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November 16, 1998

7 Min Read
Adjustable Vents in Three Shots


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Editor's note: This issue's featured injection mould produces an adjustable climate control vent via three-shot moulding. Design and construction are from Fickenscher, Selb, Germany, which is also the patent-holder and manufacturer of the part.

If you want to manufacture a part consisting of five individual elements in a ready-to-install condition, the production mould has to be special. How to improve part quality and reduce manufacturing costs must be considered during design. Here is a creative solution.


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Figure 1. Climate Control vent.












A climate control vent (Figure 1) consists of a housing with louvers that can be rotated around their axis lengthwise. In addition, a linkage is connected to the louvers that permits smooth, simultaneous adjustment of all louvers and thus directional control of the air flow. The vent is assembled from different thermoplastic materials in three mould stations by multishot/multicomponent injection moulding.

The plastics are selected largely on an empirical basis and, in addition to meeting a large number of specific requirements (gloss, scratch resistance, and combustion characteristics), they must exhibit incompatibility in order to assure movement of the individual components. The three louvers are 20 percent glass-microsphere-filled PBT, the linkage is 20 percent talc-filled PP, and the housing is modified PPO. Bonding of the components must be prevented under all circumstances. The smaller the surface areas in contact, the less likely is the risk of any initial melting.


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Figures 2A (above) and 2B (below). Injection mould with three stations. (A1, A2, A3) Runners; (4) Indexing mechanism; (5, 6, 8) Slides; (12, 13, 16, 17) Split cavities; (18) Hydraulic motor; (19) Locator. 2B shows view of parting line (stationery side). (A1, A2, A3) Runners; (19) Locator; (20) Angled rod.
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Mould -- Principle of Operation

The five individual components are produced in one mould with three stations (Figures 2A and 2B). The three louvers are moulded at Station 1, the linkage at Station 2, and the housing at Station 3. The linkage operates the three louvers, each of which rotates around two projecting studs (which function as journals) and is guided by eight support surfaces in the housing. The three materials selected as components are injected simultaneously at the three stations. At the end of each cycle, three runners are ejected and the complete climate control vent is released and then removed by a part handling device.

The connecting element between the three mould stations is the indexing plate (4) which is integrated in the moving mould half. The plate advances (moving the mould sections out of the moving mould half after each cycle and after the finished part is ejected at Station 3), rotates by 120°, and then retracts. This motion transfers the moulded louvers from Station 1 to 2, and the louvers with overmoulded linkage from Station 2 to 3. When the mould starts up, the louvers are moulded at Station 1 during the first cycle. During the second cycle louvers are moulded at Station 1, while the linkage is moulded at Station 2. Injection takes place at all three stations only as of the third cycle.


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Figure 3, Station 1 -- Louvers.(1, 2, 3) Mould inserts; (4) Indexing plate; (5, 6) Slides; (21) Support journal; (22) Guide surface; (23) Tongue; (24) Linkage journal.


Station 1--Louvers

The three louvers are formed (Figure 3) by the stationary-side mould insert (1), the moving-side mould segments (2, 3), the mould core on the indexing plate (4), and the two slides (5, 6). Slide (5) serves two functions: to form the linkage journal without a parting line and to provide space for ejection of the louver runner system during mould opening. Located between the tongues (23) of the louvers are guide surfaces (22) in the shape of half-cylinders that permit smooth, defined movement of the louvers within the overmoulded housing.

Slide (6) forms both the support journal (21) and the linkage journal (24) without a parting line. In addition, this slide forms a portion of the adjacent louver edge. The reason is that space must be provided for subsequent forming of the linkage. The three louvers are filled via a runner (A1, Figures 2A and 2B) with tunnel gates. Only the runner is ejected at Station 1. The louvers remain in the mould core on the indexing plate (4) and are ejected at Station 3 only after two more cycles have occurred.


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Figure 4. Station 2 -- Linkage. (4) Indexing plate; (7, 9, 10) Mould inserts; (8) Slide; (25) Linkage.


Station 2--Linkage

The linkage (25) is formed (Figure 4) by the slide (8), the mould core on the indexing plate (4), and the three louvers from Station 1. It is also filled through a runner (A2, Figures 2A and 2B) with tunnel gate. Again, only the runner is ejected in this station.


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Figure 5. Station 3 -- Housing. (4) Indexing plate; (11, 14, 15) Mould inserts; (12, 13) Splits.


Station 3--Housing

The function of this mould section is more extensive than that of the others. The four outside surfaces are formed by the splits (12, 13, 16, 17; Figures 2A and 5). The inside surfaces of the housing are formed by mould segments (14, 15) and the mould core on the indexing plate (4). The stationary-side mould insert (11) forms the visible surface of the climate control vent. The louvers moulded at Station 1 serve to form the support area between housing and louvers. Filling is operated through a runner (A3) with tunnel gate. The completed climate control vent and runner are ejected by a two-stage ejector. The reason for this is that the ejector pins behind the louvers may be moved only at this station. And the stroke of the louver ejector pins (for reasons of space and stability) is shorter than the stroke of the ejector pins for the runner and housing. The ejector mechanism is actuated by two hydraulic cylinders integrated into the mould.

Indexing Plate--Connecting Element

The indexing plate (4) participates at all three stations in the formation of the individual moulded parts, which differ completely from one another in their geometry. Each of the three arms forms a part of the mould section at a station. The mould cores on the indexing plate shut off against other part-forming inserts or slides at all three stations. Therefore a high-precision manufacture of the mould is necessary.

Of the three slides (17) attached to the center of the indexing plate, only the one at Station 3 is in the moulding position and forms an outside surface of the housing (compare angled rod (20) in Figure 2B). The ejector advances and retracts the plate; the 120° indexing motion is performed by an hydraulic motor (18) and gear belt. In order to achieve the most accurate possible positioning when stopping, two different speeds are employed during rotation. The initial, relatively high speed is intended, above all, to minimize cycle time. The second, lower speed, which starts after rotation of about 100°, is intended to stop the indexing plate as accurately as possible at the 120° position. Final positioning is accomplished with the aid of three locating pins (19) in the mould.

Mould Temperature Control

The mould incorporates three independent cooling circuits. Extreme temperature differences within the mould result in binding due to differential thermal expansion. The temperature of the splits (12, 13, 16, 17) at Station 3 is selected to provide a good surface on the housing without visible flow lines. A change in cavity wall temperature in certain areas of the mould can have a negative impact on louver motion, and thus the functionality of the climate control vent.

Contact information
Fickenscher & Co. GmbH
Werkzeug- und Formenbau
Mr. Reinhard Krause,
Head of R & D
Am Schreinersteich 4
D-95100 Selb
Germany
Tel: +49 (9287) 9965-23
Fax: +49 (9287) 9965-65

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