Code of practice for testing of timbers for plywood manufacture

IS 12077: Scope - Key Specifications & Tables

Scope (Clause 4.2.1.1 and related):
IS 12077 covers the standards for plywood manufacture from timber veneers, including veneer characteristics, lathe settings, shrinkage, and glue adhesion.

Key Tables & Specifications

Important Notes on Timber Suitability:

• Avoid timber with internal stresses, shakes, mineral deposits (silica), or poor glue adhesion.
• Veneer must not dry patchily or distort.
• Lathe settings must minimize wooliness and veneer defects.

Basic Formula for Veneer Shrinkage (%):

[ \text{Shrinkage} = \frac{\text{Initial Dimension} - \text{Final Dimension}}{\text{Initial Dimension}} \times 100 ]

Units Used (SI Units):

flowchart LR
    A[TIMBER] --> B[VENEER PEELING]
    B --> C{VENEER QUALITY CHECK}
    C -->|Shrinkage| D[Measure Width & Thickness]
    C -->|Glue Adhesion| E[Test Failing Load]
    C -->|Surface Defects| F[Adjust Lathe Settings]
    D --> G[Accept/Reject]
    E --> G
    F --> G

Summary: IS 12077 defines veneer and plywood quality parameters, lathe settings, shrinkage measurement, and glue adhesion tests to ensure plywood performance and durability.

IS 12077 Key References: Formulas, Tables & Specifications

1. Veneer Lathe Settings (Clause 4.2.1.1)

2. Veneer Shrinkage (Clause 4.2.2.2)

• Shrinkage % = (\frac{Initial - Final}{Initial} \times 100)
• Table 4 records shrinkage in width and thickness based on moisture content changes.

3. Glue Adhesion Strength (Clause 4.2.4)

4. Timber Unsuitability Criteria

• Internal stresses causing bolts to break
• Narrow veneer width due to growth features
• Mineral deposits (silica)
• Poor lathe setting adjustments
• Patchy drying, splitting, brittleness
• Poor glue adhesion
• Failure in CWR adhesive tests
• Strong distortion in plywood form

5. SI Units & Definitions

IS 12077: Definitions Summary & Key Tables

1. Definitions Reference:

• Clause 2.1 states that definitions from:
  • IS 303:1975 (Rules for rounding off numerical values)
  • IS 707:1976 (Specification for plywood for general purposes) apply to IS 12077.

2. Key Tables from IS 12077:

Important Notes on Timber Suitability:

• Unsuitable timber shows internal stresses, shakes, mineral deposits, poor glue adhesion, or veneer defects (splitting, brittleness).
• Veneer shrinkage and glue adhesion tests are essential for quality control.

SI Units Used (from IS 12077):

Veneer Shrinkage Calculation (Example Formula):

[ \text{Shrinkage %} = \frac{\text{Initial dimension} - \text{Final dimension}}{\text{Initial dimension}} \times 100 ]

flowchart LR
    A[Timber] --> B{Check for Internal Stresses}
    B -- Yes --> C[Unsuitable Timber]
    B -- No --> D{Check Mineral Deposits}
    D -- Yes --> C
    D -- No --> E{Veneer Drying Quality}
    E -- Poor --> C
    E -- Good --> F{Glue Adhesion Test}
    F -- Fail --> C
    F

IS 12077: Requirements & Test Methods - Key Points

1. Veneer Shrinkage (Clause 4.2.2.2)

• Shrinkage measured by initial and final width & thickness.
• Percentage shrinkage formula:

[ \text{Shrinkage (%)} = \frac{\text{Initial dimension} - \text{Final dimension}}{\text{Initial dimension}} \times 100 ]

• Recorded as per Table 4:

2. Lathe Settings (Clause 4.2.1.1)

• Critical for veneer quality.
• Table 1 specifies:

3. Glue Adhesion Strength (Clause 4.2.4)

• Tests in dry, wet, and mycological states.
• Table 5 format:

4. Unsuitability Criteria for Timber

• Internal stresses, shakes, mineral deposits, poor glue adhesion, veneer defects, etc.

5. Units & Symbols (SI Units)

• Length: m, Mass: kg, Force: N (1 N = 1 kg·m/s²), Stress: Pa (1 Pa = 1 N/m²)

Summary Diagram: Veneer Shrinkage Test Flow

flowchart TD
    A[Start: Veneer Sample] --> B[Measure Initial Width & Thickness]
    B --> C[Dry Veneer to Final Moisture Content]
    C --> D[Measure Final Width & Thickness]
    D --> E[Calculate % Shrinkage]
    E --> F[Record in Table 4]

This concise summary helps ensure compliance with

IS 12077: Timber and Log Examination - Key Points

1. Sampling and Treatment (Clause 3.2)

• Use freshly-felled logs, preferably from separate trees.
• Keep bark on logs.
• Apply end coating and spray treatment immediately after felling to prevent fungal and insect attack.

2. Timber Identification (Clause 4.1.1)

• Record:
  • Source of timber species (trade & botanical names).
  • Density in green state and at 12% moisture content.

3. Lathe Settings for Veneer (Clause 4.2.1.1, Table 1)

(Exact values depend on veneer thickness and bolt diameter)

4. Green Veneer Yield (Clause 4.2.1.2, Table 2)

• Typical green veneer yield: 40% to 60% of timber volume.
• Losses to consider:
  • Rounding loss
  • Spur trim loss
  • Green clipping loss

Summary Diagram: Timber Examination Process

flowchart TD
    A[Freshly-felled Logs] --> B[Keep Bark On]
    B --> C[Apply End Coating & Spray]
    C --> D[Record Species & Density]
    D --> E[Lathe Settings for Veneer]
    E --> F[Measure Green Veneer Yield]
    F --> G[Calculate Losses]

Note: For detailed lathe settings and yield measurement, refer to IS 12077 Tables 1 & 2.

IS 12077 - Processing Tests Key Points

1. Processing Trials (Clause 4.2)

• Objective: Identify the most efficient timber processing method at each plywood manufacturing stage.

2. Lathe Settings (Table 1, Clause 4.2.1.1)

3. Drying Time (Table 3, Clause 4.2.2.1)

4. Veneer Shrinkage (Table 4, Clause 4.2.2.2)

Important Formulas:

• Shrinkage % = (\frac{\text{Initial dimension} - \text{Final dimension}}{\text{Initial dimension}} \times 100)

flowchart LR
    A[Raw Timber] --> B[Lathe Settings]
    B --> C[Cut Veneer]
    C --> D[Drying Process]
    D --> E[Measure Moisture Content]
    E --> F[Calculate Shrinkage]
    F --> G[Optimize Processing Parameters]

This summarizes key tables and concepts for processing tests per IS 12077. For exact values, always refer to the specific timber species and thickness in the code tables.

IS 12077 - Peeling: Key Formulas, Tables & Specifications

1. Lathe Settings Affecting Veneer Quality (Clause 4.2.1)

• Parameters:

  • Horizontal gap (mm)
  • Vertical gap (mm)
  • Knife angle (degrees) at max & min bolt diameter
  • Knife bevel angle
  • Knife height relative to spindle center

• Effect: These settings control uniformity in thickness, surface roughness, and lathe checks.

2. Table 1: Lathe Settings for Veneer Thickness (Clause 4.2.1.1)

3. Veneer Shrinkage (Clause 4.2.2.2 & Table 4)

• Formula:

[ \text{Shrinkage %} = \frac{\text{Initial dimension} - \text{Final dimension}}{\text{Initial dimension}} \times 100 ]

• Measured for: Width and Thickness during drying.

4. Gluing Properties (Clause 4.2.4)

• Tested on 3-ply plywood with 1.6 mm veneers per IS 303-1975.
• Results ensure conformity to bonding quality standards.

flowchart LR
    A[Timber Bolt] --> B[Lathe Settings]
    B --> C{Parameters}
    C --> D[Horizontal Gap]
    C --> E[Vertical Gap]
    C --> F[Knife Angle]
    C --> G[Knife Bevel Angle]
    C --> H[Knife Height]
    B --> I[Veneer Quality]
    I --> J[Thickness Uniformity]
    I --> K[Surface Roughness]
    I --> L[Lathe Checks]

Summary: Proper lathe settings per Table 1 and

IS 12077 – Drying of Veneers: Key Specifications and Tables

Drying Temperature & Moisture Content (Clause 4.2.2)

• Drying Temperature: Around 140°C.
• Final Moisture Content:
  • 6-8% for phenol-formaldehyde plywood.
  • ~10% for urea-formaldehyde plywood.
• Post-drying: Stack veneers for 8-10 days for uniform moisture.

Drying Time (Clause 2.4 & Table 3)

Veneer Shrinkage (Clause 4.2.2.2, Table 4)

Shrinkage % = ((Initial dimension - Final dimension) / Initial dimension) × 100

Drying Defects to Monitor

• Splits
• Waviness
• Metal staining
• Gum exudation

flowchart TD
    A[Start: Green Veneer] --> B[Set Dryer Temp ~140°C]
    B --> C[Drying Time per Thickness]
    C --> D[Check Moisture Content (6-10%)]
    D --> E{Drying Defects?}
    E -- Yes --> F[Record Defects]
    E -- No --> G[Stack for 8-10 Days]
    G --> H[Use for Plywood Manufacture]

Summary: Dry veneers at ~140°C until 6-10% moisture, adjust drying time by thickness (4-21 min

IS 12077 - Splicing Veneers: Key Points & Specifications

1. Splicing Speeds (Clause 4.2.3)

• Veneers of different thicknesses (e.g., 1.0, 1.6, 2.4 mm) can be spliced at varying speeds.
• Typical splicing speed: 5 to 26 m/min (linear speed of jointed veneer length).
• Conditions: Veneers 1.0 to 2.4 mm thick, spliced at 175℃ using UF resin adhesive.
• Speed depends on species and adhesive properties (UF resin, UM resin).

2. Lathe Settings for Veneer (Clause 4.2.1.1 - Table 1)

(Exact values depend on veneer thickness and machine settings)

3. Veneer Shrinkage (Clause 4.2.2.2 - Table 4)

• Shrinkage measured by initial & final moisture content.
• Percentage shrinkage in width and thickness recorded.

4. Gluing Properties (Clause 4.2.4)

• Tested on 3-ply plywood with 1.6 mm veneers.
• Conformity tested as per IS 303-1975.
• Results recorded in Table 5 (adhesive bond strength, durability).

Summary Formula for Splicing Speed (Approximate):

[ \text{Splicing Speed} = 5 \text{ to } 26 , \text{m/min} \quad \text{(for 1.0 to 2.4 mm thickness at 175℃ with UF resin)} ]

flowchart LR
    A[Veneer Thickness] --> B[Splicing Adhesive Type]
    B --> C[Splicing Speed (5-26 m/min)]
    C --> D[Splicing

IS 12077: Gluing Properties Key Points

• Test Panels: Use 3-ply plywood panels with 1.6 mm veneers for gluing property tests as per IS 303-1975.
• Splicing Speeds (Clause 4.2.3):
  • Veneer thickness: 1.0 to 2.4 mm
  • Splicing speed: 5 to 26 m/min
  • Temperature: 175°C
  • Adhesives: UF (Urea Formaldehyde), UM resins
• Drying Time (Clause 4.2.2.1, Table 3):
  • Depends on veneer thickness, moisture content, and dryer temperature
  • Typical drying times vary and must be recorded for each veneer thickness and moisture condition

Summary Table: Splicing Speed for Veneers

Important Notes:

• Gluing tests must conform to IS 303-1975.
• Veneer thickness and moisture content significantly affect drying and gluing.
• Knife angle and lathe settings (Clause 4.2.1.1) influence veneer quality but specifics depend on bolt diameter (see Table 1 in the code).

flowchart LR
    A[Veneer Preparation] --> B[Drying (Time & Temp)]
    B --> C[Gluing with Adhesive (UF/UM)]
    C --> D[Splicing at 175°C]
    D --> E[Testing (IS 303-1975)]

For detailed lathe settings and drying times, refer to Tables 1 and 3 in IS 12077.

IS 12077: Assessment and Reporting for Timber Species in Plywood Manufacture

Key Points from Clause 4.3 & Related Clauses:

• Assessment Report: Must include detailed technical data on veneer properties, aiding suitability evaluation for plywood manufacture.

• Veneer Shrinkage (Clause 4.2.2.2 & Table 4): [ \text{Shrinkage %} = \frac{\text{Initial dimension} - \text{Final dimension}}{\text{Initial dimension}} \times 100 ]

  • Measured for Width and Thickness at specified moisture contents.

• Lathe Settings (Clause 4.2.1.1 & Table 1):

  • Parameters: Veneer thickness (mm), horizontal & vertical gaps (mm), knife angle (degrees).
  • Adjustments affect veneer quality and peeling efficiency.

• Glue Adhesion Strength (Clause 4.2.4 & Table 5):

  • Tested in Dry, Wet, and Mycological states.
  • Report failing load (kg) and percentage glue failure.
  • Poor adhesion or wood failure indicates unsuitability.

Unsuitability Criteria (Summary):

• Internal stresses causing peeling issues
• Large unusable core in timber
• Mineral deposits causing knife blunting
• Persistent wooliness or surface defects despite lathe adjustments
• Veneer drying issues (splits, brittleness)
• Poor glue adhesion or failure under tests
• Strong distortion in plywood form

Example: Veneer Shrinkage Calculation

Reporting Checklist:

• Timber source and species details
• Lathe settings used
• Veneer shrinkage data
• Glue adhesion test results
• Observations on veneer quality and defects
• Conclusion on suitability with justification

flowchart TD
    A[Timber Sample] --> B{Tests Conducted}
    B --> C[Veneer Shrink

IS 12077: Marking and Documentation - Key Points & Tables

1. Marking Requirements

• Each timber sample or plywood batch must be clearly marked with:
  • Source and details of timber (see Table 4.1 in Clause 4.2.1.1)
  • Identification of grade and type
  • Date of manufacture and batch number
• Marking ensures traceability and quality control during testing and production.

2. Documentation Essentials

• Complete records of:
  • Timber source and species
  • Lathe settings used (refer Table 1 for veneer thickness and lathe parameters)
  • Glue adhesion test results (see Table 5 for glue adhesion strength in dry, wet, and mycological states)
  • Observations on timber suitability (internal stresses, mineral deposits, veneer quality, glue failures, etc.)

3. Key Tables

4. Timber Unsuitability Indicators

• Internal stresses causing bolt breakage
• Large core of unsuitable timber for peeling
• Mineral deposits blunting knives
• Persistent wooliness or veneer defects despite lathe adjustments
• Patchy drying, splitting, brittleness
• Poor glue adhesion (below required failing load)
• Strong distortion in plywood

Summary Diagram: Marking & Documentation Flow

flowchart TD
    A[Timber Source & Details] --> B[Marking on Timber]
    B --> C[Lathe Settings Recorded]
    C --> D