Ballscrews Prove Bigger Isn’t Necessarily Better

By specifying THK’s innovative ballscrews, AddisonMcKee successfully reduced the size of its latest tube-bending machine, while increasing controllability and slashing energy consumption. Although some believe bigger is better, others consider smaller sizes more appealing. Mobile phone manufacturers, microchip producers and personal computer designers have all seen the extreme benefits of going small with compact automation components.

In the world of original equipment manufacturers, however, power, accuracy and reliability prevail, although relative downsizing is increasingly being seen as a way of effectively differentiating products.

For UK-based tube-bending machine manufacturer AddisonMcKee, the unwavering performance of its specialist products has been key to the success of the company, which now employs 150 staff at its 4800m2 production facility in Preston UK, and similar in the USA.

That said, a bespoke request for a system capable of producing tight-radius elbow bends in difficult materials such as stainless steel and copper, gave the company an opportunity to test the latest ballscrew technology from THK, the world’s leading manufacturer of linear motion systems.

The compact automation components not only reduced the size of the resulting machine, known as EB110, but also improved controllability and overall energy efficiency.

As Andy Carruthers, Technical Director at AddisonMcKee, points out, the project marked a landmark development in terms of machine design and performance.

‘With THK’s HBN ballscrews we were able to reduce the size of the EB110 and introduce more controllability’.

‘Since size is a relatively important issue for us, it meant we could make significantly smaller systems’.

‘As a result, we’ll probably move our other machines on to this new design of ballscrew’.

Carruthers says the EB110 system uses three HBN ballscrews to apply speed, force and movement to the machine’s elements.

These fundamental constituents – a boost follower, reaction slide and mandrel retractor – form the mainstay of the EB110, delivering the force required to produce bends in the tube.

Their significance is such that by simply introducing a more compact power-delivery mechanism, AddisonMcKee was able to make significant design improvements.

Measuring 63mm in diameter and 1m in length, the HBN ballscrews were around half the size of the automation components previously specified by AddisonMcKee, yet the extreme load capability of the Caged Ball design in conjunction with its high operating speeds meant that HBN ballscrews increased the overall efficiency of movement over standard non-caged ballscrew technology.

As Carruthers explains, this made a noticeable impact on the design of the EB110.

‘The THK components were selected primarily because they were heavy-duty ballscrews’.

‘If we had bigger ballscrews, the structure of the machine would have been bigger, increasing the footprint of the system’.

‘The HBN ballscrews are more compact, so you get far greater force from a smaller size’.

In addition, the virtually maintenance free design of the Caged Ball HBN ballscrews has enabled AddisonMcKee to significantly reduce maintenance intervals on the EB110 machine, resulting in the elimination of costly and time consuming downtime and the associated drawbacks.

As well as reducing the overall machine size by around 15%, the HBN ballscrews also provided AddisonMcKee with more controllability through lower inertia ratings.

In turn, this enabled the company to produce a machine capable of producing extremely precise parts using less energy.

‘Larger diameter ballscrews are more difficult to control because they have higher levels of inertia’, Carruthers says.

‘Because the HBN is smaller, it’s dynamically better, so we can put more controllability into producing the part’.

‘For instance, on some servomotors, you can consume 40% of the power just by accelerating the motor and the ballscrew’.

‘By specifying a smaller ballscrew, you need less power because more of it gets directed to actually doing the work’.

The impact of THK’s HBN ballscrews at AddisonMcKee has been considerable.

The improvements in energy efficiency, size and control have convinced the company to undertake a cost assessment exercise looking at introducing the compact ballscrew across the firm’s entire range of tube-manipulating equipment.

‘Since the HBN ballscrews gives us smaller units with more controllability’, Carruthers says, ‘we will certainly look at employing them on all our new products and our existing range’.