Architectural metalworker achieves right-first-time output using unique bend correction system
PUBLISHED: 09 Jan 12
Unison's all-electric tube bending machinery has accelerated the manufacture of prestige architectural metalwork designs for the fabricator Lee-Warren.
An all-electric tube bender equipped fitted with a unique laser-controlled bend angle error correction system has dramatically accelerated the production of prestige tubular parts at the architectural metalworking specialist Lee-Warren. The investment reduces throughput times from two or more days to just a couple of hours - and is achieving the company's objective of 100 percent 'right-first-time' manufacturing.
Lee-Warren specialises in the production of large tubular finished metal parts for prestige building projects. Its work includes manufacturing decorative balustrades, staircases, bollards and walkways, as well as sheet metal components for aesthetic cladding purposes. The company is currently producing staircases and balustrades for several of the UK's highest-profile building projects, including a new education academy and a railway terminus redevelopment in London.
Lee-Warren invests heavily in automation to optimise quality and reduce fabrication times, and makes extensive use of CNC machines. These include a high tension saw with auto-feed for batch cutting, a press brake capable of handling up to 10 mm thick material, and a water-jet cutter which creates very smooth cuts that require little or no secondary finishing.
Lee-Warren invested in a Unison Breeze all-electric tube bending machine in late 2010. The main reasons for choosing a Unison machine were its bending accuracy, ease-of-use and energy efficiency. This particular machine is capable of bending stainless steel tubes of up to 76.2 mm (3 inch) diameter, and features an extended bed to accommodate very long tube lengths. Lee-Warren typically fabricates balustrade components - one of the main uses for the machine - from 2.5 metre lengths of stainless or mild steel tubing, and lengths up to 5 metres are not uncommon.
Before the arrival of the machine, the company sub-contracted tube bending operations, and then cut and welded the parts together. This procedure could take several days from start to finish, during which time Lee-Warren did not have complete control of the process. Inevitably, there was a degree of scrap, as parts that had not been bent to specification could not be re-bent or used for other purposes.
Lee-Warren produces a large proportion of its balustrade components in batch sizes of one to completely custom specifications. This type of business means that every part has to be manufactured right first time. Raw material in the form of metal tubing is first cut to length and then loaded onto the bending machine. The entire bending process is then handled automatically. According to Michael Higgs, Lee-Warren's Designer, "The majority of our customers submit CAD drawings of the parts they require, often in the form of a PDF, and we extract the dimensions from these and input them manually to the tube bending machine. This task only takes a few minutes, thanks to Unison's easy-to-use software."
Lee-Warren usually employs a combination of mandrel and die bending for the tight radius bends on balustrade components, and the machine's roll forming capability for larger curvatures. The company uses the bending machine's laser-based angle correction system on every tight radius bend. This system - which is unique to Unison machines - automatically compensates for the tendency of metal tubes to spring back slightly after they have been bent. After the initial bend, the laser measurement system measures the actual bend angle achieved, and then re-applies the clamping and bending dies and exerts an automatically calculated bending force to correct any deviation. As Michael Higgs points out, "We find that by using the spring-back compensation system for every mandrel bend we can achieve a very tight working tolerance of plus or minus 0.2 mm. So, although we are effectively performing a double pass on each bend, slowing potential throughput slightly, we obtain 100 percent right-first-time output. Another cost-saving advantage of the Unison bend angle correction system is that it can eliminate the need for a separate coordinate measuring system."
As an example of the speed, a balustrade component involving two 90 degree bends and a single wide curve typically takes less than a minute to produce on the Unison bending machine. After bending, the component is polished and if necessary has retaining lugs welded on, before being ready for despatch. The entire process, including preparation of the raw material, takes less than two hours. This contrasts sharply with the typical two-day production cycle required before bending was brought in-house.
The ability to handle all aspects of production in-house has also enabled Lee-Warren to further improve customer responsiveness. Michael Higgs adds that this is a key business advantage, "Building to demand is central to our business. The Unison machine helps us ensure that the right parts are delivered at the right time, but it also enables us to accommodate production changes - such as last-minute requests from architects, for example - in a very flexible manner. These attributes are vital to helping large building projects stay on-schedule."
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