Mold temperature affect the molding cycle and forming quality, which in practice is set by the lowest appropriate mold temperature starting material, and then according to the quality of the situation to appropriate increase.
Correctly speaking, mold temperature refers to the temperature of the cavity surface at the time of forming, and it is important not only to maintain the proper temperature but also to distribute the conditions uniformly in the mold design and molding process.
Uneven mold temperature distribution, will lead to uneven shrinkage and internal stress, so that the forming mouth prone to deformation and warpage.
Increase mold temperature to obtain the following effects:
Addition of product crystallinity and more uniform structure.
So that molding shrink more fully, after shrinkage decreases.
Improve the strength and heat resistance of molded products.
Reduce the residual stress, molecular orientation and deformation.
Reduce flow when filling negative resistance, reduce pressure loss
Make the appearance of the product more shiny and good
Increase the chances of burrs on the molded product.
Increase near the gate parts and reduce the length of the gate part of the sunken opportunities.
Reduce the obvious degree of binding line
Increase cooling time
Pressure regulation in injection molding Whether in hydraulic or electric injection molding machines, all the movements in the injection molding process generate pressure, and with the proper control of the required pressure, a reasonable quality product can be produced.
Pressure Regulation and Metering System In a hydraulic injection molding machine, all the movements are carried out by the oil line responsible for:
Screw rotation in the plasticizing stage.
Slider channel (nozzle near the nozzle bushing)
Axial movement of the shooting screw during injection and dwell
Closing the substrate to the projectile rod until the toggle lever is fully extended or the piston clamping stroke is completed.
Start the assembly ram to eject the part
On full voltage machines, all the movements are performed by a brushless synchronous motor with a permanent magnet, which transforms the rotary motion into a linear motion by the ball bearing screw that has been used in the machine tool industry.The efficiency of the overall process depends in part on the plasticization process, where , The screw plays a very crucial role.
The screw must ensure that the material is melted and homogenized, and this process can be assisted by backpressure to avoid overheating, which can not result in an excessive flow rate that would otherwise cause degradation of the polymer.
Each polymer has a different maximum flow velocity beyond which the molecules will stretch and the polymer backbone breaks, but the focus is still on controlling the forward axial movement of the screw during injection and dwell Subsequent cooling processes, including inherent stress, tolerances and warpage, are important to ensure the quality of the product, all due to the quality of the mold, especially for optimizing the cooling channels and ensuring effective closed loop temperature control. System completely independent, will not interfere with mechanical adjustment.
Mold movements such as mold closing and ejection must be precise and efficient. Velocity profiles are usually used to ensure that the moving parts are in close proximity. The contact force can be adjusted so it can be concluded that the additional conditions are the same irrespective of energy consumption and mechanical reliability Mold quality), the quality of the product depends mainly on the system that controls the forward movement of the screw, and on the hydraulic injection molding machine, this adjustment is achieved by detecting the oil pressure.
Specifically, a set of valves is activated by hydraulic pressure through the control panel, through which the fluid acts and is regulated and released.
Injection speed control options include open loop control, semi-closed loop control, and closed loop control Open loop systems rely on a common proportional valve Proportional tension is applied to the desired ratio of fluid, causing fluid to create pressure in the syringe barrel, allowing the injection screw To a certain forward speed of movement.
The closed-loop system uses a closed-loop proportional valve that closes at the position where the closed port is located, and the closed port controls the flow rate of the oil through the movement within the valve.The closed-loop system closes at the screw translation speed. For the potentiometer type), timing detection tension down.Pressure valve out of the oil through the adjustment, to compensate for the emergence of the speed deviation.
Closed-loop control relies on dedicated electronic components integrated with the machine Closed-loop pressure control ensures uniform pressure during injection and holding, as well as uniform back-pressure across all cycles Adjustable by proportional valve for detected pressure, Set the pressure value for offset compensation.
In general, the hydraulic pressure can be monitored, however, it is another effective method to detect the melt pressure in the nozzle or cavity. A more reliable solution is to manage the proportional valve by reading the nozzle or cavity pressure reading. Pressure detection based on the increase in temperature detection, especially conducive to process management.
Understanding the actual pressures that a material can withstand can also help predict the actual weight and size of the molded part based on set pressure and temperature conditions.In fact, by changing the pressure holding pressure value, more material can be introduced into the mold cavity, To reduce component shrinkage, to fit design tolerances, which include preset injection shrinkage, and close to the melting conditions, the semi-crystalline polymer shows a very large specific volume change, in which case overcharging does not hinder the ejection of the component.