How to Produce the High-Quality Veneer?

A tree grows in the forest, its branches swaying in the breeze and leaves absorbing sunlight. Alone, it is just a plant. Yet when it creates economic value, it can be converted into money—because economic value is essentially its usefulness to others.

Once felled, sawn, and peeled into veneer, then made into plywood for furniture, flooring, or construction, the tree transforms from a natural resource into an economic product.

Economic value depends mainly on scarcity and quality. Scarcity comes from the wood’s species and characteristics, and under specific conditions, the veneer peeling process can significantly enhance its value.

What Makes Good Quality Veneer

In the market, the price of veneer mainly depends on thickness and surface quality. The more uniform the thickness and the better the surface, the higher the economic value. To reach normal economic value, veneer should meet the following basic standards:

1. Uniform Thickness

• Consistent thickness ensures strong bonding between layers, stability, and a smooth panel surface.
• Smaller thickness tolerance leads to higher customer satisfaction and repeat orders, ensuring stable factory revenue.
• Recommended standards:
  • Softwood: ±0.1 mm
  • Hardwood: ±0.05-0.1mm (depending on the precision of the rotary cutting machine)

2. Smooth Surface

• Rough veneer surfaces make it hard for glue to penetrate evenly, which can lead to poor bonding, delamination, or warping in plywood.
• so the rough veneer can cause:
  1. Higher defect rates in plywood
  2. Using extra glue to compensate and increased production costs
• Therefore, surface smoothness is the second most important quality factor after thickness.

3. Minimal Defects

• Veneer should have as few knots, cracks, or pinholes as possible to maintain plywood strength.
• Since wood is naturally grown, some defects are unavoidable. These can be graded as B or C quality to prevent affecting the final panel strength.

4. Flatness and No Warping

• Veneer must be flat, without bends, twists, or curls.
• Warped veneer can cause plywood to blister, delaminate, or deform, reducing stability and strength.
• Flatness is mainly affected by two stages: Peeling and drying.

Common Causes of Warping During Peeling

1. Uneven moisture content in the wood
2. Bent or twisted logs, or off-center heartwood
3. Excessive peeling pressure
4. Freshly peeled veneer not laid flat or not properly conditioned

Common Causes of Warping During Drying

1. Too high temperature or too fast heating, causing surface water to evaporate quickly while internal moisture remains
2. Low or uneven air humidity, making some areas dry faster than others
3. Uneven veneer thickness or moisture content, or insufficient drying time
4. Uneven airflow in the dryer, causing some veneer to dry faster than others

How to Produce High-Quality Veneer

For the veneer factory, producing good quality veneer is the key to profitability—and sometimes even survival. The quality of veneer mainly depends on three factors: logs,peeling machines, and peeling knives.

1. Log Selection

The quality of veneer starts with the logs.

• If the logs are bent, full of knots, wormholes, or decay, the veneer will be low grade and low priced.
• Good logs should have a proper diameter, uniform texture, no knots, no wormholes, and no decay. This ensures veneer quality right from the source.

2. Veneer Peeling Lathe (Rotary Peeling Machine)

There are two main types of veneer lathes:

• Spindle (with chuck) peeling lathe: Very accurate, thickness tolerance ±0.05 mm, but slow, expensive, and low capacity. Mostly used for face veneer.
• Spindleless lathe: Thickness tolerance about ±0.1 mm, which is acceptable for core veneer. It is faster, higher output, and more cost-effective, so it is widely used for core veneer.

The key factors that decide the accuracy and stability of thw spindleless peeling lathe are:

(1) Guide Rail Precision

• The guide rails must stay very straight and parallel. If not, the knife carriage will shift, and the veneer thickness will be uneven.
• High-quality machines use hardened steel rails with fine grinding or coating to improve wear resistance and maintain accuracy.
• Normal lathes: 0.05–0.1 mm/m; high-precision lathes: 0.02–0.03 mm/m.

(2) Feeding Screw Accuracy

• Each turn of the screw should move the knife carriage a fixed distance (lead). If the lead is inaccurate, veneer thickness will vary.
• High-quality feeding screws can reach an accuracy of ±0.01 mm / 300 mm.
• Wear or backlash between the screw and nut will cause vibration and thickness variation over time.

(3) Main Motor Speed Stability

• Veneer thickness = feed speed ÷ spindle speed.
• If the speed is unstable, even with constant feed, veneer thickness will go up and down.
• Unstable speed also causes:
  • Changing peeling force → wavy veneer or even breakage
  • Micro vibration → uneven or rippled surface
• Modern CNC lathes use servo motors with frequency converters, giving much better stability than traditional systems.

3. Knife Material and Sharpness

The knife directly affects veneer thickness and surface quality:

• Knife material:
  • Hardwoods → need knives with toughness
  • Softwoods → need knives with high hardness and wear resistance
• Sharpness:
  • Sharp knife → less cutting resistance, stable thickness, smooth surface
  • Dull knife → uneven thickness, rough or torn veneer
• Knife angle:
  • Common range: 18°–22°
  • Larger angle → more durable, but rougher veneer
  • Smaller angle → sharper cut, but shorter life, easier to chip

To guarantee veneer that is uniform in thickness, smooth in surface, and with fewer defects, factories must carefully choose knife material, keep the right knife angle, and follow a strict grinding and replacement cycle.

In summary:
High-quality veneer comes from good logs, precise veneer peeling machines, and sharp peeling knives. Only by controlling all three can a factory consistently produce veneer that meets high market standards and creates strong economic value.