Comprehensive Analysis of Sun Visor Molds and Passenger Car Interior Part Manufacturing

I. Why start with "Sun Visor" when discussing Passenger Vehicle Interior Trim Manufacturing?

The sun visor is one of the passenger vehicle cockpit's most frequently moved, directly interactive, and functionally important interior trim components, despite its small volume. It not only performs the basic function of **blocking sun glare** and enhancing driving safety, but also progressively integrates various features such as a **vanity mirror, lighting, airbag labels, sensor interfaces, and card slots**, making it a "mini interior system" that combines structure, wrapping, mechanism, electronics, and decoration.

Precisely because the sun visor involves a complete process chain—from substrate molding, hardware insert molding, foam filling, fabric wrapping, functional module assembly, to appearance and durability testing—it serves as an excellent entry point for a systematic study of the **entire manufacturing process of passenger vehicle interior trim components**, including materials, molds, processes, quality control, regulations, and lightweighting trends.

II. Functional Evolution and Product Types of Sun Visors

2.1 Basic Function: Blocking Direct and Oblique Sunlight

• Main visor (above the front windshield)
• Auxiliary visor (for side window blocking, rotatable)

2.2 Integrated Function Upgrades

Function	Description	Process Impact
Vanity Mirror	Flip-up or lidless mirror integration	Mold needs to reserve assembly positions or insert areas
LED Lighting	Mirror frame integrated lights or touch-sensitive light strips	Requires wiring channels, snap-fit designs, thermal management
Ticket/Card Slot	For inserting tickets, cards	Wrapping layer opening, assembly tolerance control
Safety Warning Label	Airbag warning, etc.	Silk screen printing, heat transfer printing or labeling process
Extension Slide Rail	Extends shading range	Increased mechanism complexity, wear validation needs strengthening

2.3 Product Structure Classification

• Hard core + foam + fabric wrapped type (Most common)
• Injection molded integral + soft-touch paint/wrapped surface type
• Composite material pressed lightweight type (Future trend, synergistic with roof module lightweighting)

III. Sun Visor Material System Analysis

The sun visor is composed of multiple material layers. Typical structure example: Outer layer (fabric/knitted fabric/PU leather) — Cushion layer (PU foam/PE foam) — Substrate skeleton (PP/ABS/composite material) — Metal shaft/pivot mechanism — Accessories (mirror frame, lights, circuits).

3.1 Substrate Materials (Core of Structural Strength)

Material	Characteristics	Application Notes
PP (with or without glass fiber)	Lightweight, low cost, easy to injection mold	Scenarios with moderate dimensional stability requirements
ABS or PC/ABS	Good dimensional accuracy, excellent surface quality	High-end vehicles or complex function sun visors
PA+GF	High strength, heat resistant	Mainly used for pivot brackets, small inserts
SMC/BMC Composite Materials	High strength/heat resistant/metal replacement	Structural innovation application under lightweighting trend

3.2 Internal Cushion/Filling Layer

• Foamed PU (Polyurethane): Soft, good filling properties, energy absorption.
• EPP/PE Foam Sheets: Easy to mold, can be heat-sealed with covering.

3.3 Exterior Skin Materials

Skin Material	Appearance/Tactile Feel	Process Method	Grade Positioning
Knitted Fabric/Warp Knitted Fabric	Soft, sound-absorbing	Hot pressing lamination, bonding	Mainstream economical
PVC Leather	Controllable cost, various colors	Hot melt lamination, sewing	Mid-range vehicles
TPU/PU Artificial Leather	Good hand feel, improved environmental rating	Vacuum laminating, sewing	Mid-to-high end
Microfiber/Eco-leather	Superior tactile feel, low VOC	Adhesive bonding, wrapping composite	High-end luxury

IV. Overview of Sun Visor Manufacturing Processes

Sun visor manufacturing typically involves multiple sequential or parallel process stages, depending on design structure, material system, and production volume requirements. The following is a typical process reference:

Raw Material Preparation → Substrate Injection Molding/Compression Molding → Hardware Shaft/Pivot Insert Molding → Foam Filling or EPP Filling → Skin Wrapping and Hot Press Forming → Functional Component Assembly (mirror, light, wiring) → Appearance Inspection → Flip Durability Validation → Packaging and Shipment

4.1 Substrate Molding (Injection Molding or Compression Molding)

• Single-piece injection molding + ultrasonic welding of halves
• Left and right shell clamp injection molding + hollow filling
• Compression molding (SMC/BMC skeleton) suitable for vehicles with higher heat resistance or rigidity requirements

4.2 Insert Molding

Pre-placing **metal rods, pivot connectors** into the mold cavity, then overmolding with plastic during injection to achieve structural and mechanical integration, reducing assembly steps and improving fit accuracy.

4.3 Foaming/Filling Process

• Low-pressure PU foam injection: Ensures complete filling and surface flatness
• Pre-formed foam sheet hot press composite: Used for thin, lightweight sun visors

4.4 Wrapping and Hot Press Forming

• Hot melt adhesive + vacuum adsorption + hot knife edge cutting
• Leather sewing + manual folding (for small batch high-end parts)
• High-frequency hot pressing (suitable for PVC/PU thin skins)

4.5 Functional Component Integration

• Vanity mirror snap-fit assembly or ultrasonic welding
• LED light wire embedding in grooves, terminal interfaces for vehicle wiring harness connection
• Spring-loaded flip mechanism pre-assembly

V. Key Considerations for Sun Visor Mold Design (Focus)

Sun visor molds are fundamental to ensuring dimensional accuracy, appearance, insert precision, and wrapping quality. The following is a systematic analysis from structural, process, durability, and maintenance perspectives.

5.1 Mold Structure Planning

1. Cavity Parting Line: Must consider areas invisible after wrapping; avoid visible flash lines in aesthetic regions.
2. Insert Positioning: Precise positioning pins or magnetic locating blocks are needed for metal rods, pivot shafts, and mirror frame areas.
3. Core Pulling Mechanism: Side core pulling is required for sun visors with sliding functions or recessed areas; complex parts may use hydraulic ejectors.
4. Uniform Wall Thickness: Reduces uneven shrinkage and warpage; recommended main structure wall thickness 2.5–3.5 mm (depending on material).

5.2 Gating System (Gates/Runners)

Mold Type	Gate Type	Applicable Scenarios
Edge Fan Gate	Thin-walled, large coverage parts	Reduces weld lines
Hot Runner Pin Gate	Multi-point filling	Improves filling balance
Submarine Gate	Parts with high aesthetic requirements	Reduces gate marks

5.3 Venting and Sink Mark Control

• Parting line vent groove depth typically 0.02–0.05 mm (depending on material and molding pressure)
• Avoid sink marks in the mirror frame area; reinforce with ribs and process specific packing points if necessary

5.4 Recommended Mold Steel

Mold Cavity Area	Recommended Steel	Characteristics
General Cavity	P20 / 718	Good machinability, moderate cost
High-Gloss Appearance Area	2738 / NAK80	High polishability, clear texture
High-Wear Core Pulling	H13 / S136	High hardness, corrosion resistant

5.5 Surface Texture and Grain Simulation

The sun visor's substrate may be partially exposed before or after wrapping, or the mold may be used to produce surface finish alternative parts. The cavity can be etched with a grain to simulate leather texture, enhancing visual consistency; pay attention to matching grain depth with draft angles.

5.6 Replaceable Inserts and Platform Design

• A single main mold base can be shared across multiple vehicle series, changing inserts to accommodate different mirror frame sizes/extension slide rail structures.
• Standardized gating and cooling systems reduce mold change and debugging time.

5.7 Mold Flow Analysis (Moldflow/Simpoe) Integration Points

• Prediction of weld line locations (around vanity mirror opening)
• Warpage simulation (long, thin parts, asymmetrical wall thickness)
• Heat transfer impact of overmolded inserts

VI. Process Commonalities between Sun Visor and Passenger Vehicle Interior Trim Manufacturing

Extending from sun visors to a wider range of **passenger vehicle interior trim components** (e.g., instrument panels, door panels, pillar trims, headliners, center armrests, trunk liners), the following cross-product process commonalities can be summarized:

Process Stage	Sun Visor	Instrument Panel	Door Panel	Headliner	Common Key Points
Substrate Molding	Injection/Compression	Foam Substrate+Skin	Injection+Wrapping	Fiberglass Substrate Pressing	Material+mold precision determines dimensions
Skin Wrapping	Fabric/Leather	Foamed Skin/Wrapped Skin	Leather/Fabric	Fiber Felt+Fabric	Wrapping adhesion, thermal stability
Insert Integration	Metal Rod	Airbag Module	Armrest Skeleton	Wiring/Sensors	Insert positioning, thermal deformation control
Surface Texture	Can be exposed	Large area visible	Large area visible	Local	Mold texture & wrapping material matching

VII. Mainstream Process Technologies Collection for Passenger Vehicle Interior Trim Manufacturing

7.1 Injection Molding

• Applicable: Pillar trims, decorative covers, small module parts, sun visor skeletons
• Key parameters: Melt temperature, injection speed, holding pressure time, cooling circuit
• Common defects: Shrinkage, warpage, weld lines, white marks

7.2 Foam Injection Molding / Lightweight Foaming (MuCell, Physical Foaming)

Used for weight reduction, reducing internal stress, and controlling deformation; suitable for large instrument panel skeletons or thick-walled interior trim components.

7.3 Hot Press Molding (Compression Molding)

• Materials: SMC, GMT, natural fiber reinforced sheets
• Suitable for structural parts + interior trim "two-in-one" lightweight solutions

7.4 Vacuum Forming / Thermoforming

• Skin sheets preheated and then adsorbed onto the mold surface
• Commonly used for headliner substrates and soft trim overlays

7.5 Wrapping / Lamination

• Adhesive bonding, flame lamination, PUR hot melt adhesive lamination
• Automated rolling lines can achieve high consistency in decorative quality

7.6 Ultrasonic / Hot Melt / Laser Welding

Low-cost methods for interior trim assembly, local reinforcement, and replacing screws with snap-fits.

VIII. Advanced Considerations for Interior Trim Mold Design

8.1 Dimensional Chains and Assembly Tolerances

Assembly deviations from the sun visor pivot to the headliner mounting holes directly affect rotation flexibility and abnormal noise; similarly, door panels, instrument panels, and center consoles require cumulative tolerance control.

8.2 Thermal Expansion Compensation

Different materials (plastics, foams, fabrics, metals) have large differences in thermal expansion coefficients, so molds need to pre-compensate for dimensional shrinkage; extreme in-car conditions can cycle between -30°C and 85°C.

8.3 Surface Grade Zoning

A-surface for visual areas, B-surface for tactile areas, C-surface for hidden areas - partitioned design to optimize mold costs.

8.4 Quick Mold Change and Flexible Manufacturing

Platformized mold bases + replaceable cavity modules enable a single production unit to cover multiple vehicle series, facelifts, or different configurations (e.g., sun visor with/without light, with sensors).

IX. Quality Control and Testing Project Checklist

Sun visors and passenger vehicle interior trim components must undergo multi-dimensional validation. Below is a list of common test items (can be expanded into an enterprise inspection SOP template).

9.1 Appearance and Dimensions

• CMM (Coordinate Measuring Machine) dimensional inspection
• Skin wrinkles, bubbles, scratches inspection

9.2 Function and Durability

• Sun visor flip life cycle (≥ 10,000 cycles, depending on OEM standard)
• Sliding/rotating torque retention
• Snap-fit assembly/disassembly force

9.3 Environmental Tests

Test	Condition Example	Judgment Criteria
Thermal Cycling	-30°C ↔ 85°C cycles	No cracks, controlled deformation
UV Aging	SAE J1885 or OEM specific	Fading level acceptable
Salt Spray	ASTM B117	Corrosion protection for metal parts
High Humidity	95%RH	Delamination, debonding check

9.4 Safety and Regulatory Compliance

• FMVSS 201 (Interior trim head impact performance, relevant to sun visor area)
• FMVSS 302 (Material flammability characteristics)
• ECE R21 (Interior protrusions, radius requirements)
• RoHS, REACH, VOC, Odor Level

X. Digitalization and Intelligence in Passenger Vehicle Interior Trim Manufacturing

10.1 Digital R&D

• CAD 3D Master Model + Parametric Dimension Derivation
• CAE Simulation: Thermal deformation, stiffness, collision, vibration
• Moldflow Simulation: Gate location, filling balance, warpage prediction

10.2 Smart Manufacturing Factory Scenarios

Aspect	Intelligent Means	Effect
Injection Molding Workshop	Closed-loop control of process parameters	Reduces batch-to-batch variation
Wrapping Line	Visual defect recognition	Real-time rejection of defective products
Assembly Station	Torque-sensing electronic tightening	Data traceability
MES System	Batch tracking/Process traceability	Quality traceability

XI. Lightweighting and Sustainable Development Trends

The automotive industry's "Dual Carbon" goals and energy-saving regulations drive continuous weight reduction and environmentalization of interior trim components, and sun visors are no exception.

11.1 Material Lightweighting

• Foamed core materials replace solid plastics
• Bio-based or recycled PP/PE substrates
• Natural fiber reinforced composite sheets (hemp fiber, bamboo fiber)

11.2 Process Material Reduction

• Local reinforcement + topology optimized skeleton
• Hollow structures, honeycomb cores

11.3 Environmental Protection and VOC

• Low VOC adhesives
• Water-based coatings and hot press lamination replace solvent-based adhesives
• IMDS data reporting and regulatory compliance for interior trim components

XII. Sun Visor Project Development Process (OEM/Tier-1 Supplier Collaboration Example)

The following is a reusable project management Gantt-style phase division (adaptable to APQP framework).

Phase	Content	Deliverables	Risk Points
RFQ Technical Review	Functions, dimensions, regulations	Technical clarification form	Unidentified regulatory differences
Concept Design	Enclosure, pivot mechanism	CAD concept drawings	Structural interference
Mold Flow/DFM	Molding analysis, mold split	DFM report	Sink mark/warpage risk
Mold Design	Parting, cooling, inserts	Mold 2D/3D drawings	Core pulling complexity
T0 Trial	First article	Appearance dimensional data	Flash, short shot
T1/T2 Optimization	Process debugging	Improvement report	Warpage, flash
PPAP/Mass Production	Batch validation	PPAP document package	Insufficient process capability

XIII. Synergistic Platform Strategy for Sun Visor Molds and Passenger Vehicle Interior Trim

OEMs and large interior Tier-1 suppliers are promoting a **component platformization + appearance differentiation** development model:

• Same mold base, different fabric colors & LOGOs
• Same structure, different electrical configurations (with/without light, with sensor)
• Multi-region regulatory versions (left-hand/right-hand drive, North America/EU label differences)

This strategy reduces mold investment and supply chain complexity, improving global synchronous development efficiency.

XIV. Cost Control Key Points for Sun Visors & Interior Trim

Cost Module	Influencing Factors	Cost Reduction Suggestions
Mold	Cavity count, steel, texture	Common mold design, standardization of parts, modular inserts
Material	Resin, foam, skin	Alternative materials, recycling, thickness optimization
Process	Cycle time	Thermal management optimization, automated part removal
Assembly	Labor, rework rate	Poka-Yoke jigs, automated welding/wrapping

XV. FAQ: Common Questions about Sun Visors and Passenger Vehicle Interior Trim

Q1: What to do if sun visor uneven foaming causes bulging?
A: Check mold clamping pressure, injection volume, foaming agent temperature; if necessary, add vents or foam diversion channels.

Q2: Sun visor loose rotation and abnormal noise?
A: Pivot material pairing, tolerance stack-up, lubricant selection, improved wear-resistant bushings.

Q3: Wrapping edge lifting?
A: Reduce rebound material tension, improve adhesive curing temperature, add folding clamps.

Q4: Interior trim VOC exceeding standards?
A: Replace with low VOC auxiliary materials, extend baking volatilization cycle, switch to eco-friendly formulations from material suppliers.