Smith G.T. Cutting Tool Technology: Industrial Handbook

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Figure 141. Presetting equipment and ‘guidelines’ for the setting of single-bladed reamers.

262 Chapter 6

treated with almost contempt, until they are required

for a repeat order, or utilised for a new machining op-

eration. Here, when the tools are not in use, problems

arise because of the following:

•

Wasted and poorly utilised space – tools are kept

either simply ‘oating around’ in an ‘ad hoc’ sys-

tem, or are just sitting on top of each other – dam-

aging the precision-ground tooling surfaces – while

being kept in the open,

•

Time is lost looking for tools – due to the lack of any

form of tool management, tools must be looked for

located, then assembled – under less than ‘ideal con-

ditions’ – so the minimum of tool control occurs,

•

Lack of eciency – as a result, more eort is re-

quired by personnel who must try to nd tools,

changing front- and back-ends to suit the selected

machine tool for the production run causing lead-

times to lengthen.

Considering that up to 10% of the machine tool cost

is tied-up in the purchase of tooling, then tools need

to be looked aer with some degree of care and atten-

tion. An area adjacent to the workshop, should be set

aside for the purposes of storing tools and associated

equipment in purpose-built tooling cabinets (Fig. 142)

and form a basis for tool presetting activities. ere

are several advantages in utilising telescoping drawer

cabinets for tool storage (Fig. 137a and b), these in-

clude:

•

Increased tool storage density – allowing the

drawer space to be completely eciently lled-up

in the minimum of space,

•

All tooling is kept under cover – thereby avoiding

tool damage, while keeping tools dust and debris-

free,

•

All tools and ‘associated paraphernalia’ are read-

ily to hand – tooling drawers can be completely

open-up, so that the contents are both easy to see

and to arrange,

•

Tooling components t into their respective

places – the drawers appropriately sectioned, to to-

tally enclose the tools and their component parts,

making it impossible for them to drop out and be

damaged,

•

An organised and practical tool management sys-

tem is achieved – within the tool store and pre-

setting facility. erefore, all of the tooling com-

ponents can be classied and categorised in the

respective drawers – with every tooling part clearly

seen.

As a result of this ecient tooling component lay-

out and tool-kitting facility, consumable tools can be

‘tracked’ within the tool store, but when these consum-

ables leave the store vicinity (Fig. 142c), they are to all

intents and purposes ‘scrapped’ as far as the tool stores

are concerned. Returnable tools destined for eventual

re-use can be ‘tracked’ around the machine shop by

a number of tool-identication means (i.e as seen in

Figs. 116 and 117 – using ‘tagged tools‘), or at the most

basic of identication levels, by judicious labelling,

or bar-coding of tools, with feed-back of information

to the tool stores. Oen, for the most frequently used

tools, they are assembled into a composite forms, then

issued as ‘grouped-tools’ in the form of kits for a spe-

cic job (i.e see Fig. 142c).

Sometimes, tools are individually issued to ma-

chine tool setters/operators and are not assembled

nto ‘kits’ , under such circumstances, the stores will

keep a record to show: to whom they were issued, the

machine tool on which they will be used, the num-

ber and identication of these tools, together with the

date of issue.

A major benet of creating an area set-aside close

to the machine tools for dedicated tool management,

is that tool kits can be made-up ahead of the time –

this being dictated by master schedule, so that they are

ready just-in-time before any machining commences.

A result of this timely tooling strategy, the lead times

are reduced, which is of prime importance to a com-

pany in a competitive fast-developing market.

Oen, it is the case that all tooling is assembled in

the tool stores /preparation facility (Fig. 142b). is

advanced preparation means that metrology-based

46 ‘Lead times’ , refer to the time taken before manufacture of

the part, or prior to a production run beginning. ese ‘times’

are dependent upon a range of interrelated factors, such as:

component stock quantities and their availability, the machine

tools that are available, plus ‘line-balance’* factors, etc.

*‘Line of balance’ (LOB), refers to a technique which permits

the calculation of the quantities of the particular activities, or

components which must have been completed by a particular

intermediate date, in order that some nal delivery schedule

might be satised. erefore, in this instance, it can be con-

sidered as a machine tool scheduling and a control technique.

In most of the LOB activities undertaken concerning machine

tools, plant utilisation levels are paramount and if possible, a

smooth and consistent LOB across all of the production ma-

chines is desirable – for both high eciency and consistent

work-throughput.

Modular Tooling and Tool Management 263

supplies such as ‘limit gauges’

, together with jigs and

xtures , are also the responsibility of the tool stores

personnel, being despatched with the tool kits for a

particular production run. When this is the case, to-

tal packages are issued, containing: cutting-tool and

work-holding kits, plus the limit gauges necessary for

metrological checking/inspection. A tool store and

prepartion facility with responsibility for all of these

tooling-related aspects, becomes a ‘focal point’ for

the machine shop for all matters relating to tooling,

whether they are for breaking-down of previously used

kits, calibration of gauges, or even purchase require-

ments for the latest tool available. Specialist personnel

in the tool stores/preparation facility, have consider-

able responsibility in servicing tooling for the overall

manufacturing resources on these machine tools and

as a result, will have amassed a large working-know-

ledge of the production tooling requirements, so their

opinions should be sought prior to any purchasing de-

cisions on new tooling.

6.5.6 Computerised-Tool

Management – a Practical Case

for ‘Stand-alone’ Machine Tools

If one considers the tooling requirement for a stand-

alone machining centre, then today the market de-

47 ‘Limit gauges’ , are based upon the stated International Stan-

dards agreed for ‘Limits and Fits’ for component toleranc-

ing. e use of limit gauges, is a form of ‘attribute sampling’*

where no attempt is made to determine the size of the work-

piece toleranced feature, but they are simply utilised to estab-

lish whether the component’s critical dimension is within the

specied limits of size, or not. In practice, a component that has

hole that has simply been drilled and reamed, might require a

double-ended plug gauge, with one ‘Go’ end of the plug gauge

being of full form and checking the maximum material con-

dition and as many dimensions as possible, with the ‘Not go’

end checking the minimum material condition and only one

dimension – which as its name implies, this latter end should

not go into the reamed hole. is limit gauging technique ful-

ls ‘Taylor’s eory of Gauging’.

*‘Attribute sampling’ techniques, are a means of sampling im-

perfections that are not in the strictest sense, measurable quan-

tities. For example, a mirror-surface that has been produced,

might be scratch-free, or may have other blemish marks, these

factors might be cause for its rejection. Hence, ‘attribute sam-

pling’ can be considered as a two-way classication system for

either acceptance, or rejection of the workpiece.

mands for its manufactured products has become

much more diversied, with the number and multiplic-

ity of tools required having also increased. As has been

shown previously in this chapter in the preparation for

workpiece machining, conrmation that all the tool-

ing – including spares (i.e. ‘Sister-tooling’ – see Foot-

note 1 in this chapter), must be loaded into the tool

magazine. A computerised-tool management system

(Fig. 143a), eliminates the possibility of mistakenly se-

lecting the wrong tool and exacerbating the situation

of placing it in the incorrect tooling pocket in the tool

magazine. With these ‘tagged tools’ (Fig. 143d) having

non-contacting read/write embedded microchips in

say, the pull-stud region of the assembled tool – allow-

ing coolant-through-spindle applications. e follow-

ing tooling data can be automatically registered into

the CNC memory (Fig. 143b), such as tool: number

and its ID number; name and the nominal diameter;

length, plus its ‘working-diameter’; thrust and power

coecients; interference data, with ‘large diameter’

tool data – if required; life accumulated/actual usage

time, wear and breakage ags.

Many quite complex and sophisticated computer-

ised-tool management systems exist, but essentially

the practical system depicted in Fig. 143, can be use-

fully applied to a machining centre in an ecient pro-

duction environment. Here, the system comprises of

three modules, these are:

•

Tool module – this being the smallest component

of the tool management system, where the tooling

data is both read/written at the machine magazine

tool loading/unloading position (Fig. 143c). e

tool data is automatically registered in the CNC

memory at the push of a button, with this tooling-

related data being continuously updated – as ma-

chining continues,

•

Tool Management module – once this is combined

with the ‘tool module’ (above), then tool manage-

ment is conducted on a much larger scale, allowing

not only all of the previous tooling data to be moni-

tored and controlled, but additional information on

the: toolholder’s bill of materials, insert inventory,

and its location, together with a graphic tooling

display of its build-up and information regarding

the correct procedure to ensure fast and error-free

tool measurement on the presetting machine (Fig.

143a),

•

Tool transportation module – consists of a tool

transporter robot having high positional accuracy

(i.e. not shown), which automatically transports

264 Chapter 6

Figure 142. An integrated tool and data management system – for complete tooling deployment. [Courtesy of Susta –

Tool Handling]

Modular Tooling and Tool Management 265

Figure 143. A computerised tool management system for an FMS facility. [Courtesy of Yamazaki Mazak].

266 Chapter 6

the tools to-and-from each machine – changing the

‘stand-alone’ machine into a simple form of ex-

ible manufacturing system (FMS). It consists of a

‘tool hive’ stocker, which acts to store tools in a cen-

tralised and convenient location within the shop,

having a tool tarnsport controller – controlling the

overall system’s operation.

Such tool management systems are becoming quite

common-place in many highly-utilised manufacturing

environments around the world of late, which consid-

erably increases the overall utilisation rate of these au-

tomated CNC machine tools.

References

Journals and Conference Papers

Chandler, B. Crib Control [Organising Tooling Workplace].

Cutting Tool Eng’g., 48–53, Sept. 1999.

Gough, J. Going Hell for Leather [High-speed Milling].

Manufact. Eng’r., 13–15, 1991.

Gust, C. Don’t Fret [How to Maintain Toolholders]. Cutting

Tool Eng’g., 53–55, July 2003.

Hanson, K. Ready, Preset, Go [Tool Presetting]. Cutting

Tool Eng’g., 30–38, June 1999.

Hanson., K. Not so Fast [Quick-change Tooling]. Cutting

Tool Eng’g., 52–55, June 2002.

Ingersoll Pub. Facing o with Stainless [Tangentially-

mounted Face Mills]. e Cutting Edge, 8–9, No.1,

1989.

Ingersoll Pub. Engineering Success [Large Special-purpose

Slotting Cutters]. e Cutting Edge, 15–16, No.4, 1988.

Ingersoll Pub. Special Tools solve Special Problems [Barrel-

screw Adjustment of Cutting Inserts in Face Mills]. e

Cutting Edge, 14–15, No.1, 1990.

Ingersoll Pub. Milling Cutters: Milling Cutters [Production

of Face Mills]. e Cutting Edge, 10–11, No.1, 1991.

Johnson, B. Reaming Technology. Industrial Tooling Int.

Conf., Southampton (UK), Molyneux Press, 132–152,

Sept. 2001.

King, D. If you’re not Presetting, you’re not Cutting It. Cut-

ting Tool Eng’g., 32–34, Jan. 1994.

Layne, M. On Balance [Milling Tooling/Spindles]. Cutting

Tool Eng’g., 52–55, June 2002.

Lewis, D.L. Factors for Successful Rotating Tool Operation at

Hi-speeds. SME High-speed Machining Clinic (Raleigh,

NC), April 1991.

Linn. T. Fundamentals of Precision in High-speed Milling.

Precision Toolmaker, 306–310, Oct. 1989.

Mason, F. Video Presetting: Reliable and Safe. American

Machinist, 36–38, Aug. 1991.

Mitchell, W.A. When and Where to ink High-speed Mill-

ing. Modern Machine Shop, 55–63, Oct. 1991.

Park, H. and Little, T.A. Assessing Machine Performance.

American Machinist, 39–42, June 1992.

Renishaw plc. Innovative Laser Tool Setting Technology pro-

vides Accuracy, Flexibility and Robust Operation. Ren-

shaw ‘White paper’ , 1–10, 2003.

Richter, A. Squeeze Play [Shrink-t Tooling]. Cutting Tool

Eng’g., 34–38, Sept. 2000.

Side and Face milling – Application Guide. Sandvik Coro-

mant Pub., 1996.

Sprow, E. High-speed Spindles for Milling? Tooling and Pro-

duction, 32–35, Mar. 1991.

Smith, G.T. Ultra-high Speed Machining – e Problems

Associated with Spindle Designs, Tooling and Machined

Parts when Milling. Proc. of FAIM Int. Conf., CRC Press

Inc. (Florida), 947– 961, 1992.

Smith, G.T. e Assessment of Machining and Turning Cen-

tres using Artifact-based Techniques, such as the Ballbar.

Proc. of: Laser Metrology and Machine Performance,

Computational Mechanics Pub., 307–316, 1993.

Zoller, C. From Presetting to Tool Management. Cutting

Tool Eng’g., 35–38, April 1998.

Books, Booklets and Guides

Ashby, M.A. Materials Selection in Mechanical Design. But-

terworth-Heinemann Pub., 2001.

Barnett, H. Operations Management (2

Ed.). Macmillan

Press Ltd., 1996.

Bergman, B. and Klefsjö, B. Quality – from Customer Needs

to Customer Satisfaction. McGraw-Hill Book Co., 1994.

Blanchard, B.S. Logistics Engineering and Management – 4

Ed. Prentice-Hall Inc., 1992.

Galyer, J.F.W. and Shotbolt, C.R. Metrology for Engineers

Ed.), Cassell Pub, Ltd, 1990.

Haberberg, A. and Rieple, A. e Strategic Management of

Organisations. Pearson Education Ltd, 2001.

Kief, H.B. and Waters, T.F. Computer Numerical Control.

Glencoe Pub. 1992.

Modern Metal Cutting. Sandvik Coromant Pub., 1994.

Oakland, J.S. Statistical Process Control – A Practical Guide.

William Heinemann Ltd, 1986.

Ránky, P.G. e Design and Operation of FMS. IFS Pub.

Ltd., 1983.

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1980.

Modular Tooling and Tool Management 267

Shotbolt, C.R. Workshop Technology – Book 1. Cassell and

Co. Ltd, 1973.

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ting Technology. IFS/Spinger Verlag, 1989.

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1993.

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268 Chapter 6

Machinability and Surface Integrity

‘It is common sense to take a method and try it.

If it fails, admit it frankly and try another.

But above all, try something. ’

FRANKLIN DELANO ROOSEVELT

(1882 – 1945)

[32

President: United States of America]

7.1 Machinability

Introduction – an Historical Perspective

Today, greater emphasis is being placed on a compo-

nent’s ‘machinability’ ,

but this term is an ambiguous

one, having a variety of dierent meanings, depending

upon the production engineer’s requirements. In fact,

the machinability expression does not have an author-

itative denition, despite the fact that it has been used

for decades. In 1938, Ernst in his book on the ‘Physics

f Metal Cutting’ , dened machinability in the follow-

ing manner:

‘As a complex physical property of a metal involving:

•

True machinability, a function of the tensile strength,

•

Finishability, or ease of obtaining a good nish,

•

Abrasiveness, or the abrasion undergone by the tool

during cutting.’

By 1950, Boulger had summarised these criteria more

succinctly in his statement: ‘From any standpoint, the

material with the best machinability is the one permit-

ting the fastest removal of chips with satisfactory tool

life and surface nish.’ is ‘Boulger denition’ leaves

some unanswered questions concerning chip-form-

ing factors, cutting forces and, has little regard for

either the physical and mechanical properties of the

mat

erial, nor potential sub-surface damage caused by

the cutting edge. By 1989, Smith made the point that

in fact machinability, had to address these properties

and the word ‘metal’ should be substituted by the ex-

pression ‘material’ ,

in a combined general-purpose

denition, as follows: e totality of all the properties

of a work material which aect the cutting process and,

the relative ease of producing satisfactory products by

chip-forming methods.’ Even these denitions still lack

sucient precision to be of much practical use and by

1999, Gorzkowski, et al., in their powder metallurgy

paper concerning ‘secondary machining’

, entitled:

1 ‘Secondary machining’ , is a term used to cover any additional

post-machining operations (e.g. drilling, turning and milling,

etc.), that has to be undertaken on powder metallurgy (i.e.

sintered’) compacts, aer compaction and sintering. Nor-

mally, these post-sintering production processes, are only car-

ried out to ensure, say: a good turned registered diameter, a

precision cross-drilled hole, precise and accurate screwthread,

an undercut, or similar* – as this is a last resort, as it adds-

value to the overall component’s cost.

‘Machinability’ , stated that: ‘Machinability is a dicult

property to quantify.’ Why is this so? It is probably is

a combination of many inter-related factors, such as:

chemical composition of the workpiece, its micro-

structure, heat-treatment, purity, together with many

more eects which inuence the overall machining

operation. In Fig. 144, this diagram attempts to high-

light some of the important factors that aect a com-

ponent’s machined state – its ‘machinability’. Although

even here, an important factor such as power con-

sumption is missing, showing that this is by no means

an exhaustive ow-chart of the complex mechanisms

that exist when a material is subjected to machining.

is is probably why it is virtually impossible to state

that one, or another material aer machining, was ei-

her a ‘good’ , or bad’ one to machine. By utilising some

‘impartial and objective testing program’ ,

it may be pos-

sible to ‘rank’ prospective or current materials, or pro-

duction tools – in some way, perhaps by way of a ‘De-

sign of Experiments’ (DoE), in combination with ‘Value

Analysis’ (VA) approach to the production problem.

is strategic technique to the problems of ‘machin-

ability comparisons’ of diering factors will shortly be

mentioned in more detail, aer a brief resumé on just

some of the machinability testing techniques favoured

today.

7.1.1 Design of Machinability

Tests and Experimental

Testing Programmes

Over the years, a range of machinability testpieces

have been developed – more on this shortly – that are

used to assess specic cutting conditions found when

machining the actual production part. e assessment

of a material’s machinability can be undertaken by two

groups of tests, these are machining and non-machin-

ing testing programmes. e former machinability

group, can be further sub-divided into either ‘ranking’

and ‘absolute’ tests and, it should be mentioned that

the latter non-machining tests fall into the ranking

category. Oen, ‘ranking’ tests are termed ‘short

*Powders when they ll the dies and are compacted, cannot

reproduce component features at 90° to the major pressing di-

rection – hence, the powders cannot readily move sideways –

as such, features, like: screwthreads, transversal features (i.e.

undercuts, etc.), must be machined aerward, hence, the term

‘secondary machining’.

270 Chapter 7

Figure 144. The major factors that inuence a machined component’s condition.

Machinability and Surface Integrity 271