I

Outer Ring

Adjusting screw MandreI

Flex Ring Tubing

m 3:~~Mf!tUJI50U~ti,'2(fJUi II1IfoLt flS2~ 1nI ~

Figure3: 150 mm Flex Ringpipe die mountedon the line, having at its end 52 adjusting

screwsaround the circumference

Flgure2:Crosssedlon of a Flex RingDiewhlch canberetrofitted Into nearty any exlstlng annulardie by slmply modlfylng the outer ring and

Insertlng the Rex RingTublng

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~fiit1f m .fflt * eq •

MA*JiIl

Multi-Walled Seetion

~1:~I~~~Ä~~~~~gJJWI!J

Fig.1: Crosssedlon of a multl-walled ftowchannelsedlon wlth seamlesstransition

regions

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During practical extrusion there are usually a lot of small imperfections which influencethe melt stream distribution in the die in a way which cannot be forecast or calculated. Inthe process they superpose each other in a complex way. As a consequence the resultingproducts have always slight variations, regarding their thickness wh ich is not desirablebut wh ich is inevitable if using conventional equipment. Therefore to further improve thequality of extruded productsa solution has been developed wh ich enables a sensitivereaction to these changes. This leads to a degree of thickness constancy in extrudedparts wh ich is impossible with conventional dies. So not only the production cost isreduced but also the quality of the products are improved in the same time.

.~~g~~~~~~~~~F~effl~ßiJ~

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16 EXTRUSIONASIA 02/2003

I

Figure 4: 200 mm Flex Ring Die for theproduction of blown film

~~~Iz**.~~~~~~~o ~~.

~~'~Ji%tl~ t±J~,~~:tQ%tl*~Jt.Iz: -1'I'fI~:tQ~o ~~ .• OOn.mM~I~Rffi

(IKV-Aachen)[1]B~21f!$71iß~ ~.:J.:&j:\-*~m=t±JJJjiij~MiP'If1= 0 ~:tQ%~tiWt~~~~~:If'~1JQ, ~~j®IH~~~~ß~j:\-~;m@:~;~:{±j:F g:. ~~ i~mffl 0 ~ f'P~tt #: z..ffi~.:J.

~1:f§*~~2;jff1M][, ~§l~'2:1f'@J~fa:7j:F~.~fi~~~~*7~~F~~J9i:~o

~~irI*4[1] W. Michaeli, R. Pelers, T. Schmitz, Mittel zur

Prozessbeherrschung, Regelung der Wulstgröße kann

Folienqualität verbessern, Kunstsloffe 11/2002,

pp. 88.90

Technical solution

Dies have been developed wh ich makea sensitive adjustment of the flowchan ne I geometry possible while theline is running. To achieve this wallsections which are extremely flexibleand wh ich thus allow for linear elastic

deformation have been integrated atcritical locations of the flow channel.The wall of these flow channels consist

of many single walls wh ich areextremely thin and therefor extremelyflexible. These thin walls are piled upon top of each other until a totalthickness is reached wh ich can

sufficiently withstand the interna I meltpressure. There is absolutely no gap in­between these single thin walls. Theyjoin around their entire circumferenceinto a thick solid wall (Fig. 1). The wallscan be shaped three dimensionally. Dueto this special construction these singlewalls wh ich can go down to a thicknessof only 0.2 mm support each other withregard to the mechanics. The geometryof the flow channel alters gradually andthus no dead spots are created by thedeformation of the wall.

18 EXTRUSIONASIA 02/2003

Examples of the integration of multi­walled flow channel seetions into

practical dies

Production lines for pipes have beenequipped with Flex Ring Dies. Fig. 2shows a cross sectional drawing of aFlex Ring Die, and Fig. 3 is an exampleof a Flex Ring Die in production. Bymeans of a locally limited deformationof the Flex Ring Tubing, the lineoperator is in the position to furtherreduce thickness tolerances wh ich

remain in the pipe after the die hasbeen centered in an ideal way. Flex RingTubings can be retrofitted into anyexisting pipe die. Even thicker regionsof a produced pipe which arepositioned opposite of each other cansimply be eliminated by reducing theflow channel gap exactly at theselocations independently. A producer ofsmall pipes made of Polyamindereported that he has reduced the start­up time of his line by 40 % and thethickness tolerances in his 30 mmdiameter pipe by 50 %. Fig. 4 shows asanother example a Flex Ring Die toproduce blown film.A great adjusting range is required inthe blow molding process when youintend to change the thicknessdistribution around the circumference

of the parison while it is extracted. Inthis application the task is to match thethickness at every point ac ross the areaof the parison with the wantedthickness and the draw ratio wh ich

exists at that special location. Fig. 5shows how enormously the Flex RingTubing can be deformed at the orifice ofa small test die.

Fig. 6 shows a solution for integrating aFlex Ring Tubing into a feed block tocoextrude a pipe with a foamed PVCco re and a compact solid outer skin. A

photo ofthe Flex Ring Tubing is shown

I!I 5: 43 i*~ t~.ff-t ~!iitiiX~m0l:tr.J~ ~%

Figure 5: Enormous deformation of a 43 mmFlex Ring integrated into a test die for

extrusion blow molding

in Fig 7. With this construction the flowchannel gap of the coextrusion flowchannel can be optimized at everywanted time while the line continues torun.

Finally partial multi-walled flow channelsections can be integrated into feedblocks for the coextrusion of sheets and

films with further reduced layerthickness. Fig. 8 shows a three layerMembrane Feed Block opened at its oneparting area which is used to coextrudea thin UV-protecting layer on both sidesof a PC sheet. With that solution the

distribution of the expensive UV­protecting layer can sensitivelyadjusted during the production at anywanted time or occasion.

Nearly every coextrusion process canprofit from flow channel sections

1!16:-t~~t~~~~~~*tr.J~~~.m*~-~~fl~~Z~~~~~

if;~9~~tr.J~~tt.

Figure 6: Drawing of a Flex Ring Feed Blockfor a pipe to cover a foamed PVCcore with a

solid outer layer

consisting of an adjustable multi-walledarea. Such membranes make a fine

tuning of the flow channel designpossible while the line is running. Thisis always of interest when somethinghas slightly changed during theprocess. For example, when thethickness of a layer is reduced, achange of the throughput rate for thecoextruded material happens as aresult. When the resin is changed itleads to deviated material behavior. For

the first time the incorporation of amulti-walled adjustable flow channelsection within a die brings the operatorinto the position to further reduce layerthickness tolerances in the final

product. He can do this without beingforced to stop the line, to dismantle thedie and to rework the flow channel

geometry. Once the flow channel isreworked in this way the processcannot be reversed.

Future aspectsIn the long run it is desirable to adjustthe flow channel situation

automatically, in order to establish athickness-controlled extrusion process.For some processes this is totally newso that the necessary control strategies

m 7: =~~~~i~(A-B-A ~>.'2f11j -Htiff.M 1jJ((.j-1'~tHf.

Figure 8: Three layer Membrane Feed Block(A-B-A-structure) opened in one of its two

parting areas

will still have to be developed in orderto establish a close loop contro!. Forthis purpose preliminary work hasalready been started on the part of theInstitute of Plastics Processing (I KV­Aachen) [1] in the field of film and sheetextrusion. The demand for control

systems will certainly increase so thatmulti-walled flow sections will further

be integrated into production lines. Thegreat economic value of the newtechnology is based on the fact that itnot only reduces production costs butthat in the same time the quality of thefinal product is improved.

References

[1] W. Michaeli, R. Peters, T. Schmitz,Mittel zur Prozessbeherrschung,Regelung der Wulstgröße kannFolienqualität verbessern, Kunststoffe11/2002, pp. 88-90

I!J 7:öl'i1!J4 81Ii~((.j~Im1f, fIIj~~~~((.j,

ljJi8];q~~}t~)jffiU~.

Figure 7:Flex Ring Tubing integrated into feed block offig. 4 being solid at its both ends and multi­

walled in its middle region

Dr. Ing. Heinz Gross Kunststoff-

o VerfahrenstechnikRingstr. 137, D-64380 Rossdorf

O. Tel.: +49 61 54/69 52 40, Fax: /69 52 41heinz-gross@t-online.de;http://home.t-online .de/ho me/heinz-gross

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• mJl~. 1%~~Q$J;:f*~1t ~• ~9JHIJ~~F~• ~f<:J*;.R.ilii~fQ ~~~&§• KARO~~t!1:f$fJl• ±~iJllfQjjJfi1~• !l*~F~~!mff• .::-'fi.\i:fi~~fQtl}imJIf'F

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Brueckner:Extensive Service Activities

• Brueckner Machinery Oiangyin) Co,. Ltd.In order to further develop the servicepresence in China, Brückner hasestablished this subsidiary company with a

production location in jiangyin, JiangsuProvince, and a sales and service office inShanghai.

• Brückner ServTec GmbH

The recently established company hasbeen formed to focus on the service needs

of Brückner cust6mers specializing forexample in the following scope ofactivities:

• Spare parts. repairs, retrofits, cleaning• Personnel services and service

contracts

• Upgradings for mechanical andelectrical equipment and software

• Special purpose lines• Condition monitoring and teleservice• The KAROlab-stretcher program• Training and seminars• Une relocations• Trade and mediation of used machines

• Brückner Formtec GmbH

The company is one of the world's mostrenowned manufacturers of Film and Sheet

Unes for the processing of raw materials,such as A-PET, PETG, PC and PP. Thecompany has successfully instalIed severallines in P.R.China in recent years .The product programe has meanwhileexpanded by compact extrusion and sheetextrusion lines with new applications forthe automotive industry and for themanufacture of technical appliances, ·suchas refridgerators. In particular in the PETfilm and sheet field, extrusion applyingtwin screw systems has proven to be mostsuitable for special applications.In the course of a technical seminar to be

held during the Chinaplas, BrücknerFormtec will give a presentation on thisrevolutionary technology.

;,-- Karlheinz Weinmann

Brückner Maschinenbau GmbH,

Königsberger Str. 5-7, 83313 Siegsdorf

Phone.: +49-8662-63-278,

Fax: +49-8662-63-220Email: karlheinz.weinmann@brueckner.de

> Phillip Chen

Brueckner Far East Ud.,

801 Eton Tower, 8 Hysan Avenue,

Causeway Bay, Hong Kong

Phone: +852-2882-1412,

Fax: +852-2882-1023,

Email: pcbfe@netvigator.com

EXTRUSION ASIA 02/2003 19