Machine builder standardises on Rexroth products

Britannia Heatex has developed an innovative new ElfinMaster CNC heat exchanger finning machine that will be exported worldwide. The company therefore needed to be sure of worldwide availability and support for all of the key components used in the machines. In addition, the components had to combine performance and reliability with competitive pricing. Britannia Heatex found that standardising on Rexroth products was the best way to meet all of these requirements.

With long experience of developing and building heat exchanger assembly machines for its own in-house, Britannia Heatex has responded to market demand and has developed a new finning machine for sale as a standard product.

Andy Price, Engineering Manager at Britannia Heatex, states: "We knew that there was substantial demand for these machines from companies all over the world, and we realised that this meant we would have to modify the design we had used for our in-house machines so that the new versions would be easy to service and support, wherever they ended up. With this in mind, when we started evaluating component suppliers, we looked very carefully at how they could help us to achieve this."

Machine architecture

The central element of the finning machine is a linear motion system that pushes finned plates onto tubes to form the heat exchanger elements. This system is required to generate a force of 2.5kN and to operate at 3.3m/s. The stroke length is 2.2m for the first fin, gradually reducing as subsequent fins are added to the stack. A complete push cycle (feed the fin, push it into position, return the pusher head) must be completed within 2.5s, and the pusher must be capable of continuous operation over long periods.

Britannia Heatex found that there were very few suppliers of suitable linear motion systems, but that Rexroth IndraDyn L synchronous linear motors met its requirements. Fully encapsulated in a stainless steel and titanium alloy case, these units are designed to combine a long service life with minimal maintenance requirements. In addition, their exceptionally low force ripple makes them well suited for applications where, as in the finning machine, high acceleration and accuracy are needed.

After deciding on the linear motion system, the Britannia Heatex engineers turned their attention to other aspects of the machine's design. For the overall structure and framework, they chose Rexroth MGE aluminium extrusions and accessories. Compared with a traditional welded steel framework, this approach provides greater versatility and, should modifications ever be needed, they can be incorporated quickly and easily. Furthermore, since the extrusions are inherently corrosion-resistant in normal manufacturing environments, the need for painting is eliminated.

In the machine, the fin plates are fed to the pusher by means of a scroll feeder driven by a speed-controlled motor. The requirements are, however, slightly unusual as the motor is a standard three-phase unit, but the supply is single-phase. Once again, however, a Rexroth product - this time an Indramotion variable-speed drive (VSD) - proved to be both efficient and cost-effective.

Pneumatics

Rexroth pneumatic products were also specified for the machine, which uses pneumatic cylinders for a whole ranger of functions. These include, for example, raising and lowering the supports that keep the tubes in place while the fins are being fitted, operating the tube clamps, and actuating the mechanism that drops the fins into position so that they can be pushed onto the tubes.

Price comments: "Using Bosch Rexroth products for every major function on our new finning machines undoubtedly simplified the design work, and the company's engineering team provided excellent support at every stage of the project. The team members were readily accessible and, whenever we had questions, they quickly provided us with detailed and reliable answers. However, there were many more important benefits.

"For example, all of the products we used are readily available on short deliveries and at competitive prices. And that is not just true in the UK - the products are available around the world, as is service and support from the Bosch Rexroth organisation. This made it possible for us to offer a worldwide extended warranty, covering both parts and labour, on our machines. That is very appealing for our overseas customers, and will undoubtedly help us to sell more machines."

International approvals

Another important benefit for Britannia Heatex is that all of the products used carry multiple approvals, including UL, CSA and the CE marking. This makes it easier to ensure that the machines are acceptable in all markets, and avoids the need to produce different machine versions to satisfy specific national requirements.

To date, Britannia Heatex has supplied five of its new finning machines. These are being used in North America to produce charge air heat-exchange coolers. In service, the machines have lived up to expectations in terms of performance and reliability.

Price concludes: "It is, of course, very comforting for us and for our customers to know that we can rely on worldwide support from Bosch Rexroth, but experience to date suggests that it is unlikely to be needed! We are delighted with the results delivered by the company's products, which are making a major contribution to the success and appeal of our new machines."

Contact Bosch Rexroth for more information about linear motors, aluminium framework components, variable-speed drives, pneumatic actuators and engineering support services.