Calculated savings

Sandvik Coromant unveiled highlights of its CoroPak 2 product launch (the second of its annual product updates) recently. But, in addition to underlining certain products, company product manager Paul Williams took time out to detail the economics of production and its part in boosting manufacturing productivity. The fundamental problem, he explains, is that, while manufacturers' input costs rise at one rate, the prices that they can charge rise at a slower rate. The difference is the 'productivity gap', and reducing that is the work of Sandvik Coromant and its product developments. Looking particularly at the UK, Mr Williams stressed that there are four strong sectors – aerospace, oil and gas, and medical, and where small batch production is the rule; plus automotive, which is high volume and, therefore, the most efficient sector. The UK doesn't manufacture so many parts, but it does assemble many cars and that is a very strong sector at the moment, he underlines. "For us in the UK, batch production is the norm, with those batches reducing in size. We have been living with that for some time in this country, of course." That being the case, the emphasis has to be on reduction of job changeover time, but after that it's cutting tools where the focus falls. In both cases, the idea is greater throughput – boost productivity – especially so in high cost industries, such as aerospace. GETTING MORE FOR NOT MORE "We need to get more out of the situation – not more for more, which is increased capacity – but more for the same cost, or the same for less, with the ultimate being more for less, of course. For us, that's more machining hours within the same production hours." So, what does Sandvik Coromant advise? Well, the key IS greater metal removal per unit time, plus appropriate economic tool life. But before getting into the detail, how do costs typically break down within a UK manufacturing environment? Well, site costs are 22 per cent; labour costs represent 31 per cent; and machines/durables account for 27 per cent – those are fixed costs, which add up to 80 per cent. Fixed costs do not change with the volume of production. On the variable cost side, Mr Williams puts tooling, at 3 per cent, and material cost, at 17 per cent. Image: The various input costs: tooling is very small, but it's influence is very large "Before we start making anything, we have 80 per cent of our costs. As we start to make things, our variable costs will increase. But I talk to many companies that have budgets for spend on cutting tools and materials, and it's right that there should be limits, but a lot of people gauge their business by what they spend on cutting tools and component materials. So, while it's right to have an understanding of that, it should not be the measure of success - driving down cost per part is achieved by increasing throughput. "So, our customers spend 3 per cent of their total manufacturing costs on cutting tools and, if you add in other consumables such as coolant, it gets to 5 per cent. I have asked many customers about this and tooling costs are never greater than 3 per cent," assures Mr Williams. The easy way to get costs out is for companies to move to a lower cost country: it's possible to take 40 per cent out of total costs through such a move, he says, achieved by lower labour and facilities costs. Back in the UK, increasing throughput is the key to closing that gap, but it's easy to be distracted by seemingly sensible cost-cutting measures. "Many tooling companies approach our customers, offering low prices, and they have a place in the market. But if you buy at a lower price, say one third lower, without affecting throughput or component quality, it will reduce cost/part by 1 per cent – but take it. If we gave our tools away, it would only reduce cost/per part by 3 per cent. If one of our new tools delivered 50 per cent more tool life, that would also reduce a customers' cutting tool spend by 30 per cent – take it and it will reduce cost per part by 1 per cent. "But if we come out with a new cutting tool or process, and we say that we will be able to increase your metal removal rate by 20 per cent, which means more throughput, that's where you should really focus. Because, even if it means a higher cost tool, you will be able to get a better return on the 80 per cent fixed cost, reducing costs by something like 15 per cent/part. So, if our UK customers can go to their customers and tell them they can give a 15 per cent cost reduction, that will keep them busy." Image: More throughput, that's where customers' focus should be, says Sandvik Coromant ECONOMIC TOOL LIFE But in boosting metalcutting performance, in terms of metal removed per unit time, a consideration is economic tool life; because you can machine as fast as you like, but if you have to keep changing tools, that will work against any gain in cutting rate, Mr Williams cautioned. However, machining too slowly will deliver less than the maximum throughput gain. And the values for economic tool life vary, depending on the industry involved and materials cut. In the automotive industry, for example, the economic tool life is around 15 minutes (roughing turning tool), because hourly rate is £40 and material is low-cost carbon steel. But, for higher cost industries, the economic tool life figure drops. Hourly rates can be from £60-£100, with higher value materials processed, too. So, for aerospace and nickel alloys, economic tool life is just 5 minutes. What that means is that, if your single point roughing tool is lasting longer than 5 minutes, what you are saving on your cutting tools, you are more than losing by way of the cost of reduced throughput, Mr Williams underlines. Worse, of course, it could mean the loss of a contract. Image: Economic tool life. Do you know what it should be? And this is a message that needs to be heard, because, according to Mr Williams, there are "very few" companies into which he goes that are actually practising this approach; the message is a "surprise". And that's because people tend to operate in their own small area, not seeing the bigger picture, he offers. The target for Sandvik Coromant's conversations on this subject are company owners, manufacturing managers; people who control the budgets and those able to take a wider view. Where the message is received and understood, it has a "big influence", Mr Williams concludes, adding that significant successes have been had in the medical sector. At the same event, Sandvik Coromant's Howard Meachin highlighted things aerospace and how the Swedish tooling giant was providing tools and process knowledge to support a burgeoning aerospace workload. The aerospace industry is facing a capacity crisis, says Mr Meachin, with forecasts for 25,000 new planes and 55,000 new engines over the period 2009 to 2028. Planes cited are Airbus' A350XWB, Boeing's 787, China's ARJ21 twin-engine regional jet, MRJ (Mitsubishi regional jet), and the Sukhoi's SSJ100 regional jet in the civil arena, plus the US-led joint striker fighter (JSF – F-35 Lightning II) development, which, even if the programme is cut in half, will still be the largest ever military aircraft programme ever seen, Mr Meachin underscored, while the materials are of the most difficult type of materials. Parts are becoming larger, more monolithic, geometry more complex, while sections are getting thinner. Surface finishes of a high order are demanded, particularly in the engines, which themselves are using high alloy steels to support ever higher engine temperatures. Against all this, highest production efficiency is required for competitive manufacture of these parts. Sandvik Coromant set up its Aerospace Applications Centre at Halesowen some three years ago to provide answers to the sector's challenges – believed to be unique, as far as its competitors are concerned, offers Mr Meakin. In fact, although it is coined an aerospace centre, it is in reality a high performance machining set-up that will also tackle applications within the energy and medical sectors, for example (Automotive and Die and Mould Applications Centres also exist globally). But to stay with the aerospace theme, Sandvik Coromant has, as a result of working on aerospace projects come up with both standard tools for standard features plus associated processes to support standard feature/part manufacture. The company has an online resource that details its solutions. Prior to the development of this standard approach, special tooling was the order of the day, Mr Meakin explains. A particular development highlighted is the use of tools having ceramic blades that can support table feedrates of up to 2m/min when milling titanium, for example. But the tools are only half the solution, the machining processes is the other, and this knowledge is guarded. CADCAM systems, explains Mr Meakin, often feature Wizards to guide programmers when generating CNC programs. "These Wizards work fine, but they are not kind to our tools, they're not applying best cutting practice, such as trochoidal milling and turning and roll-in/roll-out, for example." In house, the company employs Open Mind's Hypermill (01865 338026), Dassault Systems' Catia, Mastercam (4D Engineering, 01285 650111), and Siemens NX (Siemens Industry Software, 01276 702000), and develops sub-routines that allow Sandvik Coromant's tools to be used in "the best possible way". Image: Optimised tooling methods are key Image: Five-axis machining requires its own optimised techniques These cutting techniques are the company's intellectual property and give it a competitive advantage, it is stressed. The tooling firm is, in fact, working with CADCAM companies to allow both its tooling (complete nomenclature, not basic as now) and its cutting technology to be applied directly. This sort of development will herald the start of something called 'Sandvik Library Services' offers Sandvik Coromant's UK managing director, Magnus Eckbäch. In its own offices, the company additionally employs CGTech's VERICUT CNC program simulation software to prove out the processes, which invariably involve high cost material and high cost machine tools, neither of which can be put risk. And some of the examples given by Mr Meakin demonstrate just how effective its Aerospace Application Centre can be. For one gas turbine engine component, a turned part, an existing cycle time of 80 hours was reduced to just 14, with an increase in tool life, better swarf control, and a freed capacity saving per part of £4,620. This also delivered a 'green button' process. Image: A saving of 80 hours, in this case In another, a titanium frame component, an existing 234 hour cycle tie was slashed to 71 hours, freeing up capacity valued at in excess of £810,000 and avoiding spindle replacement every six months. And with only a few of these expensive machined each year, meaning scrapping any is simple not acceptable, right first time was achieved. Image: A saving of £810,000 for this customer Another titanium frame component of somewhat smaller proportions saw a 23 our 11 min cycle reduced to 11 hours 12 minutes, with tool life increased by 200 per cent, freeing up capacity valued at almost £360,000, again with this delivering a 'green button' process. This solution was subsequently spread across a family of parts, with a further 10 added after the initial solution. This also meant that an additional machine tool was not required. With such savings, it may be a surprise to hear that it can be difficult to get customers to actually believe this is possible and to get them to come and visit to the AAC. One reluctant visitor, who thought he knew the Inconel 738 job best and had tried everything, was finally encouraged to pay a visit to Halesowen, with the result that he achieved "the biggest step-change in machining this component that I have seen in 15 years". The company has gone from using five cutters per slot, which it was machining at full width, to five slots per cutter with a trochoidal milling approach, in a better cycle time and with a 'green button' process. Another example has meant the difference between a company losing or keeping a job, which will be running in the UK for many years to come. Moving onto more generic product developments and Sandvik Coromant's Alan Cawtheray revealed some of the latest milling developments, with these taking in a new stainless steel insert grade, new titanium grades, a new gear milling concept, exchangeable head end mills and a heat resistant super alloy high speed milling insert grade. The CoroMill 316 exchangeable head end mill system now covers the range 10 to 25 mm diameter, with a 3 mm corner radius now available for aerospace applications. There's also now a chamfer end mill for UTS threads, with a chamfer angle of 82°, and which is of particular interest to the oil and gas sectors. Titanium milling grades S30T and S40T bring productivity and security to titanium milling. There are over 200 'articles', with these covering many CoroMill ranges, from 216 to 490. For high productivity milling of heat resistant super alloy, there's a new ceramic grade – CC6060. Sandvik Coromant highlights that ceramics offer a dramatic productivity increase over carbide, supporting a cutting speed of 1,000 m/min versus 30 m/min. The inserts come in RPGN 060300E, RPGN 0980300E, RPGN 120400E, RNGN 120700T01020, and RNGN 120700E styles for cutter diameters of 25 to 80 mm. For the wind power industry, the tooling giant has launched its CoroMill 170 roughing milling cutter. This provides a technology shift from HSS to carbide inserted tooling, and is intended for use on multi-tasking machines or 5-axis technology. The cutter is for gears with a 20° pressure angle and shaped in accordance with DIN3972-4. This joins a number of Sandvik Coromant gear milling products. In the stainless steel milling area, the tooling expert has added grade GC1040, a broad grade that is "easily applied in every milling application". The grade sits between GC2040 (more unstable conditions) and GC2030 (more stable conditions), overlapping at the lower cutting speed range but supporting lower cutting speeds than either. It has two geometries, E-ML for more stable and M-MM for more unstable cutting. Image: GC1040 is a broad range for stainless steel milling Moving on to turning products and Paul Williams highlighted new ISO S geometries, predominantly for the aerospace industry and HRSA and titanium. The S range comes in four types - SF, SGF, SM and MR, where F = finishing, M= medium and R= roughing; the G = ground. The new S range also features optimised macro and micro edge conditions. A number of insert grades can be employed, with PVD-coated GC1105 always the first choice. Cutting at up to 80 m/min in Inconel 718 is possible. Image: Image: S grade design features Further advise on improving productivity was offered in the form of a suggestion to use inserts with lower approach angles rather than the typical CNMG (95°) – CNMX (45°), SNMG (45° and 75°) or even circular (RCMT) will offer major improvement, if they can be applied – up to 60 per cent increased feed for a circular insert. Using CoroTurn HP holders, which direct 70 bar coolant along the surface of the insert and between the insert and underside of the chip, cutting data can be boosted by up to 50 per cent. Image: High pressure coolant, directed correctly pays massive dividends New S grade CBN inserts for superfinishing are another element of the S launch. The RE style inserts come in seven diameters – 3 to 8 mm. In a test finishing an aerospace disc, a surface finish of Ra 0.3 was achieved, using a 6 mm diameter, 7015 grade insert. This tool is also intended for the medical parts industry, allowing superior finishes to be turned on such things as ball joints. When machining cobalt chrome F75, using a 6 mm diameter grade 7015 insert, a surface finish of Ra 0.1 mm was achieved. Image: A finish of Ra 0.1 was achieved on this medical part A new rough turning concept – Xcel – has been introduced, too. Xcel is a unique new turning concept offering significant benefits to the traditional nose radius inserts in the turning of case-hardened components. Compared to carbide, which took 12.5 mins on a 400 mm diameter part, the CBN insert took just 1.5 minutes, achieving a spiral cut length of 1,823 m, with an in-cut time of 5.3 min. Image: Xcel – a new concept A straight cutting edge blending into a wiper provides constant chip thicknesses and wear patterns to boost productive machining capabilities. Maximum depth of cut (ap) is limited to below the straight cutting edge of the new design inserts, while the approach angle determines the maximum depth of cut and chip thinning effect relative to the feed rate. The smaller approach angle (kr) of the new insert design reduces chip thickness greatly, relative to the feed rate, so that higher feed rates can be applied. This is in comparison to standard nose radius inserts, which give a varying chip thickness, with the largest generated at the depth of cut where the greatest wear also occurs. Significant productivity gains over standard radius inserts with increased feed rates are possible, due to lower cutting temperatures The wiper allows feed to be increased to 0.4 mm, while still maintaining good surface finish (Ra 0.5 µm). Xcel also increases the number of parts produced per edge over standard radius inserts. First published in Machinery, November 2010