If the wall thickness is not reached, the product is generally faulty and therefore must be discarded. If the wall thickness is exceeded, on the other hand, it creates unnecessary costs. Increased, irregularly distributed wall thickness also affects cooling time negatively, reducing the achievable production quantity per hour.
B. Eng. Max Feuerherm – Design
On the basis of our experience of almost 40 years, we offer our customers products that can be adapted to any application. An optimal combination can be achieved from the twelve PWDS® versions and eleven SFDR® variants that have been patented worldwide. Today, PWDS®/SFDR® systems are available for the manufacture of hollow blow-moulded bodies of all difficulty classes in a diameter range of 50 to 675 mm.
Our products are continuously refined: so that we can offer our customers a concept that can always be adapted to changing market requirements.
The radial wall thickness system, the Partial Wall Thickness Distribution System (PWDS®) allows the dynamic influence of the radial die gap along the parison length in accordance with prescribed programme curves. The heart of the PWDS® system is the dynamic flexible die ring (DFDR), which is moved with servo hydraulic or electrical actuators. Each PWDS® actuator is connected to the machine control in its own monitoring loop.
This makes it possible to control each actuator according to the requirements of the different wall thickness profiles and independently of other actuators. This allows the adjustment of symmetrical and asymmetrical deformations of the die ring and its displacement and any combination of these movements that influence the die gap. PWDS® works synchronously with the axial wall-thickness-control (AWDS). It has also been possible for several years to equip any PWDS® system with electrical drives. Consistent refinement of the PWDS® system has made a wide variety of designs available today. The original PWDS® variants, D1/D3/D5/D7, which were susceptible to wear and therefore required a great deal of maintenance, have been replaced by wear-free versions with improved performance due to this refinement.
These are the current, cutting-edge versions:
The SFDR® (Static Flexible Deformable Ring) unit replaces the solid mandrel: This flexible adjustable unit allows profile modifications that can be reproduced at any time and do not require de-installation of the mandrel tool. This has two advantages: During mould validation for the article, the profiling can be changed as often as is necessary. This is not possible with a profiling that has been mechanically incorporated.
The second advantage is the adaptation to changes in production. Corrections based on materials that are used in different ways or a profiling for a completely different article can be implemented quickly and easily. This allows modification times to be optimized, which is especially important for standard blow-moulded articles, since they are often manufactured with the same containers but different weights and materials or different hollow bodies with the same diameter. Market requirements and practical experience have led to systematic refinements in the SFDR® mechanism as well.
The standard SFDR® designs used today are the following:
The WDLS (Wall Thickness Position Control) that we have developed ensures that the condition that has once been optimized can be maintained permanently and the wall thickness distribution and net weight of the blown part can be held constant at the lower weight limit.