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Overview of process capabilities (reference values)

The following are general experience values ​​in the design stage, which are used to quickly determine "whether it can be manufactured" and "whether the cost/delivery time is controllable". Actual results depend on materials, dimensions, structural complexity, surface requirements, lot size and inspection method; If you need a more accurate conclusion, it is recommended to upload a 3D file and mark the key dimensions/datum/appearance surface (A surface) definition.

Craftsmanship 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 (SLA/SLS/FDM/MJF) Single piece/prototyping/rapid iteration/small batch of functional parts Related to craftsmanship/material/posture (it is recommended to click on the material page) Related to equipment, posture, support and post-processing Lamination/warpage, support marks, anisotropy, post-processing deformation, dimensional consistency fluctuations

Comparative dimension description (you should judge from these perspectives)

Process selection is not just based on "whether it can be done", but "whether it can be done stably, whether the cost is controllable, and whether the delivery date can be promised." The following are the most commonly used comparison dimensions and judgment logic.

1) Batch size (amortization logic)

  • 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.
  • Tip: The larger the batch size, the more critical "mold/jig amortization"; when the batch size is uncertain, it is more stable to take the verification path of lowering the promised cost first.

2) Accuracy and consistency (inspection caliber)

  • 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.
  • Tip: The more strict tolerances, the higher the inspection cost (CMM/jigs/sampling inspection frequency), and the more unstable the delivery time is.

3) Appearance and post-processing (Side A and defect tolerance area)

  • High-appearance parts need to define the main view surface (Side A) and the defect tolerance area (parting line/ejector pin mark/gate/knife pattern/repair point).
  • Spraying/coating/silkscreen printing will introduce additional processes and consistency risks (color difference, adhesion, masking boundaries).
  • Tip: If the appearance standard is unclear, the probability of repair will increase significantly; the longer the appearance chain, the more the acceptance criteria should be defined in advance.

4) Structural characteristics and risks (yield driven)

  • Deep cavity/thin wall/acute angle: CNC cost and yield risk are higher (tool/clamping/deformation).
  • Undercut/Side Draw: Injection mold cost and cycle increase significantly (slider/inclined top/mechanism).
  • Trapped air/bubbles: Vacuum casting is more sensitive, so parting and exhaust paths need to be optimized.
  • Tip: Changing high-risk features during the design stage is usually the step that saves the most money and shortens the delivery time.

Decision variable link (variable → influence → consequence)

The most common "engineering variables" in process selection are broken down into communicable links below: as long as you can explain the variables, you can get executable evaluation conclusions faster (instead of asking repeated questions).

Variable: Material System

  • Influence:Shrinkage/deformation, strength/toughness, surface consistency, processability and post-treatment adhesion.
  • as a result of:When using the same structure with different materials, the warpage and dimensional consistency of injection molding, the knife pattern and burr control of CNC, and the bubbles and repair probability of the duplicate mold will all change.
  • Suggested description: material grade/flame retardant/glass fiber content/transparent or high-gloss requirements.

Variables: critical dimensions and inspection caliber

  • Influence:Number of processes, tool path/machine adjustment, fixture and CMM inspection, and frequency of random inspections.
  • as a result of:Tight tolerances spread from "processing costs" to "inspection costs and delivery uncertainty".
  • Suggested description: datum A/B/C, critical dimension chain, position/coaxiality, acceptance method (CMM/pass and stop gauge/jigs).

Variables: appearance standards and side A definition

  • Influence:Parting line/ejector mark/gate/knife mark/patch point visibility, post-processing chain length.
  • as a result of:The higher the appearance standard, the easier it is to trigger polishing/spraying/repair, and the fluctuations in unit price and delivery time will increase.
  • Suggested description: Side A location, gloss/texture, color, acceptable defects and masking area.

Variable: Structural Risk Characteristics

  • Influence:Accessibility (tool/bending/ejection), trapped air path, deformation and assembly tolerance.
  • as a result of:Structural characteristics determine yield: a decrease in yield will directly translate into uncontrollable costs and delivery times.
  • Suggested description: deep cavity depth-to-diameter ratio, thin wall area, number of undercuts, closed cavity, long cantilever and assembly method.

Capability boundary stratification (regular/requires assessment/high risk)

This part is not a "recommendation", but a layering of common requirements: allowing you to quickly judge which ones are routine and controllable, which ones will significantly increase the cost/delivery period, and which ones are high-risk and require engineering review.

CNC machining: typical boundaries

  • conventional:±0.05mm, internal angle R≥0.5mm, metal wall thickness ≥0.8mm, plastic wall thickness ≥1.2mm.
  • Need to evaluate:Deep cavity/deep groove (large tool overhang), large area of ​​thin wall, local ±0.02mm level, coaxiality/position accuracy requirements.
  • High risk:Full-size tight tolerances, deep holes/deep threads, high aspect-to-diameter ratio, high main view surface + difficult-to-clamp structure.
  • Typical consequences: small tools/slow feed/multiple clampings + high-frequency inspection → high costs and fluctuating delivery times.

Injection Molding: Typical Boundaries

  • conventional:The wall thickness is 0.8–3.0mm and should be as uniform as possible, the appearance surface draft should be ≥1°, and the rib thickness should be ≤60% of the main wall thickness.
  • Need to evaluate:Risk of warpage of transparent/high-gloss parts, long thin parts, and A-side sensitive to parting line/ejector pin print/gate position.
  • High risk:Multiple undercuts and side pulls, insufficient drafting on deep cavity textured surfaces, extremely strict dimensional consistency + high appearance requirements at the same time.
  • Typical consequences: mold complexity and narrowing of the machine adjustment window → long mold period, unit price and yield fluctuations.

Sheet metal fabrication: typical boundaries

  • conventional:Inner bending radius R≥t, hole to bending line ≥1.5t, hole to edge ≥t.
  • Need to evaluate:Accumulated errors of multiple bends, springback-sensitive materials (stainless steel/high-strength steel), post-weld deformation and assembly tolerance chain.
  • High risk:The hole spacing is extremely close + the appearance requirements are high, the welding assembly is complex + multiple post-processing, the assembly consistency requirements are very strict, and the benchmark is not clear.
  • Typical consequences: Increased demand for plastic surgery/rework/jig positioning → increased costs and uncertain delivery times.

Vacuum replica/3D printing (including MJF): typical boundaries

  • conventional:The wall thickness of the replica is 1.5–4mm and sharp corners should be avoided; 3D printing is used to verify structure and assembly interference, and small batches of functional parts can be included in MJF for comparison.
  • Need to evaluate:Duplicate deep cavity/enclosed area exhaust, batch-to-batch consistency; printing critical dimensions falling on support dense surfaces or posture-sensitive directions (SLA/FDM), and powder bed process (SLS/MJF) surface and size consistency strategies.
  • High risk:The replica mold requires "dimensional consistency like mass production injection molding/zero repair of side A"; 3D printing functional stress-bearing parts require isotropic strength or extremely strict appearance consistency.
  • Typical consequences: increased repair/post-processing and consistency control costs; need to switch processes or introduce secondary processing strategies.

3D printing (SLA/SLS/FDM/MJF) (process description and key points)

3D printing is useful for rapid prototypes, complex geometry and early structural checks without tooling. Watch for layer marks, support marks, orientation-related size differences, strength anisotropy and post-processing deformation. If the goal is repeatable production, compare CNC machining, injection molding, vacuum casting or secondary machining early.

Applicable scenarios

  • 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).
  • Small batch functional parts: available SLS/MJF As a comparison option (common in engineering plastics powder bed routes).
  • Tip: When you need to "get closer to the appearance/feel of mass production", the common path is: print verification → print master mold / master part → copy mold in small batches or transfer to injection molding.

Design Essentials (DFM)

  • Posture and support (SLA/FDM is more sensitive):Key dimensions should be avoided as much as possible on densely supported surfaces and overhanging areas; support removal and grinding will change the boundaries and flatness.
  • Powder Bed Route (SLS/MJF):Pay attention to the surface roughness and the powder cleaning accessibility of holes/slots; it is recommended to reserve secondary processing allowance for key matching holes/surfaces.
  • Source of size deviation:Post-processing such as printing direction/posture, thermal shrinkage/warping, and post-curing/annealing will introduce secondary deformation (sensitive points are different in different processes).
  • Anisotropy:The strength difference in the layer direction of the stressed parts needs to be considered; if necessary, change the stress path, reinforce it, or switch to a more stable process.
  • Appearance strategy:It is recommended to reserve a margin for grinding/spraying on the high-appearance surface, and clarify the direction of surface A and the acceptable layer/texture.
  • Tip: If the printed parts are to participate in assembly verification, it is recommended to design the key mating holes/surfaces as secondary processing areas (drilling/milling allowances).

Main drivers of cost and delivery time

  • Volume and filling, support complexity, posture requirements (specific placement may be required to control deformation).
  • The post-processing chain (removal of support/powder cleaning/polishing/spraying/assembly) and the increase in man-hours brought about by the high appearance grade.
  • Tip: The "body cost" of printing is not necessarily high, but "post-processing man-hours" are often the main cost source of high-appearance projects.

CNC machining (process description and key points)

CNC is good at high precision and complex geometry, suitable for single parts and small batches of metal/engineering plastics. Cost and delivery time are often driven up by "deep cavities, thin walls, sharp angles, tight tolerances, and difficulty in clamping"; Following machinable geometry and reasonable tolerance/inspection strategies during the design phase can significantly reduce multiple clamping, deformation scrapping and inspection costs.

Applicable scenarios

  • 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 Essentials (DFM)

  • Avoid sharp angles at interior corners; recommendations R ≥ 0.5mm And try to make it bigger.
  • 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).
  • The tolerance only tightens the key mating surfaces, and defines the reference A/B/C and inspection caliber.

Main drivers of cost and delivery time

  • Deep cavity, extremely small tool, complex clamping, tight tolerance + high frequency inspection (CMM).
  • High appearance grade (main view surface knife pattern control, secondary grinding/sandblasting/polishing).
  • Tip: Define the "main view surface (A side)" and key functional surfaces first, which can significantly reduce communication and rework costs.

Injection molding (process description and key points)

Injection molding is suitable for mid-batch and mass production, and the core is "uniform wall thickness + reliable demoulding + controllable defects + the mold is not overly complex". Appearance parts must define the main view surface (Side A) and acceptable parting line/ejector pin mark/gate positions in advance. This will directly determine the appearance yield and final unit price.

Applicable scenarios

  • Medium batch/mass production plastic parts: shells, fasteners, brackets, functional structural parts.
  • Scenarios that require stable consistency and low unit cost.
  • Tip: When the quantity is uncertain, you can first use vacuum casting/3D printing to verify the appearance and assembly before deciding whether to open the mold.

Design Essentials (DFM)

  • 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°.
  • Undercutting will introduce side drawing/sliding blocks, significantly increasing mold cost and cycle time.
  • Appearance parts define the A side and defect tolerance area (parting line/ejector pin mark/gate).

Main drivers of cost and delivery time

  • Mold structural complexity (number of side draws, stroke, precision inserts).
  • High appearance grade (glossy/transparent parts, textures, masking and spray chains).
  • Tip: Eliminating undercuts at the design stage is often more economical and stable than "doing side pulls".

Sheet metal fabrication (process description and key points)

The cost and consistency of sheet metal parts are often determined by "bending accessibility + hole distance and avoidance + springback control + assembly benchmark". For assembly parts, it is recommended to prioritize the reference edge/datum hole, and use the "positioning hole + oblong hole" combination to improve assembly error tolerance.

Applicable scenarios

  • 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 Essentials (DFM)

  • 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.
  • Multi-bending parts clearly define the reference and expansion diameter to reduce cumulative errors.

Main drivers of cost and delivery time

  • 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.
  • Tip: It is recommended that the assembly parts clearly define the "datum edge/datum hole" and the matching strategy (positioning hole + oblong hole), which can more stably control the assembly consistency.

Vacuum casting (process description and key points)

Vacuum casting is suitable for rapid verification of small batches. The advantages are fast delivery and strong appearance plasticity. Key risks focus on "trapped air/bubbles, parting line position, thin-wall deformation, and batch-to-batch consistency." Thinking clearly about the parting and exhaust paths during the design stage is more cost-effective and more stable than repairing later.

Applicable scenarios

  • Appearance review parts, functional verification parts, low-volume pilot production replacement injection molding (especially in the stage where the quantity is not determined).
  • Appearance samples that require painting/screen printing/coating (can be made close to mass production).

Design Essentials (DFM)

  • 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).
  • When the quantity increases, it is more economical to evaluate mold preparation or switch to injection molding/machining; secondary processing can be considered for critical hole locations to improve consistency.
  • Tip: When "consistent appearance and low repair" are the core goals, parting surfaces and pouring/venting schemes are often more critical than post-processing.

Main drivers of cost and delivery time

  • Complex parting, difficult exhaust, appearance repair and multi-channel post-processing (spraying/silkscreen/coating).
  • The increase in batch size leads to an increase in mold preparation and consistency control costs; the higher the A-side requirements, the higher the risk of repair and rework.

FAQs

Focusing on the most frequently searched and asked questions by customers before manufacturing customized parts, combined with process selection, cost, delivery time, accuracy, tolerance, appearance and DFM risks, it helps engineering, procurement and product teams to more quickly determine the next manufacturing path.

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