How Do Mixing, Stirring, and Aging Improve Fired Brick Quality and Molding Performance?

The Future of Brick Manufacturing: Automation Drives the Development of Modern Brick Factories

The brick manufacturing industry has been developing for thousands of years, but modern construction requirements have created new challenges for brick producers. Customers today demand bricks with better appearance, higher strength, accurate dimensions, and consistent quality. At the same time, brick manufacturers are looking for ways to reduce labor dependence, improve production efficiency, and achieve more stable operation.

With the development of intelligent manufacturing technology, traditional manual brick handling processes are gradually being replaced by automatic brick production solutions. Among these technologies, the automatic loading and unloading system has become an important part of advanced brick production lines, especially for manufacturers producing high-grade face bricks, hollow bricks, and premium wall materials.

Challenges Facing Traditional Brick Production

In traditional brick factories, many processes rely heavily on manual operation, especially during:

•   -Green brick handling
•   -Brick stacking
•   -Pallet transportation
•   -Dry brick unloading
•   -Brick setting before firing

Manual operation can create several production challenges:

1. Inconsistent Brick Arrangement

High-quality bricks require accurate positioning during drying and firing. Small differences in spacing or placement may influence the final product appearance.

2. Higher Labor Requirements

Large-scale brick plants need continuous operation. Manual loading and unloading require more workers and increase operational pressure.

3. Lower Production Stability

Human operation speed and accuracy may vary, which can affect the consistency of the production process.

Therefore, modern brick factories are increasingly adopting industrial automation systems to improve production reliability.

What Is an Automatic Loading and Unloading Twice Stacking System?

The Automatic Loading and Unloading Twice Stacking System is an advanced automation solution designed for modern clay brick manufacturing plants and high-grade wall material production lines.

This system completes multiple processes automatically, including:

•   -Green brick cutting and grouping
•   -Pallet loading
•   -Pallet transportation
•   -Temporary storage
•   -Dry brick unloading
•   -Brick grouping and spacing
•   -Automatic setting preparation

The complete system is controlled by an intelligent PLC control system, which coordinates different production units and allows automatic parameter adjustment through industrial computer technology.

How Does Twice Stacking Technology Improve Brick Production?

The biggest advantage of a twice stacking system is that bricks can be separately arranged during drying and later transferred for firing preparation.

This production method provides several benefits:

1. Better Surface Quality

For premium face bricks, surface appearance is extremely important. Separate pallet drying helps reduce contact marks and improves the finished brick surface quality.

2. Higher Production Accuracy

The automatic positioning system ensures accurate brick arrangement, reducing mistakes caused by manual handling.

3. Improved Factory Efficiency

By connecting multiple processes into one automated system, factories can achieve smoother production flow and reduce unnecessary manual operations.

Key Advantages of Automatic Brick Handling Equipment

-High Automation Level

The system integrates transportation, loading, unloading, grouping, and setting processes into one complete solution.

-Stable Production Performance

Servo positioning technology and intelligent control help maintain accurate operation during continuous production.

-Flexible Production Options

The system can be customized according to:

•   1. Brick type
•   2. Production capacity
•   3. Drying method
•   4. Factory layout

Suitable for High-Grade Brick Production

It is widely suitable for:

•   1. Face bricks
•   2. Hollow bricks
•   3. Clay blocks
•   4. Premium wall materials

Running a profitable fired brick manufacturing factory requires systematic thinking of the whole brick production line. Every procedure, starting from raw material mining to finished brick stacking, connects tightly. Just like the bucket analogy: the total holding volume is controlled by its shortest plank. In brick manufacturing, your factory’s profitability is limited by the weakest process segment.

Most brick investors focus merely on headline daily or annual brick output during planning. For instance, they target 500,000 or 800,000 bricks per day. Yet they ignore total internal material turnover. For a nominal daily output of 500,000 bricks, the whole factory may circulate up to 5 million bricks of raw materials and green bodies in the whole system. Let’s break down typical weak points in brick manufacturing.

Raw Material Storage & Raw Material Preparation

On-site mining of coal gangue or shale saves the cost of large raw material yards. If raw materials need transportation from remote mines, multiple stockyards are necessary to guarantee stable feeding for your brick making machine.

Raw material crushing workshop only operates 8–10 hours daily, so its processing capacity must exceed your designed daily brick output. Engineers need to decide crushing stages, mixer type, sieve specification, conveyor speed and magnetic separator layout. Maintenance accessibility is easily overlooked.

Many brick plants use manual handling for heavy screen plates because they have no overhead crane. Replacing crusher hammerheads takes a long time, and mechanic turnover is high. This slows down your actual production rate heavily.

Aging Bin & Raw Material Homogenization

Aging treatment stabilizes raw material plasticity. A proper aging chamber holds raw materials enough for 72 hours of production. When crushing equipment stops for repair, aged raw materials can keep production running.

Sandy and hard rock raw materials require anti-seepage design inside aging bins to avoid uneven moisture distribution. Adding soil shredder after aging mixing improves raw material consistency for extrusion.

Green Body Extrusion, Cutting and Setting

Extrusion, mixing, cutting and setting are core sections for brick green body. Equipment performance varies under different raw materials and local climates.

One real case: brick factories in Lanzhou adopted process parameters from central China. Green bodies looked good after extrusion, but drying speed was low, cracking rate high and final output far below expectation. Raw material difference created a hard-to-solve bottleneck.

Drying Chamber Design & Moisture Exhaust

Various tunnel kiln for brick firing combinations exist with different drying and firing zone layouts. Raw material plasticity, shrinkage sensitivity and local climate determine which layout fits you best.

For drying-sensitive raw materials, direct drying direct firing kiln is not recommended. In dry regions like Kuitun Xinjiang, low air humidity causes green body cracking immediately after cutting. Raising local humidity in green body storage area and increasing kiln car quantity can solve the cracking problem. Drying heat sources include flue gas drying, waste heat drying and combined drying. High sulfur raw materials cannot use flue gas drying, as sulfur pollutants will contaminate finished bricks and raise environmental expense. Combined flue gas and waste heat drying saves fuel and power for low-sulfur raw materials.

For moisture exhaust design: pure centralized exhaust has high power consumption and poor effect. The optimized scheme combines decentralized and centralized exhaust, positive pressure as primary and negative pressure auxiliary. This reduces green body collapse risk and energy consumption. Many rotary tunnel kilns have poorly designed drying sections with extremely high fan power consumption.

Kiln Type Selection & Firing System

Multiple kiln types are available for fired brick production line: masonry tunnel kiln, combined tunnel kiln, rotary tunnel kiln and different flue structure tunnel kilns.

Rotary kiln has about 300 bricks per cubic meter loading capacity, while tunnel kiln can load 400–500 bricks per cubic meter. If we can overcome cross-section temperature difference and kiln car burning defects of conventional tunnel kilns, tunnel kilns will deliver superior output and energy efficiency. The classic structural bottleneck of tunnel kiln is that bricks move while kiln shell remains fixed. New technical innovation is needed to tackle this issue.

Kiln Operator Training & Brick Setting Technology

Many firing workers misunderstand kiln operation as only observing flame color. A professional kiln operator must understand air flow, kiln structure, waste heat system, temperature monitoring and brick setting strategy. Poor operator skill is repairable by professional training.

A well-known rule in brick industry: brick setting accounts for 70% of firing results, while firing operation only accounts for 30%. Good kiln operators analyze raw material test reports and heat distribution to optimize brick setting scheme. Factory operators are prohibited to add coal at kiln car joints and open fire holes at high-temperature zones, which will burn kiln cars. Kiln car burning is also affected by insulation and air balance in the trench, a common pain point for brick manufacturers.

Unloading Track, Finished Yard and Factory Layout

A brick factory with 3.7m wide kiln designed for four drying three firing only equipped one unloading track, without space for expansion. It could never reach designed capacity, limited by insufficient unloading tracks. The quantity of unloading positions, packing stations and kiln car parking positions must be calculated in the initial design. This layout defect is hard to fix after factory construction.

Insufficient finished brick yard is another widespread bottleneck. Factories with limited storage space need to reduce production in rainy season. Hollow brick production heavily depends on finished yard space, because construction projects order hollow bricks for later installation.

Raw Material Test & Environmental Protection

Pre-construction raw material testing is essential. Raw materials with 4–5% sulfur bring huge environmental pressure without alternative raw materials. High calcium content causes brick deliquescence; high potassium and magnesium lead to efflorescence (white bloom) on brick surface.

Many factories rebuilt desulfurization towers twice. Desulfurization suppliers often lack kiln fluid mechanics knowledge. Improper tower design leads to poor moisture exhaust and output drop. Horizontal plus vertical combined desulfurization and dust removal performs better than single vertical tower. The air inlet slightly above kiln surface saves power.

Natural gas firing is the cleanest solution for brick kilns. Factory owners need to assess whether existing kilns can be retrofitted for natural gas combustion during factory planning.

Conclusion

When designing a fired brick production line, you need to calculate capacity for every link: raw material stock ≥ multiple days output; raw material processing ≥ 1.5 × daily output; aging chamber for 2–3 × daily output; extrusion workshop completes one daily output in 8–12 hours; green body storage for 1.5–2 × daily output; spare empty kiln cars ≥0.5 × daily output; drying chamber, firing section each match daily output; finished track ≥0.75 × daily output; unloading station ≥0.3 × daily output; finished yard for multiple days output.

Your brick plant’s real capacity and profit are determined by the weakest link in the whole systematic production chain.

Automation is becoming increasingly important in modern brick manufacturing plants. As brick factories increase production capacity and introduce tunnel dryers, tunnel kilns, and automated handling systems, the process of moving and stacking green bricks has become an important part of overall production efficiency.

One of the key technologies used in this stage is the brick stacking robot.

A brick stacking robot is designed to automatically pick up freshly formed green bricks, transport them to a predetermined position, and arrange them according to a programmed stacking pattern. Instead of relying entirely on manual handling, the robotic system can coordinate with brick cutting, grouping, drying, and kiln-loading equipment.

Automatic green-brick handling systems are commonly positioned between forming/cutting equipment and drying or firing equipment. Their main functions include grouping, transferring, positioning, and stacking bricks according to the requirements of the production line.

What Is a Brick Stacking Robot?

A brick stacking robot is an industrial robotic system used to handle and stack bricks during the production process.

After bricks are extruded and cut, they are still relatively fragile. These freshly formed bricks are commonly called green bricks. Before entering the drying or firing process, they need to be arranged in a suitable pattern.

The robot performs several basic operations:

1. Pick up green bricks from the transfer or grouping system.
2. Move the bricks to the designated stacking position.
3. Rotate or adjust the bricks when necessary.
4. Release the bricks according to the programmed pattern.
5. Repeat the cycle until the required stack is completed.

The exact movement pattern depends on brick dimensions, production capacity, kiln or dryer configuration, and the required stacking method.

Why Is Green Brick Stacking Important?

The stacking stage may appear simple, but it can influence the efficiency of the entire brick production line.

Poorly arranged bricks can create problems during subsequent drying and firing. For example, inconsistent spacing may affect airflow, while unstable stacking can increase the possibility of collapse or damage.

For this reason, modern automated brick plants often focus on stacking consistency and positioning accuracy rather than simply increasing robot movement speed.

A properly designed automatic stacking system can help create repeatable brick arrangements and reduce dependence on manual stacking operations. Industry equipment suppliers commonly identify stacking pattern, green brick strength, robot reach, payload, and dryer/kiln layout as important factors when selecting a robotic stacking system.

How Does an Automatic Brick Stacking Robot Work?

A typical automatic brick stacking machine works through coordination between mechanical movement, sensors, control software, and the robot's gripping system.

Step 1: Green Brick Transfer

After extrusion and cutting, green bricks move through a conveyor or grouping system.

The bricks are organized into a predetermined arrangement before being picked up by the robot.

Step 2: Brick Gripping

The robot moves its gripper toward the green bricks.

The gripping mechanism must be designed according to the brick size, shape, weight, and strength. Different brick products may require different gripping configurations.

Step 3: Robotic Movement

The robotic arm lifts the bricks and moves them toward the target location.

Servo-driven movement can provide controlled positioning and repeatable operation. Industrial brick stacking systems may also use programmable positioning so that different stacking patterns can be implemented.

Step 4: Positioning and Stacking

The robot places the bricks at the programmed location.

Depending on the production design, the robot may change orientation between layers to create a stable stacking structure.

Step 5: Repeated Operation

The robot repeats the pick-and-place cycle until the required stack is completed.

The finished stack can then proceed to the drying or firing stage.

Key Features of the Brick Stacking Robot

The Brick Stacking Robot shown in the product design is built around several important components and functions.

Flexible Working Positions

The robot can be configured to operate at different positions according to the production line layout.

This is particularly useful when the available factory space, conveyor direction, dryer entrance, or kiln-car arrangement differs between projects.

Servo Motor Drive

A servo motor provides controlled movement and positioning.

For robotic brick handling, accurate movement is important because the gripper needs to repeatedly approach, lift, transport, and release bricks at predetermined positions.

RV Reducer

The RV reducer is an important mechanical transmission component used in robotic motion systems.

It helps transmit torque and supports controlled movement of the robot arm.

Customized Stacking

Different brick factories may produce different sizes and types of bricks.

Therefore, a stacking system should not be treated as a one-pattern solution. The gripper, movement path, stacking program, and final arrangement can be designed according to the actual brick production conditions.

Two Typical Production Routes

Route 1 (High Automation)

Raw coal gangue → Coarse hammer crusher → Belt conveyor → Plate feeder → Multi-stage crushing and screening → Double-shaft mixer → Reversible belt conveyor → Aging silo → Multi-bucket excavator → Box feeder → Mixing extruder → Two-stage vacuum brick extruder → Strip cutting and brick cutting → Automatic brick stacking machine → Kiln car → Brick dryer system → Tunnel firing kiln → Automatic unloading → Finished brick inspection and delivery.

Route 2 (Semi-Automation)

Raw material bin → Vibrating feeder → Coarse hammer crusher → Belt conveyor → Hammer crusher → High-frequency vibrating screen → Double-shaft mixer → Aging silo → Manual reclaiming → Box feeder → Mixing extruder → Two-stage vacuum brick extruder → Strip cutter, brick cutter and green body conveyor → Manual brick setting → Tunnel drying kiln and tunnel firing kiln → Manual unloading → Quality inspection and shipment.

Engineers can mix these two workflows according to factory scale, labor cost and raw material situation.

Raw Material Crushing & Equipment Selection

Raw material particle size directly affects the final quality of green brick body. Two major brick categories have distinct crushing requirements:

1.  1. Solid bricks and low-porosity perforated bricks: particle size below 2.5 mm. Two-stage crushing system: jaw crusher + hammer crusher.
2.  2. High-porosity non-load-bearing hollow bricks: particle size below 1.5 mm. Two-stage or three-stage crushing can be used. A fine roller mill with grinding function can be added to achieve finer particles. Materials with poor plasticity benefit greatly from aging after crushing.

Coarse hammer crusher: Designed for medium-hard raw materials such as coal gangue and shale. It can handle raw lumps up to 500 mm. Large materials are split by impact force in primary chamber, and medium-sized materials are further crushed in secondary chamber. The bottom sieve plate separates qualified fines automatically. It is widely used for primary crushing on automatic brick plant.

Hammer crusher: Impact crushing equipment for brittle raw materials. Users can replace screen plates to adjust output fineness. Single rotor hammer crusher has crushing ratio of 10–15; double rotor reaches 20–30. Raw material moisture must be kept ≤8%, otherwise screen clogging will occur. It is not suitable for sticky or very hard rock.

Aging Silo Selection for Raw Material Homogenization

Raw material aging treatment homogenizes moisture and particle distribution inside coal gangue mix. After aging, the plasticity index rises, drying and firing defects drop significantly. 4 days of aging reduces drying scrap rate by 12% and firing scrap rate by 6%.

Three widely used aging silo types:

1.  1. Loader reclaim aging silo: Cone stacking method, simple structure. Best for raw materials with minor composition variation.
2.  2. Manual reclaim aging silo: Compact building area, less air contact. It delivers excellent aging effect. For a plant with annual output of 60 million standard bricks, only two workers per shift are required. It is popular for small and medium brick factories.
3.  3. Multi-bucket excavator aging silo: Semi-underground design. Multi-bucket excavator evenly takes materials from the silo. One operator can finish reclaiming work. Wave-shaped stacking option reduces particle segregation. This design requires stronger building structure for suspended distribution belts, raising construction cost, and is preferred for large modern brick plants.

Forming Control of Green Brick Bodies

Forming determines the dimension accuracy and mechanical strength of green brick body. After aging, raw materials are extruded by two-stage vacuum brick extruder. The standard requirement: extrusion pressure ≥1.5 MPa, vacuum degree >80%. For premium load-bearing fired bricks, pressure ≥2.2 MPa and vacuum ≥88% are mandatory.

Common forming defects: insufficient green body strength, low bulk density, unstable cutting dimension. Root causes: excessive raw material moisture, insufficient extrusion pressure, unreasonable particle grading or misaligned cutting blades. Solutions include adjusting raw material moisture, boosting extrusion pressure, optimizing particle grading and calibrating cutting machines.

Drying Process Optimization

Brick dryer system prevents cracking during moisture removal. Key drying medium parameters: inlet temperature 120–150℃, exhaust temperature 35–45℃, exhaust RH 90–95%, airflow velocity 1.5–4.5 m/s.

Temperature and humidity curves must rise and fall gently without sudden changes. Factory operators must maintain stable zero-pressure point inside drying chamber. The drying cycle is determined by drying sensitivity coefficient K:

•  1. K＜1: 12–20 hours
•  2. K=1~1.5:20–26 hours
•  3. K=1.5~2:26–32 hours
•  4. K＞2:32–48 hours

Firing Process and Kiln Types

Three kiln types for coal gangue fired brick production:

1.  1. Annular kiln (ring kiln): Suitable for small and medium brick plants. Continuous firing with fixed brick setting. Flue gas preheats green bricks, and hot air from cooling zone supports combustion. Outlet flue gas temperature around 100–150℃.
2.  2. Improved three-centered arch annular kiln: Smoother arch shape, smaller cross-section temperature difference, lower gas resistance and faster firing speed. Main flue ducts are built above ground, simplifying civil works. Mechanized loading and unloading reduce labor intensity, with lower investment than large flat-top tunnel kilns.
3.  3. Large-section flat-top tunnel kiln for bricks: The top choice for modern coal gangue fired brick projects. It delivers high output, low fuel consumption and consistent brick quality. Available widths include 4.6 m, 6.9 m and 9.2 m.

The firing curve includes preheating, high-temperature soaking and cooling phases. Standard firing temperature for coal gangue brick is about 1050℃. The low-temperature long-soaking method creates uniform sintering. Special cooling control is needed at 573℃ and 230℃ to avoid crack from quartz phase transformation.

For modern brick and tile production line, green body drying cracks caused by overly rapid drying remain a major technical headache that hurts production efficiency and fired brick quality. Many brick plants face crack defects after stacking green bodies by brick stacking system, simply because the drying speed is poorly tuned. Understanding root causes and applying standardized process control can effectively prevent green body drying cracks.

Abnormal drying and cracking of the brick green body mainly arise from two factors. First, sudden shifts of the overall drying regime. Temperature and humidity spikes or drops inside drying tunnels break the gradual dehydration rule of the brick green body. Uneven water loss stops synchronous shrinkage and creates green body drying cracks. Second, high-speed drying starts too early before the drying critical point. Fresh brick green body has low structural strength and poor toughness. Excessively fast drying damages its structural stability directly.

As a core drying variable, drying medium temperature defines the dehydration capacity of your drying system. Within a reasonable range, raising drying medium temperature improves drying efficiency and shortens the production cycle of fired brick. However, extreme temperature or sudden heat surge triggers severe imbalance of moisture movement. The surface of the brick green body loses water and shrinks rapidly, while internal moisture cannot diffuse outward quickly enough. This creates a large shrinkage gap between surface and core.

This shrinkage difference builds continuous tensile stress inside the brick green body. When stress exceeds the inherent surface strength of the brick green body, visible green body drying cracks appear. To optimize drying technology for your brick and tile production line, manufacturers should avoid sudden changes to the drying regime and control drying rate before the drying critical point, so as to eliminate fast drying cracks fundamentally.

1. Maximize Heat Output via Complete Fuel Combustion

Combustion is an oxidation process that releases thermal energy. Complete fuel combustion requires adequate supply of combustion air. When fully burned, no combustible gas remains in flue gas and solid fuel leaves no combustible residue.

Incomplete combustion wastes fuel energy. Two scenarios:

1.  1. Gas incomplete combustion: shortage of oxygen supply. Fuel cannot finish oxidation, leaving combustible gas in flue gas.
2.  2. Solid incomplete combustion: sufficient air volume, yet poor contact between fuel and air creates local oxygen deficit.

Full combustion ensures all fuel heat is used to heat green brick for firing.

2. Optimize Kiln Heat Exchange and Internal Gas Flow

Brick firing relies on heat transfer from hot flue gas to green brick. The airflow runs through all kiln zones: preheating zone, firing zone and cooling zone.

Preheated air from cooling zone enters firing zone to support fuel burning. Hot flue gas from firing zone flows to preheating zone to evaporate moisture in wet green brick. Cold air entering the kiln cools finished hot bricks. Stable gas flow is the foundation of efficient heat exchange in the tunnel kiln. Without good gas circulation, much heat will be lost and energy consumption rises sharply.

3. Optimize Brick Stacking Layout to Adjust Airflow Resistance

Brick stacking forms brick piles inside kiln. The layout must match gas flow characteristics, kiln structure and fuel type. Brick piles create airflow resistance that can be adjusted.

Lower stacking density reduces resistance and increases airflow rate, improving heat transfer and combustion conditions. When designing stacking schemes:

•   1. Keep sparse stacking within proper limits.
•   2. Externally fired brick: top dense bottom sparse; middle dense, inner secondary dense, outer sparse; transverse dense, longitudinal sparse; curved kiln inner dense outer sparse.
•   3. Internally fired brick: top dense bottom sparse, edge dense middle sparse. Create gaps near branch flues for uniform airflow distribution across kiln cross-section.

Good stacking design improves kiln throughput, brick quality and lowers fuel consumption. Poor stacking causes uneven temperature and extra energy waste.

4. Refine Kiln Operation Management

Fine operation control helps reduce energy loss during brick firing:

1.  1. Control residual moisture of dry green brick. Less water content cuts heat needed for evaporation and speeds up preheating.
2.  2. Maintain stable position and length of preheating zone, firing zone and cooling zone. Thermal zone drift will cause extra heat waste.
3.  3. Adjust kiln dampers properly to recover waste heat. Higher waste heat recovery lowers overall energy consumption.
4.  4. Maintain good kiln sealing. Hot gas leakage and cold air infiltration are major sources of heat loss.
5.  5. Shorten kiln cycle time to reduce heat storage loss of kiln body and kiln cars.
6.  6. Improve finished brick rate. It brings the most obvious energy-saving effect, saving heat, electricity, labor and raw materials, extending machine lifespan.