Smith G.T. Cutting Tool Technology: Industrial Handbook

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cic location within the company’s premises. A list is

then compiled, allocating every machine tool’s: power

capacity, spindle taper, number of spindles, its current

operating condition

, present tooling utilised, plus the

current and past operations performed on each ma-

chine tool. By organising information concerning the

capital equipment capability and availability, produces

a number of distinct benets, including a knowledge of

the machines basic characteristics, thus ensuring that

the most advantageous machine tool can be selected

and any machining operation is performed using the

optimum parameters.

Knowledge gained from such a study of perishable

and capital equipment, allows for improvements in

both: process planning – the action plan for the manu-

facturing of a certain part, together with production

planning – the best use of a factory’s resources for a

particular workload.

Building-Up the Tool File

Probably the principal users of a tool le within any

manufacturing organisation are the Process Engineer

and Part-programmer, with perhaps the Tool-preset-

ting operator and Stores-personnel, also making use

of this ‘le’. It should be stressed that new tools are

only added to the tool le aer a proper investigation

of the need for them, assuming that such tooling was

not previously listed. By accepting this limitation on

25 ‘Operating condition’ , this machine tool activity is invariably

of some concern, as although some form of periodic mainte-

nance is likely to be undertaken, perhaps less attention is given

to the machine’s current state of calibration. is situation can

be diagnostically-achieved, both speedily and eciently by

the use of telescoping ‘Ball-bars’. is calibration equipment

can undertake a quick ‘health-check’ and assess both the static

and dynamic machine tool’s performance, indicating the fol-

lowing important characteristics: Servo-mismatch, Stick-slip,

Reversal spikes, Scale uncertainty, Straightness, Squareness,

Lateral play, Back-lash, Cyclic error. ese machine tool re-

lated-factors are automatically prioritised by the soware,

then they can then be simply: analysed, diagnosed and then

corrected, together with a machine tool ‘health-check’ report.

NB Many companies perform these full diagnostic ‘health-

checks’ , periodically, or simply prior to a shi commencing,

as they can be undertaken in just a few minutes for a ‘quick

assessment’ , or perhaps a more thorough ‘Ballbar’ assess-

ment can be achieved in just a few hours – when a convenient

‘maintenance window’ occurs.

the number of dierent tools in the tooling inventory,

then a company can be assured that when the tools are

‘called-up for use’ in the manufacturing process they

will be available and backed-up with spares, since the

‘stores’ has access to this ‘le’. An important feature of

any tool le is the cutting data and machining times

listed. ese machining data are known to be achiev-

able and will be those values expected to be employed

during component production. More specically, the

data values are the ones utilised to calculate quotation

prices for the product, for any future customer ap-

praisal. e editor of the tool le has a key role to play

in the acquisition of tooling data, so when building up

he ‘le’ , they have to:

•

Scrutinise any reported deviations – from the re-

corded cutting data and the original tool le,

•

Investigate higher productivity ratings – some

newly-available tooling may lay claim to be both

faster and more ecient in comparison to either its

predecessor, or competitors tooling products,

•

Obsolete tooling should be ‘weeded-out’ – particu-

larly with the introduction and addition to the tool

le of newer high-technology tooling,

•

Investigation of new tooling – to see if claims of

new tooling products, with regard to their: geom-

etry, coatings, performance, etc., are a genuine im-

provement over the previous versions used.

e systematic accumulation of tooling knowledge in

the tool le for each section of the manufacturing

operation, ensures that the cutting performance will

‘

continuously improve’

. Such improvements may be

considered to be analogous to improving the skill of

an operator on a conventional machine tool, but with

more exibility, as the tool le system soware is able

to cope with much more diverse and complex tooling

26 Continuous improvement programs’ , were originally devel-

oped in Japan and are now well-known and are oen termed

‘Kaizen’ *, which is a philosophical and rigorous approach to

process/product improvements, based upon:

(i) Satisfying the customers – in order to keep the business

alive and to be more protable,

(ii) Being both customer- and process-oriented – to promote

vigorous improvements here,

(iii) Requiring commitment and participation of a company’s

personnel – using their knowledge and experience to achieve

continuous improvements in both working practices and in

the product’s quality.

*In Japanese, Kaizen, approximates to: ‘Change to the better’.

242 Chapter 6

situations. A ‘well-disciplined’ and ‘active’ tool le,

completely eliminates the anticipated ‘hiccups’ that are

likely to occur, whenever a new Part programmer is

employed, or even when hiring new Stores personnel,

or Machine operators, for that matter!

With the soware structure of the tool le – of

necessity – being highly complex and interrelated in

nature, it is not possible within the connes of this

chapter to go into too much detail showing how the

operating system works. However, an appreciation of

a simpler, but still valid tool le format can be gleaned

by describing how a ‘manual le’ is produced. Prior to

constructing this manual tooling data-base, a separate

record is produced for each tool, which is cross-refer-

enced to separate cards for cutting inserts that can be

utilised with the tool. In essence, there are four ‘elds

of tooling information’ that are needed for a usable tool

le, these are:

1. T

ooling is built-up from modular elements – which

are the ‘key’ to eective management and control,

as they allow the widest range of tooling for an ex-

tensive assortment of machine tools available, from

the minimum number of tooling elements in stock.

Hence, a tool for a given machining application may

be assembled from dierent modular elements, to

suit a range of machines,

2. Materials Requirement Planning (MRP)

– the

system together with the tool stores should support

the tooling from the tool le, with such items as:

spares, consumables, plus back-up tooling. In order

to achieve this objective, the tool le record would

include details of the build-up for each tool as well

as the stores location for each part, using a specic

‘key’ notation,

27 ‘Materials Requirement Planning’ (MRP*), is a soware-

driven system that enables manufacturing companies to

calculate: how many materials are needed, what particular

types that are required, plus at what times they are needed. To

achieve this level of control, the system utilises a sales order

book, which records known future orders and also a ‘fore-

cast’ of what sales orders the business is reasonably condent

it might have won. en, the MRP soware interrogates and

checks all the ‘components/ingredients’ which are required to

make these future orders and ensures that they are ordered in

time.

*MRP, was originally developed in the 1960’s and is some-

times termed MRPI, to dierentiate it from the ‘derived’ MP-

RII system – see Footnote 18.

3. Certain ‘steering comments’ on tooling – normally

these statements are based upon shop-oor expe-

rience, that are included to enable the Process-, or

Planning-engineer to select the appropriate tool for

the desired machining application,

4. O

rganisation of basic cutting data – this is nor-

mally produced so that the data can readily be in-

cluded into the CNC program.

NB 

is cutting data is organised according to the

component to be machined and the optimum or-

ganisation of this machining data will vary from

one company to another, depending on their needs.

Of course, all of this data listed reects the compa-

ny’s actual experience, in particular, it includes the

results of any ‘optimisation exercises’ (i.e. Machin-

ability trials – more on this later) previously under-

taken in the machine shop.

Practicalities when Star ting-Up a Tool File

Whenever a tool le system is initiated, the important

point to observe is to: start small and keep the tooling

information to be included ‘sound’. Having accepted

this principle, a company may start to build-up the

tool le steadily – over perhaps a month, including

any practical test data for maybe a hundred, or so of

the most popular tools utilised. is information now

residing within the tool le, will ow through the tool-

management system and, it will begin to highlight

the requirements of the system users, driving forward

the le’s further development. Conversely, a company

may embark on a more comprehensive tool le sys-

tem, incorporating all the machining data available on

perhaps two thousand tools, but utilising provisional

cutting data, instead of well-proven information. With

this rather heavy-handed and rapidly-built tool le

approach, the probable outcome will mean that the

whole ‘le’ has incorporated many ‘dud tooling solu-

ions’ , thereby ensuring that the system is discredited,

even before it is correctly operating at anywhere near

its optimum level.

Obtaining meaningful test results and tool assess-

ments does not necessarily demand extra eort from

the company, merely the organisation of endeavour

already being made by the company’s ‘Tooling-engi-

neers’ and those from the tool suppliers. Oen, most

of the tooling trouble-shooting activities will dissipate

once the current component batch is completed, sim-

Modular Tooling and Tool Management 243

ply because there is no framework in which this vital

information can be recorded – for future usage. So,

all the time and pain’s-taking eort needed to collate

‘sound’ tooling data is disregarded and the informa-

tion is discarded. So, when then a repeat batch order

duly arrives, the whole tooling-related data-gather-

ing process must once again begin, by ‘re-inventing

the wheel’ – this being a total and unnecessary, but is

costly waste of everybody’s time!

Tool-kitting servicing to the machine shop must

be based upon the assurance that the completed kits

are dependable, whilst providing the maximum secu-

rity from a limited budget for tooling stock. Usually

there is a nite tool stock available, with the objec-

tive being to utilise, for example, the same modular

tools across a range of machine tools. For this reason,

modular quick-change tooling, has seen a widespread

acceptance by machining-based companies of late.

Yet another important factor in any tooling requisi-

tion for a specic machining operation, is the inherent

quality of the tools used. One of the major function’s

of the tool-kitting area, is to monitor and control the

quality of delivery of tooling within the manufactur-

ing environment, by accessing the ‘tool data ow’ for

both out-going ‘new kits’ and in-coming tooling ‘old

kits’ from completed production runs. As batch sizes

become smaller, the ‘logistical-ow’ of kits speeds-up.

e eectiveness of the tool-kitting personnel will be

inversely-proportional to the number of tooling items

on the inventory and the ‘standard’ they must control.

is problem of eective tool control, is a further ar-

gument in favour of a factory-wide standardisation of

the tooling inventory. erefore, in summing up tool-

ing-related activities within the production location,

two main factors emerge, these are:

1. L

inking every tool with its application technology

– this is normally achieved in such a manner that it

is the most productive tools that are chosen for new

jobs and not the old ones – just because they have

been previously used and are known to be sup-

ported by the tool stores. is tool selection strat-

egy, will result in the optimum cutting conditions

being selected,

2. F

ormulating a rationalised and optimised tool

management ‘standard’ – this is essential as it sup-

ports tooling across the breadth of the whole fac-

tory.

NB W

hen purchasing any new tooling, or machine

tools, reference to this ‘standard’ is of the essence

for the overall system to operate eectively.

6.5.3 Overall Benefits of a Tool

Management System

By the correct implementation of a basic, but compe-

tent tool management control system, the following

list highlights the ‘rewards’ that can be expected:

•

Manpower is conserved and training requirement

minimised,

•

e number of tools lost, or misplaced is reduced,

•

Timely and up-to-date information on tool usage is

produced,

•

Tool inventory shortages are identied and pre-

vented,

•

e accuracy of the tooling inventory is improved,

•

Inventory levels and excess purchasing are mini-

mised,

•

Time spent on re-ordering, etc., plus ‘piecemeal

purchasing’ are reduced,

•

Record-keeping functions are consolidated,

•

Tool tracking and tooling availability within the

machine shop is monitored,

•

Tools in rework can be tracked,

•

A record of scrapped tools can be kept,

•

Obsolete tooling can be identied and then elimi-

nated,

•

e cost of the total tooling inventory can be criti-

cally-assessed,

•

e gauges and xtures supplied with the tool kits

can be identied and tracked,

•

Machine tool set-up, tool-return and withdrawal

times are reduced,

•

Possibility of pin-pointing over-use machining

problems, by specic personnel,

•

Improper charge-outs, losses, or pilferage can be

minimised,

•

Space requirements and overheads are reduced,

•

Possibility of incorporating existing tool numbers

and current mode of operation into an automated

system, without making radical changes.

Tool management systems provide all of the above

benets, by allowing the operations to be easily re-

ported, analysed and corrected, enabling timely de-

cisions to be made, concerning the tooling, with the

minimum of manpower and operational changes

ecessary. So that the information required by a com-

pany can be obtained, the system should be organised

to allow personnel responsible for the tools to record

heir activities. On the ‘shop oor’ , it is the usual prac-

tice to allow two basic groups of the workforce levels

of responsibility/access to the system to provide both

244 Chapter 6

vital and helpful tooling information, these are the:

Tooling-supervisor and Stores personnel.

So far, the information on Tool management sys-

tems has been principally concerned with the justi-

cation and benets that accrue through the adoption

by a company and the philosophy underpinning its

practical application. In the ‘continuous circle’ of tool

monitoring and control, the tool-kitting area is at the

‘heart’ of the overall tool management procedure. is

vital day-to-day activity of tool preparation and set-

ting, will be the subject of the following section.

6.5.4 Tool Presetting Equipment

and Techniques

for Measuring Tools

Introduction

Cutting tools that are to be utilised on CNC machine

tools for the production of workpiece features, need to

have exact measurement information regarding their

osets known, so that the CNC program can automati-

cally displace (i.e. oset) the tool these dimensional

distances, in order to perform the intended machining

task. Otherwise, major errors in the machined com-

ponent’s dimensional features would result. Hence,

cutting tooling can be classied under three distinct

headings, these are:

1. Unqualied tools – these are tools that do not have

known dimensions, therefore they must be inde-

pendently measured and these values can then be

located and placed into a ‘suitable eld’ within the

CNC Controller’s tool table. Typical of such tooling,

are special-purpose form tools that may be consid-

ered to full this classication,

2. Semi-qualied tools – these are tools where not all

of the tool measurement oset data are known. For

example, a typical Jobber drill’s diameter would be

normally be known – say, φ1

2 mm

, but perhaps its

length for the purposes of utilising it immediately

would not. erefore, it would necessitate measur-

28 Whenever a tool’s dimensional size is known, it is necessary to

refer-back to the individual tooling manufacturer’s tolerance

specication, in order to establish the limiting values when

this data is utilised, when the tool is to be used without any

form of pre-measurement being undertaken.

ing the drill’s length, once it has been suitably lo-

cated and held in an appropriate chuck,

3. Qualied tools – are when all the tool oset data

are known and this information can be readily in-

put into the CNC controller’s tool table. Typically,

‘Modular quick-change tooling’

, can be consid-

ered under this category.

Presetting on the Machine Tool – Tool Contacting

When setting an ‘unqualied’ tooling dimension –

such as a drill’s length, on the machine tool, this being

the crudest form of tool presetting*. It is achieved on

say, on a vertical machining centre, in the following

manner: the cutting tool’s tip is held in the machine’s

spindle and is positioned over the table, being slowly

‘

jogged-down’

until its just touches a suitable ‘setting

29 Modular quick-change tooling, such as the ‘front-end’ cutting

units, tted into the already machine tool-pocketed and lo-

cated ‘back-ends’ , typied by the ‘KM tooling’ ranges (i.e. see

Figs. 120 to 122), would give the following repeatability read-

ings:

• Axial tolerance ±0.0025 mm,

• Radial tolerance: ±0.0025 mm,

• Cutting-edge height tolerance: ±0.025 mm.

NB All of these tooling manufacturer’s tolerances, limit the

machining tolerances that can be held, unless they (i.e. already

placed within quick-change tools in their respective holders)

themselves are measured, which tends to negate the rationale

for their original purchase!

‘Jogging-down’

– sometimes referred to as ‘inching-down’ , is

a manual means of slowly lowering the tool’s tip down onto a

surface – in this case a known height ‘setting-block’. is lin-

early-controlled action is achieved, by employing the ‘hand-

wheel’ , which allows the handwheels angular rotation to be

equated to an operator preselected incremental amount. is

incremental motion can be changed to a smaller value, as the

block is slowly approached, to give a sense of ‘feel’ (i.e some-

what like using a ‘feeler-gauge’), as contact is made between

the tool and the block.

NB e tooling is usually kept stationary while this manual

setting activity is undertaken.

* is is not strictly the most basic tool setting method, as the

‘cut and measure’ technique – then setting this measured value

in the tool table, is the most primitive and time-consuming

procedure of tool oset setting.

Modular Tooling and Tool Management 245

block’

. e Z-axis position is then noted and its value

is automatically entered into the tool table, giving a

‘semi-qualied’ tool oset, that can then be used for

the important Z-axis motion – when coming down

onto the workpiece’s surface to begin engaging in the

rst cut. If each tool length has to be input into the tool

able’s ‘osets’ , then this simple procedure has several

disadvantages: it is labour-intensive, ties-up cycle con-

siderable time, it is rather inaccurate and, it sets only

one oset dimension. In the case of turning centres,

the technique of determining osets is dierent, but

similar limitations still apply.

A tool presetting device is oen used on many of

today’s machine tools, this technique is typied by the

ubiquitous ‘

touch-trigger probe’

. Hence, this type of

tool-contacting presetting probe fulls a number of

‘

quoted benets’ , such as:

•

Setting/re-setting of tool length and diameter (Fig.

133b) – automatically up-dating, or correction of

the respective tool table osets, even while the tool

is still rotating,

•

Measurement of a complete tool station – automat-

ically in just a few minutes,

31 ‘Setting blocks’ , are usually manufactured from hardened steel,

that have been accurately and precisely ground to a known di-

mensional size and tolerance, nominally to some conveniently

‘round gure’ , for example:100 mm in height. ese ‘blocks’

are usually either rectangular, or round in cross-section. e

rectangular ones are preferred, because dierent nominal di-

mensions can be utilised for each adjacently at and square

face. e tolerance for the ‘Setting block’ should be ‘very close’ ,

as any dierence from the nominal size when input into the

tool table, will impinge on the overall workpiece tolerance, in

essence, somewhat reducing the tolerance’s ‘working range’.

32 ‘T

ouch-trigger probes’ **, in the simplest form these ‘tool

probes’ are omni-directional switches, that are sprung-loaded,

which when the tool makes contact with either an attached

setting cube, or a cylindrical ‘setting gauge’ (Fig. 133b), it im-

mediately breaks the electrical circuit. is loss of electrical

contact occurs when the three equi-spaced precision rods:

each one seated on two precision balls (i.e. each rod being po-

sitioned at 120° to each other) in a simple kinematic seating

mechanism, are lied/pushed either individually, or ‘as one’

out of their respective seating(s), which triggers an ‘electrical

pulse’ representing a nominal dimension and is automatically

recorded as either a length, or radius – in the case of a rotating

tool, which then automatically up-dates the tool table’s osets

for this tool.

**On a turning centre (Fig. 133a), this tool setting touch-trig-

ger probe, is termed a ‘tool eye’.

NB A small vertical machining centre with a 12 to

15 tool station, would take at least 5 minutes per

tool, with the traditional manual technique, men-

tioned above (i.e. see Fig. 133-bottom right, inset

graph/description).

•

Elimination of manual setting errors – tools that

are set manually, particularly tooling such as a large

diameter face mill, it will be open to errors when

setting both height and diameter osets. is is

because each cutting insert may ‘stand proud’ in

its respective seating, giving a false oset reading

– when stationary. Ideally, the whole tooling assem-

bly needs to be rotated as its oset is set,

•

No presetting of tools is necessary – as this is auto-

matically undertaken on the machine tool,

•

Accurate and precise ‘First-o machining’

– this

is the result of condence in the tool osets, set by

he ‘probing system’ ,

•

In-cycle tool breakage detection – at convenient

and programmed pre-selected intervals, the tool’s

osets can be checked for either: tool wear – to a

prescribed level, or tool breakage, which will auto-

matically stop the machine preventing either fur-

ther workpiece damage, or part-scrappage,

•

Improved condence in unmanned machining

– due to the fact that tool breakage detection pe-

riodically occurs, untended machining operations

can be undertaken.

ese are ‘real benets’ that occur when using ‘on-ma-

chine’ tool presetting equipment, but the ‘down-side’ of

such systems is they do utilise some potential in-cycle

cutting time. is negative eect using some of the cy-

cle-time, can be signicantly reduced for the following

presetting system, employing non-contact laser-based

tool setting techniques.

33 ‘First-o machining’ , this term is self-explanatory, in that it

is the rst component produced in a batch which is simply

known as the ‘First-o’ the machine. Invariably, this initial

component produced, is subject to rigorous inspection proce-

dures, being the ‘initiator’ for calculated data concerning the

whole batch’s metrological and statistical variability/consis-

tency.

246 Chapter 6

Figure 133. Cutting tool osets being set on a turning and machining centre. [Courtesy of Renishaw plc].

Modular Tooling and Tool Management 247

Presetting on the Machine Tool –

Non-Contacting Tool Setting

In recent years, laser systems for tool setting and bro-

ken tool detection on CNC machining centres have

become popular (Fig. 134), as manufacturers realise

the benets of fast process set-ups and in-process

feed-back on the tool’s current condition, particularly

on diminutive tooling that cannot be easily measured

by the more usual contact-type sensors.

Laser non-contact tool setting systems, utilise a

beam of laser light which passes between a transmit-

ter and a receiver, located either on the bed of the

machine, or on each side of it allowing the beam to

pass through the ‘working volume’ (Figs. 134a and b).

Hence, the tool’s passage through this beam, causes a

reduction in light as seen by the receiver, which will

then generate a ‘trigger-signal’. is ‘triggered-signal’

for the machine’s actual position, is instantly recorded

and from which, the tool’s dimensional characteristic

can be derived. Not only can the system measure the

required tool’s dimensional parameters, it can also be

used to detect broken tools. is tool breakage process

involves rapidly moving the tool into a position where

it can intersect the laser beam, so, if the light reaches

the receiver, then the tool’s tip, or point, must be either

missing, or broken. ere are quite considerable ben-

ets that accrue by the application of a non-contact

laser tool setting system, these include:

•

Rapid measurement of both tool length and di-

ameter – tools can be moved into the laser beam

at high speed, without risk, or any attendant dam-

age and the tool osets are automatically up-dated

(Fig. 134a),

•

Fast tool setting times can be achieved – tools can

be measured at normal rotational speeds, allowing

tooling assembly and taper tment errors such as

radial run-out, taper ‘pull-back’ to be identied,

then compensated for by the system,

•

Minute, or delicate cutting tools can be conve-

niently measured – without any subsequent tool

wear, or damage (Fig. 134b),

•

Tool breakage can be checked at very high

feedrates – this ecient process minimises cycle-

time, while increasing condence in untended ma-

chining applications,

•

Multi-point tooling can have each facet checked –

this is automatically undertaken while the tool ro-

tates,

•

Monitoring tool settings on the machine – enables

compensation for any ‘t

hermal movement’

of the

machine spindle.

Although the measurement process lasts for only a few

seconds, this is long enough for the chance of a falling

coolant drip to intersect the laser beam, possibly creat-

ng and attendant measurement error. Hence, the laser

tool setting equipment, must be able to distinguish

between reductions in light at the receiver, created by

a ‘falling object’ (i.e. termed: ‘drip-rejection’) as com-

pared to rotating tool, if it is to avoid ‘false-triggering’

producing tool measurement errors. is elimination

f ‘false-triggers’ , is achieved by the ltering-out of

signals by the electronic interface, this value being set

at a pre-determined ‘trigger-threshold’. It should be

noted, that the laser tool setting system cannot cope

with following circumstances: the presence of ‘ood-

oolant’ , cutter edge and prole checking, nor with

radial broken tool rejection processes.

e cutting edge laser measurement is quite a

complex process, when the tooling assembly is both

rotating and in linear motion simultaneously. If one

considers the relative motion of just one of these cut-

ter’s teeth, then, its edge moves in a circular path and

superimposed onto which will be the axial feedrate,

this motion being perpendicular to the laser beam.

Hence, for each of the tool’s revolutions, the promi-

nent edge approaches the laser beam by an increment,

this value is the feed per revolution. Such incremental

movement, introduces a potential error into measure-

ment of the tool’s size. For instance, if a tool rotates

t 1,000 rev min

–1

while feeding toward the laser beam

at 100 mm min

–1

, it will be seen to advance by 100 µm

between intersections of its prominent cutting edge

34 ‘ermal movement’ of the machine spindle, is important, as

the whole tooling assembly can eectively ‘grow’* due to ther-

mal eects, which may present problems – if not compensated

for – when very tight machining tolerances have to be held, or

maintained across either a high-quality machined component,

or for consistency in a large batch run.

*Tests undertaken, on a vertical machining centre equipped

with a ball bearing spindle – utilising a special-purpose ‘Invar’

spindle analyser – with the tooling being rotated at 3,000 rev

min

–1

under ‘no-load conditions’ for one hour, have produced

the following thermal results: Z-axis dri 9.2 µm, Y-axis dri

6.3 µm and X-axis dri 0.7 µm. Additionally, the bearing itself,

had some radial error motion present – as indicated in a ‘po-

lar-plot’ , this value being typically: 4.6 µm for the total radial

error.

248 Chapter 6

Figure 134. Automatic cutting tool setting and tool breakage detection, utilising an ‘on-machine’ non-contact laser.

[Courtesy of Renishaw plc]

Modular Tooling and Tool Management 249

to that of the ‘stationary position’ of the laser beam

– this being the maximum possible ‘feed per revolu-

tion’ error for any one particular reading. Conversely,

an improved accuracy can be obtained by rotating the

cutter faster, but advancing more slowly. For example,

f one wants only a 1 µm rev

–1

intersections, this level

of accuracy can be obtained by rotating the tooling at

,000 rev min

–1

,while advancing at only 3 mm min

–1

In order to minimise cycle times, the tool measure-

ment soware, programs the machine tool to move the

tooling into the beam initially from a ‘stand-o dis-

tance’ that is adequate to account for the uncertainty of

tool assembly build-up – this is important when setting

the tool’s length, if the tool is held in a collet, or simi-

larly-designed toolholder. So, the initial move is a fast

feedrate to gain an approximate position with respect

to the laser’s beam, from which the tool is backed-o

by a small linear distance. Here, the tool is ‘probed’ at

a reduced reduced feedrate, this is necessary to more

accurately nd the tool’s location, from where a very

short distance ‘back-o’ move is executed. Finally, a

easurement move is completed at a very low feed-

rate, so that an accurate measurement is tenable. is

complete tool checking process is considerable quicker

than approaching with the laser beam at a constant,

but low feedrate, from a larger ‘stand-o distance’ – see

Fig. 134c. While, yet another challenge to precise and

accurate tool measurement, is the result of the pres-

ence of either coolant, or debris on the tool’s tip which

is about to be measured. e most signicant prob-

lem facing non-contact sensing, when compared to its

equivalent contacting techniques – this latter method

achieves ‘hard-contact’ with the tool and can thereby

safely ignore any coolant lms, or liquid drips – is that

in the former case no actual tool contact occurs. is

lack of contact in the presence of uid media, can be

overcome by rotating the cutting tool assembly at very

high speeds, so as to dislodge any uid residue, or per-

haps another strategy is by utilising an air-blast on the

tool for non-contact measurement.

Yet another soware technique that can be used, is

the capacity to measure the tooling several times and

apply a ‘scatter tolerance’ to check for any variation

esulting from measuring ‘something’ , other than the

tool itself (Fig 134d). is soware routine will retake

readings until it obtains several values within the re-

ired tolerance – these ‘tool-checking retries’ , plus

the ‘scatter tolerance bandwidth’ can be pre-selected

by the user.

e detection of broken tools is somewhat less de-

manding than for tool measurement – in terms of ac-

curacy and precision, although the cycle-time tends to

be more critical. e demands on a laser broken tool

detection system require it to be ‘active’ at the instant it

is required and, be able to operate under the prevailing

conditions, instantaneously aer machining stops. e

laser transmitter for the non-contact tool detection

system shown in Fig. 134ai, has been designed with a

‘MicroHole™’

, this ensures that the presence of cool-

ant does not aect the integrity of the laser system. In

practice, the laser system reliably operates under rela-

tively ‘harsh’ workshop conditions and the broken tool

detection system works in the following sequential

manner:

. Tool’s end is moved at rapid traverse into the laser

beam by 0.2 mm,

2. Tool breakage cycle is activated via an M-code from

the CNC controller,

. End of tool dwells in the laser beam for between 0.1

to 0.3 seconds,

. If laser light is received by the optical receiver unit for

more than a specied time-period, typically 10 µs,

then this distinguishes a broken tool is present,

. If laser light is not received by the optical receiver

unit, then the tool’s condition is satisfactory,

. Tool is the moved rapidly to its respective home po-

sition – end of cycle.

NB 

is detection cycle also enables small tools to

be inspected, even when in the presence of ‘ood-

oolant’ , thereby minimising cycle-times.

ese laser non-contact tool setting systems, oer

many more soware-based features, not described

here, such as: cutter prole checking routines, together

with many inspection/checking routines for either tool

measurement, or broken tool detection. Furthermore,

laser tool setting systems provide machining-based

companies with a rapid, exible, accurate and precise

approach to control tooling dimensions and oer the

techniques necessary to increase machining automa-

tion.

35 ‘MicroHole™’ – both for the laser transmitter and the opti-

cal receiver, incorporate an angled aperture of just 0.75 mm

diameter, as this ensures that protection from: coolant, chips,

swarf and other debris such as machined graphite nes oc-

curs, because of a continuous stream of air that ows through

and along the laser beam – protecting it as schematically il-

lustrated in Fig. 134ai.

250 Chapter 6

Figure 135. An automated ve axis CNC universal tool measuring machine for metrological and geometric inspec-

tion. [Courtesy of E. Zoller GmbH & Co. KG]

Modular Tooling and Tool Management 251