A Unison all-electric CNC tube bending machine is helping the specialist tube bending company T+T Tubecraft to accelerate production of precision tubular parts and eliminate material waste through right-first-time manufacturing.

Tubecraft has a long-established reputation for metal tube, pipe and section bending. Founded in 1949 to produce parts for aircraft and motorcycles, the company nowadays serves a diverse customer base including pharmaceutical, petrochemical, aerospace and food processing industries. Tubecraft also has a strong presence in the oil and gas sector – including bending rigid small-bore hydraulic tubes for several subsea equipment manufacturers.

Tubecraft’s pipe and tube bending services have been based on hydraulically-powered machines, although in recent years it also invested in several hybrid hydraulic-electric machines. However, an increasing proportion of the company’s business is for very demanding shapes and smaller batch runs – which are not ideally suited to production on hydraulic tube benders. Many of the company’s oil and gas projects fall into this category. For example, the tubular parts for subsea ‘Christmas’ trees, hydraulic flying leads and associated equipment are usually manufactured from expensive corrosion-resistant materials such as duplex, super duplex or 316L stainless steel, or more exotic alloys such as 6Mo, and invariably demand highly complex bends of exceptionally high accuracy.

Setting up a hydraulic tube bending machine to consistently produce parts of this complexity can be very time-consuming; it usually takes Tubecraft’s specialists about 90 minutes to fit the tooling and configure a machine for bending a particular part. It’s then necessary to bend two or three trial parts, making minor machine adjustments each time, before a part passes measurement inspection and production can begin. Given that more and more projects are generally produced in small batch sizes – sometimes as small as one – before the machine is retooled for the next part, this time overhead soon mounts up. On average for instance, for manufacturing subsea parts, Tubecraft performs eight complete tool changeovers a week – representing as much as 12 hours lost production time.  

Aside from the time overhead, Tubecraft was also concerned about scrap material issues. On many bending contracts the tube material is supplied by customers, who often make no allowance for the waste incurred by trialling parts; and with the material costs of even mid-range alloy tubing easily exceeding £200/m, producing multiple trial parts for low volume, small batch size production runs was becoming uneconomic.

Tubecraft therefore sought to implement a right-first-time manufacturing strategy, based on a tube bending solution that combined ease of set-up and fast tool changeover with high accuracy and repeatability. The company had looked at numerous tube bending machines over the years, including offerings from American, German, Swedish and Chinese manufacturers, and concluded that UK-based Unison’s all-electric technology represented the optimal way forward. Another key factor behind the purchasing decision was Unison’s reputation for support, which Tubecraft regards as vital for any business that is introducing new production technology.

The Unison tube bending machine – a 50mm Breeze all-electric model with a multi-stack tool head for fast, automated tool changeover – was installed at Tubecraft’s factory in Woking in January 2014. It is networked to the company’s CAD facilities and a coordinate measuring machine (CMM) that is used to verify bend accuracy and design conformity. The tube bender can be programmed manually or by importing CAD data using industry-standard IGES or STEP files, while data obtained by the CMM from the first manufactured part can be used, if necessary, to automatically adjust the bending machine ready for a production run.

According to Tubecraft’s managing director, Ross Turner, “The all-electric architecture and automated software-controlled set-up of the Unison machine has major advantages over hydraulic machines. Bending accuracy and repeatability are improved. For repeat orders we now achieve right-first-time manufacturing, and even for new projects, where measurements from the first manufactured part might be used to adjust bend parameters, the second part is usually perfect. It also only takes about 20 minutes to fully configure the electric bender, which is less than a quarter of the time it took with our hydraulic machines – giving us at least 9 hours a week extra production time.”

The multi-stack tool holding capability of the electric bending machine further helps to reduce the need for manual intervention, by allowing complex parts with multiple different bends to be made in one uninterrupted machine cycle. Although Tubecraft makes full use of Unison’s bar code scanning system to verify which tools are installed and configure the machine automatically, it does not yet use Unison’s quick-change tooling system.

As Ross Turner pointed out, “We appreciate that quick-change tooling, as well as Unison’s laser spring-back correction system, will enable us to further reduce set-up time, but we have a huge investment in tools and therefore intend implementing these features over time. What I would say is that having made the switch to Unison all-electric tube benders and experienced their advantages, we would find it very difficult to return to hydraulic benders! Also, the Unison machine is the only one we have that is capable of push bending. Unison will help us to develop skills and knowledge of this technology, which is starting to become popular for the efficient production of parts that combine long sweeping curves with tight radius bends.”