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Process Selection Guide

Injection Molding vs CNC Machining

3-Line Decision Card

Quantity
1–200 pcs → prototyping200–1,000 pcs → depends1,000+ pcs → molding
Design stability

Revision still moving? CTQs not frozen? Choose CNC first. Revision frozen + repeat builds? Molding becomes defensible.

Risk

Watch shrinkage / warpage, undercuts / slides, and cosmetic texture—these drive tooling NRE and iteration time.

For design engineers validating new plastic parts, NPI teams balancing schedule and risk, and purchasing managers comparing injection molding vs CNC machining for real RFQs.

When selecting a manufacturing process for plastic parts, injection molding and CNC machining solve very different problems. The right choice depends on volume, design stability, tolerances, lead time, and total cost—not just unit price.

Injection molding shifts cost into upfront tooling (NRE) in exchange for very low unit cost at steady volumes. CNC machining stays flexible, making it ideal for prototypes, engineering builds, and programs where CTQ features may still change.

Get a break-even + CTQ feasibility check (DFM / Moldflow)

Upload STEP/PDF + quantity + CTQs. We’ll reply with an engineering recommendation you can use in RFQ.

  • Break-even range (sensitivity to cavities, mold actions, cosmetic finish)
  • CTQ risk list (shrinkage/warpage/gating + what to change)
  • Recommended route (CNC → rapid tooling → production mold)
Read the full guide Injection Molding vs CNCRapid Tooling bridge-to-moldDesign guide molding DFMDesign guide CNC DFM

Process Selection Guide

The 200–1,000 pcs Gray Zone: Bridge Options

Bridge production

This range is where “rules of thumb” break: you’re balancing revision risk, per-part cost, and the time/value of getting parts in hand.

CNC bridge when revisions are still likely

You avoid tooling lock-in and can ship functional batches while you validate fit, CTQs, and assembly.

Rapid tooling when you need production resin + repeatability

Useful for EVT/DVT and early customer samples with consistent gating and shrink behavior—before cutting hard steel.

Soft tooling (aluminum / soft steel)

Best when geometry is mostly frozen but demand is uncertain: faster and cheaper to cut, but expect lower tool life and tighter limits on texture/actions.

Practical decision notes

  • Decide by revision risk: if CTQs, interfaces, and material grade are not locked, stay with CNC/rapid options; if they’re frozen and volume is credible, step into tooling.
  • Watch the hidden drivers: slides/lifters, cosmetic class (SPI/VDI), and multi-cavity ambitions push cost and rework risk—sometimes break-even shifts.
  • Practical rule: if you expect redesign within 1–2 iterations, bridge first; if revision history is quiet and annual demand is predictable, tool sooner.
Rapid Tooling bridge-to-moldCNC Machining fast iterationsInjection Molding scale-upMain guide compare methods
Request an Engineering ReviewSee Rapid Tooling

Tip: include your STEP/PDF, target quantity, material, and CTQ callouts—engineering review is the fastest way to avoid premature tooling in this gray zone.

Core Differences

Core Differences at a Glance: CNC Machining vs Injection Molding

Use this side-by-side view to compare cost, lead time, change risk, and tolerance behavior—so you can pick the process that best fits your project stage and volume.

FactorCNC MachiningInjection Molding
Upfront costLow
Very low or none (no tooling)		High
High tooling / NRE
Unit costHigher at volumeVery low at volume
Lead timeTypically 3–10 daysTypically 3–8 weeks (tooling)
+ approval & sampling cycles
Revision cost (design changes)Update the program and/or fixtures—usually low costModify steel, actions (slides/lifters), or textures—can be costly
Tolerance controlHighly predictable on defined CTQsMaterial shrink + cooling + process dependent
Part-to-part variationStable when machining variables are controlledProcess-window driven; sensitive to cooling balance and material lot
Design constraintsTool access, minimum internal radii, deep-pocket machining timeDraft, parting line, gating, shrink management
Cost driversMachine time + setup + material removalTool complexity + cavity count + cycle time
Quality / PPAP readinessFAI with CMM reports straightforward; control plan lighter for low volumePPAP depends on stable process window, control plan, and production consistency
Surface finishTool marks possible; secondary finishing as neededMold polish or texture (SPI/VDI); gate and weld-line management required
Geometry limitsInternal and access limits; undercuts may need secondary opsDraft, parting line, wall thickness; undercuts require slides or lifters
Best use casePrototypes, EVT/DVT, and bridge productionStable designs and high-volume production

Engineer takeaways

  • Use CNC to prove CTQs; use molding to lock in Cpk at volume.
  • Molding tolerances are driven by material + cooling, not steel alone.
  • Design-change risk is the real hidden cost of early tooling.
CNC Machining capabilitiesInjection Molding capabilitiesMain guide full comparisonFree DFM engineering review

Cost model & break-even

Cost Model & Break-Even Point

Understand what you actually pay for with CNC machining versus injection molding, and where the cost curve crosses over from prototype quantities to production volumes.

CNC machining

What You Pay for with CNC Machining

Best suited for prototypes, engineering samples, and low-to-medium volumes where flexibility matters more than the absolute lowest piece price.

  • CAM programming & setup: typically low to moderate, especially when design changes are frequent.
  • Machine time + material removal: the main cost driver; more complex geometry or heavy stock removal increases cycle time.
  • Cost scales almost linearly with quantity: each additional part costs roughly the same, with only minor efficiencies from batching.

If you expect frequent drawing revisions, staying in CNC machining avoids re-cutting tools or modifying molds.

Injection molding

What You Pay for with Injection Molding

Optimized for stable designs at higher volumes where a one-time tooling investment can be amortized across many parts.

  • Mold tooling (one-time NRE): the largest upfront cost; complexity, cavity count, and steel selection all influence tooling price.
  • Very low per-part cost after tooling: once the mold is built, cycle times are short and resin utilization is efficient.
  • Cost advantage increases rapidly with volume: the more parts you mold, the less the tooling cost per part matters.

For design-locked parts with stable annual demand, tooling cost is quickly offset by the low molded unit price.

Break-Even Example (Simplified)

The example below uses typical assumptions to illustrate where injection molding starts to beat CNC machining on total cost.

Input assumptions

  • CNC unit cost$40 / part
  • Injection molding unit cost$2 / part
  • Mold tooling$18,000 one-time

Break-even when: Tooling + (Molded unit cost × Q) = (CNC unit cost × Q)

The break-even range shifts mainly with tooling complexity (cavity count, steel, and mold actions like slides/lifters) and CNC cycle time (depth, features, setups). If your part needs slides, tight cosmetic requirements, or multi-cavity tooling, the break-even volume often moves higher.

Break-even sensitivity (ranked)

Break-even is most sensitive to:

  • 1) Mold actions (slides, lifters, unscrewing)
  • 2) Cavity count (single vs multi-cavity)
  • 3) Cosmetic class / texture (SPI/VDI, gloss, grain)
  • 4) CNC cycle time & setups (features, depth, fixturing)
  • 5) Resin cost + yield/scrap (runner, warpage risk, rejects)

Boundary condition

If annual demand is uncertain or the revision level may change, treat tooling as a risk cost, not an amortizable cost.

Inputs → break-even direction

Input / constraint Direction Why it moves
Slides / lifters (mold actions) Break-even ↑ More tooling complexity, higher NRE, higher risk of tuning and maintenance.
Multi-cavity (well-balanced) Break-even ↓ Lower molded unit cost at volume—only if demand is high enough and the tool can be balanced.
Tight cosmetic requirements (finish/texture) Break-even ↑ Higher polish/EDM/texture cost, higher defect risk (flow lines, weld lines, gate blush).
High CNC cycle time & multiple setups Break-even ↓ Raises CNC unit cost, so injection molding wins earlier once tooling is justified.

Direction is for typical cases. Real break-even depends on geometry, material, tolerances/CTQs, gating/runner strategy, inspection level (FAI/PPAP), and expected revision risk.

How this impacts process selection

  • With the above assumptions, the break-even point is typically around 500–800 parts, depending on geometry, material, and quality requirements.
  • Below break-even: CNC machining is usually cheaper and more flexible, especially for prototypes, engineering builds, and small pre-production runs.
  • Above break-even: injection molding becomes significantly more economical, particularly for repeat orders and stable annual demand.

For deeper guidance on process selection, see our pages on Injection Molding and 5-Axis CNC Machining.

Accuracy, Tolerances & CTQs

Accuracy, Tolerances & CTQs: CNC Machining vs Injection Molding

Understanding how CNC machining and injection molding behave on tolerances helps you set realistic CTQs, avoid unnecessary cost, and choose the right process for each critical feature.

Why CNC machining holds tighter tolerances

Direct cutting from solid stock makes dimensional control more predictable, especially on defined CTQs.

CNC

In CNC machining, parts are cut directly from solid stock on stable, repeatable equipment, which makes tight dimensional control more achievable—especially when features are tied to a clear datum scheme.

  • Parts are cut directly from solid stock, without cavity-driven shrinkage or warpage effects.
  • Dimensions are defined by toolpaths and fixturing, with in-process verification where needed.
  • Datum control and repeatability are straightforward through fixturing and probing.
  • Critical features can be measured and adjusted per operation before moving to the next setup.

Typical achievable tolerances: ±0.01 mm on defined, datum-controlled features with stable fixturing; thin walls or long, slender parts may require looser tolerances.

For complex 3D geometries, combining 5-axis CNC machining with robust fixturing and the right datum scheme often provides the best balance of accuracy and cost. See also our CNC design guidelines for design-side tips.

Why injection molding requires more caution

Molding tolerances depend on shrinkage, cooling balance, and the process window—not just steel dimensions.

Molding

Injection molding produces parts through melt flow, packing, and cooling inside a steel cavity. Tolerances are driven not only by tool geometry, but also by material behavior and the validated process window.

Key drivers of molding tolerances

  • Shrinkage behavior – resins shrink differently in flow vs transverse directions, especially with fillers.
  • Wall thickness variation – thick sections cool slower, increasing sink and local distortion.
  • Cooling balance and warpage – non-uniform cooling can twist parts or shift datums.
  • Gate location and fiber orientation (filled plastics) – anisotropic shrinkage can move CTQ features.

How to control CTQs in molding

  • DFM + Moldflow before cutting steel to flag CTQ risks early and avoid tooling rework.
  • Moldflow outputs we check: warpage tendency, sink/hotspot risk, and weld line risk near CTQ features.
  • Tool design response: gate/cooling adjustments plus a steel-safe strategy on CTQ-critical areas.
  • Validation: T0/T1 sampling and FAI (CMM where applicable) on CTQ features to confirm capability.

For molded projects, we recommend early collaboration: combine our injection molding team with free DFM & Moldflow review and, when needed, rapid tooling to confirm CTQs before committing to full production tooling.

CTQ callout example

Drawing note
Bore A: Ø10.000 ±0.010 mm (CTQ) Flatness: 0.02 mm to datum A Datums: A (primary), B (secondary), C (tertiary)
Tip: mark CTQs directly on the drawing and reference the same datums in the inspection plan (FAI/CMM) to avoid interpretation gaps.

Practical tolerance behavior: CNC vs molding (what drives variation)

A quick engineering view of which parameters move your dimensions—and where capability risk typically comes from.

Reference
Use this as a “what-to-control” checklist when defining CTQs. If your part has thin walls, long spans, or cosmetic surfaces, the right process window matters as much as the nominal dimension.
Variation driver CNC machining (what shifts) Injection molding (what shifts)
Datums & fixturing Fixture repeatability, setup count, probing strategy, part distortion after clamping. Datum shift from warpage, ejector forces, part “relaxation” after ejection and cooling.
Feature slenderness Tool deflection, chatter, and heat input on thin walls/long features. Warpage risk rises quickly with thin walls, ribs, and uneven cooling.
Material behavior Material lot variation, residual stress (especially after roughing), thermal growth during machining. Shrinkage (anisotropic for filled resins), moisture sensitivity (e.g., nylon), packing sensitivity.
Surface finish / cosmetics Tool marks vs secondary finishing (blast/polish/anodize) can move dimensions slightly. SPI/VDI finishes depend on tool condition; gate/weld line management affects appearance and local geometry.
Process window Mostly driven by machine stability, tool wear, and controlled setups. Highly sensitive to melt temperature, mold temperature, packing/hold, and cooling time—must be validated.

If you need accurate capability estimates for your specific geometry, resin, and CTQ scheme, our engineers can run a proper DFM review and tolerance/capability check—please contact us.

Not sure whether a critical feature should go to CNC machining or injection molding, or if your tolerance/CTQ stack-up is realistic for mass production?

Discuss tolerances with our engineers Upload drawing for free DFM & Moldflow

Design constraints

Design Constraints You Must Consider

Geometry, features, and surface finish place different constraints on CNC machining and injection molding. Understanding these limits early helps avoid expensive rework and unmanufacturable drawings.

Poor vs Optimized: a quick drawing check

A fast way to catch avoidable cost and tooling risk before RFQ.

Poor

  • Sharp internal corners + deep narrow pockets
  • Hidden undercut with no slide direction
  • Thick-to-thin transitions near cosmetic faces
  • No cosmetic class / texture spec; gate area undefined

Optimized

  • Fillets added; pockets opened or relieved
  • Parting line + slide direction planned early
  • Uniform wall targets; ribs used instead of mass
  • SPI/VDI spec + gate vestige zone called out

Internal corners & radii

Corners

Sharp corners behave differently in cutting vs molding. Plan radii early to keep cost and risk under control.

CNC impact

Small tools drive cost

  • Sharp internal corners require very small tools, which increase tool wear and cost.
  • Deep cavities force longer tools and multiple step-down passes, increasing cycle time.

Molding impact

Flow + durability need radii

  • Internal corners need radii for material flow and mold strength; sharp corners raise tooling risk.
  • Vertical walls need draft to allow clean ejection and reduce scuffing.
Design action Add fillets (avoid sharp internal corners) and avoid deep, narrow pockets that force long small-diameter tools.

Undercuts / slides

Hidden features

Undercuts are achievable in both processes, but they add cost in different ways: tool access in CNC, mold actions in molding.

CNC impact

Access dictates operations

  • Undercuts often need special tooling or secondary operations to access hidden features.
  • Multiple setups may be required to reach different sides, increasing handling time.

Molding impact

Slides/lifters add complexity

  • Undercuts normally need slides, lifters, or collapsible cores, adding tooling complexity.
  • More mold actions can increase lead time and maintenance risk over long runs.
Design action Re-orient the parting line, convert an undercut into a snap feature when possible, and define slide direction (and shut-off faces) early.

Wall thickness / sink & warpage

Stability

Thickness distribution affects machining time and molding stability. Uniform walls reduce distortion, sinks, and rework.

CNC impact

Thin walls increase risk

  • Thin sections can vibrate or deflect during cutting, affecting dimensional stability.
  • High material removal increases cycle time; consider splitting parts or simplifying pockets.

Molding impact

Rules prevent defects

  • Thin walls and snap-fits must follow molding rules to avoid short shots, warp, and breakage.
  • Thick-to-thin transitions can cause sink marks and warpage; uniform walls are preferred.
Design action Target a uniform wall, apply rib rules (use ribs instead of mass), and avoid thick-to-thin transitions—especially on cosmetic faces.

Lead time & ramp planning

Lead Time & Scaling Strategy

A practical way to de-risk NPI is to run early builds in CNC, validate function and CTQs, then move into molding once the revision is frozen and demand is predictable.

Ramp-up playbookFrom EVT/DVT to production tooling

  • 1

    CNC machine early batches

    Use CNC machining at EVT/DVT and for bridge production. Parts can be delivered in days, enabling fast iterations without committing to tooling too early.

    Typical deliverables / milestones

    • Functional parts for fit, assembly, and test
    • CTQ inspection approach (datums, method, gauge plan)
    • Initial measurement evidence (e.g., CMM report for key CTQs)
  • 2

    Validate design & freeze revisions

    Prove functional performance, run pilot builds, and align on what must be held as CTQ before you lock geometry for molding.

    Typical deliverables / milestones

    • Revision-freeze criteria (which CTQs are frozen and why)
    • Approved datum scheme + CTQ callouts on drawings
    • Risk review for changes that would impact tooling (actions, textures, gating)
  • 3

    Tooling, sampling & ramp to volume

    Once requirements are stable, invest in rapid tooling or full export mold production to achieve repeatable cycle times and low unit cost at scale.

    Typical deliverables / milestones

    • T0/T1 samples and feedback loop (sampling iterations as needed)
    • FAI on CTQs (CMM report + dimensional summary)
    • Process stabilization plan (process window, control plan inputs)

Where each process excelsCNC vs molding in the ramp curve

  • CNC machining excels in EVT/DVT and bridge production when revisions are still expected and lead time matters more than unit cost.
  • Injection molding excels once the revision is frozen, demand is stable, and scaling to thousands (or millions) of parts is required.
  • Quality at volume depends on a stable molding process window, not tooling alone—plan for sampling and process stabilization.

Rule of thumb: Use rapid tooling when you need production resin + repeatability before full steel tooling.

This staged approach reduces risk and avoids premature tooling investment while keeping your program on schedule. See Rapid Tooling and Export Mold Production for transition options.

Discuss a CNC-to-molding ramp plan

Send your STEP/PDF, target volumes, material, and CTQs—we’ll recommend a realistic lead time and ramp path.

Hybrid process strategy

Hybrid Strategy: When Using Both Makes Sense

Many successful programs start with CNC machining and then transition into injection molding once the design and demand are stable. The key is to time the switch so you avoid premature tooling while not overpaying for CNC at production volumes.

Start with CNC machining

Use CNC machining first if:

Keep the process flexible while you are still learning from the market and your test builds.

  • Design is not frozen: geometry, wall thickness, or features may still change based on test feedback.
  • Market demand is uncertain: you are exploring fit, pricing, or application scenarios without firm volume commitments.
  • Functional testing is ongoing: you need quick design iterations for performance, reliability, or certification tests.
At this stage, CNC parts from 5-axis CNC machining or Swiss turning help you iterate fast without locking into a mold.

Switch to molding

Switch to injection molding when:

Once your design and forecast are stable, you can safely invest in tooling and drive the unit cost down.

  • Design is validated: form, fit, and function are confirmed by testing and pilot builds.
  • Annual volume is predictable: you have realistic demand forecasts and repeat orders from key customers.
  • Unit cost becomes a priority: BOM cost reduction and margin improvement are now key program metrics.
At this point, moving into injection molding and rapid tooling typically delivers the best lifetime economics.

Need help planning a staged CNC → molding ramp? Our engineers can review your drawings, CTQs, and volume roadmap to propose a hybrid strategy that balances time-to-market with total landed cost.

Discuss a hybrid ramp plan Or upload drawings for free DFM & tooling readiness review

Reverse selection guide

When NOT to Use Injection Molding / When NOT to Use CNC

Engineers save the most time by ruling out the wrong process early. Use this checklist to avoid mismatched RFQs and prevent the most common cost traps (premature tooling, unstable design, or over-spec’d tolerances).

When NOT to use injection molding

Avoid molding when tooling risk or design uncertainty dominates the cost equation.

  • Design is still changing (rev not frozen)

    Frequent ECOs can force mold rework, timeline slips, and cost re-approval. Start with CNC for EVT/DVT and lock CTQs first.

  • Volume is low or forecast is uncertain

    Tooling amortization becomes the dominant cost driver. If you cannot defend annual demand, CNC or rapid tooling is safer.

  • Geometry forces heavy mold actions

    Multiple slides/lifters, deep cores, or complex parting lines increase tool cost and failure risk. Consider redesigning features or splitting the part.

  • CTQs require ultra-tight, highly predictable tolerances

    Molding tolerances vary with resin shrink, gate location, and thermal stability. For critical bores/flatness, CNC is often more repeatable.

  • Cosmetic class is strict but not fully defined

    If SPI/VDI level, witness areas, gate vestige, and weld line zones are unclear, you risk expensive finish changes and re-polishing.

When NOT to use CNC machining

Avoid CNC when scaling cost and repeatability matters more than tooling flexibility.

  • High volume where unit cost must be minimized

    Once demand is stable, CNC cost scales with cycle time, setups, and labor. Injection molding typically wins on price at scale.

  • Thin-wall or snap-fit plastic design is required

    Molded parts can achieve consistent thin walls and integrated snaps. Machining thin features can be slow and risks warpage or chatter.

  • Large batch repeatability with short takt time is critical

    For stable, repeatable output (same resin, same tool, same cycle), molding is often easier to control at high throughput.

  • Part cost is dominated by deep cavities / long toolpaths

    Deep pockets, complex surfacing, or multiple orientations can explode CNC cycle time. If the design is frozen, tooling may be the better path.

  • Material and finish are optimized for molding

    Some molded grades and cosmetic textures are best achieved directly from the mold; machining + secondary finishing may add variability and cost.

Request an Engineering ReviewInjection Molding5-Axis CNC MachiningRapid ToolingExport Mold Production
Tip:Place this section after Hybrid Strategy or Design Constraints to pre-qualify inquiries.

FAQ

FAQ (Featured Snippet–Ready Answers)

Short, decision-focused answers designed for quick scanning—ideal for engineering reviews and procurement comparisons.

What is the break-even point between CNC machining and injection molding?

Break-even is typically 500–1,000 parts when the design is stable and tooling can be amortized. It shifts mainly with tooling actions (slides/lifters), cosmetic class (gating/ejector constraints), and CNC cycle time (depth, features, setups).

Which process offers tighter tolerances?

CNC machining is typically tighter and more predictable for defined CTQs, especially on datum-controlled features. Injection molding tolerance depends on shrinkage, fiber orientation, and process window, so CTQs often require tooling and process controls to stay consistent.

Which process is faster for prototypes?

CNC is usually fastest (often days) because it does not require mold tooling. Injection molding typically takes weeks due to tool build + sampling iterations, especially if cosmetic or CTQ requirements are strict.

Can injection molding produce sharp internal corners?

No—molded parts should use radii for flow and mold durability. Sharp corners increase stress concentration and raise tooling risk, so fillets are typically required.

Is CNC machining suitable for small batch production?

Yes—CNC is ideal below ~200–500 parts when tooling cost is not justified or revisions are expected. It also works well for bridge production while preparing injection molds.

Can the same plastics be used for both CNC machining and injection molding?

Many overlap (ABS, PC, Nylon), but molded grades may behave differently when machined and vice versa. Always confirm final-process grade for shrinkage, warpage risk, and cosmetic requirements.

How do undercuts impact cost in CNC vs molding?

Undercuts raise cost in both, but for different reasons: CNC pays for tool access (special cutters, extra setups), while molding pays for tool actions (slides/lifters/collapsible cores) that add lead time and maintenance risk.

When does a hybrid CNC → molding strategy make sense?

Use CNC first when the design is not frozen, then switch once volume and requirements are stable. This avoids premature tooling rework while preventing long-term unit-cost penalties at production volumes.

What changes are needed when switching a CNC CAD design to injection molding?

Expect 4 core changes: draft, wall strategy, undercut actions, and gating/cosmetic planning. Add draft to ejection faces, target uniform walls + ribs, convert or plan undercuts with slides/lifters, and define cosmetic class so gate location, weld lines, and ejector marks are controlled early.

How do glass-filled plastics affect warpage and CTQs?

Filled plastics can improve stiffness but increase warpage risk because fiber orientation creates anisotropic shrinkage. CTQs may shift with flow direction, so plan datum/CTQs around the flow, and budget for tool tuning + process window control to stabilize dimensions.

If you need an accurate break-even or tolerance risk check, a detailed DFM review is still required—please contact us and share your STEP/PDF, material, quantity, and CTQs.

CTQ & Variation Drivers

Practical Parameter Ranges (What actually drives variation)

When a CTQ is tight, the real question is whether the process window can hold it consistently. Use the ranges below as a quick engineering checklist—then confirm with DFM, material data, and measurement strategy.

Parameter range table (scan-friendly)

These are practical engineering levers that move the outcome. Focus on the items that match your failure mode (warpage, sink, ovality, runout, cosmetic defects).

Driver Typical range / window How it shows up on CTQs What to control
Molding Shrinkage Material + packing dominated Resin-dependent; varies with pack/hold and wall thickness Expect directional (flow vs transverse) differences for filled resins. Hole position shift, flatness drift, assembly mismatch Lock resin grade, define gate location, stabilize pack/hold, use consistent melt & mold temps
Molding Wall thickness Geometry-driven Prefer uniform; avoid thick-to-thin transitions Ribs: keep proportional and avoid over-thick root areas. Sink marks, warpage, short shots, weak snap features Target uniform wall, tune ribs & bosses, add fillets, use core-outs where needed
Molding Fiber orientation GF/CF anisotropy Strongly direction-dependent for glass-filled materials More pronounced with long flow lengths and thin walls. Warp/twist, oval holes, inconsistent fit Orient gates for balanced flow, adjust parting & flow path, consider lower fill or different grade
Molding Mold temperature Thermal stability Process-window dependent; stability matters more than the setpoint Temperature gradients create repeatability issues. Dimensional drift over time, cosmetic variation Improve cooling layout, balance circuits, confirm with IR/thermocouples during trials
Molding Tooling actions Slides / lifters More actions = more stack-up and wear risk Each action adds alignment & timing sensitivity. Flash, witness mismatch, CTQ shift near shut-offs Minimize undercuts, define shut-off angles, harden wear areas, plan maintenance intervals
CNC Workholding Clamping strategy Primary source of repeatability issues on thin parts Distortion risk rises with thin walls / large flats. Flatness, parallelism, datum shift, chatter marks Design soft jaws/fixtures, support thin sections, control clamp force, use datum-first sequencing
CNC Tool reach Stick-out Long reach increases deflection & chatter risk Small cutters amplify runout sensitivity. Wall thickness variation, corner radii drift, poor surface finish Reduce depth, open pockets, add fillets, split ops, use stable tooling and appropriate feeds
CNC Thermal growth Machine + part Drift during long cycles or warm-up Especially noticeable on tight bores and long parts. Bore size drift, position error, runout changes Warm-up routine, in-process probing, stable coolant temp, control cycle batching
CNC Burr & edge condition Secondary handling Edge breaks vary by tool wear and material Manual deburr adds variability. Assembly interference, cosmetic rejection, inconsistent fits Specify edge break, standardize deburr method, add chamfers where functional, inspect critical edges
Measurement Gage strategy Metrology Method must match CTQ intent Different gages can disagree if the spec intent is unclear. False rejects or false passes, CTQ disputes Define datums, measurement method, sampling plan (FAI/PPAP), and gage R&R as needed
Use this as a checklist, not a promise. For an accurate break-even or CTQ capability prediction, we still need an engineering-led DFM review—please contact us with your STEP/PDF, quantity, material, and CTQs.