Parting plane for bezel

For the laptop bezel, the parting line can be radiated outward to form the parting surface. it can be observed that all of the out of plane feature along the parting line now become complex surfaces on the parting plane. These surfaces pose two significant issues during mold operation.First,any misalignment between the sharp features on core and cavity inserts will cause wear between the sliding surfaces if not an outright impact between the leading edge of the core and the mating cavity surface.

Cavity and Core insert Creation

With the definition of the parting plane and all necessary shut-offs,the core insert and cavity insert have been completely separated.To create the cavity and core inserts,the length,width,and height of the inserts must be defined.

All of these requirements suggest making the core and cavity inserts as large as possible.For smaller molded parts,increasing the sizing the core and cavity inserts may have little added cost. 

However,the cost of larger core and cavity inserts can become excessive with increases in the number of cavities or molded part size.

The mold layout design assumes that the number of mold cavities and type of mold has been determined.To develop the mold layout, the mold opening direction and the location of the parting plane are first determined. Then, the length, width,and height of the core and cavity inserts are chosen. Afterwards,a mold base is selected and the inserts are placed in as simple and compact a layout as possible.It is important to develop a good mold layout design since later analysis assumes this layout design and these dimensions are quite expensive to change once the mold making process has begun.

Mold base Sizing

The size of the mold base is determined primarily by the area required to accommodate the designed cavity layout.A primary issue, however,is the potential for conflict between the placements of the cavities and other mold components(such as leader pins,guide bushings,and others).Furthermore,there is the potential for conflict between cavity support systems(such as cooling lines,ejector pins,support pillars,etc.)

and other mold components(such as leader pins,guide bushings,and others.)Due to these conflicts, mold bases are often sized larger than what would first be considered.

Overview of injection molding process

An operating injection molding machine is depicted in figure 1.1.Injection molding is called a net shape manufacturing process because it forces the polymer melt into an evacuated mold cavity,after which it cools to find desired shape.

While molding processes can differ substantially in design and operation,most injection molding process generally include plastication ,injection,packing,cooling, and mold resetting stages.During the plastication stage,the polymer melt is plasticized from solid granules or pellets through the combined affect of heat conduction from the barrel of the molding machine and into the mold,The molten resin travels down a feed system ,through one or more gates and throughout one or more mold cavities where it will form one or more desired products.

Over the years we have been taken advantages of with the low cost of plastic injection mold manufacturing in China. You get what you pay for. I have heard of an injection mold cracking in half just last year from China, water poring out of it in the press. As an injection mold maker back in the 80's and 90's we started to see import steel making its way to our machines. We could tell on theCNC's or polishing we were not getting what we bargained for. After heat treat OMG, warp. We use to say they put old "bed springs" in the alloy mix. When drilling a hole in this steel it would not be constant feed rate by hand, you could feel the drill push easy then hard etc. So we had to be very precise in ordering our plastic injection molds with certification. We ordered 4 large injection molds from a Chinese manufacturer in 2004, the heat treat was horrible, we did not get our certification, it looked fake. Someone was trying to pull a fast one. I hardness tested several blocks from the plastic injection molds, not good. We spent approx $450,000 for those injection molds back in 2004 and we tried to outsource and handle the engineering real close. We tried to do everything real and it back fired. These injection molds were for electrical components and tolerances on my parts were critical, 4 to 8 cavity molds, the quality was just not there. Glass filled nylon wore down these plastic injection mold in 8 months, we had to retool.

Chinese Injection Mold Making Companies Development Trends