System Design Cycle: V) Preliminary Design and Development

The next important step of the system design cycle or machine design cycle is making the preliminary design and the development of the product (see the fig below). Remember this is just the preliminary design and not the final design. After using his/her creativity the designer designs one or more designs for the product or machine fulfilling all the given set of the specifications and requirements for the product. From the multiple solutions available for the product, the one with the best solution will be selected for the important stage of the preliminary design and development. The basis for selecting the best design as the preliminary design for development can be varied.

After selecting the best design of the machine as the preliminary design for the further development, the next important step is taken of making all the important drawings of the machine. The drawings of the machine are made to determine the overall configuration and to establish the functional relationship between the various parts of the machine or product.

The drawings will contain all the important dimensions and notations as well as various views like auxiliary and sectional. The main purpose of the preliminary design and developmental stage is to check the validity of the functional and the overall size requirements of the specifications.

In actual practice not all the specifications and the requirements desired from the product are met entirely at this stage. Hence from this step of the machine design cycle the feedback is given to the specification and requirements stage of the cycle (see the fig). Here some changes are made in the specifications and the requirements of the machine and again the next steps of the cycle are taken. This process is repeated until the machine designed at the preliminary stage is found to meet all the functional requirements as per the specifications. Once this is done, this stage is completed and the next step of machine design cycle is taken which is detailed design.

Before we close this article let us see the summary of this important stage of preliminary design and development:

1) From the suggested set of various designs, select the best one that fulfills all the specifications and the requirements of the machine.

2) For the selected solution carry out the various mathematical calculations and make the mathematical model of the machine with the proper dimensions for the overall machine as well as the machine elements.

3) Make the detailed drawings of the model.

4) Analyze this model and see how various parts of the machine are affecting each other.

5) Make the changes in specifications and requirements if required.

5) Optimize the design so as to meet all the specifications and the functional requirements at the lowest possible cost.

6) Prepare the layout of the selected solution considering that it meets all the specifications and the functional requirements.

Book: Machine Design by Dr. P. C. Sharma and D. K. Aggarwal