Roller Conveyors: Types, Applications and Benefits

Chapter 1: What is a Roller Conveyor?

Roller conveyors play a crucial role in material handling systems. They use a sequence of uniformly spaced cylindrical rollers to efficiently transport boxes, materials, objects, and parts over open spaces or between varying elevations. These roller conveyor frames are crafted at a convenient height, facilitating effortless manual loading and unloading. For optimum performance, items transported via roller conveyors should possess firm, flat surfaces to glide smoothly over the rollers.

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These conveyors offer great versatility, being employed in a range of applications such as accumulation, inertia reduction, and swift sorting of products. Driven roller conveyors have rollers connected to a motor through mechanisms like chains, shafts, or belts, which control the consistent movement speed of items. These systems can be bi-directional, allowing for reversible movement and transport of products between different levels, with the motor capable of changing the direction of the items being moved.

Chapter 2: How is a Roller Conveyor Constructed?

Roller conveyors are critical components in material handling systems and warehouse automation, renowned for their efficient transport of goods, boxes, and palettes across production lines and distribution centers. Engineered with precision, modern roller conveyors are designed with specific features to meet the varied needs of industries such as manufacturing, logistics, packaging, and food processing. While roller conveyors can differ in structure, drive mechanism, and manufacturer-specific features, they share several fundamental characteristics. An understanding of how these conveyors are constructed can help facility managers and engineers select the optimal conveyor solution for their application requirements.

Powered roller conveyors, also referred to as live roller conveyors, utilize small belts, poly-v belts, or plastic spools to provide consistent traction to the rollers. Friction belts or durable roller chains positioned beneath the conveyor bed engage with heavy-duty rollers to move products smoothly. These drive systems are connected to a central shaft that runs the length of the conveyor frame and links to an energy-efficient electric motor, which powers the conveyor rollers and delivers reliable motion control.

Rollers

Conveyor rollers are cylindrical metal components fitted into the conveyor frame with high-precision sets of bearings on either end. Several types of conveyor rollers are available, each designed to fit different load capacities, operational speeds, and environmental conditions. Rubber and plastic rollers increase friction for gentle product handling, while steel and aluminum rollers offer low rolling resistance and durability for heavier industrial applications. When choosing rollers, end-users must consider factors like load type, maintenance needs, and wear-resistance to ensure seamless material flow and product integrity throughout the material handling system.

Plastic Rollers

Plastic conveyor rollers are lightweight, cost-effective, and designed for light-duty applications. Simple to install and boasting minimal maintenance requirements, plastic rollers comply with OSHA workplace noise standards, reducing sound levels on busy production floors. With their inherent resistance to corrosion, rust, and moisture, these non-metallic rollers excel in harsh or washdown environments and offer a longer useful life. Their easy-to-clean properties make plastic rollers ideal for transporting packaged goods, pharmaceutical items, and food products in the food and beverage industry. They also support sanitary conveyor system standards required for hygienic applications.

Nylon Rollers

Nylon rollers offer superior durability and strength for medium to heavy-duty load handling. Manufactured from synthetic polymers, nylon conveyor rollers provide excellent abrasion resistance, chemical stability, and operational reliability in high-traffic logistics and distribution centers. Like plastic variants, nylon rollers are lightweight, easy to install, and contribute to operator safety by generating minimal vibration and noise. These characteristics make nylon rollers popular in e-commerce fulfillment, packaging, and parcel delivery sectors where quiet, efficient operation is valued.

Rubber Coated Rollers

Rubber-coated rollers feature a protective layer of natural or synthetic rubber bonded onto steel, stainless steel, or solid plastic cores. This specialized coating increases grip, cushions fragile products, and provides long-lasting protection for both the roller and transported goods. Selection of rubber composition and hardness is based on specific industry and product needs, such as anti-static, abrasion-resistant, or chemical-resistant properties. Commonly used in the automotive, packaging, printing, textile, and metal fabrication industries, rubber-coated rollers are prized for their durability, slip prevention, and ability to move products securely across inclined or fast-moving conveyor lines.

Rubber-coated rollers are customizable to various load requirements and operational environments. Their increased surface friction helps prevent product slippage and improves throughput in automated material handling systems.

Steel and Stainless Steel Rollers

Steel and stainless steel rollers represent the gold standard in conveyor roller construction for heavy-duty industrial and commercial use. These metal rollers offer unmatched longevity, strength, and resistance to wear, making them ideal for moving pallets, bulk containers, and other high-weight materials. Stainless steel rollers add corrosion resistance for applications in cleanrooms, food production, and harsh chemical processing environments. Both steel and stainless rollers can be customized with different diameters and wall thicknesses for maximum structural integrity.

In complex conveyor systems, steel roller cores are often overmolded with plastic, nylon, or rubber to provide targeted performance benefits. With compatibility across a wide variety of driven and gravity-fed conveyors, stainless steel rollers support precision bearings, adjustable shafts, and tailor-fit solutions for the demands of modern automated warehouses.

Structure of a Roller Conveyor

Roller conveyor frames form the backbone of any conveyor solution, providing essential structural support and alignment for efficient material transfer. Frames can be either permanently installed or configured as portable conveyor units, adaptable to dynamic facility layouts. Typically constructed from steel, stainless steel, or lightweight aluminum, each material offers distinct benefits: aluminum is rust-resistant and easier to relocate, while steel and stainless steel afford robust durability for continuous heavy-duty use.

Support legs for roller conveyors come in a range of sizes, materials, and configurations to address varied load capacities, conveyor lengths, and installation conditions. These legs generally feature tripod or "H" designs—the "H" type is subdivided into light duty, medium duty, and heavy duty construction. Manufactured from sturdy channel material, support legs are engineered to fit a variety of roller diameters and can be customized with leveling feet, casters for mobility, or even shock-absorbing mounts for vibration isolation.

Roller Conveyor Motor

At the heart of a powered roller conveyor is the motorized drive system. Roller conveyor motors are typically 24-volt DC motors, valued for energy efficiency, low noise output, and safer operation compared to higher voltage solutions. In advanced motorized roller conveyor systems (MDR), the conveyor is divided into individually controlled zones, with each segment powered by its own motor-driven roller. This zoned approach facilitates accumulation, product sorting, and merge/diverge functions crucial for order fulfillment and warehouse automation. Operators can precisely control speed, direction, and sequencing, optimizing flow for both batch and continuous processing environments.

These modular MDR conveyor systems enable scalability, minimize energy consumption, and reduce downtime for maintenance—making them an increasingly popular choice for smart factory and Industry 4.0 applications.

Non Precision Bearings

Non-precision bearings, such as sleeve bearings and bushings, are economical solutions suited for conveyor rollers operating at lower speeds and under light-to-moderate loads. Manufactured using the same base materials as precision bearings, these components feature looser tolerances, which allow them to accommodate small misalignments and reduce production costs. Their primary applications are in package handling, assembly lines, and sortation conveyors, where precise positioning is less critical than in high-speed or automated systems.

Angular Contact Ball Bearings

Angular contact ball bearings are designed to support combined radial and axial loads by providing stable contact at a specific angle relative to the bearing axis. The close spacing of the inner and outer ring raceways allows these bearings to withstand high dynamic forces encountered in fast-moving or heavily loaded conveyor lines. Several configurations exist, including single row, double row, and four-point contact bearers, each optimized for different operational needs and installation footprints.

Within motorized roller conveyor systems, angular contact bearings are vital for supporting the conveyor's line shaft, ensuring stable, low-noise, and low-maintenance operation. Their integration with high-tensile shafts, drive belts, and spools enables smooth, efficient product movement, increasing productivity in automated packaging lines and high-throughput distribution centers.

Pillow Block Bearing

Pillow block bearings, also called plummer block bearings, are a trusted means of supporting rotating shafts in both static and dynamic conveyor applications. The bearing is encased in a sturdy mounting block, bolted parallel to the conveyor line for optimal shaft alignment. Conveyor systems rely on pillow block bearings for their capability to accommodate misalignments and deflections, ensuring uninterrupted product flow and system longevity.

These bearings deliver reliable performance for both axial and radial load scenarios and are available with features such as grease fittings, dust covers, and anti-corrosive housings to suit even the most demanding industrial environments.

Roller Conveyor Sprockets

Roller conveyor sprockets are engineered gears that synchronize with conveyor chains to transfer drive power through the system’s rollers. Sprocket configurations are chosen based on tooth count, torque requirements, roller diameter, and bore length to match the specific conveyor design. For lighter loads, plastic hubs are suitable, while robust steel sprockets handle the stresses of bulk material movement in manufacturing and heavy industry. Proper sprocket selection enhances overall conveyor performance, prolongs component life, and supports maintenance-friendly conveyor designs.

Roller Conveyor Curves

Roller conveyor curves are essential modules that introduce flexibility and direction changes to conveyor layouts, facilitating smooth transport of goods around corners and obstacles without the risk of jams or misalignment. These curves are engineered with precise angles, typically from 30° up to 90°, but custom engineering allows for complex transitions in space-constrained facilities. Curved conveyor sections help maximize available floor space and ensure optimal layout efficiency in distribution centers and production environments.

Specialized rollers for conveyor curves—often tapered, conical, or cylindrical—accommodate the radius of the curve and efficiently handle a wide range of items including cardboard boxes, totes, crates, tires, and small packages. Properly engineered curves take into account the size, weight, and center of gravity of each item to prevent tipping or blockages and may include adjustable side guides and reinforced support rollers for added stability.

Innovative curve solutions include S-curves for space savings, spiral roller conveyors to move goods between elevations, and split or multi-track curves for high-volume sortation. By integrating expertly designed conveyor curves, operators can optimize their material handling systems for future expansion and evolving business needs.

Chapter 3: What are the Different Types of Roller Conveyors?

Roller conveyors are essential components in material handling systems, widely employed across manufacturing, warehousing, distribution, and packaging industries. They enable the efficient, safe, and cost-effective transfer of products, packages, and materials within facilities. Broadly, roller conveyors are categorized into two main types: powered (motor-driven) roller conveyors and gravity roller conveyors. Gravity roller conveyors function on the force of gravity or manual intervention, while powered roller conveyors utilize electric motors or other drive systems for automated material flow. Within each category exists a diverse range of roller conveyor solutions, including belt-driven, chain-driven, line shaft, zero pressure, motor-driven, and merge roller conveyors—each engineered to suit specific load requirements, facility layouts, and automation levels.

Gravity Roller Conveyor

Gravity roller conveyors are the most basic and widely used type of roller conveyor. These systems feature a straightforward design with a frame that supports rotating roller bars and sturdy support legs. Gravity roller conveyors efficiently transport light to medium weight loads by exploiting gravity for movement—no external power source is required. This makes them exceptionally cost-effective, low-maintenance, and energy-efficient.

Constructed from robust materials such as steel, galvanized steel, aluminum, or high-grade plastics, gravity roller conveyors can be customized with various components, including curved and straight sections, guide rails, supports, hanging brackets, sensors, and pop-up stops. Common in shipping, receiving, assembly, and order picking areas, these conveyors offer flexibility and modular setups—often serving as ideal alternatives to skate wheel conveyors in heavy-duty and bulk material handling applications. Their ability to be moved or reconfigured as layouts change makes them invaluable for dynamic warehouse and logistics environments, improving workflow and minimizing processing time.

• Material Flow Optimization: Gravity conveyors are often used for applications needing minimal manual interference, line balancing, or buffer systems before further processing.
• Industry Uses: Found in parcel sorting, e-commerce fulfillment centers, packaging operations, and temporary workstations.
• Limitations: Best suited for flat-bottomed products; less effective on inclines or for heavy, irregular loads without additional features.

Belt Driven Live Roller Conveyor (BDLR)

Belt-driven live roller (BDLR) conveyors are equipped with an electric motor connected to a continuous belt that transmits power to individual rollers. This configuration grants precise control over directional movement, speed, and load separation. Belt-driven roller conveyors are highly adaptable—capable of halting, turning, side-unloading, sliding, and reversing load flow—making them well-suited for facilities needing material accumulation, diverting, and controlled product orientation.

Often manufactured with rollers positioned above or flush with the conveyor frame, BDLR systems accommodate oversized goods and irregularly shaped cartons. These roller conveyors are optimal for clean, dry, medium to heavy-duty applications, such as handling boxes, totes, and palletized loads. Additional advantages include reliable stops, start/start transfer points, and energy efficiency in automated assembly lines and distribution operations. Their seamless integration with gravity or chain-driven conveyors further enhances workflow customization.

• Applications: Package handling, product assembly, distribution centers, and mail sorting facilities.
• Advantages: Gentle product handling, reversible operation, and cost-effective maintenance.

Chain Driven Roller Conveyor

Chain-driven roller conveyors utilize a robust power transmission chain attached to sprockets, which are fixed to each individual roller. Unlike standard chain conveyors that might drive all rollers with a single, continuous chain, this system enables more precise and uniform movement—especially vital when transporting heavy loads, pallets, drums, or containers through manufacturing and industrial environments.

These conveyors offer greater torque and power transfer, making them ideal for heavy-duty, high-impact, and high-throughput applications. Chain-driven systems can also handle reversing operations and are less prone to slippage, delivering consistent and reliable transport for demanding material handling tasks.

Commonly deployed in palletizing, filling, load staging, assembly, and strapping applications, chain-driven roller conveyors offer unparalleled durability, resistance to abrasives, and reliable performance even in harsh and hazardous industrial environments. Their construction supports high load capacities, and the modular design allows for easy maintenance and integration with automated systems for plant-wide material flow.

• Key Features: High torque output, bidirectional operation, heavy-load handling, long service life.
• Industries: Automotive, heavy manufacturing, lumber mills, foundries, and chemical plants.

Line Shaft Roller Conveyor

Line shaft roller conveyors utilize a continuous rotating shaft connected beneath or beside the conveyor's frame. Drive spools and elastomeric belts link the shaft to individual rollers, providing smooth and reliable movement for light to medium-weight items. An electric motor, frequently governed by a programmable logic controller (PLC), turns the line shaft, enabling synchronized movement along extensive conveyor lengths and around curves without the need for separate drives, chains, or complex mechanical linkages.

Line shaft systems can move products efficiently over distances exceeding 100 feet, managing both straight and curved conveyor segments. Favored for accumulation, gentle sortation, induction, and low-back-pressure conveying, these conveyors excel in order fulfillment, packaging, postal, and distribution centers where quiet operation and versatility are priorities.

However, line shaft roller conveyors are not ideal for wet, oily, or extreme environments and are best used in applications with consistent product contact over at least three rollers. They operate most effectively on flat surfaces at moderate speeds, ensuring smooth product flow and reduced risk of jams or product gaps.

Zero Pressure Roller Conveyor

In conventional accumulation conveyor systems, products can collide and create unwanted pressure, resulting in potential product damage and reduced processing efficiency. Zero pressure roller conveyors—also recognized as pressureless or accumulation conveyors—address this by utilizing advanced controls and zoned drive systems to prevent product contact during accumulation.

Zero pressure systems use 24-volt DC motors to power specific conveyor zones, each managed by integrated photoelectric sensors and a central controller. When a sensing zone detects a stationary product ahead, it halts its own operation, ensuring no back pressure or product collisions. This level of control dramatically enhances material flow safety, product integrity, and throughput in facilities handling delicate or high-value goods.

Each zone in a zero pressure roller conveyor includes a powered roller, multiple slave rollers, and a dedicated sensor. Motor power is transmitted—often via internal bands such as O-rings—to slave rollers, allowing for modular system expansion and efficient maintenance.

Zero pressure roller conveyors are ideal for applications requiring high-precision automated flow—such as order fulfillment, pharmaceutical packaging, electronic assembly, and fragile product transport. Available as both new installations and retrofit kits, these conveyors bring superior control, speed, and overall efficiency compared to older accumulation methods, making them a top choice for advanced material handling systems seeking reliable, damage-free throughput.

Motor Driven Live Roller (MDR)

Motor-driven live roller (MDR) conveyors utilize low-voltage (typically 24V DC) motors seamlessly integrated into the roller shafts themselves. Each conveyor section is divided into multiple independently-driven zones, with each zone equipped with a motorized roller and accompanying slave rollers. Photoelectric sensors and controller cards facilitate zone-based accumulation, selective product movement, and high system flexibility—all without the need for extensive PLC programming or pneumatic controls.

MDR roller conveyors provide energy savings through on-demand, zone-based operation—only activating motorized rollers when a product is present. This greatly reduces operating costs and system wear. These conveyors are highly configurable, easy to install or expand, and excel in accumulation, sortation, and transfer applications within e-commerce, postal, and high-speed distribution environments. MDR conveyors can readily integrate with belts for inclines/declines and facilitate seamless integration with modern warehouse automation technologies.

• Industry Uses: E-commerce fulfillment, parcel sorting, order picking, and food/beverage distribution.
• Benefits: Quiet operation, modular scalability, energy efficiency, and reduced maintenance requirements.

Merge Roller Conveyors

Merge roller conveyors—also known as combiner roller conveyors—are engineered to channel products from multiple inbound conveyor lines into a single unified flow. These conveyors are critical for merging and sorting applications within distribution hubs, packaging lines, or facilities with parallel processing streams. Merge roller conveyors efficiently combine two or more product lines, streamlining operations and maximizing throughput while reducing upstream and downstream handling complexity.

Engineered for light to medium-duty materials, these systems leverage either fixed or powered roller sections to control product entry and exit, ensuring smooth and precise merging with minimal manual input. The ability to reconfigure, adjust, or expand these conveyors makes them especially valuable for facilities with regularly changing workflows or fluctuating product mix.

• Advantages: Labor savings, improved process integration, increased throughput, and high adaptability.
• Applications: Distribution centers, manufacturing lines, packaging operations, and order picking systems.

For optimal results, merge roller conveyors can be combined with automatic sensors, diverters, and programmable controls—enhancing their performance as part of an integrated conveyor system designed for lean manufacturing and just-in-time delivery methodologies.

Chapter 4: What are the applications for roller conveyors?

Since their debut in , roller conveyors have become crucial in product handling, assembly, and supply chain management. These conveyors are versatile and can manage loads of various sizes. Over time, their designs and functions have evolved significantly, with continual innovations and improvements being introduced.

Roller conveyors are used for a variety of applications, including:

• Moving products across large areas with less labor
• Transportation of heavy and cumbersome goods and materials
• Saving labor costs by moving products while other activities are completed
• Prevent injuries to workers from the stress of lifting to items falling
• Ensure the safe transport of products with damaging them
• Integral parts of robotic functions and actions.

Custom Designs

Each application for roller conveyors requires a bespoke design tailored to specific needs. For optimal performance, a roller conveyor must be engineered to fit its intended environment. Custom roller conveyors often include modular components like straight sections, curves, transitions, mergers, power types, and separators. Every aspect must be carefully integrated into a cohesive system.

Designing a custom roller conveyor presents challenges, such as deciding whether the system will operate as a standalone unit or be part of a more complex setup with interconnected components. It’s also essential to determine the type of power used—whether chain, belt, or roller—based on system requirements.

Airport Roller Conveyors

Roller conveyors play a critical role in airports, including applications like check-in counters, baggage handling systems, and loading areas. Depending on the handling requirements, both gravity and powered roller conveyors are utilized to manage different types of baggage and packages.

Assembly Roller Conveyors

In assembly settings, roller conveyors come in various forms such as overhead, belt, and traditional roller types. While conveyor systems can sometimes be noisy and disruptive, roller conveyors are preferred for their reliability, durability, and quieter operation, which enhances worker comfort.

Supply Chain Roller Conveyors

In supply chain and warehouse operations, roller conveyors offer a cost-effective alternative to forklifts for product movement. They simplify logistics by reducing manual handling, speeding up product flow, and easing the workload on workers.

Packaging Roller Conveyors

The packaging industry relies heavily on roller conveyors for moving, stacking, and sorting packages. Depending on the specific requirements, either gravity-fed or powered roller conveyors are employed to facilitate efficient package processing.

Food and Beverage Roller Conveyors

Designing roller conveyors for the food and beverage sector is complex due to stringent industry regulations and standards. These conveyors must meet high cleanliness and hygiene standards to be suitable for use in food and beverage applications.

Metal Working Roller Conveyors

In metalworking, roller conveyors are primarily used for sorting and identifying scrap materials. Their robust construction and adaptability make them well-suited for handling heavy loads and various metalworking processes.

The industries mentioned above are just a few examples of how roller conveyors are integral to diverse sectors. From automotive manufacturing to robotics, roller conveyors are crucial for efficient product handling and movement.

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Chapter 5: What are the benefits of roller conveyors?

Roller conveyors are highly valued for their adaptability and versatility, allowing them to be configured for various conditions. Temporary roller conveyors can be relocated as needed, while permanent ones are designed for durability and long-term use. Since their inception in the early 20th century, roller conveyors have been employed across a wide range of industries, serving both traditional and innovative applications.

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• Speed - Roller conveyors are a safe and fast transport system, which reduces the risk of damage to goods due to mishandling.
• Reliability - One of the reasons for the continued use of roller conveyors is their reliability as a long lasting logistics solution.
• Cost Effectiveness - Roller conveyors are long lasting due to their toughness and durability. The initial investment in their cost is amortized over their many years of use.
• Efficiency - The speed at which roller conveyors can move goods enhances and improves material movement.
• Maintenance - Roller conveyors require limited maintenance due to their simple design and few moving parts, which reduces material handling downtime.
• Safety - The continued use of roller conveyors has significantly reduced injuries due to the removal of the need to lift and move products by hand. This is one of their main benefits since workers no longer need to lift heavy packages or containers, a process that can be completed using various lifting mechanisms.
• Customizable - The versatility, structural flexibility, and conformability of roller conveyors makes it possible to place them in any space where product movement is required. Every roller conveyor has to be engineered to fit the conditions where it will be used.

Chapter 6: What are the regulations regarding roller conveyors?

Safety Requirements of Conveyors

The Occupational Safety and Health Administration (OSHA) provides guidelines for the safe operation of conveyor systems. Additionally, the American National Standards Institute (ANSI) offers safety standards for conveyor design, in accordance with the American Society of Mechanical Engineers (ASME) guidelines. Both organizations regularly review and update their standards to incorporate new developments and technological advancements.

OSHA Guidelines

• .555(a): General requirements.
• .555(a)(1): A motor stop switch should be found at the operator’s position. The system must have a pilot light with a sound that rings when the system is powered on.
• .555(a)(2): Remote operations should have a stop switch at the motor.
• .555(a)(3): The emergency stop button avoids reactivation of the system until the emergency button is reset to "ON."
• .555(a)(5): Overhead conveyors should have a protective covering below the conveyor. If the position of the conveyor is far from employees, this can be ignored.
• .555(a)(6) & .555(a)(6): Warning signs must be put on aisles, crossovers, and passageways.
• .555(a)(7): Conveyors should have warning signs or be locked out during regular maintenance.
• .555(a)(8): Conveyors should be made and maintained according to ANSI B20.

ASME Guidelines

Conveyor safety standards are included in:

• ASME B11.0-, which mentions safe use of machines and mentions several safety devices that must be part of the construction and installation process.
• ASME B20.1-: ASME B20. 1 - has the design requirements, maintenance, construction, and operation of a conveying system concerning hazards. It’s a set of general safety guides. ASME B20. 1- is for industrial use conveyors and not those which are designed to mobilize people.
• ASME B20. 1- is part of the specifications in ASME B20.1, ANSI B11.19, ANSI A.1, ANSI 244.1, which mention safety guides for conveyors.
• ASME B20.1 and ANSI B11.19: These are in ASME B20. 1- that explains the requirements for installation, construction, inspection, maintenance, and operation of a conveyor system.
• ASME B20.1, ANSI B11.19, ANSI B11.0: These are more details concerning safety processes for temporary, permanent, and portable conveyors.

Chapter 7: What is involved in the maintenance of roller conveyors?

Conveying systems consist of interconnected components that rely on each other for optimal operation. Different types of roller conveyors require regular maintenance to ensure they function correctly. To prevent issues and maintain system efficiency, it's crucial to schedule routine inspections of the conveyor's components that impact its overall performance.

Conveyor Maintenance Steps

The drive chain and sealed roller bearings must be oiled. Operators should be trained as to the proper inspection procedures in regard to bearings, rollers, shafts, belts, and DC motors.

Driver rollers should be regularly cleaned to prevent blockages in the system. Residue or debris that accumulates during operation needs to be removed from the roller surfaces. Use cleaners specifically designed for each type of roller; for instance, stainless steel rollers should be rinsed with water and cleaned with detergent. Implementing preventative maintenance helps to address minor issues before they escalate and ensures the equipment operates effectively.

Preventative Conveyor Maintenance

Preventative maintenance includes inspecting conveyor rollers for smooth and consistent movement, checking for wear on drive chains or belts, and ensuring rollers are level. Rollers should operate uniformly in the same direction; any wobbling or lack of movement indicates a problem that requires immediate attention. Bearings, which are prone to wear, should also be regularly examined to ensure they are functioning properly.

Roller conveyors, like any continuously operating equipment, experience wear and degradation due to environmental conditions. High temperatures and humidity can adversely affect their performance, necessitating more frequent inspections. To maintain optimal performance, it’s crucial to allow the system to cool down periodically and schedule regular maintenance checks.

Chapter 8: What considerations should be taken into account when choosing roller conveyors?

A conveying system can be incorporated into operations in multiple ways to enhance efficiency and speed. Before installing a roller conveying system, it's essential to evaluate several factors to tailor the system to the specific needs of the application.

Available Space

When designing a conveying system, manufacturers take into account the available space to ensure effective integration. This involves identifying key interaction points, required clearances, and any potential obstacles that could hinder material movement. The choice between automated and manual systems depends on the specific application and operational requirements.

Roller Frame Material

The frame of a roller conveyor is typically constructed from aluminum or steel, chosen based on the load requirements and the frame's capacity rating. Rollers, which directly contact the products and influence their movement, come in a variety of materials. Some are coated with plastic or rubber to enhance friction, while others are made of aluminum or steel. Properly selecting roller materials ensures reliable product transport without compromising system integrity.

Roller Size and Orientation

Determining the size of the material to be conveyed and the optimal conveyor layout is crucial to avoid obstructing product movement. Roller sizes should match the load and operating conditions: heavy or high-impact loads require larger rollers, while lighter or slower loads can be managed with smaller rollers.

The spacing of rollers is calculated to ensure that three rollers are always in contact with the load. For wider loads, high-set rollers are used, while low-set rollers help keep products within the conveyor frame.

Load Capacity

Establishing the load capacity is vital once the system layout is finalized. Overloading can cause system malfunctions or stoppages. Factors affecting load capacity include overall length, bed width, and the drive system. Gravity roller conveyors are suitable for flat-bottomed, light to medium-weight items like totes, boxes, and bags but are not ideal for fragile or irregularly shaped products.

System Speed

The speed of a conveying system, measured in feet per minute (fpm), typically averages around 65 feet per minute, similar to the walking speed of a person carrying a 50-pound load. While this is a standard speed, the system can be adjusted to meet specific application needs.

Roller Conveying System Configuration

Roller conveying systems come in various shapes, styles, sizes, and configurations, including straight, angled, horizontal, or curved designs with pockets, slats, or Z-frames. For long distances, more efficient designs like line shaft roller conveyors can be used to conserve energy. Roller conveyors can be installed in various facilities or structures, provided that all relevant factors are carefully considered.

Drive System

The drive system in an automated conveying system facilitates the movement of materials and includes counter bearings to maintain smooth operation. Drive systems offer the flexibility to transport goods in both directions and can be installed at various locations within the system—whether in the middle, at the start, or at the end.

Depending on the design of a drive system, it can have single or variable speeds that are driven by a 24 V DC motor attached to gears, rollers, or a shaft. Variable speed drives allow variations in material flow rates.

Behavior, Control, and Environment

When designing a roller conveyor, key factors such as product mobility, control, and placement are crucial considerations. The performance of a roller conveyor can be influenced by environmental factors like heat, dust, dirt, and moisture. In such cases, more robust designs, such as shaft-driven or chain-driven models, may be necessary. Zero-pressure models with precise timing are well-suited for conditions where back pressure might occur. Although gravity conveyors have a simpler design, they are equally vulnerable to the effects of wear and environmental degradation as more complex systems.

Conveying System Safety

The Occupational Safety and Health Administration (OSHA) oversees the regulation of conveyor systems to ensure they comply with federal safety standards. Conveyor manufacturers are required to adhere to these regulations. Conveying systems serve as a preventive measure, reducing the need for personnel to manually lift and transport heavy objects.

Disadvantages of Roller Conveyors

In addition to the regular maintenance required for all equipment, roller conveyors have certain drawbacks that can affect their selection and use. It’s important to consider these factors carefully to ensure that the chosen conveying system aligns with the specific needs of the application.

• Damage to Goods - Gravity conveyors have little control over the movement of goods, which can lead to goods being damaged.
• Weight - Roller conveyors are very heavy and get heavier as they get longer.
• Conveyor Speed - Roller conveyors that are not power driven do not have any control over the rate of speed at which goods are moved.
• Cleaning - Keeping roller conveyors clean is difficult due to the number of rollers and its constant use. In locations with multiple roller conveyors, a janitorial staff is assigned to cleaning rollers. In all cases, keeping the rollers clean and free of debris is essential for optimum performance.
• Space - All forms of conveying systems take up a great deal of space, which is calculated into the customized design of roller conveyors. When the decision is made to install a roller conveying system, it must be noted that large areas of a facility will be devoted to it.

Conclusion

• Roller conveyors are part of material handling systems that use a series of evenly spaced cylindrical rollers to move boxes, supplies, materials, objects, and parts across an open space or from an upper level to a lower level.
• Each roller conveyor system is designed to meet the needs of a specific application.
• Though gravity roller conveying systems are the most well-known, other types include belt driven rollers, chain driven rollers, line shaft rollers, and zero pressure rollers.
• Roller conveying systems, like any other type of machine, require routine maintenance and cleaning.
• OSHA and ASME provide regulations and guidelines for the use and design of conveying systems.

Important rolling processes and tools

Specialist topic thread rolling told in an exciting way ... basics, processes, tools, applications of rolled high-tech threads

Various rolling technologies

Several rolling technologies have become established in industrial practice. Even in the early days of thread rolling, a distinction was made between processes that work with round tools and flat tools (flat dies). Sometimes the rolling processes are subdivided according to the number of tools used.

In the following description of the different rolling processes for high-tech threads, we will only deal with general issues.

Rolling process with two round tools,
symmetrical or asymmetrical

In the case of thread rolling with two externally profiled tools, the two driven rollers rotate in the same direction. A distinction is made between a symmetrical and an asymmetrical variant. In the symmetrical version, both tools move towards the blank, whereas in the asymmetrical version, one of the (rotating) tools remains stationary while the other moves towards the blank. The major advantage of the symmetrical variant is the significantly longer tool life.

The blank is always located between the rolling tools. If the moving tool touches the (still) stationary blank, it is set in rotation by the very fast build-up of frictional locking. The tool profile then forms a thread in the blank.

Grooving process

Every mechanic is familiar with grooving during turning: The supplied turning tool pierces the blank and forms a predetermined geometry. In the grooving process, the two movable tools move towards the blank and groove it with the profile. The tools have grooves with the pitch angle of the thread to be rolled.

Very precise, but finite threads

The principle of the grooving process allows the production of very precise threads. The disadvantage is obvious: because the blank is not fed, the maximum thread length is limited to the tool length.

The accuracy of the thread largely depends on the tool, which is manufactured in several steps. The tool profile is most often produced by grinding. In order to eliminate the distortion of the heat treatment, grinding only takes place after hardening. The surface finish of the roll profile is decisive for the quality of the threads produced.

Their manufacturers - specialist companies - use high-quality tool steel for the tools. Most manufacturers prefer special alloys, but some also offer tools made from other materials and with different heat treatments on request.

Continuous process

The two tools for the throughfeed process have several grooves without pitch on their circumference, which run in a circle around the tool. The two rollers lying horizontally in the machine are tilted in opposite directions around their horizontal transverse axis, in each case by the pitch angle of the thread to be rolled. If the front end of the right-hand roller is tilted downwards and the left-hand roller is tilted upwards, a right-hand thread is produced and, conversely, a left-hand thread.

As the tools swivel, the blank also moves forwards in the horizontal axis (parallelogram of forces!). The rotating blank thus runs through the machine - the throughput speed can be influenced by the rotation speed of the rollers.

"Infinite threads"

The advantage of the throughfeed process is that it is (theoretically) possible to produce an infinitely long thread. The length ultimately only depends on the length of the blank. However, a somewhat lower dimensional accuracy must be accepted compared to the grooving process.

The machine must be equipped with swiveling roller spindles for the throughfeed process with two pitchless tools.

One pair of tools for different core diameters

Another advantage is that the thread manufacturer can roll the same pitch on workpieces of different diameters with a single pair of tools - apart from a few restrictions. However, if very tight thread tolerances are required, it may still be necessary to produce a separate tool for each batch of material.

The choice of material for through-feed tools is the same as for grooving tools. The grooves are applied by grinding and, more recently, increasingly by hard turning with special inserts. Because an axial feed takes place, the tools have three zones with different outside diameters, analogous to the three phases of the rolling process: A run-in zone, a calibration zone and a run-out zone.

The transition from the run-in zone to the calibration zone determines whether the tools achieve the required service life. Throughfeed tools from different manufacturers differ relatively greatly in this detail. If "difficult" base materials are to be rolled, it is recommended to seek the advice of the tool manufacturer.

Partially corrected continuous process

The partially corrected throughfeed process is a combination of the plunge-cut and throughfeed processes. The grooving process contributes the pitch on the tools, while the swivel capability of the rolling spindle was adopted from the throughfeed process. The profile pitch of the tools is not identical to the pitch of the thread to be rolled. The angle difference is compensated by tilting the rolling spindles, as described for the throughfeed method. Thread rolling tools for the partially corrected throughfeed method also have a run-in, calibration and run-out zone.

Large inclines

With the partially corrected pass-through method, considerably greater gradients can be achieved than with the pure pass-through method. An example will illustrate this: The thread must have a lead angle of 15°. However, a rolling spindle for the throughfeed method can be swiveled by 5° at best. To achieve the required 15°, the tools are given a profile pitch of 10° and the missing 5° is set on the machine.

The blank undergoes an axial movement during the forming process, as in the continuous process. The service life of the rollers depends to a large extent on the tool design and the material of the blank.

Throughfeed process with corrected tools

The throughfeed process with corrected tools makes it possible to work with a machine without swivel roller spindles in the throughfeed process. However, it is only recommended if no machine with swivel roller spindles is available.

The throughfeed process with corrected tools is similar to the partially corrected throughfeed process. The lead angle of the tool profiles is either larger or smaller than that of the thread. However, unlike the partially corrected throughfeed method, it is not possible to correct the pitch by swiveling the rolling spindles. The disadvantage is therefore that pitch errors must be accepted.

Rolling process with three or more tools

Thread rolling with three or more driven tools is always a method derived from the methods described with two rollers. As a rule, three rollers are used, which are arranged symmetrically around the blank at angles of 120° to each other. As with the plunge and throughfeed method, the blank is gripped centrally by the tools and rotated. The multi-roller principle makes support rulers and holding devices superfluous.

Suitable for pipes and hollow parts

It is mainly used for pipes and hollow parts. The disadvantage is the high investment for the machine and tools.

Supplementary rolling procedures

The most important rolling processes for high-tech threads - especially for threaded spindles - are the grooving process, the through-feed process and the partially corrected through-feed process. In order to provide interested readers with as comprehensive an overview as possible of the thread rolling processes used in industry, further processes with the associated tools are described below, but without any claim to completeness.

Cross rollers with two flat tools

Cross rolling is characterized by two opposing flat tools (flat jaws) that engage with the rotating blank. During thread rolling, they generally move past the blank in opposite directions. There is also a variant in which one flat die is fixed in the machine while the second flat die - mounted on a slide - moves past the workpiece. This method has found its place in mass production - e.g. of standard screws - and where accuracy requirements are low. It is a standard process, but its possibilities have been exhausted.

Thread rollers with the segment roller

In thread rolling with the segment roller, three thread segments fixed in the machine body with an inlet and outlet zone press the rotating and passing blank against a rotating thread ring. The advantage of this thread rolling process is the uniform rotary movement of the threaded ring sitting on the driven shaft.

Thread rolls with rolling heads

Thread rolling with rolling heads is a process that is used quite frequently when threads are to be produced on a lathe. Non-driven tools are used. The rotary movement of the blank is generated by the machine tool. This type of production is very economical. Turned parts can be produced completely on automatic machines - including the threads - i.e. without reworking (décolletage).

Thread rolling with thread rolling dies

Due to its compact design, the thread rolling die enables the production of threaded bolts without clamping, even in the tightest of spaces, e.g. in the machining area of a machine tool. The thread length that can be produced is limited by the machine tool. After the rolling process, the thread rolling die must be turned back in the resulting thread.

A distinction is made between adjustable and non-adjustable tools. Adjustable thread rolling dies are set with the aid of a holding device. Thread rolling with adjustable dies has a not insignificant advantage in general mechanical engineering: without special rolling machines, the use of adjustable dies is extremely economical and therefore recommended for small and medium series. In the case of non-adjustable thread rolling dies, it is particularly important to specify the thread tolerances and the material in advance. Non-adjustable thread rolling dies are suitable for larger series.

 To the blog overview

Technical principles of thread rolling

Service provider in development

With state-of-the-art production methods, many years of expertise and our tool inventory of over rolling tools, we produce rolled threads that meet even the most unusual requirements:

• Gradients up to 6 × diameter 
• Spindle lengths up to 6 m
• Spindle diameter from 2 to 160 mm
• All standard profiles (M, Tr, UNC, UNF, UNEF, Whitworth)
• Multi-start threads, also as right/left-hand threads
• Steep thread profiles
• Ball screw profiles
• Special profiles
• Screw profiles (special quality and price advantages!)
• Serrations and knurling
• Conical thread
• Threads on prefabricated and/or bulky parts, e.g. also on forged parts

The 9 blogs contain excerpts from the - Library of Technology -, Volume 286, Thread rolls, included.

This book was compiled with the technical support of Kurt Husistein and published by Verlag Moderne Industrie, ISBN 978-3--30-6. 

Literature and sources

Kübler, Karl-Heinz, Mages Walter J. Handbook of high-strength screws, 1st ed. Essen: W. Girardet Buchverlag, .

http://www.hp-gramatke.de: Hans-Peters Mathematical-Technical-AlgorithmicA linguistic smorgasbord.Verein Deutscher Eisenhüttenleute (ed.): Werkstoffkunde Stahl, vol. 1 Berlin: Springer, . Apel, Heinz: Gewindewalzen: Kaltverformen von Präzisionsgewinden und Spindeln, Munich: Hanser .

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