comparison

Jump to the decision criteria, process details or quotation information relevant to your project.

Process Capabilities at a Glance

Use these reference values to compare feasibility, cost and lead-time risk. Actual capability depends on material, size, geometry, finish, quantity and inspection requirements; upload your model for a part-specific review.

Process Typical batch size Minimum wall thickness (recommended) General tolerances (reference) Typical risk points
CNC machining Single piece / small batch / precision parts Metal ≥0.8mm; plastic ≥1.2mm ±0.05mm (normal); more stringent evaluation is required Deep cavity, thin wall, sharp angle, deep thread, tight tolerance, difficult to clamp
Injection molding Mid-batch/mass production 0.8–3.0mm (as uniform as possible) Subject to mold, material and shrinkage control Sudden changes in wall thickness, sink marks, warping, insufficient draft, excessive rib thickness, undercuts and side pulls
Sheet metal fabrication Small batch / medium batch / structural parts Commonly used: 0.5–6mm (selected according to material) Comprehensive evaluation of cutting + bending + assembly tolerance chain Insufficient hole spacing, bending interference, cracking, springback, assembly deviation, post-weld deformation
Vacuum casting Low volume (prototype/pilot run) 1.5–4mm (recommended) Depends on master mold accuracy, material and post-processing Bubbles, trapped air, thin wall deformation, unreasonable parting, and batch-to-batch consistency
3D printing Single piece/prototyping/rapid iteration/small batch of functional parts Depends on process, material and build orientation Depends on equipment, build orientation, supports and post-processing Lamination/warpage, support marks, anisotropy, post-processing deformation, dimensional consistency fluctuations

What to Compare Before You Choose

A workable process must also deliver stable quality, controllable cost and a realistic schedule. Compare these four factors before committing to a route.

1. Quantity and Tooling Cost

  • Single piece/small batch: CNC, 3D printing, and vacuum casting are more flexible.
  • Mid-batch/mass production: Injection molding (or sheet metal standardization) has more cost advantages.
  • Higher quantities can spread mold and fixture costs across more parts. If demand is uncertain, validate the design before committing to tooling.

2. Precision and Repeatability

  • High-precision fit: CNC is more controllable, but is sensitive to structure and clamping.
  • Volume production consistency: Injection molding can be stable, but depends on mold/process window and shrinkage control.
  • Tighter tolerances increase inspection requirements, including coordinate measuring machine (CMM) checks, gauges and sampling frequency.

3. Appearance and Finishing

  • Cosmetic parts need a defined primary appearance surface (Side A) and clear limits for parting lines, ejector marks, gates, tool marks and repairs.
  • Painting, coating and screen printing add process steps and consistency risks such as color variation, adhesion and masking boundaries.
  • Define acceptance criteria before production to reduce cosmetic rework and approval delays.

4. Geometry and Yield Risk

  • Deep cavity/thin wall/acute angle: CNC cost and yield risk are higher (tool/clamping/deformation).
  • Undercuts and side actions increase injection mold complexity, cost and cycle time.
  • Trapped air/bubbles: Vacuum casting is more sensitive, so parting and exhaust paths need to be optimized.
  • Changing high-risk features before release is usually the fastest way to reduce cost and lead time.

How Project Inputs Affect the Process

Share these inputs with your drawings so an engineer can assess feasibility, risk and cost without repeated clarification.

Material and Grade

  • Impact: Shrinkage, deformation, strength, surface consistency, machinability and finish adhesion.
  • Result: Changing material can alter molding warpage, CNC tool marks and burrs, or vacuum-casting bubbles and repair rates.
  • Provide the grade, flame-retardant rating, glass-fiber content, transparency and gloss requirements.

Critical Dimensions and Inspection

  • Impact: Process steps, tool paths, setups, fixtures, CMM inspection and sampling frequency.
  • Result: Tight tolerances add both manufacturing and inspection cost, with greater schedule risk.
  • Provide datums A/B/C, critical dimension chains, position or coaxiality requirements, and the acceptance method.

Appearance Standards and Side A

  • Impact: Visibility of parting lines, ejector marks, gates, tool marks and repairs, plus the finishing sequence.
  • Result: Higher cosmetic standards add polishing, coating and repair work, increasing price and lead-time variation.
  • Define Side A, gloss or texture, color, acceptable defects and masking areas.

High-Risk Geometry

  • Impact: Tool, bend and ejection access; venting; deformation; and assembly tolerance.
  • Result: Difficult geometry lowers yield and makes cost and lead time less predictable.
  • Identify deep cavities, thin-wall areas, undercuts, closed cavities, long cantilevers and the assembly method.

Typical, Review-Required and High-Risk Features

Use these ranges for early screening. Requirements outside the typical range may increase cost or lead time and need an engineering review.

CNC Machining Boundaries

  • Typical: ±0.05mm, internal corner radius R≥0.5mm, metal walls ≥0.8mm and plastic walls ≥1.2mm.
  • Review required: Deep cavities or grooves, broad thin walls, local ±0.02mm tolerances, coaxiality or position requirements.
  • High risk: Tight tolerances across many dimensions, deep holes or threads, high aspect ratios, or cosmetic surfaces that are difficult to clamp.
  • Small tools, slow feeds, multiple setups and frequent inspection increase cost and schedule variation.

Injection Molding Boundaries

  • Typical: Uniform 0.8–3.0mm walls, appearance-surface draft ≥1° and ribs ≤60% of the main wall thickness.
  • Review required: Transparent or high-gloss parts, long thin parts, and Side A surfaces sensitive to parting lines, ejector marks or gate position.
  • High risk: Multiple undercuts or side actions, insufficient draft on deep textured cavities, or combined tight dimensional and cosmetic requirements.
  • Mold complexity and a narrow process window increase tooling time, unit-price variation and yield risk.

Sheet Metal Fabrication Boundaries

  • Typical: Inside bend radius R≥t, hole-to-bend distance ≥1.5t and hole-to-edge distance ≥t.
  • Review required: Accumulated error across multiple bends, springback-sensitive materials, weld distortion and assembly tolerance stacks.
  • High risk: Very close holes with cosmetic requirements, complex welded assemblies with several finishes, or strict assembly consistency without clear datums.
  • Straightening, rework and dedicated fixtures add cost and schedule uncertainty.

Vacuum Casting and 3D Printing Boundaries

  • Typical: Vacuum-cast walls of 1.5–4mm without sharp corners; 3D printing for structure and assembly checks; Multi Jet Fusion (MJF) for selected low-volume functional parts.
  • Review required: Venting in deep or enclosed vacuum-cast features; critical dimensions on support-heavy stereolithography (SLA) or fused deposition modeling (FDM) surfaces; and surface or dimensional consistency in selective laser sintering (SLS) and MJF.
  • High risk: Injection-molding-level consistency with no Side A repair in vacuum casting, or printed load-bearing parts that require isotropic strength or very tight cosmetic consistency.
  • These requirements may need extra finishing, secondary machining or a different process.

3D Printing: Fast Iteration Without Tooling

Stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM) and Multi Jet Fusion (MJF) support rapid prototypes and complex geometry. Compare orientation, surface finish, strength and production repeatability before choosing a process.

Best-Fit Applications

  • Proof of concept, form review, assembly interference inspection and rapid iteration.
  • Complex internal structures or geometries that are difficult to process in one molding (used to verify structural feasibility).
  • Low-volume functional parts in engineering plastics using SLS or MJF.
  • For production-like appearance, validate with a printed part, then consider vacuum casting or injection molding.

Design for Manufacturability

  • Orientation and supports: Keep critical dimensions away from support-heavy and overhanging surfaces where removal and sanding can affect flatness.
  • Powder-bed processes: Allow access for powder removal and leave machining stock on critical holes or mating surfaces when needed.
  • Dimensional change: Orientation, thermal shrinkage, warpage, post-curing and annealing can change final dimensions.
  • Anisotropy: Account for direction-dependent strength in loaded parts; adjust the load path, reinforce the design or change process if needed.
  • Appearance: Define Side A, acceptable layer texture and any allowance for sanding or painting.
  • Add drilling or milling allowance to critical mating holes and surfaces used in assembly checks.

Cost and Lead-Time Drivers

  • Part volume, infill, support complexity and orientation needed to control deformation.
  • Support removal, powder cleaning, polishing, painting and assembly, especially for cosmetic parts.
  • Post-processing labor is often the main cost driver for high-appearance printed parts.

CNC Machining: Precision in Production Materials

Computer numerical control (CNC) machining suits precise single parts and small batches in metals or engineering plastics. Deep cavities, thin walls, sharp internal corners, tight tolerances and difficult setups increase cost and lead time.

Best-Fit Applications

  • High-precision fitting parts, assembly positioning surfaces, and functional verification parts.
  • Metal structural parts, parts requiring threads/counterbores/precision holes.
  • Tip: If mass production is possible in the end, you can first use CNC to verify the structure and assembly, and then evaluate mass production processes such as injection molding/die casting.

Design for Manufacturability

  • Avoid sharp internal corners; use R ≥ 0.5mm and increase the radius where the design allows.
  • For deep cavities/deep grooves, pay attention to the risk of tool overhang and tool vibration; try to enlarge the opening or split the design.
  • Thin wall: metal ≥0.8mm; plastic ≥1.2mm; reinforce or retain support if necessary.
  • Hole/Thread: Blind hole depth ≤ 3 × hole diameter; thread depth ≤ 3 × diameter (experience value).
  • Apply tight tolerances only to critical mating features, and define datums A/B/C and the inspection method.

Cost and Lead-Time Drivers

  • Deep cavities, very small tools, complex setups, tight tolerances and frequent CMM inspection.
  • High cosmetic standards, tool-mark control, sanding, blasting and polishing.
  • Define Side A and critical functional surfaces to reduce clarification and rework.

Injection Molding: Repeatable Volume Production

Injection molding suits stable designs at medium to high quantities. Uniform walls, adequate draft, manageable undercuts and clear cosmetic limits improve yield and keep tooling and unit costs predictable.

Best-Fit Applications

  • Medium batch/mass production plastic parts: shells, fasteners, brackets, functional structural parts.
  • Scenarios that require stable consistency and low unit cost.
  • If demand is uncertain, validate appearance and assembly with 3D printing or vacuum casting before investing in tooling.

Design for Manufacturability

  • The wall thickness should be as uniform as possible; the rib thickness is recommended to be ≤ 60% of the main wall thickness.
  • Draft angle: appearance surface ≥1°; texture/deep cavity ≥2°.
  • Undercuts require side actions or sliders, increasing mold cost and cycle time.
  • Appearance parts define the A side and defect tolerance area (parting line/ejector pin mark/gate).

Cost and Lead-Time Drivers

  • Mold complexity, including the number and travel of side actions and any precision inserts.
  • High appearance grade (glossy/transparent parts, textures, masking and spray chains).
  • Removing undercuts during design is usually more economical and reliable than adding side actions.

Sheet Metal Fabrication: Efficient Formed Structures

Sheet metal fabrication suits panels, brackets and enclosures. Bend access, hole spacing, springback and clear assembly datums determine consistency; locating and slotted holes can help manage assembly variation.

Best-Fit Applications

  • Structural brackets, chassis cabinets, mounting plates, guards, and bent structural parts.
  • Quick delivery of small and medium batches; also suitable for standardized mass production.

Design for Manufacturability

  • Bending radius recommendations R ≥ t(t is plate thickness).
  • The recommended distance from hole to bending line is ≥ 1.5×t (2×t is more conservative).
  • It is recommended that the hole to edge should be ≥ t; try to use rounded transitions for sharp corners.
  • Define datums and flat-pattern dimensions for multi-bend parts to reduce cumulative error.

Cost and Lead-Time Drivers

  • Complex bending, welding assembly, polished appearance and multiple surface treatments.
  • When the requirements for hole position accuracy and assembly consistency are high, the cost of inspection and repair will increase.
  • Define the datum edge or hole and use locating and slotted holes where appropriate to control assembly consistency.

Vacuum Casting: Production-Like Low-Volume Parts

Vacuum casting supports fast, low-volume validation with production-like appearance. Parting, venting, wall thickness and Side A placement should be reviewed early to limit bubbles, deformation and cosmetic repair.

Best-Fit Applications

  • Appearance models, functional validation and low-volume pilot parts before injection molding.
  • Appearance samples that require painting/screen printing/coating (can be made close to mass production).

Design for Manufacturability

  • The wall thickness is recommended to be 1.5–4mm; avoid sharp corners and add rounded corner transitions to reduce the risk of air trapping and tearing.
  • Deep cavities and closed areas need to design exhaust paths: the end of deep cavities, closed annular cavities, and sharp turns in thin walls are areas with high incidence of trapped air.
  • It is recommended to define surface A to reduce the probability of parting lines/repair points appearing on the main view surface (and to clarify the acceptable repair range).
  • As quantity increases, compare new silicone tooling, injection molding or machining; secondary-machine critical holes when tighter consistency is needed.
  • Tip: When "consistent appearance and low repair" are the core goals, parting surfaces and pouring/venting schemes are often more critical than post-processing.

Cost and Lead-Time Drivers

  • Complex parting, difficult venting, cosmetic repair and multiple finishing steps such as painting, screen printing or coating.
  • Larger batches need additional silicone molds and consistency controls; stricter Side A requirements increase repair and rework risk.

FAQs

Quick answers to common questions about process fit, cost, precision, lead time and design for manufacturability.

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