Efficient sheet die adjustment technology

The design and adjustment of sheet die is the key to the sheet extrusion technology. Reasonable flow path design and multi-purpose adaptability have become the full expression of the company's technical strength. The high-efficiency adjustment technology undoubtedly represents the highest level of sheet die design and technology.

Die adjustment system with roll-controlled bearing structure
Sheet extrusion die is a key component in ensuring sheet quality. In the sheet extrusion process, the material expands from a circular strand to a flat, rectangular, sheet-like stream where temperature, pressure, velocity, and various resistance variations and factors are complex, plus the polymer itself. Due to the complex rheological characteristics of the machining process, the precise design of the sheet nose is almost impossible to achieve. The qualified die after debugging still has to face the difficult adjustment process in the production process. Therefore, some people refer to the die adjustment process as a kind of "sweating" exercise, which is evident in the workload.

Basic die adjustment system

The extruder conveys the material to the head through the screw system, which is processed into sheet products, involving complex flow processes. In order to extend the material from an approximately circular cross-section to a rectangular sheet-like stream, various types of flow passages have been designed. Such as T-die, fish-tail die, coat hanger die. Although the difficulty and cost of the coat hanger die is much higher than that of the former two, it has better flow distribution uniformity and better flow velocity distribution, thus becoming the most important structural form of the sheet extrusion die.

Although coat hanger die has many advantages, there are still too many problems to be solved, such as the rheological properties of materials, the complexity of pressure changes, the need to adapt to different formulations, and the design of runners. The limitations of its own, as well as the need for replacement of product specifications, etc., require die head design, must be equipped with a corresponding adjustment system.

In the initial flow path adjustment, the damper strip (or adjustment row) is often used to adjust the internal flow path. Based on the complexity of extrusion behavior of polymer materials, mold lip adjustment structures are gradually added to meet higher product quality requirements.

The most commonly used adjustment method is the adjustment of the adjustment rows in the flow path, usually by adjusting tension and compression bolts alternately arranged at intervals of 40 mm to 60 mm in the width of the die. Sometimes it is also designed to rotate the bolt clockwise or counterclockwise to adjust the row up and down. For flat film or sheet extrusion, it is often necessary to adjust the die lip area to adjust the flow. For this purpose, a special flexible lip was designed to facilitate adjustment.

In order to increase production efficiency, different manufacturers have successively developed an automatic controlled mold adjustment system, which automatically measures the wall thickness of different parts, and then replaces the manual adjustment by various automatic control mechanisms, and directly controls the adjustment distance, becoming the mainstream of the market; This technology is mainly in the hands of some large international die companies or extrusion equipment companies. In recent years, the domestic die technology has also made considerable progress. For example, Zhejiang Jingcheng Mould Co., Ltd. has developed a self-developed fully automatic adjusting sheet and sheet die system to open a new page for Chinese sheet extrusion technology. .

With the continuous improvement of the degree of automation, the extrusion die adjustment technology is developing in the direction of higher efficiency and more stability. The following two special foreign extrusion die adjustment technologies are introduced.

Non-stop efficient mold adjustment system

EDI Die Industries is a professional company that supplies a variety of extrusion die, and has unique advantages in the processing of sheet materials. Recently, EDI has introduced two new technologies that are suitable for the adjustment of flat seam dies. These two technologies help sheet or film processors directly adjust the film and sheet processing without stopping the machine.

Double reaction speed

According to reports, the new Autoflex VI-L die system is equipped with an innovative thermal control device. The adjustment distance of the flexible upper lip can be double that of the Autoflex VI-R, and the adjustment speed of the die lip is faster. Can reach twice the original. The standard AutoflexTM die is only equipped with a basic control system.

This system will bring the greatest benefits to suppliers. The adjustment range can reach 3.8mm, which is the maximum adjustment range that the thermoformed sheet manufacturer can achieve after the die lip is automatically adjusted. With this automatic adjustment system, the thickness fluctuations that can be obtained are only half that of the original, and therefore can more satisfy the requirements of product specifications, and can greatly save raw materials and reduce production costs. In addition, adapting to the requirements of various users to quickly change product specifications can ensure that the film or sheet manufacturing process can reach the standard process faster without the need for operator intervention.

Lubricated new structure

EDI has also improved the efficiency of its FastGapTM system, which is complemented by an improved die gap adjustment system, resulting in lubrication-free operation of the system. The new Toggle FastGapTM system uses a row of toggle linkages instead of the original lip adjustment mechanism. While reducing lubrication, the structure of the toggle lever is superior to the manual adjustment by the operator.

Both the new and the old FastGap systems from EDI use a single-point adjustment device to reduce the need to readjust the flexible die lip bolts or add a lower die lip when adjusting the product thickness. When changing the product specification in actual production, the operator only needs to use the special torque wrench provided by EDI to adjust the adjustment nut located next to the operator.

EDI's FastGap system adjusts clearance by adjusting the lip of the lower die, while the Autoflex system adjusts by adjusting the upper die lip. Compared to the usual systems, systems with both FastGap and Autoflex VI-R or VI-L have three times the adjustment capability. For example, EDI has developed a system where the lower lip can be adjusted to a distance of 5.1 mm, and the upper lip can be adjusted to 2.5 mm. Together, the two can be adjusted from 2.5 mm to 7.6 mm. Therefore, the range that can be adjusted is wider and the range of adaptation is wider.

Quick change of product specifications

Reifenhäuser is one of the world's largest manufacturers of extrusion equipment and extrusion lines with advanced technologies for a wide range of extruders and extrusion lines. Reifenhäuser's patented ISR II technology brings the shortest possible specifications for narrow-slot die change times.

In the process of sheet or thermoforming sheet extrusion, it is commonplace to replace the product specification several times in a single shift. Shortening the product specification replacement time has become a very important link for sheet manufacturers to increase production efficiency. In the thermoforming line, it is the most critical factor affecting the production efficiency.

In general, shutdown adjustments are required when changing product specifications. Use more methods to loosen the fixing bolts, adjust the adjustment bolts, and adjust by pushing and pulling to move the lower die lip to adjust the flow uniformity. Today, the amount of time and labor required for the adjustment process can be replaced by Reifenhäuser's ISR II technology.

The advantages of ISR II technology

The use of lower die lip adjustment does not require stoppage, nor does it require loosening of the fastening bolts; the entire adjustment system is designed with a special roller bearing structure, which requires less adjustment force; manual adjustment only requires adjustment of one adjustment mandrel on the operating side Yes; the roller bearing structure used to move the lip protects against excessive friction and wear on moving parts; the entire system does not require regular maintenance.

This easy-to-operate adjustment system is suitable for adjusting sheet and board production up to 14 mm that is not easily adjustable with a flexible die lip.

The ISR II structure with roller bearings facilitates quick adjustment of the parallel clearance of the lower lip. After applying this system, the time required for die lip adjustment is reduced by 85%. System investment can be quickly recovered in a short time. The ISR II system is fast, efficient, and precise in adjusting technology, and the resulting benefits are considerable. In particular, the time for a die adjustment was reduced from the original 30 minutes to about 3 minutes, and its efficiency is self-evident.