PRODUCTION ENGG.

CHAPTER1 THEORY OF METAL CUTTING

CLASSIFICATION OF MANUFACTING PROCESSES:-

1) shaping and forming----change the shape only a.k.a ZERO PROCESS
2) JOINING ----eg welding , fastener , adhesive bonding etc.. a.k.a POSITIVE PROCESS
3) REMOVAL PROCESS -- here mat. is removed eg. machining a.k.a NEGATIVE PROCESS
4) REGENERATIVE PROCESS--(MOST ADVANCED OF ALL)---PRODUCTION OF SOLID PARTS IN LAYER BY LAYER FROM RAW MAT IN DIFFERENT FORMS.
PROCESS IS VERY RAPID ANDACCURATE AND IS USED FOR RAPID PROTOTYPING AND TOOLING.

ADVANTAGES:-

Ø  Process is independent of part (W/P) feature.

Ø  No blanks are required.

Ø  Tooless process.

Ø  Easily automated process.

Ø  No labour is required.

DISADVANTAGES:-

·         Very expensive.

APPLICATION:- For at a time requirement, of machinery component if cost not bar. E.g. - Repair shop.

 MACHINING:-

Machining is an essential process of finishing by which jobs are produced to the desired dimensions and surface finish by gradually removing the excess material from the performed blank in the form of chips with the help of cutting tools moved past the work surface.

Machining is a removal process.

MACHINING AIM TO:-

o   Fulfill its functional requirements.

o   Improve its performance.

o   Prolong its service.

DRAWBACK IN MACHINING:-

v  Loss of material in the form of chips.

ORTHOGONAL MACHINING:-

  Rake surface:- the surface along which the chip moves upwards is called “Rake surface of tool”.

 Flank surface:-the other surface which is relieved to avoid rubbing of tool with the machined surface is called “flank”.

  Rake angle (α) :-angle of inclination of rake surface from reference  plane,i.e,normal to horizontal machined surface.

ü  Clearance angle or Relief angle:-angle of inclination of clearance or flank surface from finished surface.

DISCUSSION ON RAKE ANGLE:-

Rake angle can be positive, negative or zero.

POSITIVE RAKE:-

v  Force (reduce putting force)

v  Power (reduce cutting power)

RECOMMENDATIONS:-

•   Machining low strength material.
•   Low power machining.
•   Long shaft of small diameter.
•  Set –up lacks strength of rigidity.
•   Low cutting speed.
•   Cutting tool material.

NEGATIVE RAKE ANGLE:-

1.   Increased edge strength.
2.   Increases life of tools.
3.   Increases cutting force.
4.  Requires high cutting speeds.
5.   Requires ample power.
6.  Heavy impact loads.

WHEN TO USE (RECOMMENDATION):-

•   Machining high strength alloy.
•  High speed cutting.
•  With rigid set-up.

ZERO RAKE:-

•   Form tools are made.
•   Avoids digging of the tool in the W/P.
•  Brass is twined in zero rake angle.
• CI uses zero rake angle.
•  Negative rake tool chip strain is more.