Car headlight is eye of car. Its main function is lighting, it also plays a role in beauty and decoration. Car headlight lens (also known as light distribution mirror) is the outermost transparent part of car headlight. Generally, car headlight is white and transparent, rear combination lamp is red (or multi-color) and transparent.
Figure below is structure diagram of headlight lens. Product material is transparent polycarbonate PC, and shrinkage rate is 0.5%. Characteristics of plastic part are as follows:
(1) Color is transparent, and appearance surface requirements are extremely high. Spots, gates and push rod marks are not allowed, and there are no molding defects such as bubbles, haloes, shrinkage depressions, weld marks and flash.
(2) Plastic part has a beautiful 3D shape, parting line is a spatial curve, and shape is very complex.
(3) Plastic part is large in size, high in precision, and complex in structure. There are 3 undercuts on plastic part: undercut 1 and undercut 2 on outer side, and undercut 3 on inner side.
(4) Inner surface of plastic part has patterns, inner and outer surface surfaces are smooth and rough, and roughness must reach Ra0.1.
Part design analyse

 

Mold opening direetion and Parting line

 

Parting method and parting line position of product are shown in figure above, please confirm.
Parting line confirmation
 

 

Parting line position is as shown in figure above, please confirm.

 

Rear mold clamp line is as shown in figure above, please confirm.
Part Draft Angle analyses vs texture vs steel fit condition

 

After mold draft test and analysis, there is no problem with front and rear molds.
Part Thickness analyses

 

Product wall thickness is relatively uniform, with main wall thickness being 3 mm
Mould Injection Point

 

Please confirm gate method and position. There may be 0.3~0.5 residue after gate is removed. Will it affect assembly? Cold runner, side gate injection.
Mould Layout

 

Slide&lifter direction analyses

 

 

Product Problems

 

 

Material is transparent polycarbonate PC, and shrinkage rate is 0.5%. Characteristics of plastic part are as follows:
(1) Color is transparent, and appearance surface requirements are extremely high. Spots, gates and push rod marks are not allowed, and molding defects such as bubbles, halo, shrinkage depression, weld marks and flash are not allowed.
(2) Plastic part has a beautiful 3D shape, parting line is a spatial curve, and shape is very complex.
(3) Plastic part is large in size, high in precision, and complex in structure. There are 3 undercuts on plastic part: undercut 1 and undercut 2 on outer side, and undercut 3 on inner side.
(4) Inner surface of plastic part has patterns, inner and outer surfaces have high smoothness, and roughness must reach Ra0.1.
Conclusion
(1) Lateral core pulling mechanism is the most important core structure of this mold. Mold cleverly uses inner core pulling mechanism of "T-slot guide block + oblique inner slider" to successfully solve problem of transparent parts leaving traces on the surface of plastic part due to lateral parting.
(2) Mold adopts a common casting system, which is fed by a fan-shaped gate tower connection. Compared with previous hot runner casting system, it not only greatly reduces cost, but also improves light transmittance of headlight lens.
(3) Mold adopts a combined cooling system of "vertical cooling water pipe + inclined cooling water pipe + spacer water well". Water channel is arranged along cavity, which effectively ensures precision of plastic part and labor productivity of mold.
(4) Plastic parts are pushed out by push blocks, which is not only stable, but also leaves no marks that affect appearance.
Since mold was put into production, operation has been stable and smooth, and all quality indicators of plastic parts have met design requirements. It is a successful example of design of large-scale, precise and long-life injection molds.