Production Automation

Production Automation Technologies

Evolution of Production Technology

Year Casting Deformation Joining Machining Ceramics Plastics

4000 B.C. Stone, clay molds

Bending, forging (Au, Ag, Cu)

Riveting Stone, emery, corundum, garnet, flint

Earthenware Wood, natural fiber

2500 BC Lost wax (bronze)

Shearing, sheet forming

Soldering, brazing

Drilling, sawing Glass beads, potter's wheel

1000 BC Hot forging (iron), wire- drawing (?)

Forge welding, gluing

Iron saws Glass pressing, glazing

0. A.D. Coining (brass), forging (steel)

Turning (wood), filing

Glass blowing

1000 Wire drawing Stoneware, porcelain (China)

1400 Sand casting, cast iron

Water hammer Sandpaper Majolica, crystal glass

1600 Permanent mold Tinplate can, rolling (Pb)

Wheel lathe (wood)

1800 Flasks Deep drawing, rolling, (steel), extrusion (Pb)

Boring, turning, screw cutting

Plate glass; porcelain (Germany)

1850 Centrifugal, molding machine

Steam hammer, tinplate rolling

Shaping, milling, copying lathe

Window glass from slit cylinder

Vulcanization

Year Casting Deformation Joining Machining Ceramics Plastics

1875 Rail rolling, continuous rolling

Turret lathe, universal mill, vitrified wheel

Celluloid, rubber extrusion, molding

1900 Tube rolling, extrusion (Cu)

Oxyacetylene, arc welding, electrical resistance welding

Geared lathe, automatic screw machine, hobbing, high-speed steel, synthetic SiC, Al2O3

Automatic bottle making

1920 Die casting W wire (from powder)

Coated electrode

Bakelite, PVC casting, cold molding, injection molding

1940 Lost wax for engineering parts, resin-bonded sand

Extrusion (steel) Submerged arc Acrylics, PMMA, P.E., nylon, synthetic rubber, transfer molding, foaming

1950 Ceramic mold, modular iron, semi-conductors

Cold extrusion (steel)

TIG welding, MIG welding, electroslag

EDM ABS, silicones, fluorocarbons, polyurethane

1960 Plasma arc Manufactured diamond

Float-glass Acetals, polycarbonate, polypropylene

Production Automation Technologies (Henry C. Co) 5


Computer managed numerical control (NC) is a generic term that encompasses. Computer numerical control (CNC), Direct numerical control (DNC), and. Industrial robots.

Computer managed numerical control, integrated with an automated material handling and storage system, form the building blocks of the flexible manufacturing system (FMS).

Numerical Control (NC)


Numerical control (NC) is a form of flexible (programmable) automation in which the process is controlled by numbers, letters, and symbols.

The electronic industries association (EIA) defined NC as “A system in which actions are controlled

by the direct insertion of numerical data at some point. The system must automatically interpret at least some portion of this data.”


Basic Components An NC system consists of the machine tools,

the part-program, and the machine control unit (MCU).


Machine Tools The machine tools perform the useful

work. A machine tool consists of.

A worktable, One or more spindles, motors and

controls, Cutting tools, Work fixtures, and. Other auxiliary equipment needed in the

machining operation.


The drive units are either powered by stepping motors (for open-loop control), servomotors (for close-loop control), pneumatic drives, or hydraulic drives.


The Part-program

The part-program is a collection of all data required to produce the part. It is arranged in the form of blocks of information.

Each block contains the numerical data required for processing a segment of the work piece.


The Machine Control Unit The machine control unit consists of the data

processing unit (DPU) and the control loop unit (CLU). The DPU decodes the information contained

in the part-program, process it, and provides instructions to the CLU.

The CLU operates the drives attached to the machine leadscrews and feedback signals on the actual position and velocity of each one of the axes. The drive units are actuated by voltage pulses.


The Machine Control Unit The number of pulses transmitted to each

axis is equal to the required incremental motion, and the frequency of these pulses represent the axial velocity. Each incremental motion is called a basic

length unit (BLU). One pulse is equivalent to 1 BLU. The BLU represents the resolution of the NC

machine tool.

Types of NC Systems


Point-to-point (PTP) NC The cutting tool is moved relative to the

work piece (i.E., Either the cutting tool moves, or the work piece moves) until the cutting tool is at a numerically defined position and then the motion is paused.

The cutting tool then performs an operation. When the operation is completed, the cutting

tool moves relative to the work piece until the next point is reached, and the cycle is repeated.

The simplest example of a PTP NC machine tool is the NC drilling machine.


Straight-cut NC Straight-cut system are capable of

moving the cutting tool parallel to one of the major axes (X-Y-Z) at a controlled rate suitable for machining.

It is appropriate for performing milling operations to fabricate work pieces of rectangular configurations.

Straight-cut NC systems can also perform PTP operations.


Contouring NC In contouring (continuous path)

operations, the tool is cutting while the axes of motion are moving.

The axes can be moved simultaneously, at different velocity.

The path of the cutter is continuously controlled to generate the desired geometry of the work piece.

Computer-assisted NC Programming


1. The computer interprets the instructions in the program into computer-usable form.

2. The computer performs the necessary geometry and trigonometry calculations required to generate the part surface.

3. The part-programmer specifies the part outline as the tool path. Since the tool path is at the periphery of the cutter that machining actually takes place, it must be offset by the radius of the cutter.


4. The cutter offset computations in contour part-programming are performed by the computer.

5. Part-programming languages are general-purpose languages. Since NC machine tool systems have different features and capabilities, the computer must take the general instructions and make them specific to a particular machine tool system. This function is called post processing.


6. After converting all instructions into a detailed set of machine tool motion commands, the computer controls a tape punch device to prepare the tape for the specific NC machine.

7. Graphic proofing techniques provide a visual representation of the cutting tool path.


8. This representation may be a simple two-dimensional plot of the cutter path or a dynamic display of tool motion using computer generated animation.

9. If necessary, part-programs are also verified on the NC station using substitute materials such as light metals, plastics, foams, wood, laminates, and other castable low cost materials used for NC proofing.

Computer Numerical Control (CNC)


The EIA definition of computer numerical control (CNC). “A numerical control system wherein a dedicated,

stored program computer is used to perform some or all of the basic numerical control functions in accordance with control programs stored in the read-write memory of the computer.”

The CNC uses a dedicated microprocessor to perform the MCU functions.


CNC supports programming features not available in conventional NC systems: Subroutine macros which can be stored in memory

and called by the part-program to execute frequently-used cutting sequence.

Inch-metric conversions, sophisticated interpolation functions (such as cubic interpolation) can be easily accomplished in CNC.

Absolute or incremental positioning (the coordinate systems used in locating the tool relative to the work piece) as well as PTP or contouring mode can be selected.


The part-program can be edited (correction or optimization of tool path, speeds, and feeds) at the machine site during tape tryout.

Tool and fixture offsets can be computed and stored.

Tool path can be verified using graphic display. Diagnostics are available to assist maintenance

and repair.

Direct Numerical Control (DNC)


The EIA definition of DNC. “A system connecting a set of numerically controlled

machines to a common memory for part program or machine program storage with provision for on-demand distribution of data to machines.”

In DNC, several NC machines are directly controlled by a computer, eliminating substantial hardware from the individual controller of each machine tool. The part-program is downloaded to the machines directly (thus omitting the tape reader) from the computer memory.

Industrial Robots


A programmable device equipped with a tool that can move along several directions.

Stand-Alone Operation: once a program is entered, the robot can function with or without further human intervention.


The Manipulator The manipulator is the equivalent of the

machine tool in CNC. It consists of a series of segments, jointed or sliding relative to one another, that performs the work such as grasping and/or moving objects.

The manipulator is composed of the main frame (the arm of the robot), and the wrist.

The tools, called the end-effectors, are attached to the wrist. The end-effectors perform a prescribed task ordinarily done by the human worker.


The Main Frame Structurally, the robot can be classified

according to the coordinate system of the main frame. The types of coordinate systems are: Cartesian coordinate manipulator, which consists

of three linear axes, Cylindrical coordinate manipulator, which consists

of two linear axes and one rotary axis, Spherical coordinate manipulator which consists of

one linear and two rotary axes, Articulated or jointed robots which consists of

three rotary axes, and Gantry robot SCARA robot.


Cartesian Robot


Cylindrical Robot


Spherical Robot


Articulated (Jointed) Robot


Gantry Robot


SCARA Robot


The Wrist The end-effectors is connected to the main

frame of the robot through the wrist. The wrist has three rotary axes -- roll, bend

(pitch), and swivel (yaw). The end-effectors. Attached to the wrist is

the end-effectors. The end-effectors is the robot's “hand.” The most common end-effectors is the gripper, which is a device by which a robot may grasp and hold external objects.

Other standard end-effectors include welding torch, magnetic vacuum, gun mounts for spray painting or coating operations, hydraulic toggle, and custom made tools.


Resolution,Accuracy,Repeatability Resolution is the smallest increment of

distance that can be read and acted upon by an automatic control system of a robot.

The unit of measure is the basic resolution unit (BRU).

The accuracy of an industrial robot is the ability of the robot to make a motion with an end point as specified by a program.

The closeness of agreement of repeated position movement under the same conditions to the same location is called the repeatability of the robot.


Programming An industrial robot can be

programmed using the Manual teaching method, Lead-through method, or a Programming language.


Applications Perhaps the most extensive

applications of industrial robots are in jobs involving repetitive tasks. Industrial robots installed to-date are in Material handling (about 40%), Painting and arc welding (45%), Inspection, assembly and Other operations (15%).


Operations that require precise positioning control. For example, in spray painting where

severe articulation is required. Use of industrial robots in sand blasting is

on the rise not only because of the abrasive environment, but the severe articulation requirements of the process.


In areas where hazardous working conditions exist and/or where heavy parts are involved. For example, in unloading of die casting

machines, the workplace is dirty and hot (molten metal); in spot welding operations, the welding guns are heavy and the work cycles rigorous; and in investment casting, the environment is abrasive and of the loads heavy.

Industrial robots are also replacing the human operator in corrosive environment, such as handling of dangerous chemicals.


Hazards, operator tasks, inspection, quality, part presentation, part weight, product variation, product runs, frequency of changeover, process variables, process equipment, floor space, and cycle time, are some of the variable that must be examined in justifying the use of industrial robots.

However, industrial robots should not be treated simply as an emulation of human work. More importantly, the justification process should reflect an accurate implementation of corporate manufacturing plans for competitive advantage and productivity improvement.

Production Automation

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