In the process of injection molding, the nozzle temperature is too low with cold residual, the pressure loss is large, and the product surface is prone to cold mark or stress mark, too easy to spill glue, and there is wire drawing. The common solutions to wire drawing of modified engineering plastic injection molding are:  

(1) Drop the nozzle temperature;  (2) Increase the pumping position;  (3) Reduce back pressure;  (4) Use automatic seat back;  (5) add paper or metal sheet between nozzle and nozzle — is actually to reduce the actual aperture of the nozzle;  (6) Add steel sheet in the choke;  

Analysis 1: there are two methods of back-pumping — front back-pumping and back back-pumping;  there are also two kinds of control methods — time and position (some machines are controlled by sensors on the front and back of the launch pad, most of them are input on the control panel) control;  most of the front suction is used in the case of holding pressure is particularly large, according to the characteristics of the force and reaction force, when the external pressure (large holding pressure) is eliminated, the glue at the front of the screw will exert a large reaction force on the screw to let the screw back, resulting in the "offside" of the screw, inaccurate measurement;  most of the back pumping is to deal with the high speed of the return, but also to avoid "offside" and protect the return oil seal (high-speed operation to suddenly stop, is very contrary to the mechanical convention).  

Analysis 2: to understand the offside of the screw, it is necessary to know the process of the screw melt glue back, the screw back is in uniform feeding, compression, transportation, metering in the end, if you do not eat material or eat material can not reach the actual amount, and the position is back to the corresponding amount, then the actual measurement and demand measurement will be different;  In short, the so-called screw offside is that in the measurement process, the screw does not rotate measurement but smoothly pulls back a certain distance, resulting in inaccurate measurement.