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• Small batch – up to perhaps 50 workpieces, • Medium batch – between 20 to 100 workpieces, • Large batch/Volume production – >100 work- pieces. NB ese classications of batch size are open to considerably much wider interpretation, obviously depending upon a specic company’s production requirements and the actual machined part’s: com- plexity, material cost, machining operations and its dimensional size and so on! At any workpiece quantity greater than the ‘Job shop’ levels having similar production processes undertaken, allows them to be grouped into ‘families’ , according to their: dimensions, tolerances, workpiece materials, etc. is technique of allocating components to be ma- chined into similar groupings is oen termed ‘Group Technology’ 24 . It is vitally important that both the Sales and Mar- keting personnel are aware of the company’s patterns of manufacture and their capabilities, if the company is to be able to rapidly respond to their customer’s needs. e sales force will be able to relate a customer’s requirements to the standard range of parts produced, with the manufacturer being in a position to ‘ne-tune’ even small production runs for maximum eciency. By comprehending the manufacturing process for the company’s standard-ranges, allows the optimum con- ditions of production to be utilised, even when ‘modi- ed standards’ , or even ‘specials’ have to be produced. Flexibility here, plus the ability to cater for unique cus- tomer needs, may oer new market opportunities for the company. 24 ‘Group Technology’ (i.e. GT), is essentially utilised for ‘group- ings’ in two distinct varieties: (i) Component geometry – the ‘closeness of shapes’ , (ii) Similar production processes – such as: Milling, Drill- ing, Turning, etc. e benets of utilising a GT-approach to manufacture are: smoother logistical work-ow, simplied work control, more ecient plant layout and improved use of oor-space, contributing to enhanced manufacturing versatility and better response to variable workpiece shop- loadings. NB e GT-approach to manufacturing lends itself to compo- nent coding systems, typically of the Opitz variety for a unique part-coding classication. Perishable and Capital Equipment Review In many cases, cutting tool manufacturers produce standard forms to enable companies to compile data on both their perishable and capital equipment needs. erefore, it is necessary to gather the data together, because the performances of either categories are independent. If a tooling survey is approached in a methodical and step-wise manner, then the following sequence, may be of some help: • Collect data on perishable tooling, a company must analyse their entire tool-ow system, includ- ing tooling inventories: high-lighting the maximum and minimum levels, quantities of new and used tooling, together with their tool-storage require- ments. As a preliminary data-gathering exercise, all the items in stock should be listed, plus the number currently in stock and, the quantity used in the last 12 months, with the last price paid for them, • Review the stock lists for tool obsolescence, by checking to see which items have not been used in the last 12 months and which can be replaced by say, an ANSI, or DIN standard item. Any tools fall- ing into this category, can be considered obsolete, it would not be a surprising fact to nd out that up to 50% of the current tooling inventory was obsolete – as has been shown in a survey in the USA. is level of obsolescence, can be regarded as money ‘tied-up’ and doing nothing for the company’s prof- itability, • Remaining ‘tooling items’ should now be reviewed, as these are not obsolete. For example, the cemented carbide insert grade of tooling, should be grouped according to their grade/coating, size, geometry, etc., then once they have been ‘grouped’ in this manner, it is now perhaps possible to order larger quantities of them, enabling the company to exert some ‘leverage’ over their suppliers and to obtain substantial cost advantages as a result. NB If tooling information of this nature is com- piled and regularly up-dated, then reviewed, future tooling decisions can be speeded-up and decisions can be taken with some degree of condence. e compiling of information concerning capital equip- ment within the factory, usually commences with the preliminary identication of such machine tools and associated equipment, then numbering them (i.e. this activity is oen termed: ‘brass-tagging’) and their spe- Modular Tooling and Tool Management cic 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 25 , 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 benets, 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 aer 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 eciently 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 soware, 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 dierent 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 specically, 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 the ‘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 ecient 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’ 26 . 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 soware 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 oen 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 protable, (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’. Chapter 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 soware structure of the tool le – of necessity – being highly complex and interrelated in nature, it is not possible within the connes 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. Tooling is built-up from modular elements – which are the ‘key’ to eective 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 dierent modular elements, to suit a range of machines, 2. Materials Requirement Planning (MRP) 27 – 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 specic ‘key’ notation, 27 ‘Materials Requirement Planning’ (MRP*), is a soware- 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 condent it might have won. en, the MRP soware 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 dierentiate 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. Organisation 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 reects 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- tions’ , 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 eort from the company, merely the organisation of endeavour already being made by the company’s ‘Tooling-engi- neers’ and those from the tool suppliers. Oen, most of the tooling trouble-shooting activities will dissipate once the current component batch is completed, sim- Modular Tooling and Tool Management 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 eort 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 specic 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 eectiveness 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 eective 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. Linking 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. Formulating a rationalised and optimised tool management ‘standard’ – this is essential as it sup- ports tooling across the breadth of the whole fac- tory. NB When purchasing any new tooling, or machine tools, reference to this ‘standard’ is of the essence for the overall system to operate eectively. .. 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 identied 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 identied 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 identied and tracked, • Machine tool set-up, tool-return and withdrawal times are reduced, • Possibility of pin-pointing over-use machining problems, by specic 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 benets, 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 necessary. 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 their 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 Chapter 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 benets 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. .. 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 osets known, so that the CNC program can automati- cally displace (i.e. oset) 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 classied under three distinct headings, these are: 1. Unqualied 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 full this classication, 2. Semi-qualied tools – these are tools where not all of the tool measurement oset data are known. For example, a typical Jobber drill’s diameter would be normally be known – say, φ12 mm 28 , 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 specication, 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. Qualied tools – are when all the tool oset data are known and this information can be readily in- put into the CNC controller’s tool table. Typically, ‘Modular quick-change tooling’ 29 , can be consid- ered under this category. Presetting on the Machine Tool – Tool Contacting When setting an ‘unqualied’ 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’ 30 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’ , typied 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! 30 ‘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 oset setting. Modular Tooling and Tool Management block’ 31 . e Z-axis position is then noted and its value is automatically entered into the tool table, giving a ‘semi-qualied’ tool oset, 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 table’s ‘osets’ , 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 oset dimension. In the case of turning centres, the technique of determining osets is dierent, but similar limitations still apply. A tool presetting device is oen used on many of today’s machine tools, this technique is typied by the ubiquitous ‘touch-trigger probe’ 32 . Hence, this type of tool-contacting presetting probe fulls a number of ‘quoted benets’ , such as: • Setting/re-setting of tool length and diameter (Fig. 133b) – automatically up-dating, or correction of the respective tool table osets, 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 dierent 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 dierence 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 ‘Touch-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 lied/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 osets 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 osets. is is because each cutting insert may ‘stand proud’ in its respective seating, giving a false oset reading – when stationary. Ideally, the whole tooling assem- bly needs to be rotated as its oset is set, • No presetting of tools is necessary – as this is auto- matically undertaken on the machine tool, • Accurate and precise ‘First-o machining’ 33 – this is the result of condence in the tool osets, set by the ‘probing system’ , • In-cycle tool breakage detection – at convenient and programmed pre-selected intervals, the tool’s osets 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 condence in unmanned machining – due to the fact that tool breakage detection pe- riodically occurs, untended machining operations can be undertaken. ese are ‘real benets’ 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 eect using some of the cy- cle-time, can be signicantly 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. Chapter Figure 133. Cutting tool osets being set on a turning and machining centre. [Courtesy of Renishaw plc]. Modular Tooling and Tool Management 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 benets 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- ets 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 osets 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 identied, 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 ecient process minimises cycle- time, while increasing condence 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 ‘thermal movement’ 34 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- ing 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 of ‘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- coolant’ , cutter edge and prole 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 at 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 eectively ‘grow’* due to ther- mal eects, 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. Chapter 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 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, if one wants only a 1 µm rev –1 intersections, this level of accuracy can be obtained by rotating the tooling at 3,000 rev min –1 ,while advancing at only 3 mm min –1 . In order to minimise cycle times, the tool measure- ment soware, 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 measurement 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 signicant 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 soware technique that can be used, is the capacity to measure the tooling several times and apply a ‘scatter tolerance’ to check for any variation resulting from measuring ‘something’ , other than the tool itself (Fig 134d). is soware routine will retake readings until it obtains several values within the re- quired 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 aer machining stops. e laser transmitter for the non-contact tool detection system shown in Fig. 134ai, has been designed with a ‘MicroHole™’ 35 , this ensures that the presence of cool- ant does not aect 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: 1. 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, 3. End of tool dwells in the laser beam for between 0.1 to 0.3 seconds, 4. If laser light is received by the optical receiver unit for more than a specied time-period, typically 10 µs, then this distinguishes a broken tool is present, 5. If laser light is not received by the optical receiver unit, then the tool’s condition is satisfactory, 6. 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- coolant’ , thereby minimising cycle-times. ese laser non-contact tool setting systems, oer many more soware-based features, not described here, such as: cutter prole 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 oer 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. Chapter . 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. value in the tool table, is the most primitive and time-consuming procedure of tool oset setting. Modular Tooling and Tool Management block’ 31 . e Z-axis position is then noted and its value. those from the tool suppliers. Oen, most of the tooling trouble-shooting activities will dissipate once the current component batch is completed, sim- Modular Tooling and Tool Management ply
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