Mechanical Measurements & Metrology Assignment ||first year engineering assignments||

 QUESTIONS:

PART A

A1.1 INTRODUCTION TO VARIOUS ASSEMBLY METHODS IN MANUFACTURING.

A1.2 IMPORTANCE OF INTERCHANGEABILITY WITH SUIABLE EXAMPLE

PART B

B1.1 ILLUSTRATION OF THE SELECTED COMPONENT AND SIGNIFICANCE OF THE                             PARAMETER TO BE MEASURED.

B1.2 SELECTION OF SUITABLE INSTRUMENT, WITH JUSTIFICATION,TO MEASURE THE GIVEN PARAMETER

B1.3 LIMITATIONS OF THE SELECTED INSTRUMENT AND SUGGESTION FOR ALTERNATIVE MEASURING INSTRUMENT

ANSWERS:

A1.1

PART-A

INTRODUCTION TO VARIOUS ASSEMBLY METHODS IN MANUFACTURING.

 

An assembly line is a manufacturing process in which interchangeable parts are added to a product in a sequential manner to create an end product. The workers and machinery used to

produce the item are stationary along the line and the product moves through the cycle, from start to finish. The sub types,

·             1)Selective Assembly.

·             2)  Interchangeability.

 

 

Selective Assembly

 

·       The selection from two or more stocks of the particular parts of a mechanism that will fit with the desired degree of clearance when assembled.

 

·       The selective assembly can be referred to as a concept where the subcomponents are assembled to form a proper final assembly which will in return provide the highest tolerance specification.

 

               ·       Using selective assembly when the parts are being manufactured, the selective assembly                                   resembles an old concept of inspection, in which the component is being identified as good or bad. If all the parts are correct and the component is good then it will be used for assembly or else it will be used for scrap purposes.

·        In selective assembly, if the components are divided into different categories, then the groups will be organized according to the sizes and dimensions. We have to make sure that all the parts are grouped together and all are ready for mating so that every component will match with the corresponding sized component to form an assembled part.

·        If a small shaft is mated with small holes, then large holes will be mated with large shafts. For clearance and interference fits in selective assembly, the minimum value increases and maximum value decreases, where as for transition fit the maximum value of clearance and interference fit decreases.

 

Interchangeability

 

·        Interchangeability can be defined as it is a system of producing the mating parts.

·        A single operator was confined with a number of units to assemble it which will take a long period of time and it won't be economical. To reduce the cost and time, mass production of the system was developed.

·        In the production systems, the components will be produced in one or more batches by different operations on different machines.

·        This system will be applied to interchangeability and then any one of the components will be selected at random to mate with other components which will also be selected at random. When this system is used for such purposes then it is called interchangeability. This system ensures that the cost will be reduced and the output will be increased.

·        In these systems, especially in the interchangeable systems, the system does some portions of the work so that the workload will be decreased for utilization purposes. Then that person can easily specialize in that work. Then that person can use the mating parts to fit the components by trial and error method and the assembly time is reduced completely and considerably.

·        If it is the case of big assemblies where big parts are being manufactured, the manufacturing of parts may be very tricky and hard because it is very difficult to find parts which are similar, because these parts need to be grouped together so that they can fit in the same batch.

 

 

A1.2

 

IMPORTANCE OF INTERCHANGEABILITY WITH SUIABLE EXAMPLE

 

·       This interchangeability allows easy assembly of new devices, and easy assembly, and easier repair of existing devices, while minimizing both the time and skill required of the person doing the assembly or repair.

•        It enhances the production rate.
•        Without interchangeability mass production is not possible.
•        Whether the interchangeability is applicable or not depends upon the different parts and tolerance to be adopted.

•        Interchangeability plays an important role economically which allows mass production,
•        reduces production cost.
•     Replacement of worn out part is easy.
• ·       These parts can be freely replacing another, without any further custom fitting such are filing or machining

 EXAMPLES

Keys, couplings, pin joint, screwed fasteners, gears, clutches etc…

PART-B

 

ILLUSTRATION OF THE SELECTED COMPONENT AND SIGNIFICANCE OF THE PARAMETER TO BE MEASURED.

 

 

 

A gear having involuted teeth either straight or helically cut on a cylindrical surface. Two such gears are used to transmit power between parallel shafts

 

Spur gears can be used to increase or decrease the torque, or power, of a given object. Spur gears are used to this effect in washing machines, blenders, clothes dryers, construction equipment, fuel pumps and mills.

 

 

Advantages

 

·       Simplicity. Spur gears feature a simple, compact design that makes them easy to design and install, even in limited or restricted spaces.

·       Constant Speed Drive. These gears increase or decrease shaft speed with a high degree of precision at a constant velocity.

·       Reliability.

·       Cost-Effectiveness.

·       Efficiency.

 

§  The parameter to measure in spur gear inside diameter or Minor diameter.

§  The space between one gears minor diameter. Dedendum: Depth of the tooth between the pitch circle and the minor diameter.

B1.2

 

SELECTION OF SUITABLE INSTRUMENT, WITH JUSTIFICATION,TO MEASURE THE GIVEN PARAMETER

 

 

The Suitable instrument for checking or Measurement of spur gear inside diameter is one of the Pin Micrometer Caliper.

 

 

B1.3

 

LIMITATIONS OF THE SELECTED INSTRUMENT AND SUGGESTION FOR ALTERNATIVE MEASURING INSTRUMENT

 

 

Limited range

Most micrometers have a measuring range of only 25mm (metric) and 1″ (imperial).

This means that additional micrometers are required to measure objects that are larger than this.

Larger micrometers can be expensive

As a result of their size, micrometers used to take larger measurements can be very expensive compared to smaller micrometers.

Different types are required for different measuring tasks. Unlike dial calipers or Vernier calipers which can take a number of different measurements (outside, inside, step and depth), micrometers are only capable of performing a single measuring task. For instance, if you wanted to measure the diameter of a hole in a piece of wood as well as the outside width of that piece of wood, you would need both an inside micrometer and an outside micrometer.

 

 

 

 

SUGGESTION FOR ALTERNATIVE MEASURING INSTRUMENT

 

The alternative measuring instrument is digital Vernier callipers. The Digital Vernier calliper least count is 0.01mm,

Vernier Callipers are precision measuring instruments with a higher accuracy level. It is one of the best calliper to measure least count of any object.

Vernier Calliper is very important tool in manufacturing industry and has lot of benefits.