TPT July 2007

S traightening & F inishing T echnology

automated tube cutting machines. High production quantities destined for automotive and domestic product manufacturers req-uired the installation of auto

Tapered tubular flagpoles – a difficult straightening application Most flagpoles and lamp stands are made from tubular aluminium or steel, gradually tapered from base to top, to reduce weight and lower wind forces. These tapered tubular products need to be straight. Normal parallel tubes are usually rotary straightened by machines that cannot straighten tapered tubes, as extremely complex changes in the roll position settings must take place to rotary straighten a tapering tubular product. Turner (see opposite) has launched a new machine for straightening both parallel and tapered tubes. The machine can track tapered tubes at speeds of up to 150 FPM (45 MPM) using AC vector drives for roll positioning and laser gauges to measure tube position. Enhanced computer software controls the entire straightening process. As the tube progresses through the machine, the roll screws down positions, straightening offset amount. All roll angles are automatically and continuously adjusted to consistantly track and straighten the tapering tube.

› Roll configuration: the 10 roll machine

tube loaders and feeding units. This higher production equipment will not successfully load or feed anything other than exceedingly straight tube. A good example of this change lies within the tubular steel furniture industry. Lower grades of welded tube have fed this industry for countless years. Provided the tube looked basically straight it met the purpose and was acceptable to furniture makers.

It is important to always keep rolls in sets with matching diameters. The amount of roll wear should also be checked on a monthly basis and logged. A simple procedure is to measure and monitor the diameter of the roll at the centre of the profile. When the difference in the diameter reaches the OEM’s advised maximum deviation, the rolls should be reprofiled to bring them back to standard. The majority of rolls are manufactured from high chrome, high carbon tool steel that is through hardened to values usually between 58 and 64 Rockwell C. Rolls can often be reprofiled until the diameter at the centre is down to about 80 per cent of the original size. The 10-roll machine, currently experiencing increased demand, can reduce tube ovality to very small tolerances and straightness of 1:2500. There has been a quiet revolution taking place in the steadily increasing demand for tube with very high straightness requirements. Year upon year, tubing customers are demanding higher tolerances of tube straightness and also tube ovality. Although the first 10-roll machine was introduced in the mid 1970s, it was not until computer machine setting systems were introduced in around 1989 that such machines became easier to set up. At that time, tube makers producing quality tube in stainless steel and other noble alloys took up the opportunity to produce straighter and rounder tube. Beginning in the late 1980s, carbon steel tube users also started to install highly fi The roll shown below has a worn profile, with wear having occurred on one side of the profile. This indicates that the rolls were not correctly aligned in the machine

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fi Computer setting systems have enabled the growth of the 10 roll straightening machine

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J uly /A ugust 2007