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MH-CHP
MINGHUNG
Synchronized tension control in the twin steel belt continuous press is like precisely balancing the force of two "steel arms," ensuring the board receives a perfectly balanced "embrace" on both surfaces during high-speed pressing. This forms the foundation for eliminating the mechanical stresses that cause warpage. Combined with optimization of other process elements, it achieves the goal of producing flat and stable warp-free OSB.
I. Basic Principle of the Twin Steel Belt OSB Continuous Press
1. Core Structure: Primarily consists of two parallel, circulating high-strength steel belts (upper and lower belts).
2. Workflow:
(1) Directed paving and pre-pressing
Directed paving:
OSB wood chips are divided into surface layer (longitudinally arranged) and core layer (transversely arranged), and are oriented by a special paving machine (such as a mechanical directional head or airflow paving system). The length of the surface layer wood chips is usually 50-100mm, and the core layer wood chips are shorter (20-50mm).
MINGHUNG OSB Forming Machine
OSB forming machine
Pre-pressing and shaping:
The paved slab enters the pre-pressing machine (pressure 0.5-1.5MPa), and the air is removed and the direction of the wood chips is initially fixed by mechanical roller pressing or high-frequency pre-pressing to prevent the structure from loosening during the subsequent hot pressing process.
(2) Continuous hot pressing stage
High pressure zone (initial curing):
Temperature 210–230℃, pressure 3.0–5.0MPa, quickly close the slab and activate the adhesive (usually phenolic resin or MDI adhesive), and the surface wood shavings directional structure is initially cured.
Medium pressure zone (plasticization balance):
Temperature 200–220℃, pressure 2.0–3.5MPa, maintain full penetration of the core layer adhesive, and balance the curing rate of the inner and outer layers.
Low pressure zone (setting and stress release):
Temperature 180–200℃, pressure 1.0–2.0MPa, control the final thickness and release internal stress to avoid board warping.
OSB continuous press
MINGHUNG OSB press production line
(3) Cooling and post-processing
Cooling section:
The pressed sheet is cooled to below 50°C by a circulating water cooling system to stabilize the sheet size.
Cutting :
The sheet is cut into standard sheets using a high-speed sawing system.
Dryer rack
trimming sawing and cutting machine
3. Advantages: Continuous production, high efficiency, large output, high automation, more uniform panel density distribution.
II. Synchronized Tension Control
This is the core technology for stable press operation and ensuring panel quality, especially flatness (warp-free).
What is Tension Control?
The process of applying and precisely controlling the internal tension force within the circulating upper and lower steel belts.
Belts require sufficient tension to:
（1）Resist enormous pressing pressure without excessive elastic deformation.
（2）Ensure adequate friction between the belts and drive rollers, guide rollers, and support systems (e.g., chain mats or roller systems), preventing slippage.
(3）Maintain stable belt tracking, avoiding deviation.
（4）Ensure belt surface flatness for uniform pressure transfer to the mat.
Why is "Synchronized" Tension Control Needed?
（1）Upper/Lower Belt Tension Balance: This is critical. Significant tension imbalance between the belts causes:
（2） Warpage Risk: The belt with higher tension tends to "pull" the board towards its side. For example, if the lower belt tension is much higher than the upper belt, the board tends to bend downward during pressing, potentially resulting in "downward warp" (concave up) after cooling. Conversely, "upward warp" (convex up) occurs. This imbalance is a primary mechanical cause of warpage.
（3） Thickness Variation: Tension imbalance leads to asymmetric effective pressure application on the mat, causing thickness deviations across the panel width.
（4）Belt Tracking Issues: Tension differences can cause belts to deviate during operation, potentially colliding with the frame causing severe damage.
（5）Dynamic Stability: During press start-up, acceleration, deceleration, shutdown, or when responding to mat thickness variations or friction changes, the tensions of both belts must be adjusted rapidly and coordinately to maintain dynamic balance.
（6） Compensating for Thermal Expansion: Belts expand under operating heat. The control system must synchronously adjust tension to compensate for this length change, preventing loss of tension control or belt slack.
How is Synchronized Tension Control Achieved?
3.1 Tension Measurement: High-precision tension sensors (e.g., hydraulic cylinder pressure sensors, load cells) installed on the belts (typically before the drive roller or after the tensioning roller) monitor the actual tension of each belt in real-time.
3.2 Tension Setpoint: Target tension values for the upper and lower belts are set based on process requirements (panel thickness, target density, line pressure). These setpoints are typically identical or maintained within a very small allowable deviation range.
3.3 Closed-Loop Control System:
（1）Core: Uses a high-performance PLC or dedicated controller.
（2）Input: Real-time signals from the upper and lower belt tension sensors.
（3） Control Algorithm: The controller compares actual tension to setpoint tension. For each belt, it independently calculates the required tension adjustment (using PID or more advanced algorithms). Crucially, the controller continuously compares the actual tension values of both belts, calculating the difference between them.
（4）Synchronization Strategy:Master-Slave Control;Direct Difference Control;Actuators.
（5）Drive Synchronization: The drive systems for the upper and lower belts (typically the main drive rollers) must also maintain speed synchronization. Speed differences cause additional sliding friction or pulling between the belts, disrupting tension balance. This is achieved via VFD/servo motors and precise speed/position closed-loop control.
Warp-Free
"Warp-free" is a critical quality parameter for OSB, meaning panels should maintain high flatness after cooling. Synchronized tension control in the twin-belt press is a core enabler for warp-free production, but not the only factor.
1.Core Role of Synchronized Tension Control:
As stated, it eliminates the primary mechanical force imbalance causing warpage. Uniform, balanced tension on both belts ensures pressure is applied vertically and evenly on both mat surfaces, preventing bending moments that cause permanent deformation during pressing.
2. Other Key Contributing Factors
(1) Uniform Temperature Field: Temperatures of the upper and lower heating platens (or belt heating systems) must be precisely controlled and uniformly distributed. Significant temperature differences between surfaces cause differential curing shrinkage between top and bottom layers, leading to warpage. Synchronized tension helps maintain good belt-to-platen contact, promoting uniform heat transfer.
(2) Precise Pressure Distribution: Line pressure (pressure per unit length) across the press width must be uniform and controllable. This depends on press frame stiffness, hydraulic cylinder arrangement and synchronization control (pressure or position), and support system design (e.g., flexible chain mats or zone-controlled rollers). Uneven pressure causes density variations and warpage.
(3) Symmetric Mat Structure: OSB is typically a three-layer structure (oriented surface layers, random/cross-oriented core). Strand geometry, moisture content, resin application, etc., should be as symmetric as possible between top and bottom faces. Structural asymmetry is an inherent cause of warpage due to internal stresses.
(4) Balanced Moisture Content: Moisture content should be uniform and matched between surface and core layers during mat forming. Uneven drying or significant moisture gradients after resin application cause stress deformation due to vigorous moisture migration/evaporation during pressing and uneven shrinkage during cooling.
(5) Stable Curing Process: Pressure profile (often staged), temperature profile, and press time (determined by speed) must be optimized to ensure uniform and complete adhesive curing throughout the panel thickness. Incomplete curing generates internal stresses.
(6) Uniform Cooling: Pressed panels require uniform, controlled cooling. Rapid or uneven cooling exacerbates the generation and release of internal stresses, causing warpage. Cooling and stacking procedures in post-press handling are crucial.
(7) High-Quality Raw Materials: Strand geometry, moisture stability, adhesive performance, etc., all influence final panel dimensional stability.
The Twin Steel Belt OSB Continuous Press is the core equipment for modern, efficient OSB manufacturing via continuous hot pressing.
Synchronized Tension Control is a core key technology of this press, with the primary goal of precisely maintaining dynamic tension balance between the upper and lower steel belts.
Tension imbalance is the main mechanical cause of panel warpage. Through high-precision sensors, fast-response servo-hydraulic systems, and advanced control algorithms (master-slave or difference control), real-time synchronized adjustment of belt tensions effectively eliminates this imbalance.
"Warp-Free" is a requirement for high-quality OSB and reflects the press system's overall performance. Synchronized tension control is the most critical and direct safeguard mechanism, but it must work synergistically with other factors like uniform temperature, precise pressure distribution, symmetric mat structure, balanced moisture content, stable curing, and uniform cooling to ultimately produce flat, stable, high-quality OSB panels.
Shandong MingHung OSB&MDF Machinery Equipment is a China professional factory who specilize in manufacturering and offering Wood based panel machine, including OSB making machine, MDF making machine, and Chipboard /PB making machine.
The machines we can offer includes: Wood chipper, Ring flaker, Strander, Wet silo, Drum dryer, Dry silo, Glue dosing and applying system /Glue blender, Mat forming, Continuous Multi-rolls pre-press, Multi opening hot press and Continuous press, Auto edge cutting machine line, Sanding machine line, kinds of related belt conveyor and so on.
Packaging & Shipping
We maintain a long-term cooperation with a well-known freight forwarding company, and adhere to the customer-first philosophy. We strictly implement the quality inspection process before shipment to ensure that each batch of products meets international quality standards, We deeply understand that high-quality service is the cornerstone of winning customer trust, and we always create value for customers with professional and efficient supply chain management. We sincerely invite you to join hands and work together to createa win-win future.
If interested please contact us for a quote.
Whatsapp: +8618769900191 +8615589105786 +8618954906501
Email: osbmdfmachinery@gmail.com
Synchronized tension control in the twin steel belt continuous press is like precisely balancing the force of two "steel arms," ensuring the board receives a perfectly balanced "embrace" on both surfaces during high-speed pressing. This forms the foundation for eliminating the mechanical stresses that cause warpage. Combined with optimization of other process elements, it achieves the goal of producing flat and stable warp-free OSB.
I. Basic Principle of the Twin Steel Belt OSB Continuous Press
1. Core Structure: Primarily consists of two parallel, circulating high-strength steel belts (upper and lower belts).
2. Workflow:
(1) Directed paving and pre-pressing
Directed paving:
OSB wood chips are divided into surface layer (longitudinally arranged) and core layer (transversely arranged), and are oriented by a special paving machine (such as a mechanical directional head or airflow paving system). The length of the surface layer wood chips is usually 50-100mm, and the core layer wood chips are shorter (20-50mm).
MINGHUNG OSB Forming Machine
OSB forming machine
Pre-pressing and shaping:
The paved slab enters the pre-pressing machine (pressure 0.5-1.5MPa), and the air is removed and the direction of the wood chips is initially fixed by mechanical roller pressing or high-frequency pre-pressing to prevent the structure from loosening during the subsequent hot pressing process.
(2) Continuous hot pressing stage
High pressure zone (initial curing):
Temperature 210–230℃, pressure 3.0–5.0MPa, quickly close the slab and activate the adhesive (usually phenolic resin or MDI adhesive), and the surface wood shavings directional structure is initially cured.
Medium pressure zone (plasticization balance):
Temperature 200–220℃, pressure 2.0–3.5MPa, maintain full penetration of the core layer adhesive, and balance the curing rate of the inner and outer layers.
Low pressure zone (setting and stress release):
Temperature 180–200℃, pressure 1.0–2.0MPa, control the final thickness and release internal stress to avoid board warping.
OSB continuous press
MINGHUNG OSB press production line
(3) Cooling and post-processing
Cooling section:
The pressed sheet is cooled to below 50°C by a circulating water cooling system to stabilize the sheet size.
Cutting :
The sheet is cut into standard sheets using a high-speed sawing system.
Dryer rack
trimming sawing and cutting machine
3. Advantages: Continuous production, high efficiency, large output, high automation, more uniform panel density distribution.
II. Synchronized Tension Control
This is the core technology for stable press operation and ensuring panel quality, especially flatness (warp-free).
What is Tension Control?
The process of applying and precisely controlling the internal tension force within the circulating upper and lower steel belts.
Belts require sufficient tension to:
（1）Resist enormous pressing pressure without excessive elastic deformation.
（2）Ensure adequate friction between the belts and drive rollers, guide rollers, and support systems (e.g., chain mats or roller systems), preventing slippage.
(3）Maintain stable belt tracking, avoiding deviation.
（4）Ensure belt surface flatness for uniform pressure transfer to the mat.
Why is "Synchronized" Tension Control Needed?
（1）Upper/Lower Belt Tension Balance: This is critical. Significant tension imbalance between the belts causes:
（2） Warpage Risk: The belt with higher tension tends to "pull" the board towards its side. For example, if the lower belt tension is much higher than the upper belt, the board tends to bend downward during pressing, potentially resulting in "downward warp" (concave up) after cooling. Conversely, "upward warp" (convex up) occurs. This imbalance is a primary mechanical cause of warpage.
（3） Thickness Variation: Tension imbalance leads to asymmetric effective pressure application on the mat, causing thickness deviations across the panel width.
（4）Belt Tracking Issues: Tension differences can cause belts to deviate during operation, potentially colliding with the frame causing severe damage.
（5）Dynamic Stability: During press start-up, acceleration, deceleration, shutdown, or when responding to mat thickness variations or friction changes, the tensions of both belts must be adjusted rapidly and coordinately to maintain dynamic balance.
（6） Compensating for Thermal Expansion: Belts expand under operating heat. The control system must synchronously adjust tension to compensate for this length change, preventing loss of tension control or belt slack.
How is Synchronized Tension Control Achieved?
3.1 Tension Measurement: High-precision tension sensors (e.g., hydraulic cylinder pressure sensors, load cells) installed on the belts (typically before the drive roller or after the tensioning roller) monitor the actual tension of each belt in real-time.
3.2 Tension Setpoint: Target tension values for the upper and lower belts are set based on process requirements (panel thickness, target density, line pressure). These setpoints are typically identical or maintained within a very small allowable deviation range.
3.3 Closed-Loop Control System:
（1）Core: Uses a high-performance PLC or dedicated controller.
（2）Input: Real-time signals from the upper and lower belt tension sensors.
（3） Control Algorithm: The controller compares actual tension to setpoint tension. For each belt, it independently calculates the required tension adjustment (using PID or more advanced algorithms). Crucially, the controller continuously compares the actual tension values of both belts, calculating the difference between them.
（4）Synchronization Strategy:Master-Slave Control;Direct Difference Control;Actuators.
（5）Drive Synchronization: The drive systems for the upper and lower belts (typically the main drive rollers) must also maintain speed synchronization. Speed differences cause additional sliding friction or pulling between the belts, disrupting tension balance. This is achieved via VFD/servo motors and precise speed/position closed-loop control.
Warp-Free
"Warp-free" is a critical quality parameter for OSB, meaning panels should maintain high flatness after cooling. Synchronized tension control in the twin-belt press is a core enabler for warp-free production, but not the only factor.
1.Core Role of Synchronized Tension Control:
As stated, it eliminates the primary mechanical force imbalance causing warpage. Uniform, balanced tension on both belts ensures pressure is applied vertically and evenly on both mat surfaces, preventing bending moments that cause permanent deformation during pressing.
2. Other Key Contributing Factors
(1) Uniform Temperature Field: Temperatures of the upper and lower heating platens (or belt heating systems) must be precisely controlled and uniformly distributed. Significant temperature differences between surfaces cause differential curing shrinkage between top and bottom layers, leading to warpage. Synchronized tension helps maintain good belt-to-platen contact, promoting uniform heat transfer.
(2) Precise Pressure Distribution: Line pressure (pressure per unit length) across the press width must be uniform and controllable. This depends on press frame stiffness, hydraulic cylinder arrangement and synchronization control (pressure or position), and support system design (e.g., flexible chain mats or zone-controlled rollers). Uneven pressure causes density variations and warpage.
(3) Symmetric Mat Structure: OSB is typically a three-layer structure (oriented surface layers, random/cross-oriented core). Strand geometry, moisture content, resin application, etc., should be as symmetric as possible between top and bottom faces. Structural asymmetry is an inherent cause of warpage due to internal stresses.
(4) Balanced Moisture Content: Moisture content should be uniform and matched between surface and core layers during mat forming. Uneven drying or significant moisture gradients after resin application cause stress deformation due to vigorous moisture migration/evaporation during pressing and uneven shrinkage during cooling.
(5) Stable Curing Process: Pressure profile (often staged), temperature profile, and press time (determined by speed) must be optimized to ensure uniform and complete adhesive curing throughout the panel thickness. Incomplete curing generates internal stresses.
(6) Uniform Cooling: Pressed panels require uniform, controlled cooling. Rapid or uneven cooling exacerbates the generation and release of internal stresses, causing warpage. Cooling and stacking procedures in post-press handling are crucial.
(7) High-Quality Raw Materials: Strand geometry, moisture stability, adhesive performance, etc., all influence final panel dimensional stability.
The Twin Steel Belt OSB Continuous Press is the core equipment for modern, efficient OSB manufacturing via continuous hot pressing.
Synchronized Tension Control is a core key technology of this press, with the primary goal of precisely maintaining dynamic tension balance between the upper and lower steel belts.
Tension imbalance is the main mechanical cause of panel warpage. Through high-precision sensors, fast-response servo-hydraulic systems, and advanced control algorithms (master-slave or difference control), real-time synchronized adjustment of belt tensions effectively eliminates this imbalance.
"Warp-Free" is a requirement for high-quality OSB and reflects the press system's overall performance. Synchronized tension control is the most critical and direct safeguard mechanism, but it must work synergistically with other factors like uniform temperature, precise pressure distribution, symmetric mat structure, balanced moisture content, stable curing, and uniform cooling to ultimately produce flat, stable, high-quality OSB panels.
Shandong MingHung OSB&MDF Machinery Equipment is a China professional factory who specilize in manufacturering and offering Wood based panel machine, including OSB making machine, MDF making machine, and Chipboard /PB making machine.
The machines we can offer includes: Wood chipper, Ring flaker, Strander, Wet silo, Drum dryer, Dry silo, Glue dosing and applying system /Glue blender, Mat forming, Continuous Multi-rolls pre-press, Multi opening hot press and Continuous press, Auto edge cutting machine line, Sanding machine line, kinds of related belt conveyor and so on.
Packaging & Shipping
We maintain a long-term cooperation with a well-known freight forwarding company, and adhere to the customer-first philosophy. We strictly implement the quality inspection process before shipment to ensure that each batch of products meets international quality standards, We deeply understand that high-quality service is the cornerstone of winning customer trust, and we always create value for customers with professional and efficient supply chain management. We sincerely invite you to join hands and work together to createa win-win future.
If interested please contact us for a quote.
Whatsapp: +8618769900191 +8615589105786 +8618954906501
Email: osbmdfmachinery@gmail.com
pre press machine 
