edge reasons

Equipment:

(1) small plastics injection molding machine capacity. When the products quality exceeds the actual maximum injection molding machine quality for quantity apparently it ends meet. If product quality is close to the actual injection molding machine quality, there is a problem of inadequate plasticized material in the machine barrel heating time is less, the results can not be provided adequate melt into the mold. This is only to replace the large capacity injection molding machine to solve the problem. Some plastics such as nylon (especially nylon 66), narrow melting range, specific heat greater need large-capacity plastics injection molding machine in order to ensure the supply of material.

(2) temperature thermometer untrue, clear high real low, causing the material temperature is too low. This is due to the temperature control device such as a thermocouple and millivolt meter line or the temperature difference between failure, or because the measurement points away from the electric coil aging or burn, heating failure but not found or not timely repair replacement.

(3) the nozzle hole diameter is too large or too small. Too small, due to the small diameter of the circulation of material of the specific volume increases, easily refrigeration, blocking the feed passage or consumption of injection pressure; too large, a large cross-sectional area of ​​the flow of plastic into the mold per unit area of ​​low pressure to form a shot small force situation. At the same time non-Newtonian plastic such as ABS for failure to obtain a large shear viscosity decreased heat without giving cause difficulty filling. Inlet nozzle and sprue bad fit, often occurring mold material spills, the mold sufficient dissatisfaction phenomenon. The flow resistance of the nozzle itself is large or a foreign body, plastic charring sediments clogging; spherical inlet nozzle or sprue damage, deformation, affect good cooperation with each other; Note seat mechanical failure or bias, so that the nozzle and the main road axis to produce tilt displacement or axial clamping surface detachment; nozzle diameter of the ball diameter is larger than the main channel entrance ball, because the edge of a gap in the overflow crowded nozzle increases under axial push force will cause product Note discontent.

(4) feeding a plastic frit clogging the channel. Too much lubricant agglomeration due partially melted plastic in the hopper dryer, or barrel feed zone temperature is too high or inappropriate choice grade plastic, or plastic are embedded in the plastic into the feed inlet necking position or screw From snail end prematurely melted deep trench, aggregates and melt bond with each other to form a "bridge" to plug the channel or wrap the screw, screw rotation along a circular slide, you can not move forward, resulting in feed interruption or random fluctuations . This can occur only dug channel, to be fundamentally resolved exclude slug.

(5) Nozzle cold material into the mold. Injection molding machines are usually only on account of pressure loss and straight-mounted nozzle. However, if the barrel at the front and nozzle temperature is too high, or too much material storage cylinder front end under high pressure, resulting in "salivation" does not begin to make plastic injection and mold open, the accidental and the first to enter the main road entrance In the cooling effect of the template harden and impede melt smoothly into the cavity. At this time, the front end of the barrel should be reduced and nozzle temperatures and reduce barrel storage quantity, reduce back pressure to avoid the front cylinder melt density is too large.

(6) Injection cycle is too short. Since the cycle is short, too late to keep the material temperature can also cause lack of material, the voltage fluctuation is large in particular. To be adjusted according to periodic supply voltage. Generally not considered when adjusting the injection and dwell time, consider adjusting the pressure mainly from insurance completed to return the screw that time, the charge will not affect the molding conditions, and may be extended or shortened pellets in the barrel of the warm-up time

Molds:

(1) die casting system was flawed. Flow channel is too small, too thin or too long, increase the fluid resistance. Sprue diameter should be increased, runner, runner should result in a better round. Runner or less mouth too much, lack of shooting ability; runner, gate impurities, foreign matter or carbide blocked; runner, gate rough injuries, or have an acute angle, surface roughness of the adverse impact of poor stream; stream Road not open cold well or cold well is too small, open the wrong direction; for multi-cavity mold to carefully arrange balanced runner and gate size distribution, there would only sprue or gate near the stubby type cavity can be filled while the case can not be filled in the other cavity. Runner diameter should be appropriately bold, flowing to the flow channel at the end of the melt pressure drop reduction, but also increase the farther away from the cavity sprue gate, so basically the same each cavity injection pressure and feed flow rate.

(2) mold design unreasonable. Die overly complex, multi-turn, feed inlet inappropriate choice, runner too narrow, inadequate or improper form of the number of gates; partial sectional thin products, should increase the thickness of the entire article or local, or an auxiliary in the vicinity at the underfilling runner or gate; the cavity caused by inadequate measures exhaust parts dissatisfaction phenomenon is not uncommon, this defect occurs mostly at the corner of products, deep depression, surrounded by the thick part of the thin-walled parts with side gate molding of thin pan bottom places. Designed to eliminate such defects including the opening of an effective exhaust channels, choose the right gate position in advance of the air discharge easily, deliberately trapped a local gas region of the cavity inserts made when necessary, so that the air from the insert slit overflow; for multi-cavity mold situation prone to uneven distribution of the gate, when necessary, to reduce the number of injection cavity, the cavity in order to ensure that other parts qualified.