New to rotary die cutting? Consider this.
According to Thomas Net:
“Die cutting is a fabrication process used to convert material by cutting, forming, and shearing it into custom shapes and designs. Due to its versatility and customizability, the process is suitable for a wide range of materials and in a variety of manufacturing applications, ranging from labels to gaskets to heat shields.
“There are several types of die cutting processes employed today, including flatbed die, laser, and rotary die cutting. Generally, the process’s name indicates its particularities: flatbed die cutting utilizes a flatbed die and press, laser involves the use of a high-speed laser cutting machine, and rotary employs cylindrical rotary dies and a rotary press. The requirements and specifications demanded by a particular die cutting application—e.g., materials, sizing, tolerances, costs, turnaround times, etc.—help determine the type of die cutting process most suitable to use for it.
“While each type has its advantages and disadvantages in regards to manufacturing, this article focuses on the rotary die cutting process, outlining the basics of the process, and the components and mechanics of the rotary die cutting machine. Additionally, the article explores various rotary die cutting capabilities and the benefits and limitations of the process.
“For the rotary die cutting process to run smoothly and at optimum capacity, several factors should be taken into consideration, such as the rotary cutting machine’s configuration and settings, the material being cut and its properties, as well as the type of rotary cutting die employed.
“Rotary die cutting is a type of die cutting which utilizes custom-designed cylindrical dies affixed to a rotary press to convert material. Web—i.e., flexible material, generally in roll or individual sheet form—is fed into the press’s die cutting station, which contains a cutting die cylinder and a hardened anvil cylinder rotating in opposite directions along their horizontal axes. The interchangeable rotary cutting die, which can be a flexible or solid die, serves as the machine tool which executes the actual cutting operation, while the anvil cylinder serves as a surface against which the cutting die performs it. As web is fed through the station between the rotating die cylinder and anvil cylinder, the cutting die’s edge compresses the web against the anvil cylinder until the edge pierces through the material. This action produces the desired cuts, slits, or perforations. Afterward, the web is either rewound onto a spindle or separated into discrete parts.
“In rotary die cutting machines, the cylinders and web are run at the same speed to ensure that the die cuts are properly aligned and that they are uniform and consistent throughout the entire length of material. Typically a series of gears rotate the die in time with the press’s feed, but machines can also employ servo motors and controls to achieve even greater precision and consistency.
“Rotary die cutting is suitable for a variety of materials, including thin metal, plastic, paper, foam, fabric, and laminates. The type of web material being converted and its properties largely determine the optimal configuration and settings of the rotary die cutting press and cutting station, as well as the design of the rotary die.
“In rotary die cutting, the clearance (i.e., the gap between the cutting die cylinder and the anvil cylinder) at normal pretension (i.e., initial pressure) contributes to the cutting pressure that is applied to the web as it runs through the cutting station. The clearance is adjusted to suit a particular material based on its thickness and compressibility. If the clearance is too small, it may result in too much cutting pressure being applied, heavier die cuts, and accelerated fatigue for the machine components. And if the clearance is too large, the cutting die may not apply enough pressure to cut through the web properly.
“The material’s properties also influence the design of the rotary cutting die, such as its cutting edge geometry and bevel angle. Its thickness and compressibility help determine the necessary cutting blade height and angle. For example, when cutting tougher and thicker materials, the required blade height is much greater and the angle steeper, whereas thinner materials require a much shallower height and angle. Multi-layered materials may also mandate several different heights and angles on a single die, and complex or difficult materials may necessitate special surface treatments or coating applications.
“The same material properties help determine the type of rotary die (e.g. flexible or solid) best suited for an application. Thinner materials, such as paper or film, can be cut by either flexible or solid dies, while thicker, tougher, and more abrasive materials are generally converted by solid rotary dies only.
“Determining the kind of rotary die that should be utilized in a particular rotary die cutting application requires several considerations, including the type of material being converted (as described above), rotary manufacturing specifications, and initial vs. overall costs. The two main types of dies utilized by rotary presses are flexible cylindrical rotary dies or solid cylindrical rotary dies. Flexible dies are composed of a thin sheet of engraved metal (usually tool steel) affixed to a separate magnetic cylinder, while solid dies are composed solely of an engraved solid metal cylinder. Although both flexible and solid dies are capable of cutting most types of materials, each carries its advantages and disadvantages in regards to manufacturing applications.
“One of the most significant benefits of flexible rotary cutting dies over solid dies is cost. Because flexible dies are composed of a thin sheet of metal rather than a solid cylinder, they are simpler and less expensive to manufacture. On the whole, they can be produced quicker and in larger quantities compared to solid dies, often within the same or next business day. Additionally, these less cumbersome dies are easier to ship to and store within manufacturing facilities which saves both on shipping costs and storage space.
“Due to their comparatively low manufacturing cost, flexible dies are readily replaced when damaged or fatigued. They can also be easily switched out from process to process with little downtime. The ease of changeout allows for faster lead times and shorter turnaround. Although flexible dies are somewhat less versatile than solid dies due to construction material limitations, improvements in die manufacturing and finishing, such as the addition of special die coatings and surface treatments, have increased the durability of and amount of suitable applications for flexible dies.
“Although improvements to flexible rotary die technology have helped to bridge the popularity gap between flexible and solid dies, especially for large production run manufacturers and machine shops, solid rotary dies still make up the vast majority of dies employed, in part because of the large initial investment necessary for flexible dies to be used in production. With flexible rotary die cutting applications, a corresponding magnetic cylinder must be procured to act as the flexible die’s base cylinder. Typically, a separate magnetic cylinder needs to be purchased for each size and circumference the die will run, which greatly increases the initial tooling costs. Additionally, while flexible dies can be easily and inexpensively replaced, the tooling has much shorter lifespans and cannot be re-sharpened once fatigued, resulting in the need for constant die replacement. Even with special coatings and surface treatments, flexible dies generally do not have the durability or life expectancy of solid dies.
Image Credit: boitano/Shutterstock.com
“While the popularity of flexible dies in manufacturing is growing, solid rotary dies are still heavily used in die cutting operations today. Newer technology has improved flexible dies to some extent, but specific manufacturing applications continue to be better suited for solid dies, including thick or abrasive materials, multi-layer construction, and long or high volume production runs.
“Due to the nature of their function and application, flexible rotary dies are limited in the types of material that can be used for their construction. Solid rotary dies, on the other hand, can be constructed out of a wider variety of metals, which allows for greater versatility and customizability in regards to die design, specification, and application. The solid design of solid rotary dies allows for deeper engravings and higher die blade heights, enabling solid dies to cut through thicker and multi-layered materials. Additionally, the dies’ solid construction provides durability and longevity, allowing them to withstand more abrasive materials, greater pressures, and exhibit longer operational life. These benefits are especially useful for high volume production runs. Besides durability and longevity, one of the other advantages of solid rotary dies is their ability to be re-sharpened. Whereas flexible dies must be discarded when dulled and fatigued, solid dies can be re-sharpened and reworked several times. Although not infinite, this ability further adds to the life expectancy of solid dies.
“While an important factor, the longevity of a die may not always be the deciding factor when choosing the die best suited for a particular die cutting application. For specific manufacturing applications, especially for machine shops which already have the necessary magnetic cylinders in their inventory, flexible dies may be more cost-effective. Solid dies are more costly to manufacture and require longer lead times, which make them more cost prohibitive for shorter production runs and lower quantities. Longer lead times also limit and impede a shop’s ability to provide and complete rush jobs.
Image Credit: F & S Engraving, Inc.
“Choosing the right type of die for a rotary die cutting operation requires a comprehensive approach. Manufacturers and machine shops need to consider not only the material being die cut and the required specifications, but the initial and overall investment costs, and the optimal lead and turnaround times as well.
“Flexible dies are generally suitable for easier, less abrasive materials and shorter runs, while solid dies are more suitable for tougher, abrasive material and long-term and large production runs. Although the initial investment in flexible die technology is more expensive than solid dies due to the costly magnetic cylinders, re-purchasing the inexpensively manufactured flexible die component can prove to be more economical in the long-term. On the other hand, solid dies may be more costly to manufacture, but when cutting consistent designs in large quantities, the cost of solid dies may be justified as the dies are less likely to need replacement mid-production. Additionally, solid dies do not require the large investment in supplementary components as with the magnetic cylinders necessary for flexible dies. Flexible dies may be simpler and quicker to procure, but they are more subject to experiencing fatigue and requiring replacement. Solid dies may take longer lead times, but they are more durable and likely to last through more production cycles.
“These are some of the considerations that may be taken into account when deciding between flexible or solid rotary dies for a rotary die cutting application.
“Rotary die cutting is a versatile fabrication process suitable for applications ranging from simple die cut labels and gaskets to complex, multi-layered parts. It can be used on a wide range of materials, including thin metal, plastic, paper, foam, fabric, and laminates, and offers several different die cutting capabilities, such as metal-to-metal, kiss cutting, and perforating.
“Metal-to-metal die cutting: For lined or multi-layered materials, the type of die cutting in which the die cuts the design through the entire material, including, but not limited to, the face, adhesive, and backing material layer. The design is fully separated from the web.
“Kiss cutting: For lined materials, the type of die cutting in which the die cuts the design through the face and adhesive material layers, but not the backing material layer. The design is not fully separated from the web, but can be easily removed from the intact backing layer.
“Perforating: The type of die cutting in which the die cut design is held in place on the web material by a series of punched-in holes. The design is not fully separated from the web, but can be easily detached from the material along the perforated lines.
“Rotary die cutting presses can also employ multiple cutting stations and dies. This configuration allows for several different operations to be performed in line along with the primary die cutting operation, such as slitting, scoring, and laminating. This approach decreases the need for operator involvement and shortens the lead and turnaround times.
“Compared to other types of die cutting, rotary die cutting offers several advantages. These include:
“Rotary die cutting presses are capable of cutting a wide range of designs with a high degree of precision and accuracy. Since the design is already engraved into the die, on a well-tuned rotary press, parts are easily and repeatedly produced. The precision enabled by this process also helps reduce material waste as the die cut designs can be more tightly spaced together.
“The interchangeable rotary dies are easily replaced within rotary presses, which decreases the downtime between production of different designs and processes. The durability of the dies also decreases the need for replacement during production runs, further shortening lead times. Additionally, the dies can handle complex designs and multi-layered materials, and, on solid dies, can have multiple blade heights and angles (i.e., different cut capabilities) on a single tool.
“Compared to flatbed die cutting, which utilizes a start-stop press and stamp method, and laser cutting, which requires constant adjustment of cut speed and depth throughout a design, rotary die cutting is more efficient and allows for faster and larger production outputs. These benefits are due to the constant and continuous pressure, web feed, and cylinder rotations. Rotary presses are also able to perform multiple fabrication operations within one cycle which further contributes to the rapid turnaround times.
“While rotary die cutting demonstrates advantages over other forms of die cutting, there are also limitations to the process. While highly versatile and customizable, it may not be appropriate for every manufacturing application, and other die cutting or fabrication processes may prove to be more suitable and cost-effective. Indicated below are some comparisons between rotary die cutting and other types of die cutting.
|Advantages||Rotary Die Cutting||Flatbed Die Cutting|
|Multiple Operations (in line)||X|
|Faster Production Turnaround||X|
|Constant Cutting Speed/Pressure||X|
|Lower Tooling Costs||X|
|Max. Material Sizes||X|
|Max. Tonnage Pressures||X|
|Long/Large Production Runs||X|
|Advantages||Rotary Die Cutting||Laser Cutting|
|Multiple Operations (in line)||X|
|Faster Production Turnaround||X|
|Constant Cutting Speed/Pressure||X|
|Intricate Design Capabilities||X|
|Quick Prototyping/Design Adjustments||X|
|Large/Long Production Runs||X|
“As indicated in Table 1, above, compared to flatbed die cutting, rotary die cutting may have faster turnaround times, but the tooling is also much more expensive. There are also stricter size constraints for rotary die cutting compared to flatbed cutting. The maximum length, width, and thickness of materials that can be processed by rotary presses are much smaller due to the size limitations of the machine. Flatbed presses, on the other hand, can provide higher tonnage pressures and process thicker materials in larger and wider sizes.
“As indicated in Table 2, above, while rotary die cutting is capable of producing precision parts, laser cutting offers even tighter tolerances for more intricate design patterns. Additionally, laser cutting is better for prototyping as the process does not require the creation of separate die components to test out new designs. Adjustments are similarly easy and cost-effective as a new die does not need to be developed for each new design iteration.”
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