This article will take an in-depth look at plastic crates.
The article will bring more detail on topics such as:
This section delves into the definition of plastic crates, explores their production methods, and examines their applications and benefits.
Plastic crates are specialized containers crafted for the effective transportation and storage of various goods. Constructed from either complete or partial plastic materials, they are noted for their robust durability. Although these crates may be priced higher than their wooden or cardboard counterparts, their extended lifespan and resilience make the investment worthwhile.
Typically, plastic crates are fabricated from high-density polyethylene (HDPE) or polypropylene (PP). HDPE is praised for excellent impact resistance and its ability to withstand UV degradation, while PP is admired for superior scratch resistance. To further boost these materials' durability, antioxidants and UV protectants can be incorporated during production.
The choice of manufacturing process for forming plastic crates is influenced by design and shape considerations. Each crate type is ideally produced by a specific fabrication technique. Below are some widely utilized methods for making plastic crates.
Injection molding is a process where molten plastic is injected into a secured mold or chamber, following three primary stages:
A reciprocating screw extruder is often utilized in mixing and kneading materials, channeling the prepared plastic into a mold. To shape the product, the mold crafted must feature specific attributes, usually split into two halves; one fixed and the other movable for product release. Multiple channels in the mold allow plastic filling, air venting, and overflow management.
Traditional injection molding has limitations and is less suited for crafting single-sided containers like tubs, pails, and bowls, or closed hollow products like bottles. Instead, gas-assisted injection molding is applied. Introducing inert gas fills a partially molded space, mitigating reactions and facilitating a hollow mold result.
Blow molding forms plastic containers by expanding softened plastic within a mold. Key steps include:
Similar to injection molding, blow molding uses screw extruders for adding, mixing, and heating plastic raw materials. In forming the preform, two types exist:
This method involves extruding a hollow tube, shaping it at an end within a mold.
Unlike extrusion, injection involves injecting plastic into a mold with an air core. Both methods rely on air to form plastic against the mold walls.
Injection molding is particularly favored for making plastic crates, whereas extrusion molding is ideal for crafting other hollow items like water containers, bottles, or storage tanks.
Rotational molding, or "roto molding," is a plastic casting method used for creating hollow, seamless items. Unlike blow molding, which uses pressure, rotational molding evenly spreads molten plastic inside the mold during rotation. The essential steps are:
Varieties of rotational molding equipment exist, differing in mold layouts, numbers, and rotational techniques during heating. Notable types include turret, clamshell, and shuttle machines.
The lack of high pressure in rotational molding makes it cost-effective for molds and suitable for larger items. The process can also produce double-walled crates without extra steps. Products often made include agricultural tanks, drums, bins, and insulation boxes.
Thermoforming involves heating thin plastic sheets to shaping temperature and stretching them over a mold. This secondary forming method uses pre-produced plastic sheets or films from extrusion or calendaring, involving steps like:
Thermoforming comprises methods like vacuum, mechanical, pressure, and twin sheet forming, each using different forces to shape the plastic. Vacuum, pressure, and twin sheet forming employ compressed air, whereas mechanical forming uses dies for shaping.
Thermoforming limits its application to thin-walled products, yet faces issues like inconsistent thickness, warp, and webbing, making it unsuitable for rigid container production.
Thermoformed items often include single-use containers for pharmaceuticals and food, like disposable cups, trays, or clamshell packaging.
Compression molding crafts plastic by pressing resin between molds, particularly for large thermosetting products. Essential steps in compression molding include:
Typically involving downward compression, presses can also close from below. Internal heating elements in molds soften the plastic and enable shape flow while simultaneously curing the plastic. During curing, gases may form and are removed in a degassing stage.
Compression molding is advantageous for designs incorporating fiber reinforcements, such as glass or carbon added during pre-forming. While similar to injection molding using two-part molds, it’s generally limited to open-sided containers. Items such as large bins, trays, and caps are typical examples.
Plastic crates are structured primarily in open or closed configurations. Closed crates feature detachable or hinged lids, while open ones are lid-free with grids for visible contents. Industries like delivery and food services frequently use these crates for items such as dairy, bread, drinks, meats, and seafood.
In storage or warehousing environments, plastic crates are vital for organizing, storing, and transporting goods. With handles for ease of handling, they are stackable or nestable to maximize space efficiency and come in myriad shapes, sizes, and colors designed for temperature resilience, weight handling, and impact resistance.
Creating plastic crates involves injecting plastic in molds, transforming raw material into functional products. The process starts with raw plastics fed into a hopper and channeled by rotating screws, liquefying it for molding.
The mold cavity shapes the plastic into the final design, and post-injection, the material cools and hardens under controlled conditions. Inspections for imperfections follow, with potential further processing before delivery.
Molds can bear custom imprints or logos through projecting letters in the mold. Generally, High-Density Polyethylene (HDPE) is the preferred material due to its robust thermoplastic properties utilized in crate manufacturing.
The advent of plastic crates has resolved numerous issues related to the use of wooden and cardboard crates for storing goods. Available in a variety of sizes and shapes, plastic crates offer specific applications and features to meet different needs. Customers can choose the quality of the crate based on their particular requirements.
In this chapter, we will explore the various orientations and types of plastic crates.
Plastic crates come in various stacking orientations, such as stack-nest, stacking, and collapsible designs. These differences are crucial, especially when transporting empty crates, as the volume can impact the transportation costs.
Among plastic crates, collapsible crates are the most expensive to purchase, followed by stack-nest crates, with stacking crates being the least costly.
These crates are designed in a square shape with rounded corners, allowing for efficient use of space by stacking them on top of one another. Depending on the crate's size, stacking can significantly reduce the loss of loading space compared to using loose break bulk.
While stacking crates have a rigid design, space can be saved on return trips by nesting one crate inside two others and overlapping crates during stacking. Allowing for some gaps in the rim of the crates facilitates easier transportation after delivery.
Stack-nest crates are available with various options, including swing bars, covers, or the ability to be stacked at 180°.
The internal volume of a stack-nest crate is less than that of a square-designed crate due to its vertically tapered shape. However, the effective loading space can be higher depending on the crate's size. For example, five nested crates will occupy the same space as two stacked crates of similar size with a swing bar design. The crates can be nested when the bars are swung out. A swing bar is moved from the outside or side over the top of the crate, providing support for the next crate.
The stack crate is somewhat stronger than the stack-nest crate because its bar rests on the corners, whereas in the stack-nest crate, the bar rests along the long side. The swing bar is positioned 1 to 2 cm below the rim of the crate, which facilitates easier stacking. When placing a crate on top, it should align within this rim. Occasionally, provisions are made on the bottom side of the crate to accommodate the swing bar.
In addition to the swing bar, stack-nest crates can be equipped with two cover parts that close the crate and allow another crate to be stacked on top. This cover helps prevent pilferage of the contents. Plastic crates with covers are typically up to 50 percent more expensive than those without covers.
The box can be stacked and nested at a 180-degree rotation by incorporating supports at various points inside the box. These supports require additional space. A collapsible crate features a base with sides connected via plastic or metal hinges.
Although collapsible plastic crates save space when folded and have an appealing design, they are generally not favored in trade, likely due to their higher purchase cost.
Below are some of the most commonly used types of plastic crates.
These crates are designed for various basic storage needs and come in a range of shapes, colors, and sizes. They are commonly used in grocery distribution to protect fragile and delicate items such as produce. These crates ensure smooth handling, excellent ventilation, and stability. In the grocery industry, returnable plastic crates are used: they fold for inbound trips and are rigid for outbound trips. These crates facilitate the transportation of produce between growers and supermarkets worldwide. They feature a standard footprint and six different stack heights to accommodate various types of produce, allowing for stable and efficient unit loads on pallets.
These crates are primarily used for storing food items and vegetables and are available in fully ventilated and nestable designs. They include crates used in the dairy industry, made from durable and resilient polyethylene. Additionally, custom-made plastic crates are available, designed for use throughout the entire material handling process—from farmers to supermarket displays and ultimately to customers' kitchens.
Dairy plastic crates are designed to withstand the rigors of handling and shipping dairy products. They are robust enough to endure automated stacking, sterilization, significant temperature fluctuations, and high-pressure washing. These features make plastic crates more suitable than wooden or cardboard crates, which are sensitive to washing, temperature changes, and cannot be integrated into processing lines.
These high-quality closed crates come in various sizes and shapes and are commonly used for different types of storage, including fish in the fishing industry and other food items. They are especially utilized in the fishing industry for transporting catches to holding tanks for processing. Seafood processors and wholesalers favor these plastic crates over wooden ones due to their ease of handling. Plastic crates offer smooth surfaces that avoid issues like nails and splinters found in wooden crates. They also feature easier opening and closing mechanisms compared to wooden crates, which may suffer from inconsistent craftsmanship.
These crates are designed and manufactured for various uses, available in dimensions of 600L and 400W.
These large-sized crates are primarily used for the storage and transportation of bulky items.
These plastic crates are designed with specific measurements to accommodate applications in poultry, document storage, and bread handling.
Plastic crates can be compared to wooden crates in the following aspects:
Plastic crates offer safer handling compared to wooden crates due to their design, lighter weight, and smooth finish. The reduced weight of plastic crates lessens the risk of back injuries for workers, making them a more ergonomic choice.
Plastic crates are more space-efficient compared to wooden crates, which helps reduce shipping and storage costs. They can be easily stacked on top of one another to optimize storage space.
Plastic crates offer uniformity, a range of designs, and ease of maneuverability, making them simpler to handle.
Plastic crates offer greater versatility compared to wooden crates. They can withstand temperatures ranging from -22°C to +60°C without damage, unlike wooden crates, which are prone to damage from even minor temperature fluctuations. Additionally, plastic crates have a high UV resistance.
Plastic crates are easier to clean and thus more hygienic than wooden crates. Their hygienic advantages are particularly significant in agriculture, pharmaceuticals, and the food industry. Plastic crates can be cleaned effectively with steam, water, or solvents, whereas wooden crates are damaged by steam and moisture.
This chapter will explore the applications and advantages of plastic crates.
The applications of plastic crates include:
In the dairy industry, milk crates serve an extremely important means to supply milk cans and packets across cities and towns. They are also important and efficient in shipping milk across long distances, holding them firmly and avoiding spillage. While compared to wooden and cardboard crates used in the prior years, plastic crates have now become an increasingly gained market due to their lightweight and resilient structures. Typically made of polyethylene (PE), plastic milk crates are resistant to repeated washing and ensure more hygiene in the supply process.
Plastic crates play a crucial role in the agriculture industry, providing a hygienic and efficient method for transporting goods. They are preferred over traditional wooden and cardboard crates due to their resistance to fungal growth. As a result, plastic crates are increasingly chosen for transporting agricultural produce, soil, and seeds on a large scale. Additionally, plastic crates withstand extreme weather conditions, ensuring the secure transport of perishable agricultural products. Their durability and hygiene benefits make plastic crates an essential component in the supply chain for agricultural products, enhancing efficiency and safety.
In the fisheries industry, plastic crates, fish tubs, and ice boxes are essential for preserving fish quality during transport. These crates are poor conductors of heat and are resistant to rain, heat, and harsh weather conditions, effectively protecting the ice within from melting and keeping the fish fresh over long distances. Additionally, plastic crates are easier to clean compared to those made from other materials, ensuring better hygiene. This ease of cleaning is crucial for maintaining hygiene and preventing rust, making plastic containers the preferred choice for storing and transporting fish.
Transporting fruits and vegetables over long distances requires careful handling and hygiene, as these products are perishable and sensitive to harsh weather conditions. Plastic crates are a popular choice for such transport due to their compact design and resistance to external factors. A wide variety of fruits and vegetables are routinely transported in plastic crates from one location to another. During the process, these crates are often stored in built-in pallet storage systems before being further distributed to markets.
Another major domain that utilizes plastic crates is the grocery industry. They are used for storing and transporting grocery items and also assist customers in carrying items easily around supermarkets. These crates help in efficiently supplying packaged grocery items to the markets. The durability and resilience of plastic crates ensure the easy transportation of even bulky grocery items.
Plastic crates are containers used for moving or transporting goods from one point to the other. Plastic crates are found in a variety of configurations including collapsible plastic crates, stack nest plastic crates, etc. Due to their different configurations, each plastic crate has its own unique suitable application, for example the stack crate with cover can be sealed, preventing pilferage of produce. Therefore it is most suitable for use in the food industry where the food needs to be kept clean and safe. Plastic crates also offer many advantages such as being strong, rigid, and easy to clean. They also have disadvantages of damaging the produce with their rough surface. Therefore it is wise to consider the configuration and properties of the plastic material used when opting for a plastic crate.
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