Melt usually flows from nozzle into gate, but for some molds, nozzle is part of mold because it extends to bottom of mold. There are two main types of nozzles: open-ended and closed-ended. In injection molding production, open-ended nozzles should be used because they are cheaper and less likely to stay. If injection moulding machine is equipped with a pressure relief device, then even lower viscosity melts can use this nozzle. Sometimes it is necessary to use a closed-end nozzle, which acts as a check valve, blocking plastic in injection cylinder. Make sure that nozzle is properly inserted into nozzle sleeve, top hole is slightly smaller than nozzle sleeve, which makes it easier for nozzle to withdraw from mold. Nozzle sleeve hole is 1mm larger than shooting nozzle, that is, nozzle radius is 0.5mm thinner than nozzle sleeve radius.
One of reasons for surface problems of TPE injection parts is poor quality of raw materials, which is also related to uneven dispersion of formula, and it is also related to setting of some parameters of injection moulding process.
Determination of number of injection molding cavity is an important part of structural design of injection moulding die. Determination of number of mold cavity is constrained by many factors. Reasonable determination of number of mold cavity is a prerequisite to ensure quality of plastic parts, reduce production costs, and give full play to equipment's production potential.
Moldflow Analysis software features injection molding simulation tools to help you validate and optimize plastic parts, plastic injection moulding die and injection molding processes. Software provides guidance to plastic injection mold designer, mold makers, and engineers to demonstrate how wall thickness, gate location, material, and geometry changes affect manufacturability through simulation setup and results clarification. From thin-walled parts to thick-walled, rugged parts, Autodesk Moldflow's geometry support that helps users experiment with hypothetical solutions before final design decisions.
When designing plastic mold, after mold structure is determined, various parts of mold can be designed in detail, that is size of each template and part, cavity and core size are determined. This will involve major design parameters such as material shrinkage. Therefore, size of each part of cavity can be determined only by specifically grasping shrinkage rate of shaped plastic. Even if selected mold structure is correct, if parameters used are not correct, it is impossible to produce a qualified plastic part.
Injection moulding process parameters mainly include baking temperature and time, injection amount, metering stroke (pre-plastic stroke), residual material amount, anti-delay amount, screw rotation speed, back pressure, injection speed and pressure, holding pressure and time, barrel temperature, mold temperature, cooling time, opening and closing speed and pressure, ejection speed, gas-assisted blowing pressure and time.
Poor flow of melt causes surface of plastic part to produce annual ring-shaped wave flow marks centered on the gate. Mold and nozzle temperatures can be increased separately, injection rate and filling speed can be increased, injection pressure, holding pressure and pressurization time can be increased. It is also possible to provide a heater at the gate to increase local temperature of gate portion. It is also possible to appropriately enlarge gate and runner area, gate and runner sections are preferably circular, which allows for optimum filling.
Hot runner system is a relatively complex technology in the field of injection moulding process. There are a number of issues that need to be considered when plastic injection mold designer / custom plastic mold manufacturers / mold users choose and purchase hot runner systems. This article lists 15 principles you need to know specifically for these who want to buy a hot runner system:
First, appearance, size, and fit of molded products 1. Defects are not allowed on the surface of product: lack of material, charring, whitening, white line, peaking, foaming, whitening (or cracking, breaking), baking, wrinkles. 2. Welding marks: Generally, length of circular perforated weld line is not more than 5 mm, length of shaped perforated weld line is less than 15 mm, and weld line strength can be tested by functional safety. 3. Shrinkage: shrinkage is not allowed in apparent surface, inconspicuous areas allow for slight shrinkage (not feeling dents).
Injection moulding process is a complex process involving plastic engineering materials, molds, injection molding machines, molding process and many other aspects. Appearance of defects in injection molded products is inevitable. Therefore, it is particularly important to find inherent mechanism of defects, location and types of defects that may be generated to guide project development. Today, we will talk to everyone about common appearance defects - flow marks.