In modern production and daily life scenarios, casters have long become an indispensable auxiliary accessory. However, most of the time, they function in an "invisible" way and rarely receive special attention. Without casters, workers in factory workshops would need to rely on manual dragging of equipment weighing hundreds of kilograms or boxes of materials, resulting in slow movement and potential physical strain due to improper exertion; in shopping mall warehouses, staff transporting goods on shelves can only repeatedly load and unload for short-distance transport, wasting time and energy; even in household life, moving heavy wardrobes or sofas requires multiple people cooperating, and careless handling may scratch the floor. The emergence of casters precisely solves these "mobility problems," bearing weight with a compact structure and making the transportation of various items easy and efficient.

1. Basic Definition and Core Functions of Casters

From the perspective of product attributes, casters belong to the category of industrial accessories. Their core structure consists of two parts: a single wheel and a bracket assembly. Their main purpose is to be installed at the bottom of instruments, equipment, carts, and other products that need to be moved. By rolling the single wheel, they reduce the friction between the item and the ground, thereby enabling assisted movement, reducing manual handling intensity, and improving operational efficiency.

According to different directional movement methods, casters can be mainly divided into the following two types:

- Fixed Casters: Composed of a fixed bracket and a single wheel. The bracket cannot rotate, so it can only move items in a straight line. In the industry, they are also commonly called "directional wheels." The advantage of this type of caster is stable movement direction and resistance to deviation, suitable for scenarios requiring fixed travel paths, such as carts transporting materials along specific channels.

- Swivel Casters: Equipped with brackets that can freely rotate 360 degrees, combined with a single wheel, they can move items in any direction, commonly known as "universal wheels." To meet safety braking needs, some swivel casters also include a brake device, called "swivel brake casters" (also known as "universal casters with brakes"). When it is necessary to fix the position of an item, stepping on the brake locks the single wheel to prevent accidental sliding.

In practical applications, fixed casters and swivel casters are usually used together to balance movement stability and flexibility. The most common example is a handcart, which generally adopts a "two fixed wheels in front and two swivel wheels in back" configuration — two fixed casters are installed at the front to ensure the cart moves roughly straight and does not easily deviate; two swivel casters are installed near the handle at the rear, allowing the user to flexibly change the cart's path by adjusting the handle direction, easily bypassing obstacles. Besides this classic combination, various other combinations have evolved according to different equipment usage needs, such as "swivel caster + fixed caster," "brake caster + fixed caster," and "brake caster + swivel caster." Some equipment requiring extremely high flexibility (such as small tool carts) may use all swivel casters to achieve omnidirectional flexible movement.

2. Main Classification Methods of Casters

Casters are widely used in various scenarios, and different scenarios have significant differences in requirements for caster performance, material, load capacity, etc. Therefore, the industry usually classifies casters based on application industry and single wheel material to help users more accurately select products suitable for their needs.

(1) Classification by Application Industry

According to the usage requirements of different industries, casters can be subdivided into several categories such as industrial casters, medical casters, shopping cart casters, and furniture casters, each with its unique design characteristics:

- Industrial Casters: Mainly used in industrial scenarios such as factory workshops and warehouses, assisting the movement of machinery, handcarts, shelves, and other products. Because heavy goods often need to be transported in industrial settings, these casters require high load capacity, wear resistance, and impact resistance. Regarding material selection, industrial caster wheels can be made of iron core polyurethane wheels, iron core rubber wheels, plastic core polyurethane wheels, nylon wheels, PP wheels (polypropylene), PVC wheels, etc. Some special scenarios also use high-temperature resistant casters (suitable for high-temperature workshops), low center of gravity casters (to improve equipment stability and prevent tipping), and shock-absorbing wheels (to reduce vibration during movement and protect precision equipment).

- Medical Casters: Specifically designed for hospitals, clinics, and other medical environments, they must meet the special requirements of medical settings. For example, hospital corridors have heavy foot traffic, so casters need to be quiet to avoid disturbing patients' rest; beds and instruments require frequent turning, so casters must have high directional flexibility; meanwhile, medical environments have strict hygiene requirements, so casters must have anti-entanglement designs (to prevent threads and hair from affecting rolling) and chemical resistance (able to withstand disinfectants and cleaning agents). Common medical casters include central control wheels (mainly used for hospital beds, allowing all casters to be locked simultaneously via a central control device for easy operation by medical staff) and bread wheels (rounded shape, often used on medical carts and instrument bases).

- Shopping Cart Casters: Designed for supermarket and mall shopping carts, the core requirements are lightness and flexibility. Shopping carts are frequently pushed by customers, so casters must have low rolling resistance, allowing even elderly and children to push easily; at the same time, shopping carts need to frequently turn and weave between shelves, so casters must balance directional flexibility and stability to avoid "wheel locking" or "deviation." Most shopping carts on the market use specialized shopping cart wheels made of wear-resistant PP or PVC, which are low cost and have a long service life.

- Furniture Casters: Mainly used for furniture in homes or offices, such as beds, wardrobes, bookcases, office chairs, etc. The design focus of these casters is "floor protection" and "quietness" — home floors are often wood or tile, so casters need to use soft materials (such as rubber wheels, TPR wheels) to avoid scratching the floor during movement; also, noise generated when moving furniture can affect living or working environments, so quiet performance is an important indicator. Additionally, furniture casters have relatively low load capacity (much lower than industrial casters), and some products are designed with a "low center of gravity" structure to improve furniture stability when placed.

(2) Classification by Single Wheel Material

The performance of casters is largely determined by the single wheel material. Different materials have significant differences in hardness, wear resistance, load capacity, shock absorption, and other characteristics. In the industrial field, the commonly used single wheel materials mainly include the following:

- Polyurethane (PU) Wheels: Excellent comprehensive performance, combining high wear resistance and certain elasticity, low noise when rolling, strong adaptability to the ground, suitable for use on smooth concrete floors as well as slightly rough surfaces. It is currently one of the most widely used materials in industrial casters, commonly used for handcarts, medium-sized equipment, etc.

- Thermoplastic Rubber (TPR) Wheels: Good elasticity, excellent shock absorption, very low rolling noise, moderate friction with the ground to prevent slipping, and good oil and chemical resistance. Suitable for scenarios requiring quietness and shock absorption, such as precision instrument carts and equipment in food processing workshops.

- Polypropylene (PP) Wheels: Lightweight material, low cost, good corrosion and impact resistance, but poor elasticity and relatively high rolling noise. Medium load capacity, suitable for lightweight equipment and ordinary hand carts in cost-sensitive and relatively smooth environments.

- Nylon (PA) Wheels: High hardness, extremely wear-resistant, excellent load capacity, can withstand relatively high temperatures (usually usable in environments from -40°C to 80°C), but poor elasticity and high rolling noise. Causes relatively severe wear on the ground. Suitable for heavy equipment and high-temperature workshops where high load capacity and wear resistance are required.

- Rubber (ER) Wheels: Good elasticity, outstanding shock absorption, low rolling noise, strong grip on the ground, and slip-resistant. However, wear resistance is relatively poor, prone to wear on rough surfaces over long-term use, and not oil-resistant. Suitable for indoor smooth floors and lightweight equipment requiring shock absorption and quietness.

- Polyvinyl Chloride (PVC) Wheels: Low cost, soft material that offers some protection to the floor, good corrosion resistance, but weak load capacity and average wear resistance. Suitable for lightweight carts and furniture with low load requirements, not suitable for long-term use under heavy loads or on rough surfaces.

3. Recommendations for Choosing Casters

Due to the wide variety of casters and the differing requirements across various scenarios, when selecting casters, it is necessary to comprehensively consider the following points based on your actual needs: First, clearly identify the usage scenario (such as industrial workshops, medical facilities, home furniture, etc.) to determine the basic category of casters; second, choose casters with the appropriate load capacity according to the weight of the items to be moved (to avoid damage caused by overloading); then consider the ground conditions of the usage environment (smooth/rough, whether scratch resistance is needed), temperature conditions (high/low temperature), noise requirements (whether quietness is needed), and select suitable wheel materials and caster types. Only by accurately matching the requirements can casters fully assist in mobility, improving operational efficiency and user experience.