back to top
My wish lists
Save your wish list
If you want to add more content to your wish list, simply log in. If you do not have a user account, please register for the Hanser Customer Center.

» Do you already have a user account? Please log in here.
» Don't have a user account yet? Please register here.
Your wish lists
If you want to use your wish list during your next visit, simply log in. If you do not have a user account, please register for the Hanser Customer Center.
» Do you already have a user account? Please log in here.
» Don't have a user account yet? Please register here.

« Back

Your advantages at a glance

  • One login for all Hanser portals
  • Individual home page for faster access to preferred content
  • Exclusive access to selected content
  • Personal wish lists on all portals
  • Central management of your personal information and newsletter subscriptions

Register now
Deutsch
Bookmark Bookmarked
02-23-2005

More Complex Parisons Through Use of Flexring Dies

Fig. 1. Test die with 32 adjustment screws. The Flexring sleeve has been deformed excessively in order to demonstrate the principle of operation

Fig. 1. Test die with 32 adjustment screws. The Flexring sleeve has been deformed excessively in order to demonstrate the principle of operation

Flexring dies for extrusion blow moulding make it possible to change the die gap at any location on the circumference of the die. As a result, production of more complex parts now becomes feasible. In addition, application of dynamic wall thickness control can be extended to small die geometries.

Blow moulded containers exhibit increasingly complex geometries. This means that parisons must be produced with appropriate, and very specific, variations in wall thickness. With Flexring technology, an interesting alternative to conventional systems for wall thickness control has been developed that permits very precise changes in parison wall thickness.

The systems employed to date for partial wall thickness control are suitable only for dies with a diameter of more than 60 mm. Moreover, the attainable variations in parison wall thickness are limited. Furthermore, these solutions are technically complex, as Heinz Groß reports in the March issue of Kunststoffe. The author has operated an engineering office that develops new production technologies for extrusion since 1992.

Fig. 2. Bottle with variations in cross-sectional geometry produced with the test die (Photo: IKV)

Fig. 2. Bottle with variations in cross-sectional geometry produced with the test die (Photo: IKV)

Extremely pliable

The newly developed wall thickness control for blow moulding dies is based on Flexring sleeves the upper ends of which utilise a multi-wall configuration. The extremely thin, nested individual walls withstand the internal pressure produced by the melt, but are still very pliable. The changes in flow channel resistance take place exactly where they are most effective, namely, directly at the end of the die.

The Flexring sleeves are extremely pliable, as a result of which they can create very large local variations in parison wall thickness. Nevertheless, there are no abrupt changes in the flow channel, since the geometry of the Flexring sleeve changes only gradually in the affected region. Because of the low mass that has to be accelerated in this system, very rapid control adjustments can be made.

Reduced production costs

With Flexring dies, the die gap can be changed at any location on the circumference. Very complex parts can be produced in this way. In addition, Flexring technology permits extension of dynamic wall thicknness control to smaller die diameters.

Optimisation of the mandrel shape can also be simplified significantly through use of Flexring technology, according to the article, since any change in a Flexring mandrel that does not yield the desired result can be corrected immediately in the next step by backing out the appropriate screw.

The above-mentioned benefits of Flexring technology thus permit production costs to be reduced. On the one hand, the system reduces material usage as a result of the improved wall thickness distribution. On the other, cycle times are shortened, since unnecessry thick regions in the blow moulded part are eliminated. It can also be expected that, in industrial use, Flexring dies will be less susceptible to problems than dies providing partial wall thickness control.

Dr.-Ing. Harald Sambale
sambale <AT> kunststoffe.de

contact
Dr.-Ing. Heinz Groß Kunststoff-Verfahrenstechnik
Ringstrasse 137
DE 64380 Rossdorf
Tel: +49 6154 6952-40
Fax: +49 6154 6952-41


Newsletter

Would you like to subscribe to our Newsletters on plastics technology and profit from the latest information?

Subscribe here

Subscribe here