Howco — one of the UK’s largest independent suppliers of low-alloy steels, stainless steels and nickel-based alloys to the global oil and gas industry — has installed two additional bandsaws to increase throughput at its Sheffield site.
These machines, which are designed for cutting with carbide blades, were built by the German manufacturer Kasto and supplied through its UK subsidiary in Milton Keynes.
Howco Sheffield supplies raw material in a range of sizes, with squares and diameters up to around 1,300mm in section. The company also has one of the industry’s best-equipped machine shops, in which it manufactures components to customer requirements; these components are used for a variety of applications, including sub-sea well-heads and top-sides.
A recent sharp upturn in business resulted in turnover increasing by 36%, and it was consequently necessary to increase the number of bandsaws on site, which at the time stood at 28 — including a Kasto HBA 1060/1260 installed in the mid-1990s.
Howco’s European operations director, Andrew Marwood, asked warehouse manager Peter Connelly to research the market for the most cost-effective way to increase sawing capacity — not only to accommodate the upturn in business but also to reduce lead times for the supply of material and components.
Highly productive bandsaws were required, especially as processed material often visits them three times: for cutting test pieces before and after heat treatment and again for sawing the required batch, which can be anything from a one-off blank to several hundred.
Mr. Connelly set about an exhaustive review of machines on the market, eventually deciding on two KastoTec AC5 bandsaws (
www.kasto.uk.com).
These machines are equipped with the German manufacturer’s optional factory-fitted ‘carbide package’, which includes patented blade back-off on both sides of the cut during the up-stroke to protect the carbide tips from damage and to improve blade life. Furthermore, a lower-speed high-torque gearbox is fitted to optimise sawing productivity with carbide blades. Other design features of the machine are focused on reducing vibrations, particularly of the bandsaw blade.
High temperatures
Howco uses carbide blades extensively because they are particularly suitable for cutting nickel alloys, which tend to close on the blade during the cut, generating a lot of heat. Tungsten carbide teeth can withstand the elevated temperatures well; they also cut the material efficiently.
Mr Connelly says: “The fully enclosed KastoTecs are top-end saws that are safe to use, quiet and extract maximum productivity from Wikus and Lenox carbide bandsaw blades. We would have needed four bandsaws from the other suppliers we considered to cut the same amount of material, which would have taken up more space in our machine shop.
“The Kasto carbide bandsaws cut all of our materials between 40 and 50% faster than the other saws on site — and compared with alternative new saws that we considered. This equates to a saving of 192hr a week when sawing ingots up to 530mm in diameter.”
Operations manager Glynn Colley adds: “The KastoTecs are also very reliable, especially with the blade deviation function switched on. For this reason, we use them almost exclusively for cutting our higher-value metals like nickel alloys. A single 500mm-diameter 6m-long bar can cost over £100,000, so security of operation is important.
“The increased capacity provided by these saws will allow us to meet projected demand both for ingot conversion and for sawing nickel alloy to produce forged and heat-treated components. Moreover, the latest Kasto saws are so productive — and require so little supervision once set — that we have calculated they will pay for themselves in 40 weeks, working 16hr a day, five days a week.”
One factor in the calculation of this amortisation period is the short rest-piece length of 35mm on the KastoTecs, compared to 80mm on the other saws that Howco uses. For each tonne of Inconel 718 processed, the saving in material is almost £140, which can add up to more than £100,000 during the course of a year.
Cost per cut
Another financial benefit of the Kasto bandsaws comes from the significantly lower cost per cut compared with other models on Howco’s Sheffield site. For example, the cost of sawing a 6m-long bar of 126mm-diameter Incoloy 925 into 53mm lengths is 59% less on a KastoTec AC5 than on another make of saw operating with a bi-metal blade. While the reduction is partly down to the sheer speed of cutting (62cm2/min), other factors include the price of the machine, blade cost (and blade life), staff wages and other overheads.
The processing of other materials has shown even higher percentage savings in cost per cut when using a KastoTec. The overall cost for sawing a length of 280mm-diameter AISI 4130 low-alloy steel is 63% less, while for 250mm-
diameter 316 stainless steel the cost is reduced by 70%.
A number of factors contribute to efficient cutting on the KastoTecs. Reduced vibration is the most important, helped by optimised blade guidance on either side of the point of cutting. More-copious and better-targeted coolant delivery to the blade and guides also promotes stable cutting performance.
A further contributory feature is automatic adjustment of blade down-feed within the program to suit the material being sawn. If the stock is round, the in-feed rate is lower as the blade enters but increases progressively as the blade penetrates the material, which acts as a support to dampen oscillations. The feed rate is lowered again as the blade exits the material and support relies increasingly on the guides once more.
Less vibration also equates to less noise. Howco measured the noise generated by a KastoTec and another make of bandsaw cutting identical material. The reading for the latter was 60 dBA, while the former was substantially quieter at 52 dBA.
In conclusion, Mr Marwood said: “The oil and gas industry demands high quality, accuracy and fast delivery. The recent multi-million-pound investment in our Sheffield operation has seen the installation of new CNC milling equipment, CNC lathes and purpose-built batch heat treatment furnaces — plus the additional sawing machines.
“We regard ourselves as the best in our business, and we have a policy of buying only the best equipment to help us stay there.”