Lecture No 10 Automation of Machining

8/12/2019 Lecture No 10 Automation of Machining

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Technology II.

Jan Tomíček



Automation of machining

Is connected with the rising demands ofsociety and industry development.Is the way to intensification ofmanufacturing – increasing productivity,improving quality and lowering costsIs the way to improvements in

manufacturing technology, spreading thetechnological possibilities and way tomake the inovation cycle faster.



What we need to automate?

Tool managementTool changeTool movementsSpindle start, devices startMaterial loading

Finished piece remove



AUTOMATION OF MACHINING

Machine tools:general-purpose, manually operated(conventional);

- The leading power is the worker




Machine tools:automated:a) fixed automation – mechanisms: cams,

gear wheels, links, levers, arms; mechanicalstops, limit switches, etc. b) flexible automation – program control,

numerical control



Fixed automation elements



Cam

Is a disc or cylinder with a curve shaped path. A boss insupport is in the path and as the cam turns the supportmoves. Cam are connected together to provide complexmovement of support, feed, rotation and other.



Cylindrical cam use – automatic lathe carriage



Disc cam use – automatic lathe cross slide





Fixed automation machine tools

automatic general-purpose machinee.g. a semiautomatic or an automatic lathe

single-purpose machine (usually unit-built)workpiece oriented function designtransfer line

integrated workpiece transport system



Unit-built machine



Feed drive unit - EV



Drilling spindle unit - BO



Slide unit - SE



Circular indexing table unit - TA



Modularunitsdesign



Single purpose machine

Just one operation, of op. Step is done.Sometimes a batch of operation stepsSpecial machine designed to maximizethe production:

Multiple spindlesHigh feed drives

Multiple clamping Automatic part in feedSpecial tooling usage



Single-purpose machineefficiency



Transfer line – a concept



Transfer line – a schema



Transfer line – a design



Block machining transfer line



Transfer line station – an example



2) Flexible automation

(soft, programable automation) is aimedat piece and small batch production dueto easy reprogramming.

Two basic formsProgram sequence controlNumerical control



Program sequence control

The sequence of motions and switchingsis controlled by relays, timers, switches,perforated tape, programable cylinders,

plugboards and other controllers.

Easier reprogramming, limited program

options, almost no adjustments



Perforated tapeEach line presents adifferent movementor switch. It has tobe printed correctly,no error control.

FYI:8 line perforated paper tape can contain one byte of information in one columnof holes. Normal pitch of columns is 2,54 mm. That means you need 2,6 m of

tape to store 1kB of data. A dual-layer DVD is then approx. 22100 km ofperforated tape.



Numerical control

The most important type of automation. Almost all of new machines arenumerically controlled.

Priciple:Machine and all of its movements arecontrolled by a program. Program is a

list of instructions written is specificsyntax and having specific format.



Mechanical vs. numerical

Limitations – speed, length of program,possible motions on cams.



FLEXIBLE AUTOMATION1. Conventional machine tool



FLEXIBLE AUTOMATION2. NC machine tool (stand-alone)



FLEXIBLE AUTOMATION3. NC machine tool with tool magazine



FLEXIBLE AUTOMATION4. CNC machine tool



Mechanization vs. automation

Mechanization – human power is replacedby machines, drives, hydraulic or mechanicdevices

Automation – human control is replaced by

sequentional machine, cams, computer, PLCcontroller



Automation degree

Semiautomatic run – tools are changedautomatically, blank or finished workpiece isrenowed by operator

Automatic run – both the tool and pieces are

placed and removed automatically by robot(line, tables)



NC / CNC definition

Originaly only NC control was used.Program was stored on tape or disc andread one line after another.

Influence of rapid development ofcomputers resulted to CNC control(Computer numerical control). Now the

program is loaded into computers memoryand executed from here.



CNC advantagesOption NC control CNC control

Program length Limited by data storagecapacity (tape)

Unlimited (limited bydata storage capacity – HDD drives over 1TB)

Program sequence One line after another Allows jump forward,backward, subprograms.

Jump to other programs N/A Yes

Canned cycles N/A Yes

Coordinates correction Manually only Yes, automatically

Tool lengthcompensation Manually only Yes, programable

Tool diametercompensation

N/A Yes, programable

Reading in advance N/A Yes, continual mode

Start after breakdown N/A Yes



Program sequenceSubprograms

A link to another then thefollowing line is entered intomain programm. This subprogram isexecuted.

After finishing this programwe return to main programa we contiue until end ofmain program (M30)



Basic principles of CNCmachines

NC/CNC machine consist of 3 basic elements.List of instructions – NC code – a mix of alphabecial

and numerical information. Contaion informationabout movements, feed, speed, tool change and

other machine functions (cooling, measuring)Control unit - control system – converts the programinto signal for machine and send them to machine(PLC controller)

Controlunit

(system)

MachineNCcode

Sensing

device

Drivemotor



Basic principles of CNCmachines

NC/CNC machine consist of 3 basic elements.Machine tool – fitted with drive motor to operate

slides, support and spindle. Also with switchesto start/stop specific functions

Sensing device – optional(closed circuit)- sensingdevice control if a specific demand was fullfilled.Support feed, Table position etc.

Controlunit

(system)

MachineNCcode

Sensing

device

Drivemotor



CNC machine tool



Motions

Three types of motion1) point-to-point motion – tool is moved to

specific location, path or speed of move

between location is not controlled.(drilling)2) Linear control – movement along one of

the axes of the machine.3) Contouring control – movement can be

made in two or more axessimultaneously.



MotionsPoint-to-point control Linear control Contouring control (continual)

drilling milling machines, lathes machining c.(milling, turning)

CNC hi i (MC)



CNC machining centre(MC)MC combine a number of different

machining processes in one operation



Modular tool set



Modular tool set – toolingsystem All manufacturers around the worldBasic concept:1) Holder with standadized conecting part

– ISO, BSK cone, CAPTO system etc.2) Extension bar – active (vibration

elimination) adujstable and balanced3) Quick change tooltip/insert



SECO - Combimaster

T l h



Tool exchange

Tool exchange



Tool exchange

Fl ibl ll



Flexible cell – a concept



Flexible manufacturing system



Conveyors

Device used for transportation of blankand semiproduct in production

Types:Belt conveyorPulley(rolls) conveyorCradle conveyor



Conveyors – Belt conveyor

Used for small parts and loose materialEndless belt made of rubber, plasticparticles, short boards (grids)



Conveyors – pulley(roller) conveyor

For large solid parts and productsLow force needed (gravity slide ways)Use of pallets



Pallet

Board used fortransportation

Equiped with jigs andother positioning

elements

Together with palletechanger is used

for automaticblank materialloading and partsunloading



Pallet changer

aka Switch table2-4 pallets in one machine



Loading of blank/semiproducts

- Manual- Accumulation conveyor

- Accumulating pieces to balance production

- Robot loading- For single standing, large production usage

(common machine tools)

- Line(conveyor) loading- For FMS and large batch production (special

machine tools)



Loading

Flexible manufacturing system



Flexible manufacturing systemFlexible manufacturing system for 4 types of automobile cylinder heads(GM 3801 – 3811)

BZ 400 BZ 500 Other Reserve

Flexible to suit various part variants

9 Flexible transfer machines (some incorporating BZ 400 machining centers),and 16 high-dynamic BZ 500 machining centers

Completely automated

Approximately 500,000 parts p.a.

Process automation and integration level



Process automation and integration level







Effects of automation

- Cost reducing(per piece)

- Higher

investments- Speed

improvement- Productivity

improvement- Repeatability

improvement

C o n v e n

t i o n a

l t o o l s

C N

C t o o

l s

F M

S

C a

m ‘ s

M a c h

i n i n g c o s

t s

( K c / p c e

)

Productivity(pcs/hour)

Documents

Lecture No 10 Automation of Machining