TABLE OF CONTENTS Plastics are such versatile materials that they have found screw thread applications from the domestic products field right through to hi-tech medical and electronic high-precision parts. Many of these parts contain screw threads that are required to be produced in a variety of different materials. These threaded components can be used in wide-ranging environments and range in application from simple, basic noncritical forms right through to highly precise instrument components.
It is important for the mould designer to ensure that the correct mould design solution is employed for each threaded component. This in turn means that the mould designer should have a thorough understanding of the working environment of the part and the tolerances and other standards that the part will have to conform to.
Basically, thread forms may be moulded by the following methods:
Using loose tool inserts
Using splits
Using collapsible cores
Using automatic unscrewing techniques
Readers should already be familiar with the first two topics, which were discussed in Chapter 12. These two categories are simply another type of undercut that may be produced by using the methods described there.
This section concentrates on discussing the last two methods in some depth. It is hoped that this will provide the mould designer, toolmaker or technician with sufficient knowledge of current design solutions to extend to new designs of their own. In particular, the following topics are discussed:
Producing thread forms with collapsible cores
Axially moving and static unscrewing cores
Axially moving and...
