Design factors in operations


In this article we are stressing on the various needs of convenient working positions for a machine operator which is essential for maintaining productivity and quality. Various factors are discussed in the ensuing paragraphs which give a clearer picture of such needs.

Layout of Equipment and Seating

It is most preferable to design the equipment used keeping in mind the operator who operates it. However, the equipment is designed first, and the operator is expected to cope with it, even though control and display are unsatisfactory. There is inertia to change. This attitude keeps the equipment as it is for a long time. Some lathes may have work carried out far from the eye, and the operator’s bent posture is therefore taken for granted. Can we not design a tilted centre lathe where the operator has not to stoop? Machines should be designed to facilitate operators’ working on them without stress on any part of he body.

Similarly, vision in cranes formerly was unsatisfactory but newer models permit unrestricted vision.

For good design, the operator and his/her anatomy should be the basis for vision, controls, seating, leg room etc. Allowances are necessary for anthropometric differences of genders—male and female. Job design has to account for a standing job or a sitting job or a combination of both. Workers may have to leave the work-place for change of posture very often. Some seats are so uncomfortable sitting on them for a long time is difficult for the operators which make them stand up to do the job.

Seating should not cause overstrain of certain muscles. Back rest must be provided to allow relaxation of back muscles. Seat should not press unduly the tissues of buttocks. It may be necessary to go to sleep by being too comfortable. Restricted blood flow may also cause numbness. Ergonomically designed seats bear the weight of the body in a good posture on hips and not on thighs. Good seating depends upon the size, shape and height of the seat, the back-rest provided, and the material used. High chairs require foot-rests which are flat-surfaced, rather than bars which cause fatigue.

It is necessary at times to provide standing support called rump rest. Some situations require floor level work, allowing greater freedom to anatomy e.g. cobbler’s work, tailor’s work.

Operatives may be provided by consultants a stool or a bench out of human consideration, to facilitate putting lunch boxes, small bags, shawls, and such personal belongings. They could not be misused for sitting. In assembly work and controls, the renewal principles of motion economy as laid down by Gilbreth should be taken as guideline

For controls, binary form information of yes-no types is preferred. Lights which alternate (green-red) can be used. For quantitative information, digital presentation is better than the reading of graded scales. Control panel instruments should have both audio and visual signals. Visual signals should not mislead. Centrally located lights are immediately visible and off-centre lights 30 degree from the centre is difficult to notice. Layout designs should anticipate future maintenance problems and hence those points that need frequent maintenance should not be inaccessible

Diagnostic studies are conducted to identify causes of failure, and rectification accordingly should be done. At various stages of design, ergonomic considerations must be kept in mind.

In conclusion we say that the above gives just a brief insight into the operators’ working positions and how the stress on any part of their bodies can be relieved by proper ergonomics. In actual practice the manufacturing firm can discuss in detail, various design factors suitable for the line operators or machine operators with the suppliers of the equipments, machines, operator seats and their layout before the installation in the shop floor area prior to commencement of any operations. The discussion shall be between experts from both sides.