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Workhead Mechanisms, Automated Assembling Part 2
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The function of a workhead mechanism Is to perform repeatedly a given manufacturing task during which parts or fasteners may be fed to the powered head to enable the operation to be carried out. For this purpose, the parts are supplied in a fully orientated manner from ducting, a magazine, or positioned in a work carrier.
Simplicity of design, compatible with the re Quired performance, should be aimed at and provision made for easy access to the workhead to allow jammed components and foreign bodies to be readily ejected and the corrective adjustments applied. Collectively these precautions will result in a minimum of machine "down-time". Consideration should also be paid to maintenance requirements.
The workhead should be sufficiently robust in construction to withstand impacts resulting from its operational sequence and from accidental strains by jamming and blows whilst performing within a production unit under shop floor conditions.
If possible, "fail safe" features should be incorporated in the workhead design and the principle of "spring in" and "cam out" is to be recommended. It will be appreciated that the"spring in" feature can be achieved by various methods, such as a pneumatic actuator, Except In the case of a continuous assembling process, a workhead is usually mounted on the assembling machine chassis, situated clear of the indexing medium.
The operational sequence of the workhead mechanism commences after the work carrier, containing a single component or a sub-assembly, has indexed into a stationary position relative to the workhead.
After completion of an operation, the functional features of the workhead mechanism return to the "commencement of stroke" position, clear of the component and work carrier. Completion of this movement is signalled before further indexing of the work carrier can take place.
A number of standard workhead units are marketed by firms reviewed in this Section. The designs and salient features of performance are illustrated. Some of the workheads reviewed are actuated pneumatically, others shown are mechanically driven, being cam operated and coupled directly to the machine transmission. The advantages of employing standard units are that in many cases they may be re- tooled to suit different applications and that the reliability pattern of performance for a given operation is known.
The feed rates quoted on the Data Memoranda Sheets apply only to when handling the typical component illustrated or to the particular machine demand. They are not intended to be considered as the maximum feed rate obtainable with the mechanism depicted. In all cases, the illustrations are solely diagrammatic. They are intended to depict the principles of performing each given function; they should not be scaled. Firms marked thus * design and manufacture the equipment illustrated by their contributions or arrange for this to be done. The equipment is applied exclusively for use within their own organisation. The firms concerned desire that any enquiries appertaining to their contributions to the Data Memoranda should be addressed to the Institution of Production Engineers Headquarters and not direct to them.
Firms marked thus ® are designers, manufacturers, or both, of the equipment illustrated by their contributions. This and similar equipment can be manufactured to customers' requirements. All enquiries appertaining to the purchase of the equipment should be made direct to the firm concerned.