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Added to MTDCNC by Kasto on 29 October 2015

Stockholding and cutting to length of titanium, nickel alloy and stainless steel bar and tube up to 250 mm diameter is the specialism of Hempel Special Metals. It is the Wokingham subsidiary of German family-owned group, FW Hempel & Co, one of the largest stockholders of such materials in Europe and Asia. To keep pace with rising orders, in February this year the UK company invested in a third bandsawing machine, a CNC model from Kasto called KASTOwin A 3.3.


Holding AS9120 quality management accreditation for stockists and distributors in aerospace as well as specific approvals from aerospace primes, Hempel Special Metals derives nearly one-third of its turnover from the aerospace and defence sectors. It is a side of the business that the company is keen to expand and it will take a stand at the Farnborough airshow for the first time next July (2016).


The medical sector contributes around one-quarter of turnover, thanks in part to quality management accreditation to ISO 13485. Oil and gas is also a major market, if somewhat depressed at the moment, while 10 per cent of the firm’s business comes from the so-called leisure industry - anything from Formula 1 to yachting to top-end bicycles.


Mark Glynn, general manager at the Wokingham centre said, 'The German-built KASTOwin A 3.3 has really opened our eyes to what is possible in bandsawing.


‘Our other two saws are seven and 15 years old respectively and manually operated, so I am not comparing like with like, but even so the improvement with the Kasto saw has been dramatic in terms of increasing throughput and lowering costs.’


Quality and IT manager Robin Dawson explained, ‘As cuts have to be set by eye on our manual saws and because the comparatively low rigidity of the machines tends to cause the blade to wander, it is necessary to set tolerances of -0 / + 3 mm when cutting stock over 100 mm diameter.


‘The waste is a little less for smaller diameters, but still appreciable. Overall, between 10 and 12 per cent of stock was lost through having to set such generous allowances.


‘In contract, tolerances on the Kasto bandsaw can be set at -0 / + 0.5 mm for all stock sizes and materials, which is a six-fold reduction in waste.’


Achieving this level of precision in positioning is partly due to ballscrew rather than hydraulic material infeed. During the cut, high squareness accuracy and good surface finish on the cut face are a result of minimal vibration. This is due to a combination of machine rigidity, use of a 41 mm wide bimetal blade rather than a 25 mm blade as on the manual saws and automatic slowing of the downfeed on entry to the material.


Blade deflection monitoring confirms that the cut is always within tolerance and stops the machine if a hard spot in the material should cause the cut to drift outside the preset limits.


In monetary terms, savings are substantial. A typical job at Wokingham involves cutting 1,000 billets from 130 mm diameter Ti64 titanium alloy bar over a three-month period. The overall amount of wasted metal resulting from the allowance has been reduced from three metres (1,000 x 3 mm) to half a metre, translating into a saving of £5,200.


Hempel Special Metals holds 50 tonnes of Ti64 alone in Wokingham for various regular customers, another of which requires 300 to 400 billets per month in diameter sizes of 85, 130 and 180 mm. Nickel alloys and stainless steels up to 152 mm and 100 mm in diameter respectively are also routinely processed. Substantial material and hence financial savings are achieved by cutting all of these metals on the Kasto bandsaw.


Time reductions are an additional benefit, especially when batch sawing. Programming is quick using the touch-screen SmartControl (also manufactured by Kasto), as cutting parameters for any given material, size and cross section are determined automatically by a built-in database. It is possible to program the saw to cut multiple different lengths from the same stock if required. Set-up is quick as well, as projection of a laser line onto the material indicates precisely the point of cutting.


Once in production, the KASTOwin is fast to complete each cut. For example, six or seven billets per hour can be achieved when processing 130 mm diameter Ti64 whereas production rate for the same stock on the other two machines is four billets per hour. Uplift in output rate on the Kasto saw is therefore between 50 and 75 per cent. Moreover, energy consumption is less, as machine movements are largely electrically rather than hydraulically driven.


Another area of cost reduction is blade purchase, which is also down to the rigidity of the KASTOwin and its ability to suppress vibration. Mr Glynn commented, ‘We made nearly 2,500 cuts in the first seven months of operation and used only three bimetal blades, whereas we were changing blades on the manual saws once or twice a week.


‘The tools were costing us £6,000 annually, but the fewer and wider blades for the Kasto saw will cost around £1,000 per year.


‘At the outset, when we had not ordered a blade for two and a half months, our supplier telephoned us to ask if we had stopped sawing material on-site.’


Apart from vibration suppression, a factor in tool longevity is the ability of the Kasto control to recognise when a new blade has been fitted and automatically reduce the downfeed rate by 40 per cent for a short running-in period.


Blades with tungsten carbide tipped (TCT) teeth have been trialled at Wokingham, as they have the potential to cut difficult alloys faster, but in this application bimetal consumables are so efficient and last so long that TCT blades are not needed, particularly as volumes are relatively low.


Mr Dawson concluded, ‘We shopped around before buying the 330 mm capacity bandsaw from Kasto but liked the security of dealing directly with a manufacturer’s subsidiary, rather than through an agent.


‘We have been delighted with the performance of the saw, which is now the mainstay of our production, and with the service we receive from Kasto in the UK, both over the phone and on the odd occasion we have called them out to tweak settings.’



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