Linear bushings improve vertical saw accuracy

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Bosch Rexroth has supplied linear bushings and shafts to Sagetech Koolkut, enabling the company to improve the accuracy, life and maintenance requirements for its vertical panel saws.

In conventional panel saws, the carriage is supported by roller bearings that travel directly on the frame of the saw. The accuracy of cut depends on the precision with which the saw frame is fabricated and machined; achieving high levels of accuracy is both difficult and expensive.

In contrast, with Sagetech's Koolkut saws, the carriage is supported by a precision-ground hardened shaft, used as the machine's top rail, along which runs a ball-bearing linear bushing. With this arrangement, the saw's cutting accuracy is determined by the performance of the shaft and bushing, rather than by the accuracy of the machine frame itself.

Keith Bunker, Managing Director of Sagetech Industries, comments: "This novel design not only allows us to deliver much better and much more consistent accuracy of cut than is usually associated with panel saws, it also means that the saws are easier and less costly to fabricate, as precision machining of the frames is not needed.

"Since small deviations in frame geometry do not affect the saw's performance, another big benefit is that we can ship the saws as flat packs for easy assembly on site. This greatly reduces shipping costs as well as making it possible to get the saws into areas where narrow doors and the like mean that access is limited. Users do not even need a forklift when installing the saws, as they can carry the components individually from the delivery point to the installation site."

Technology, pricing and support

When developing its new Koolkut saws, Sagetech carefully researched the market for suitable linear motion products. It believed that Rexroth linear bushings and shafts not only offered the best technical solution, but also the most competitive pricing. In addition, Bosch Rexroth products are available and supported worldwide, which was a particularly important consideration for Sagetech, as its saws are currently manufactured in the Czech Republic.

The bushings chosen to support the carriage – a load of around 300kg – have facilities for radial clearance adjustment, making it possible to set them up to provide very high traverse accuracies. Additional bushings and shafts are used for the vertical movement of the cutting head but, in this application, non-adjustable bushings proved satisfactory.

In operation, panel saws unavoidably generate dust. Although Koolkut saws incorporate effective dust extraction systems, it is impossible to completely protect the motion components against exposure to these contaminants. This problem has, however, been successfully addressed by the double dust seals that Bosch Rexroth offers as an option on its bushings.

Successful sealing

Keith Bunker says: "With most saws, the build up of dust and debris in the bearings creates a big maintenance headache. When the saws have been in use for a while, all of the motions become gritty, and accuracy suffers. In contrast, with our machines, thanks to the excellent seals on the bushings, you can still move the carriage with one finger, even after extended periods of service. And, of course, there is absolutely no fall off in accuracy."

The efficiency of the bushing seals also minimises lubrication requirements and, since they ensure that the rolling elements of the bushings are effectively always operating in a clean environment, the seals help to prolong the overall life of the equipment.

Keith Bunker adds: "The bushings and shafts were easy to specify and easy to build into our designs, but there were a few occasions when we needed a little technical support. At these times, the Bosch Rexroth engineers were always readily accessible, and were invariably able to provide us very quickly with the answers we needed. All in all, the company has given us excellent service and support throughout the project."

Building on the success of its original range of Koolkut saws, which have now been in production for over two years and are available with horizontal cutting capacities of up to 4.2m, Sagetech Industries has recently released two new ranges. One has a 7.5kW motor for heavy-duty applications, and the other incorporates a scoring facility that allows laminates and other brittle materials to be cut with no risk of chipping.

Once again, the new designs make use of bushings and shafts from Bosch Rexroth as the key to providing outstanding performance combined with convenience, reliability and value for money.

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