Stockholder halves bandsawing costs using KASTO carbide technology

Saw News

The new KASTOtec AC4 carbide bandsaw in operation at Hytemp Nickel Alloys, Sheffield.

Stockholder halves bandsawing costs

Nickel alloy stockist, Hytemp Engineering, changed from conventional bimetal bandsawing to tungsten carbide tipped (TCT) blades following the installation of its third automatic bandsaw, a KASTOtec AC4 from Kasto, Southampton. Within eight months, TCT blades were performing half of the sawing at the Sheffield works, routinely cutting at speeds up to two and a half times those attainable with bimetal blades.

Offsetting the speed advantage of carbide cutting on the KASTOtec AC4 bandsaw is the higher cost of a TCT blade, which is typically three times more expensive than bimetal. Nevertheless, there is still an overall reduction in the cost of the consumable, as carbide blades can cut four to five times more material.

Taking these factors into account as well as labour savings resulting from the higher productivity, Hytemp has typically halved its cost per cut, even after allowing for the greater investment in carbide-specific machinery. (A detailed cost-per-cut calculation spreadsheet is available from Kasto).

This latest technology bandsaw, built by Kasto in Germany, is a programmable, 430 mm diameter capacity machine that is purpose-built for carbide sawing, having a one-piece construction, polymer concrete in the saw head to dampen vibrations, twin column guides and linear slides on the ways. Rest piece in automatic mode is only 35 mm. To avoid damage to the carbide tips during blade return, there is the patented facility to retract the bar slightly and displace the blade so that it travels back without touching the stock on either side. This has the additional advantage of protecting the surface finish on the sawn faces. The larger of the other Kasto bandsaws on site, which has a capacity of 520 mm, and one other machine are also sufficiently rigid to be capable of efficient operation using TCT blades.

Hytemp's stock falls within the diameter range 10 mm to 400 mm and up to four metres long. Sixty per cent of output is in the form of nickel billets and ingots for forging, heat treating and machining by local companies. The remainder goes out to subcontract machine shops mainly as round bar but also as ring and flat bar and includes superalloys and other non-ferrous metals. A majority of the finished products is used within the petrochemical industry, particularly offshore, owing to the corrosion resistance of the materials. Over 70 per cent of the 500 tonnes annual output is exported, mainly to Singapore and the USA.

Said Hytemp's Operations Manager, John Cotterill, "Over the past five or six years, customers have become more cost conscious, ordering shorter bar lengths to their exact requirements, rather than over-ordering and risking being left with unusable stock. You cannot blame them, with nickel costing up to £8,000 per tonne. At the same time, during this period our turnover has increased by 260 per cent to £5.5 million.

"As a result, we have a lot more sawing to do now, particularly of the more expensive, large diameter stock. Materials like Inconel 718 and the slightly less tough 625 grade are very testing on saw blades. One of our bimetal blades will typically cut 1,000 in2 before it dulls, whereas a band with carbide tips can manage four or five times that area."

A couple of tests carried out by Hytemp on 718 alloy using the KASTOtec AC4 achieved 4,120 and 4,802 in2 respectively. Machine operator Ian Cocking advised that TCT blades can run comfortably at up to 30 m/min band speed and 4 - 5 mm/min infeed rate. With bimetal blades, typical cutting parameters are 12 m/min speed and 2 mm/min feed, and it is not possible to increase these by much without stripping the teeth on the first cut.

Not so using TCT blades, which can even be turned up to 50 m/min and 10 mm/min if there is a rush order, although blade life will be reduced by about half. Conversely if the parameters are backed off by five or ten per cent of normal speed and feed, the ensuing higher reliability of operation is ideal for unattended running from 5.00 pm through to 8.00 am. John Cotterill also finds TCT blades more consistent in quality whereas he says that it is not unusual in a batch of bimetal blades to have one or more "duff" ones; indeed, sometimes all of them can be of inferior quality.

Monitoring of blade deviation and coolant flow built in to the KASTOtec AC4 gives added security for unmanned operation and ensures a good quality cut, even if hot spots are encountered in the material. In such cases, a TCT blade will normally cope without deflecting or seizing. A bimetal blade, on the other hand, sometimes fails to get through at all, so is less suited to unmanned operation. There is also a chance of a blunt bimetal blade welding itself in the material, wasting both expensive alloy and the time needed to remove the blade, which can be one or even two days.

A view from the rear of the KASTOtec AC4 at Hytemp, Sheffield, showing nickel alloy being cut.