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Nylon production process said

Nylon production process said

【Date】:2013-12-31 【Hit】:13643
1 , the drying temperature and manner of


The drying methods include materials , temperature and time . Drying the raw material used mainly oven or dryer hopper , the study found that both methods can only remove surface moisture and drying of raw materials, inherent moisture of raw materials can not be removed , so you should use a vacuum drum dryer to dry . Advantages dry vacuum to remove materials not only in its deep water , better use of vacuum to increase drying efficiency and prevent yellowing oxide materials . Drying process should adopt 0. 25MPa pressure steam , drying time can also be reduced to the previous 10 h 3 h, the drying temperature can be reduced to the previous 105 ℃ 100 ℃. With this drying process the moisture content of the raw material can be controlled at 0.2% or less , but also solve the degradation and yellowing material previously appearing in the drying process , the material to maintain the original flexibility .


Between the drying device and the injection molding machine is generally not directly connected to the barrel , after drying the raw material needed in the middle of the silo storage. Pay particular attention to the problem of raw material after drying sealed during storage , and water absorption occurs if the secondary storage process , in production will produce bubbles or hollow phenomenon .


2 , injection


More satisfactory injection process through a lot of experiments. The injection temperature of the first three steps of the previous four steps to a temperature of 1 to 4 above , respectively : 270 ~ 275 ℃, 280 ~ 285 ℃, 285 ~ 290 ℃ and 280 ~ 285 ℃. Then the injection rate can be changed from the previous two three , injection rate of 1 to 3 , respectively 35,60,50 ( relative value ) , which by the early injection from fast to slow to slow - fast - slow.


3, the nozzle temperature


Nozzle temperature should be below the barrel temperature, generally controlled at about 280 ℃. If the nozzle temperature is too high, there will be holes or parts parts yellow , brittle parts of severe ; If the nozzle temperature is too low, the nozzle solidified melt easily blocked or condensate material is injected into the nozzle , parts hair brittle or weld marks evident.


4 , the mold temperature


The mold temperature should be controlled at 70 ~ 90 ℃. If the mold temperature is too high , the cooling rate is reduced , thus extending the molding cycle, the dent parts or bubbles . On the contrary , the cooling rate increases , prone to crystallization of the melt flow , brittle parts , weld lines significantly .


5 , injection pressure


In injection molding , the injection pressure is a key factor. Injection pressure and injection pressure comprises plasticized pressure . Plasticizing screw plasticizing pressure should be smooth and appropriate feed , should be maintained at 60% to 80% plasticizing maximum pressure injection molding machine ; article to ensure that the injection pressure should not completely fill the cavity is preferably produced peak batch production when nylon shuttle blanks , generally maintained at 40 ~ 60MPa. When the injection pressure is too high , melt filling fast, near the gate to enter the turbulence occurs in the form of "free jet " , wrapped with air into parts, so that the workpiece surface defects clouds golden spots or flashes . When the injection pressure is too low , the raw material into the cavity slowly close the cavity wall temperature due to the rapid decline in raw material leaving the viscosity increased, and soon spread to the flow axis , so that the plastic flow channel in a very short period of time to become very narrow , greatly reducing the cavity pressure , the result will ripple the surface of the workpiece , material shortage , bubbles and other defects, sometimes brittle fracture .


6 , cooling , pressure and injection time


The length of time directly affects the quality and productivity of parts . Billet production of nylon shuttle time includes cooling time , dwell time and injection time . Cooling time is too short , easy to produce sticky mold sprue , outlet rupture and other issues, the cooling time is generally located in 8 ~ 10 s appropriate. Length and dwell time is directly related to the material temperature , melt temperature , long gate closure time , dwell time is long ; contrary short dwell time . When the dwell time is too short , brittle prone parts , dimensionally unstable , prone to dents , bubbles , etc. ; When the dwell time is too long , the product easy to stick mold . Generally dwell time in 10 ~ 15 s appropriate. Injection time determined by the second -stage injection grade , produced in the previous process of two to three injections of injection time may be different for each level of control. When filling time when appropriate , consistent parts inside and outside the stress , depression small shrinkage , color uniform , to better ensure parts of fullness . If the injection time is too short , insufficient filling materials , parts prone to dents , delamination, poor bonding , brittle hair and other symptoms, if the injection time is too long , the peak slope prone parts , yellowing , warping or even burn zoom. The total time of injection generally set at 20 s, according to three levels of distribution , can be adjusted according to actual situation between each level .


7 , nylon shuttle billet stereotypes and post-processing


Nylon shuttle blank stereotypes and post-processing is mainly to stabilize the workpiece size and eliminate stress parts , improve the dimensional stability of the parts . The absorbent can be achieved by setting the first block into the prepared cavity in the bobbin blank , then placed in water or a solution of potassium acetate ( not into it all ), the control temperature of the solution was 100 ℃, 24 h, balance. Then remove the module , wipe dry and qualified for the finished product after the shuttle blanks, can enter the next process.
Currently the world´s nylon fiber production reached millions of tons of nylon for its high strength, wear and other unique superior performance, in terms of civil and industrial been widely used.

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