Tag: TTT

Torsten’s Training Tip: Thermal Properties

During the injection molding process, a polymer is heated in different ways, beginning inside the machine cylinder. Electric heater bands around the cylinder create heat which is transferred through convection from the cylinder to the polymer. Then, the rotating screw creates shear heat which transfers to the polymer on top of the convection transfer. In […]

Torsten’s Training Tip: Jetting

Injection molding polymer through small gates creates complex three-dimensional fluid flow behaviors. Jetting occurs in injection molding when polymer material is injected through a nozzle, runner, or gate at high velocity, into open, thicker areas, without forming contact with the mold wall.  The jetting effect is like water flowing through a hose. If you place your thumb on […]

Torsten’s Training Tip: Parallel and Serial Coolant Circuits

An injection mold is effectively a heat exchanger. Molten polymer material that is injected must be cooled by the mold cooling system. As part designs become more complex, cavitation requirements increase, and larger overall mold bases are needed. Mold designers have several options when designing effective heat removal systems. Coolant circuits can be parallel or […]

Torsten’s Training Tip: Understanding Flow-Induced Molded-In Stress

Injection molding is a complex manufacturing process involving temperature and pressure. During the molding process polymer materials experience complex molecular chain deformation while undergoing temperature and pressure changes. Molded part properties and performance are dependent on, and influenced by, design complexity and the molding process. Understanding molded-in stress, specifically flow induced molded-in stress, is an […]

Torsten’s Training Tip: Polymer Materials Overview

It is important for part and mold designers not only to understand design principles, but also to understand the fundamentals of plastics. The choice of a plastic, or polymer, has a strong impact on the outcome of a molded part. Polymers are categorized by processing methods and temperature behavior. The major groups are thermoplastics, thermosets, […]

Torsten’s Training Tip: Short Shots

Injection molding is a complex scientific manufacturing process. By following a methodical set-up process, molders aim to minimize or eliminate common molding defects that affect part quality. Generally, molding defects are either part design, mold design, or process related. This training tip focuses on short shots. There are various potential design-related causes for short shots. […]

Torsten’s Training Tip: Sink Marks and Voids

Two common and related injection molding defects, sink marks and voids, are the result of excessive polymer material shrinkage. Because it is essential to produce high quality parts free of molding defects, understanding the causes in order to reduce or eliminate sink marks in molded parts can be very helpful. Let’s review some basics. A […]

Torsten’s Training Tip: Gate Seal Time

Gate seal time is an important aspect of the packing phase that needs to be understood to produce high quality molded parts.  Setting proper gate seal time plays a key role in packing parts. Properly packed parts will have even internal polymer molecular structure, fewer volumetric shrinkage differences, optimized part dimensions, and fewer sink marks […]

Torsten’s Training Tip: Thermal Pins

Designing thermally optimized molds becomes more challenging as part designs become more complex. There are various cooling design strategies, from using drilled coolant circuits or baffles and bubblers, to selecting mold steels or thermal pins (sometimes called heat pipes or heat tubes.) Thermal pins are a cooling strategy to optimize thermal behavior inside a mold. […]

Torsten’s Training Tip: Cashew Gates

Injection molded part quality is highly dependent on gate designs, sizes, and location. Because cashew gates, also called banana gates, can be placed in areas that are not visible, they are an option for molded parts that require perfect surface quality. Cashew gates, or banana gates, are sub-gates that are automatically de-gated and can be […]