Car ,automotive Grille Mould makers in China,car trim mold manufacturers
Every designer of plastic car grille moulds keeps three factors or elements in mind, consciously or subconsciously, as he proceeds with a design.
- the design of the finished grille part or casting;
- the skill and the equipment of the men who will actually make the grille mould;
- the experience or preference of the designer himself.
Obviously, there are occasions when one or other of the factors will be of more importance than others.The alternate designs to be reviewed are not exceptions. The fact that the shop which was to build the grille moulds had better than usual lathe operators with adequate lathe and surface grinding equipment available was naturally taken into consideration. It is also logical that any designer will lean toward features of design which have proven successful in practice.
Another element which influences car grille moulds designt and which will become more and more important as many grades of steel become more difficult to secure, is economy of design to conserve metal. This will include designs which will be practical with a second or third choice of metals when the first choice is not available.
Figures 50, 51 and 52 show an alternate design for the ink bottle cap of Fig. 47. The main parts of the mould are round, and they may be completely machined in a lathe, as might be convenient in a mould shop which has little lathe work and much shaper and mill work ahead. This is an example of the influence of the mould shop’s equipment on design.
Details 9, 19, 20, 21 and 22 make up the injection or cover-half assembly of the mould. This mould half is clamped to the stationary mounting plate of the moulding machine and the slot or groove (detail 3) is provided for this purpose.
The ejector mould half consists of the following parts-details 2, 4, 5, 6, 7, 12, 13, 15, 16, 17 and 18. This mould half assembly is fastened to the movable mounting plate of the machine in a manner similar to the injection or cover mould half. In both cases a register (detail 11) is provided to facilitate mould setup in the moulding machine.
To understand the construction of this mould design, let us follow the plastics material from the time it enters the mould until the mould is opened and the casting removed. The plasticized material enters through the tapered hole in the sprue bushing (detail 22) toward the sprue pin (detail 5) and is directed to the six cavities (cavity insert, detail 20) by runners or gating (detail 23). At the completion of the cooling period (detail 8 shows one of the water lines), the mould is opened or parted where the core and cavity retainer plates meet (details 6 and 19). The moulded shot or casting will shrink to the raised cores of the core inserts (detail 17) and the sprue will be pulled from the sprue bushing due to the undercut on the sprue pin.
How Ejector Rods Function on car grille mould
Several types of injection moulding machines are equipped with adjustable ejector rods which operate essentially as follows: Assume the machine opens eight inches and the casting must be pushed out of a one-inch cavity or off a one-inch core. When seven inches of the movement is accomplished the ejector rod will strike the ejector plate (detail 12). The ejector rod itself is detail 1. If the plate travels toward the parting line plane, the ejector pins (detail 16) will lift the casting off the raised cores, the sprue pin (detail 5) will protrude from the core retainer plate, and the casting will be free to fall or to be moved from the mould. Surface or push back pins (detail 7) will be pushed out of the ejector mould half in the same manner as the sprue and ejector pins. The surface pins push the ejector plates along with the ejector pins back into the moulding position by contact with plate 19 as the mould closes.
The ejector box (detail 2) can be of cast iron, burned out of machine steel or machined out of the solid. The latter method is rather costly and sometimes wasteful if the ejector box is deep. The box is lathe machined and later finished by grinding the surface that fits against the core retainer plate. The box is fastened by four socket head screws through a clearance drilled hole in the core backing plate into tapped holes in the core retainer plate (detail 6). In many cases the ejector plates (details 12 and 13) are cold rolled steel—the ejector pin retainer plate (detail 13) is drilled first for all holes. The holes are countersunk to provide for peening on the drill rod pins (peened before hardening). The ejector pin retainer plate is then fastened to the knockout side of the ejector plate. The plates can be machined together. Ample clearance all around should be allowed for the plates where they fit into the ejector box bore.
The core insert back-up plate (detail 15) in this case is specified to be made of alloy steel to provide resistance to sinking of the cores in service. This plate is lathe machined and ground on both sides. All pin holes are clearance drilled with the exception of the sprue and surface pins—these should be lapped fits. Four socket head screws (detail 27) extend through this plate into the core retainer plate (detail 6). Some China car grille mould makers believe that it is advantageous to place socket head screws close to the inserts to prevent moulding carbon, formed by gases present in moulding, from forming under the cavity inserts, thus assuring a cleaner and more positive mould.
The boring of insert retainer holes in the core and cavity retainer plates (details 6 and 19) must be done carefully; guide pin bushing and sprue pin hole must also be bored carefully since mating core and cavity inserts (details 17 and 20) are nitride or matched before assembly and ground for parallelism. The guide pin bushings (detail 18) are press fitted in this core retainer plate (detail 6). The guide pins (detail 21) are press fitted in cavity insert retainer and cavity back-up plates. The cavity insert back-up plate is made of alloy steel, lathe machined as is its counterpart, the core insert backing plate.
Changeable Inserts on car grille mould
This mould is designed so the cavity and core inserts may be removed after the run is completed. Thus a fully constructed holder mould or mould shoe is left for future use and a variety of inserts of the same diameter and height may be installed therein. This feature is particularly valuable to the shop where a variety of items is moulded of approximately the same size or complexity.
Since no side or parting line cores are required in this mould the guide pins are extended from the injection or cover mould half. Because the car grille mould is an ejector type design, the pins do not have to guide or carry a stripper plate. The advantages of this type of design are:
- longer guide pins may be used since they are not in the operator’s way;
- the finished casting is free to fall or be removed without obstruction;
- the use of a swinging or brush-off bar as furnished with some moulding machines is facilitated.