Signals that point to material
- Haze tracks resin lot or regrind change
- Improves on a freshly dried lot
- Haze with silver streaks or bubbles at gate
- Fix path: drying, contamination control, shear reduction
Injection molding defects
Surface haze
Surface haze is a cloudy or dull film that reduces clarity on transparent parts or gloss on polished surfaces. Causes include moisture volatiles, mold release residue, incompatible additives, excessive shear, or worn cavity polish.
Defect troubleshooting
What is surface haze in injection molding?
Haze may cover large cosmetic faces or appear patchy near vents and gates. It differs from gate blush by footprint and from flow lines by lacking a directional streak history.
Haze may cover large cosmetic faces or appear patchy near vents and gates. It differs from gate blush by footprint and from flow lines by lacking a directional streak history.
Clear polycarbonate and acrylic programs are especially sensitive to drying and contamination. Document dryer performance and whether haze returns after mold cleaning.
Mold finish and release agent discipline matter for high-gloss parts. Define acceptable viewing method in the cosmetic spec before debating floor fixes.
Root causes
Surface haze causes mapped to signals
Use this table to decide whether the next change belongs in material prep, process, mold steel, or part design.
| Likely driver | What you see | First lever to try |
|---|---|---|
| Undried hygroscopic resin | Haze with splay risk; lot humidity exposure | Verify dryer; compare to retained dry lot |
| Mold release or lubricant overload | Patchy haze after manual spray | Clean cavity; eliminate non-approved release for production |
| Excessive shear on clear grades | Haze increases with fill speed | Profile fill; review gate size for shear-sensitive resin |
| Worn or etched cavity polish | Haze fixed to steel texture pattern | Re-polish per finish class; inspect for chemical attack |
Diagnosis
Material condition versus mold surface
Splitting ownership tells you whether material, process, or tooling is the honest fix path.
Signals that point to mold surface
- Haze footprint matches cavity texture or vent region
- Improves immediately after approved mold clean
- Haze persists across multiple lots at same fill speed
- Fix path: polish, cleaning procedure, release discipline
Troubleshooting
Surface haze troubleshooting order
Document what you see, prove a fair process window, then escalate to steel or design when the limit is proven.
- 1
Define viewing standard
Cosmetic
Agree light source and background with customer.
- 2
Prove drying
Material
Run with verified dry lot; log dew point if available.
- 3
Clean mold per approved procedure
Steel
Remove release buildup without attacking polish.
- 4
Tune fill profile
Shear
Reduce gate entry speed for clear grades.
- 5
Inspect polish and vent regions
Maintenance
Plan re-polish when haze maps to steel texture.
Prevention
Checklist to prevent surface haze
Most recurring defects trace to setup discipline and design margin rather than a single out-of-spec shot.
Dry clear and hygroscopic grades per supplier sheet with logged dryer checks.
Ban unapproved mold release on high-gloss production without quality sign-off.
Document fill profile for cosmetic faces.
Store resin sealed; minimize hopper open time.
Include cavity polish class on mold drawings.
Upload CAD for cosmetic face and gate review at instant quote.
Program context
Clarity programs on production steel
Haze acceptance is cosmetic and viewing-angle dependent; lock the spec early.
- One hardened steel tool carries the cavity finish defined at build; maintenance restores polish when approved.
- Instant quote DFM flags gate placement on show surfaces for clear parts.
FAQ
Surface haze injection molding FAQ
Is surface haze the same as gate blush?
Gate blush is localized at the gate. Haze can cover broader areas and often ties to drying or mold surface condition.
Can too much pack cause haze?
Excessive pack can increase stress whitening on some grades. Tune fill and hold together with drying verified.
Will a mold release fix haze long term?
Release may diagnose friction or contamination but is not a production substitute for drying and polish control.
Does regrind cause haze on clear parts?
Contamination and degraded fines from regrind can dull clarity. Track regrind ratio on cosmetic lots.
How can NetProto help before surface haze shows up on T1 shots?
Upload CAD for an instant quote and DFM feedback. Engineers can review gates, vents, wall transitions, and ejection risk while the hardened steel tool is still in planning, depending on part size and complexity. There is no minimum order quantity once the tool is running.
Ready to quote
Protect cosmetic faces before T1
Share clear or high-gloss CAD via instant quote for gate and finish planning.