Mechanical Interview questions

What will happen if we use petrol on diesel engine?

Petrol in Diesel:

ABNORMAL COMBUSTION

1. Combustion: initially the combustion process will be fine.. Until we get the combustion chamber temperature pretty high, then due to detonation, the mixture will start firing before TDC(As the compression ratio is much higher in Diesel)... As a result, abnormally it will fire and the forces on the mechanical components will be high.

2. Fuel system: This is about the Fuel injection system that includes fuel pump and all in the diesel engines.

Since fuel needs to be pumped in Diesel engines, they need to be self lubricated. I.e. the fuel is the lubricant for movable parts of the pump.

If petrol is put in a diesel engine, since it is less viscous, it will rather act as a solvent and the friction generated will be higher in the rubbing parts and that may fail.

What will happen if we use diesel on petrol engine?

Diesel in petrol:

NO COMBUSTION

1. Won't work: as diesel is more viscous and its comparatively non volatile. The air fuel mixture will be a non homogenous mixture. As a result it wouldn't burn.

2. Fuel system components: Even if we use GDI(Gasoline Direct Injection), the spray pressure of diesel in diesel engines is around 1500 bar, in gas it's a Max of 800-1000 bar. As a result, the atomisation of diesel won't take place. And again, it won't burn.

Mention any five engine manufacturers?

 Caterpillar Inc.

 JCB (company)‎

Perkins engines‎ 

Wärtsilä‎ 

Mention five machine tool manufacturers?

     

Kennametal   

Lokesh Machines   

United Drilling   

Tulive Develop   

Rapicut Carbide   

Rishi Laser   

Birla Precision   

ITL Industries   

Solitaire Mach   

Kulkarni Power   

Miven Machine   

EMA India   

Solid Carbide  

What is meant machine feed?

Cutting speed is defined as the speed at which the work moves with respect to the tool (usually measured in feet per minute). Feed rate is defined as the distance the tool travels during one revolution of the part. Cutting speed and feed determines the surface finish, power requirements, and material removal rate.

What is meant by depth of cut?

Depth of cut is the distance that the tool bit moves into the work. usually measured in thousandths of an inch or in millimeters. General machine practice is to use a depth of cut up to five times the rate of feed, such as rough cutting stainless steel using a feed of 0.020 inch per revolution and a depth of cut of 0.100 inch. which would reduce the diameter by 0.200 inch. If chatter marks or machine noise develops, reduce the depth of cut.

Difference between turning and facing?

The primary difference is that in Facing/ Turningoperations, your work piece that you need to machine is going to rotate, while in a milling operation, your tool is going to rotate. Turning is usually defined for cylindrical workpieces. This is used to reduce the diameter of a workpiece.

What is meant by knurling why its need?

Knurling is a manufacturing process, typically conducted on a lathe, whereby a pattern of straight, angled or crossed lines is cut or rolled into the material.

Purpose and meaning of knurling. Cylindrical parts, such as screw heads, round nuts, gripping surfaces on measuring tools and all kinds of handles or grips which have to be gripped firmly, must have roughened gripping surfaces.

Who is the father of industrial engineering?

Many sources say IE began with Frederick W. Taylor (1856-1915), who is often considered the father of industrial engineering/management science, and others say it was James Watt (1736–1819) inventing the steam engine, and some say it may have been Adam Smith (1723-1790), the laissez-faire economics pioneer who wrote 

What is meant JIT?

Just-in-time (JIT) is an inventory strategy companies employ to increase efficiency and decrease waste by receiving goods only as they are needed in the production process, thereby reducing inventory costs. This method requires producers to forecast demand accurately.