T O O L I N G

The mold concept for gating

from two sides is currently

undergoing field test

Double Sided Gating with Needle Valve Glass Substitute. A new hot runner system was reeentiy developed for the p ro ­

duet ion of pref i l lable disposable syringes of COC, w i t h its core component being a

sidegate needle valve nozzle tha t was tai lored to comply w i t h these plastics' high

viscosity and temperature sensit ivity. It provides for safe processing and high gat ­

ing qual i ty , wh ich is critical w i t h pharmaceutical packagings. The modular design

of the mold enables produet ion of d i f ferent syringe models in a variety of sizes and

w i t h various t ips.

E V E L I N E G E P P E R T

S W E N S P U L L E R

P harmaceutical primary packagings such as ampules, vials or prefillable syringes pose high demands to the

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materials employed. The packaging must protect the pharmaceutical from environ­mental impact, not reacting with its Con­tents, so as not to affect the stability and therapeutic effects of the substances. While glass used to be the preferred ma­terial, it is increasingly replaced by plas­tics today.

Mainly cyclic-olefin-copolymers (COCs) are used for these applications.

Th eir purity and transparency equals th at of glass, while the materials have better chemical and physical properties: They are lighter, though more break-resistant than glass, while offering excellent barri-er properties against water steam, and they have only a minimum share of ex-tractable substances that might react with the pharmaceutical, thus complying with pharmaceutical regulations.

© C a r l Hanser Verlag, Munich Kunststoffe i n t e r n a t i o n a l 11/2013

T O O L I N G

Fig. 1. In the nozzle special ly developed for side

gating, the needles move at right angles to the

mold's opening direction

Prefillable Disposable Syringes - A Difficult Subject

Due to the demand for vaccines growing at a global scale, and as a result of the rise in the biopharmaceutical market, prefill­able disposable syringes for injectable medicine are increasingly required. They are comfortable and safe to use for both the physician and the patient. In addition, they are more cost-effective, because less medicine remains, as eompared to the ampule-syringe combination, which is particulariy interesting i f used with ex-pensive biopharmaceuticals.

However, manufacturing these prefill­able syringes from COC means an enor-mous ehallenge to plastics processors: First, the syringe bodies' tube-shaped geometry with its narrow, long cores, and with its openings on both sides, calls for side gating. Second, processing COC in­volves high demands in terms of mold de­sign and hot runner layout. Cyclic-olefin-copolymers are highly viscous and ex-traordinarily sensitive to temperature im­pact - possibly leading to pressure loss, with the high injection speeds required. Quality requirements to dimensional sta-bility and hygiene for pharmaceutical packagings make high process safety and clean and hygienic gating crucial aspects to be considered during produetion.

Layout for Stressfree Material Processing

For lateral injection molding, Otto Män­ner GmbH in Bahlingen, Germany, spe­

cialist in precision forming and hot run­ners, offers a hot runner system with nee­dle valve nozzles (type: Sidegate). In this nozzle specially developed for side gating (Fig. 1), the needles do not move in the di­rection of mold close and open, but rather in a right angle. The nozzle body, includ­ing its pneumatic unit, sits in mold direc­tion, as usual. At the same time, a pneu-matically driven control needle operates the valve needles positioned vertically. Thanks to this patent nozzle, the user is

creased in the sidegate nozzle for COC processing, in order to step up the flow di-ameter inside the nozzle itself, too, thus diminishing the high pressure losses in­cluded in these special polymers. This way, components with signifieantly higher weights and/or volumes can be produced by injection molding. The valve needle of the new nozzle, in analogy with the other needle valve nozzles of the supplier from Baden in the Southern part of Germany, is precentered right in the nozzle.

Fig. 2. Sidegate needle valve system: To eliminate the issue of weld lines, large syringes are given

two gating points, one at each side

able to make use of the benefits provided by the Männer hot runner Systems with cylindrical needle valve, i . e. defined open and close of the needle valves, gating qual­ity, material saving, and, most of all, the high process safety- even with side gating.

High pressure is required when pro­cessing cyclic-olefin-copolymers, due to their high viscosities. Featuring large flow diameters, Männer hot runner Systems al­low for processing of the plastic material in a way as stressfree as possible. More-over, the needle opening stroke was in-

To comply with the small temperature window that exists when processing cyclic-olefin copolymers, the sidegate nozzle was segmented into several com­ponents lined with different isolating or conduetive materials, respectively. Along with additional active heating and con­trol areas for each nozzle tip, and, i f required, for the nozzle flange, this main-tains an optimum temperature profile over the entire flow path. In-house tests proved the nozzle's reliability: Not even after 30 minutes of residence in the hot

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T O O L I N G

Fig. 3. The various cavity inserts of the mold are exchange-

able, thus enabling the produetion of different syringe sizes

Fig. 4. The stripper plate moves forward to demold the syringe bodies ( f i gu res : M ä n n e r )

runner system at processing temperature did the melt show any degradation effects.

Two Gating Points and a Safe Demolding Mechanism

Männer uses two gating points, each at the side walls of the component (Fig. 2), thus eliminating weldlines in larger sy­ringe bodies. A 2-fold hot runner and two singie-point nozzles are employed here. The concept was specially developed for this application, reducing flow paths of the highly viscous melt and improving cavity filling when producing large tube-shaped bodies.

Injection at the side walls ineurs de­molding of the syringe bodies at a 90° an­gle to the valve needles. At closing, the nee­dle dips into the molding by a few hun-dredth of millimeters. So as to prevent the valve needle from damaging the surface of the syringe body at demolding, the needle

experienees a brief back stroke when the mold opens. During this patent back stroke movement, the valve needle remains in the connecting orifice, thus avoiding un-controlled exit of the melt. The needle, which is still heated from the friction of in­jection, is removed from the molding by the back stroke. This way, better cooling behavior of the sprue is achieved along with a flawless surface - even though it is impossible, due to the small space avail­able, to include active cooling in this area.

The mold System serving to produce disposable syringes of COC consists of a modular mold with two cavities and a 4-fold hot runner System with four singie-point nozzles (Fig. 3). Exchangeable cavity inserts allow for various sizes of syringes to be manufactured. Large syringe bod­ies are injection molded from two gating points each, small syringes from just one. A stripper plate helps demold the syringe bodies (Fig. 4).

Flexible Mold Solution for up to 64 Cavities

Other than with conventional units with their mandrel and stripper plates sitting at the moving side, these structural ele­ments are integrated at the side of the nozzles, here. This is how this mold Solu­tion offers perfect freedom of design at the ejector side, concerning the syringe tip, be it for instance a thread or luer lock, enabling the produetion of complete dis­posable syringes by overmolding a nee­dle insert. The concept (patent pending) allows for up to 64 cavities, and is cur­rently undergoing field tests. •

T H E A U T H O R S

E V E L I N E GEPPERT, b o r n in 1 9 6 9 , is a m a r k e t i n g

C o n s u l t a n t a t O t t o M ä n n e r G m b H in B a h l i n g e n ,

G e r m a n y .

S W E N S P U L L E R , b o r n in 1 9 6 9 , w o r k s in t h e

R e s e a r c h & D e v e l o p m e n t s e c t o r o f M ä n n e r .

A Whole Case of Safety Mold Insert Leak Pressure Test Unit. Checking temperature control cireuits for density is part of toolmakers' everyday business. Until today, this could only be done with the mold sitting in the machine. Should the tempering medium leak in a certain spot, elaborate work has to be done. The mold must be dismounted from the

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machine to detect the leak. And it must be cleaned before it can be remounted.

The patent mold insert leak pressure test unit by Strack Norma GmbH &Co. KG in Lüdenscheid, Germany, named Z7755, now allows for testing the mold before mounting. Potential leaks can thus be eliminated beforehand. Set-up and idle times are considerably reduced, because mold set-up is accelerated. According to

producer information, this saves 90 % of costs.

The Z 7755 kit eomes with the test unit itself, along with three pairs of different size adapters that can be used for the com­mon M5/M6, M8/M10 and M12 sizes. All components are supplied in a handy stor­age case. Customers have the option of ordering a test pump and connector.

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© C a r l Hanser Verlag, Munich Kunststoffe i n t e r n a t i o n a l 11/2013