Parts Of Injection Mold

  

Parts Of Injection Mold

1. Fixed Clamping Plate or Top Plate  
2. Runner Stripper Plate 
3. Cavity Plate 
4. Core Plate 
5. Back Plate 
6. Spacer Block 
7. Ejector Retainer Plate 
8. Ejector Back Plate   
 9. Movable Clamping Plate 
10. Impression 
11. Sprue 
12. Runners 
13. Gates 
Fixed Clamping Plate or Top Plate

It holds the fixed side of the mold to be attached with the fixed platen of the injection molding machine. On this plate, locating ring, eye  bolt and sprue bush are attached.
Runner Stripper Plate
This plate is used in three-plate molds. The function is to cut the runner from the nozzle and pull the runner by length bolts and puller pin. 
Cavity Plate
It is used to hold cavity side of product, leader pin, guide pillar, support pin, puller bolts and finger cam with the slider attached.
Core Plate 
It is used to attach the core side of product, return pin, leader bush and split, if needed.
Back Plate
It is used to support cavity plate and to attach the hole for return pins and cooling channel.  
 Spacer Block 
It is mounted between the bottom mounting plate and the movable core back plate to give space for ejection system. The required length to spacer block depends on ejection stroke required to eject the component. 
Ejector Retainer Plate
It is used to hold the ejector pin, sprue puller, push back pin, and place for ejector pin and support pillar. 
Ejector back Plate 
It pushes the ejector pins and return pins, fixed in the plate. 
 Movable Clamping Plate
It holds the movable side of the mold like spacer block, support plate, core plate and ejector mechanism to the movable platen of the injection machine. 
Impression
When the fixed and moving platens are touching, the space formed by the cut-out portion is called impression, which defines the shape of the part. It means the space between core and cavity when molds are in closed position.
Sprue
The sprue is a tapered pathway for plastic material from machine to runner through a hole cut into a bush fixed in the Centre of the fixed platen. Molten plastic flows from the sprue to fill the cavity. 
Runners
Runners are channels or pathways machined through which the plastic melt passes from the sprue to the gate.
Gates 
Gates are small openings between runners and impression, through which the plastic melt enters the cavity. They are generally small so that the finished part may be easily broken away from the sprue and runner material.

Steps for Quality Molding

1. Sharp corners  and sudden changes in section must be avoided. This may waken the plastic molding wall.

2. Large, flat surfaces should be avoided on a mold as the plastic will not come out completely flat.

3. All surfaces on the mold should be smooth and highly polished.

4. The sprue  bush is to be designed very carefully. Its passage are to be mirror finished for allowing easy flow to resin. The sprue also needs to be small to allow the mold to be filled very quickly.
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