By:

SUBHRAT SHARMA

MECHANICAL ENGINEERING

PRODUCTION INSIGHT

Numerical Control (NC) Defined Programmable automation in which the mechanical actions of

a ‘machine tool’ are controlled by a program containing coded alphanumeric data that represents relative positions between a work head (e.g., cutting tool) and a work part

CNC MACHINING

MachineControl Unit

Power

ProgramInstructions

TransformationProcess

For flat and prismatic (block-like) parts: Milling and drilling operations Conventional Cartesian coordinate system Rotational axes about each linear axis

For rotational parts: Turning operations Only x- and z-axes

NC Coordinate Systems

Storage of more than one part program Various forms of program input Program editing at the machine tool Fixed cycles and programming subroutines Interpolation Acceleration and deceleration computations Communications interface Diagnostics

Computer Numerical Control (CNC)

Distributed Numerical Control

MachineControl Unit

Transformation

Process

MachineControl Unit

MachineControl Unit

CentralComputer NC Pgms

Computer Network

Batch and High Volume production Repeat and/or Repetitive orders Complex part geometries Mundane operations Many separate operations on one part

NC Application Characteristics (Machining)

Three critical measures of precision are:ResolutionAccuracyRepeatability

Control resolution (BLU) is the distance separating two adjacent points in the axis movement (the smallest change in the position)

Accuracy = (1/2) resolution +machining inaccuracy =BLU.

Repeatability refers to the capability of a positioning system to return to a programmed point

Precision

Block FormatAlso known as tape format because the original

formats were designed for punched tapeWord address format - used on all modern CNC

controllersUses a letter prefix to identify each type of wordSpaces to separate words within the blockAllows any order of words in a blockWords can be omitted if their values do not change

from the previous block

NC part program

Example: Word Address Format

N001 G00 X07000 Y03000 M03N002 Y06000

Cutter OffsetCutter path must be offset from actual part outline by a

distance equal to the cutter radius

ExampleNC part program code

N001 G21 G90 G92 X-050.0 Y-050.0 Z010.0; N002 G00 Z-020.0 S1989 M03; N003 G01 G94 G42 Y0 D05 F398; N004 G01 X075.0; N005 G01 X150.0 Y043.02; N006 G01 Y070.0; N007 G01 X080.0; N008 G17 G02 X050.0 Y100.0 R030.0; N009 G01 Y125.0; N010 G01 X0; N011 G01 Y0 N012 G40 G00 X-050.0 Y-050.0 Z010.0 M05; N013 M30;

Comments

Define origin of axes. Rapid to cutter depth, turn spindle on. Bring tool to starting y-value, start cutter offset. Mill lower horizontal edge of part. Mill angled edge at 35 degrees. Mill vertical edge at right of part. Mill horizontal edge leading to arc. Circular interpolation around arc. Mill vertical step above arc. Mill top part edge. Mill vertical edge at left of part. Rapid move to target point, cancel offset, spindle stop. End of program, stop machine.

NC Part Programming Using CAD/CAM

:

FLUIDISED BED FURNACESALT BATH FURNACEHIGH TEPERATUREVACUUM FURNACECNC SPOT WELDINGPIT FURNACESROBOTIC ARM WELDINGHYDRALIC PRESSURE TESTING

HEAT TREATMENT

FLUIDISED BED FURNACE

•PRINCIPLE• Fluidized bed furnaces employ an alloy

retort filled with sand-like alumina particles

• When a controlled stream of air or gas is passed upward through a distributor below the retort, the particles float on a cushion of the air / gas stream and move around turbulently without elutriation

• The now “fluidized” bed looks and behaves remarkably like a boiling liquid bath.

• The fluidized bed becomes an excellent heat treatment furnace for components that are immersed into it.

PROPERTIES RAPID & UNIFORM HEAT TRANSFER TEMPERATURE UNIFORMITY CLEAN, SAFE & NONE POLLUTING FLEXIBILITY

EFFECT OF VARIOUS GASES LPG(HIGH)

CARBURISING CARBONITRING

AMMONIA(HIGH) NITRIDING NITROCARBURING

LOW LPG HARRDENING

LOW AMMONIA CARBONITRIDING

ADVANTAGESQUALITY: Consistent hardness and case depth

due to the high degree of temperature uniformity.

PRODUCTIVITY: Rapid and uniform heat transfer rates, shorter process cycles and increased throughout.

FLEXIBILITY :The ability to operate at any temperature and with a wide variety of gas mixtures allows process fine tuning for different components.

EASY MAINTENANCE: The plant construction is simple without any hot moving parts.

SAFETY: Fluidized bed furnaces are inherently safe to operate being an open system unlike sealed quench and other atmosphere furnaces

Work is fully immersed into a salt bath furnace, no air can contact it.

With the salt bath heat treatment steel scaling, oxidation and decarburization can be avoided.

It is common to process low, medium, and high-carbon steels in the same medium without surface carburization or decarburization.

A thick salt film adhering to the surface serves as protection which continues when the work is removed and transferred (in the case of hardening) to the quench operation.

SALT BATH HEAT TREATING

The electrode furnace generates direct heat in salt by using its resistance to current passage. Salts are insulators in the solid state, while excellent high-resistance conductors in the molten state. Potential is applied to the molten salt by use of heavy electrode bars. These are connected to the secondary of special multiple voltage air cooled transformers. Electrodes are located in a recessed area of the bath and cause salt circulation by electromagnetic forces when energized. A strong magnetic field is created between electrodes when located close together.

Using Maxwell’s Law, this field will cause salt particles between electrodes to move downward in a whirlpool fashion. This electrodynamics circulation assures absolute temperature uniformity through the bath and eliminates danger of undesirable differentials.

Operating principle

A vacuum furnace is a type of furnace that can heat materials with high consistency and low contamination.

Some of the benefits of a vacuum furnace are:Uniform temperatures in the range 1100–

1500°C (2000–2800°F)Temperature can be controlled within a small

areaLow contamination of the product by carbon,

oxygen and other gasesQuick cooling (quenching) of product.The process can be computer controlled to

ensure metallurgical repeatability.

VACUUM FURNACE

Double chamber vessel furnace

Types of different electroplating:Anodizing

Sulphuric Acid AnodisingHard AnodisingChromic Acid AnodisingHARD ANODISING

Electro less depositionELECTROLESS NICKEL PLATING

ELECTROPLATING

Following are the machines :UNIVERSAL TESTING MACHINEX-RAY (RADIOGRAPHY)HARDNESS TESTING MACHINES

VICKERS HARDNESS TESTINGROCKWELL HARDNESS TESTER

BRINELL HARDNESS TESTING

MATERIAL TESTING LAB