This is an introduction to injection molding process of headlight reflectors, which is suitable for production of headlight products and has a guiding role in processing of BMC products of headlight companies. Because BMC materials are also used in many other industries, they only serve as a reference.

Product name: headlight reflector product
Product features: reflective part inside main functional area, village material BMC, shrinkage rate */1000, wall thickness 3mm. Adopt rectangular gate side injection. Processing technology: thermosetting single-color injection molding, one mold with two products on the left and right, UV paint sprayed on the surface to increase surface effect, and vacuum aluminum plating on outer layer.

 

BMC materials are processed by thermosetting injection molding machines. Size of equipment is determined according to size of mold and weight of product, etc.
KM420 injection molding machine: horizontal two-platen thermosetting injection molding machine, processing material BMC, main product headlight reflector

 

Barrel and screw materials of BMC injection molding machine are processed with wear-resistant materials, and screw also has a three-piece set.

 

BMC materials are lumps and require a special feeding device. There are structural differences between domestic and foreign machines. Most injection molding machine manufacturers have ability to make thermosetting injection molding machines.

 

BMC molds need to be heated. There are two ways to heat mold: electric heating and oil temperature machine heating. It depends on how product is designed.
Auxiliary machine introduction
(1) Mold temperature controller
Function: Control and maintain mold at a certain temperature through a certain medium (water, oil, etc.) or through electric heating.

 

BMC barrel requires a constant temperature device to control temperature within processing range.
Auxiliary machine introduction
(2) Constant temperature machine
Function: Control and maintain equipment barrel at a certain temperature through a certain medium (water, oil, etc.) or through electric heating.

 

Introduction to main structure:
(1) Single-color mold, 2 products per mold, 1 fan-shaped side gate for glue injection at both ends.
(2) Mold adopts an oil heating system and is equipped with a high-temperature oil nozzle interface.
(3) Top and side of mold are attached with an insulation layer.
(4) Cavity is processed with exhaust grooves.
(5) Demolding adopts a matching ejector pin to eject and force it back.

 

BMC material is a thermosetting material. There are differences in properties of BMC materials for different uses. Specific performance should refer to physical property table provided by supplier.

 

Difference between thermosetting materials and thermoplastic materials:
2. Definition of two types of plastics
(1) Thermoplastic plastics: refers to plastics that melt when heated, flow into a mold and cool to form, and melt again when heated again: that is, they can be heated and cooled to produce a [reversible change] (liquid to solid), which is so-called physical change.
(2) Thermosetting plastics: refers to plastics that, when heated, will cause their molecular structure to combine into a network. Once combined into a network polymer, it will not soften even if heated again, showing so-called irreversible change, which is caused by changes in molecular structure (chemical change).
BMC materials should be sealed and packaged:

 

Viscosity of BMC materials will change over time.
Explanation of BMC material viscosity change
(1) Production time: date on which material is produced by BMC manufacturer. Date of transportation and storage for 10 days is date we are allowed to use.
(2) Use date: effective use period, which is date on which we are allowed to use it. In principle, the best use date. Early or delayed use requires process verification and permission.
(3) Kettle number is a number used to distinguish different processing equipment of same batch of materials from material manufacturer. It can be tracked by manufacturer when using it.
(4) A feature of BMC material is that wetting effect and viscosity of material change with extension of storage time. Generally, storage time is short (within 15 days), wetting effect is poor, product fluidity is good, additive is easy to volatilize, and product is prone to air trapping pits. Long storage time (more than 25 days), wetting effect is good, fluidity becomes poor, pitting and pitting defects are prone to occur during use. Changes in injection molding process parameter monitoring are mainly reflected in maximum injection molding pressure and conversion pressure. Pressure value is small when storage time is short, and it will gradually increase when storage time is long.

Main focus:
(1) Mold should be heated 4 hours in advance.
(2) Align mold with positioning hole according to reference line.
(3) Press mold with a pressing plate.
(4) According to mold process requirements, connect mold heating oil pipe, one set for front and rear molds.
(5) Return mold position, ejection position, and shooting platform position to zero.
(6) Adjust injection molding parameters and robot parameters.

 

BMC mold cleaning guide
Main focus:
1. Retracting table.
2. Wear gloves.
3. DOP oil is heavy, fold it in half and apply it evenly on the non-woven fabric.
4. Focus on cleaning the surrounding areas, and focus on cleaning the sticky parts found during inspection.