Table of Contents
What is undercut injection molding?
In molding, an undercut is an indentation or protrusion in a shape that will prevent its withdrawal from a one-piece mold. Undercuts on molded parts are features that prevent the part from being directly ejected from an injection molding machine.
What is the use of undercut?
On turned parts an undercut is also known as a neck or “relief groove”. They are often used at the end of the threaded portion of a shaft or screw to provide clearance for the cutting tool.
What is undercut analysis?
You can use Undercut Analysis to find trapped areas in a model that cannot be ejected from the mold. These areas require a side core. When the main core and cavity are separated, the side core slides in a direction perpendicular to the motion of the main core and cavity. Undercut Analysis works only on solid bodies.
What is external undercut?
Any recess or projection on the outer surface of a molded part that prevents its direct removal from its mold cavity.
How do you size an undercut?
A rule of thumb is that the undercut should be at least 1.5 threads long and the diameter should be at least 0.015 in (0.38 mm) smaller than the minor diameter of the thread. Strictly speaking the relief simply needs to be equal or slightly smaller than the minor diameter of the thread.
What is the purpose of thread relief?
Thread Relief, a radial reduction of the taps major and pitch diameters from the cutting edge to the heel. Relieving of the pitch diameter results in the minor diameter being relieved as well due to the manufacturing process whereas the major diameter is relieved separately.
What are undercuts in injection molding?
Undercuts are those features in an injection-molded part that prevent its ejection from the mold. With straight-pull molds such as the ones used by Protolabs, these are any protrusions, holes, cavities, or recessed areas in the part where alignment is not perpendicular to the mold’s parting line.
How can I eliminate undercuts in the mold?
Minor part design changes can often eliminate undercuts in the mold. For example, adding through holes can give access to the underside of features that would otherwise be undercuts, simple modifications enable the mold to form a hole in the sidewall rather than with a side-action mechanism. See below figure.
How does an injection moulding machine work?
An injection moulding machine consists of a material hopper, a plunger and a heating barrel. The machine works to exert pressure and secure the mould in place during the injection process, and the type of machine that is used will be determined by the type of part being moulded and the material being used.
What are the different parts design techniques in molding?
1 Parting Lines. Sometimes the easiest way to deal with an undercut is to move the mold’s parting line to intersect it. 2 Side-Actions. Consider a tubular-shaped part, as in the hose-barb example. 3 Bumpoffs. 4 Hand-loaded Inserts. 5 Telescoping Shutoffs. 6 Part Design and Secondary Operations.