Cold heading and thread rolling are important links in the production of threaded fasteners. In these two links, there are also some potential failure modes. If corresponding control measures are not taken, the use of bolts will be affected.
In the process of cold heading (heading) of bolts, potential failure modes include: the blank diameter of the screw is unqualified; the rod length of the screw is unqualified; the head and rod of the screw are eccentric; the appearance of the screw is not good; the R angle of the screw is not qualified qualified. The consequences of these potential failure modes include: subsequent thread sizes are unqualified; screw sizes are unqualified; screw assembly is difficult; product appearance cannot meet customer needs, etc.
In the cold heading process of fasteners, the main causes of these failure modes are molds, such as unqualified mold manufacturing, mold wear, unreasonable mold design, poor mold production, etc. In addition, machine adjustment errors can also cause product dimensions to fail. During this process, in order to prevent bolt failure, the main control measures that can be taken are the first inspection of mold changes, such as using inspection tools such as vernier calipers, micrometers, projectors, and concentric meters, and the inspector changing molds and inspecting 5 pieces/batch for the first time. Workers and inspectors inspect 5 pieces/2h.
After the fastener is cold-headed, the next process is thread rolling, that is, thread rolling. In this process, the potential failure modes include: poor thread accuracy; the thread part and the ending R shape are too small; the thread is folded, and the lower part of the thread is There are wrinkles; the thread size is unqualified; the thread has harmful defects such as burrs, oblique buckles, and double teeth. The consequences of failure will be: the thread cannot pass the regulations and cannot meet customer requirements; the fatigue life of the screw is short; the fatigue strength of the screw is reduced.
In the thread rolling process, the causes of the above failures can be: loosening of the die plate, bruised teeth, improper adjustment of the die plate; poor manufacturing of the thread rolling plate, etc. Like cold heading, the main control measure to prevent bolt failure in the thread rolling process is to change the first piece of the mold. For example, the inspector changes the mold and inspects 5 pieces/batch for the first time, the operator and inspector inspect 5 pieces/2h, and the thread diameter is X-R Figure control.
