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Basic knowledge of mold


"Mold is the mother of industry" this sentence has been familiar, the importance  of  mold  is  increasingly  recognized  by  people,  mold design   and   mold   manufacturing   technology   has   made   great progress.
The innovation of mold processing technology, the wide application of   various   new   materials   of   mold,   the   standardization   and specialization of mold parts and components, all force us to design faster and more suitable for the development of mold. The  increase  of  speed  requires  that  the  design  section  can  be completed to the post section in about 3 days; The improvement of accuracy  requires  that  the  processing  method  of  each  part  be considered clearly in the design process, and the processing method of high precision and low processing cost should be adopted as far as possible.
The improvement of precision and speed is mutually connected. The improvement of speed must require the improvement of precision; The improvement of precision will inevitably drive the improvement of speed.
According to the overall functional structure of  plastic  mold, it can be divided into: guiding system, supporting system, forming parts  system,  pouring  system, cooling  system, ejecting  system and exhaust system.
Definition: A  plastic  flow  channel  in  a  mold  from  the  injector nozzle to the cavity. It consists of a main flow channel, a diverter channel, a gate and a retainer hole.

(I) Main flow way:
1. Definition:
The main stream refers to the section from the point where the injector nozzle contacts the mold to the diverter.
2. Points to note on design:
 (1) . The end face shape of the main channel is usually round .      
 (2).   In  order  to  facilitate  demoulding,  the   main  channel  is generally made with slope, but if the main channel passes through multiple boards at the same time, it is necessary to pay attention to the slope and the size of the hole on each piece.
 (3).  The  design  of  the  size  of  the  main  channel  should  be determined   according  to  the   flow  characteristics   of   plastic
 (4) The main stream is mostly conical in design. (as shown in the picture) When making it, please pay attention to:
  A . Small end diameter D2=D1+ (0 . 5~1mm)
  B . Radius of small end ball R2=R1+ (1~2mm)(D1   and   R1   are   respectively  the  diameter  of  the   injection        machine's exit and the ball radius of the injection head)
3. Gate cover
Due to the contact and collision between the main channel and the high -temperature plastic and nozzle, the main channel part of the  mold  is  usually designed  as  a detachable  and  replaceable bushing, referred to as the pouring sleeve or gate sleeve
 (1) . Its main function is:
  A .   Make   the   mold   installation   into   the   positioning   hole convenient and in the injection machine is  well  positioned and injection  molding  machine  nozzle  hole  anastomosing,  and  can withstand the back pressure of plastic, not be pushed out of the mold
  B . As the main channel of the pouring system, the plastic in the cylinder is transferred to the mold to ensure that the material flow reaches the cavity effectively and smoothly, there should be no plastic overflow during the injection process, and the condensate in the main channel is convenient to be released .
4.The structural form has integral and split type
Integral style: that is, the shoulder is integrated with the part that constitutes the main channel
Split pose: The shoulder is made separately from the parts that make up the main path                                                    Japanese industrial standard :JIS                    China's industrial standard :SJB

(II). Diversion channel:
Definition: The  section  between the main stream and the gate, which is the transition section through which the molten plastic flows  into  the  cavity from  the  main  stream  and  the  transition section  through  the  change  of  section  area  and  the  plastic steering  in  the  pouring  system,  so  that  the  plastic  can  be smoothly converted.
1. Section design
A . The general design section is circular
B . From the point of view of processing convenience, the general design is U shape,V shape, trapezoid, regular hexagon
C. The section shape and size of the shunt should be determined according to the  molding volume of  the  plastic  parts, the wall thickness of the plastic parts, the shape of the plastic parts, the plastic process characteristics, the injection rate, the length of the shunt and other factors.
2. The layout of the distributary has two forms: balanced feed and non- balanced feed . Balanced feed is to ensure that each feed port is balanced at the same time, non -balanced feed is that each feed port can not be balanced at the same time, generally to do mold flow analysis to evaluate

(III) . Gate
1. Definition: Gate is also called feed port or inner runner. It is the
narrow  part  between  the  diverter  and  the  plastic  parts,  also known as the shortest part of the gating system;
2. Function: can make the flow rate of the molten plastic to the diversion channel  acceleration,  the  formation of  an ideal  flo w pattern, sequence, and speed to fill the cavity, but also plays a closed cavity to prevent the reverse flow of molten material, and after forming to facilitate the gate and plastic parts separation.
3. The form of the gate:
Inside gate
Normal side gate (edge gate) :
Outside gate
Fan gate: Commonly used to form large width sheet plastic parts
Flat seam gate
Ear guard type sprue
Gap type gate
Generally point the gate
Latent gate (most of our company uses this method)
Disk ring gate
Spoke type gate
Claw gate
Garden ring gate