OEM and precision subcontractor back a favorit

A Studer favorit CNC cylindrical grinding machine is being successfully used in the production of precision drive shafts for lightweight diesel outboards. PES reports.    

In 2010, West Sussex-based Cox Powertrain began its mission to deliver a revolutionary new concept in ultra-lightweight diesel outboards.

This was the genesis of the CXO300. Since then, Cox has successfully raised over £120 million of private investment in order to bring the outboard from a dream to a reality. Having commenced production in May 2020, the CXO300 is now becoming hugely popular throughout the global maritime market.

Cox Powertrain has invested £6.7m in a world-class production facility and all components are procured using a range of OEMs. All items are manufactured to Cox designs and drawings unique to the CXO300 which remains the company’s IP. As the CXO300’s drive shafts have specific requirements, the decision was taken to manufacture them at Delta Tooling (Horsham) and to supply Delta with the machine tools to produce the shafts. Delta is a highly skilled machining subcontractor which has provided Cox with many prototype, pre-production items over the last six years and is now manufacturing production parts.

When Cox Powertrain’s head of DFM & Manufacture, Colin Stapley identified the need to introduce grinding capacity and capabilities into the business related to the production of critical drive shafts, a search was made for a high-precision, CNC universal cylindrical grinding machine.

Having considered the offerings from several leading manufacturers, with input from Gary Childs, the MD of Delta Tooling, Mr Stapley decided that the Studer favorit was the ideal, premium quality model for ensuring that the shafts’ demanding dimensional and surface finish tolerances could be met.

Dedicated cell

Whilst Cox Powertrain retain ownership of the recently purchased Swiss grinding machine, given the subcontractor’s capabilities, and as it made logistical and operational sense, the decision was made to locate the favorit at Delta Tooling’s premises. Consequently, the Studer machine was installed in a new, dedicated facility adjacent to Delta Tooling’s main factory.

Garry Childs explains: “Delta Tooling have been supplying designers with precision CNC machining services for over two decades. In addition to serving challenging industries such as the motorsport, automotive and medical sectors, we are delighted to have formed a close working relationship with Cox Powertrain.

“After refurbishing a vacant unit next to our main production facility, the Studer favorit was installed in what is now our dedicated Cox Powertrain production cell. Given their demanding specifications, the machine has proven to be ideal for the precision grinding of Cox Powertrain’s drive shafts.

“With the assistance of Peter Harding, the owner of UK Studer Agent, Advanced Grinding Supplies, Colin Stapley of Cox Powertrain and I were able to precisely specify the favorit to exactly meet Cox Powertrain’s demanding needs.

“Peter worked closely with us in areas such as developing the grinding process and ensuring the use of the correct wheels, he also helped organise the machine’s trouble free installation and operator training. The favorit’s logical control system and its easy to use software ensured that we were quickly able to exploit all of its advanced capabilities.

“The machine is now in regular use and the high-quality of the drive shafts produced by it adhere to their challenging dimensional and surface finish specifications. In addition, the highly productive machine is helping us to satisfy ever increasing demand for our output.”

A century of grinding expertise

For more than 100 years Studer has been designing and producing high-quality precision cylindrical grinding machines. The Studer favorit is designed for the grinding of medium-sized workpieces in individual and serial production. Owing to the availability of a range of options, such as in-process gauging, balancing systems, contact detection and length positioning, the machine can be precisely supplied to correspond with users’ needs.

The favorit’s machine bed is made of solid Granitan S103. The Studer developed material has proved its efficiency over many years. The excellent dampening characteristics of the machine base ensures outstanding surface quality of all ground workpieces. The use of Granitan S103 also leads to the increased service life of grinding wheels.

The machine’s cross slides V and flat guideways are moulded directly into the machine base and are finished with a non-abrasive Granitan S200 slideway coating. This patented surface structure prevents the slides from ‘swimming’ and also eliminates the stick-slip effect, present in conventional guideways.

Both longitudinal and cross slides are manufactured from high-quality grey cast iron and have highly precise, ground V and flat guideways. The slides rest entirely on the guideways of the machine bed through the entire speed range, which is the basis for excellent straightness (0,0025mm over 650mm measuring length).

The favorit’s slides are advanced by 40mm diameter circulating ballscrews connected to a three-phase servomotor via torsion-resistant, bellow-type couplings. This efficient arrangement enables the axes to achieve high process speeds and maximum precision with in-feed movements of 0.0001mm. Use of the swivelling machine table on the longitudinal slide enables the whole length of the surface to be ground and acts as a support for the workhead, tailstock and accessories.

The favorit’s turret wheelhead can be used for both external and internal grinding and can be equipped with an external grinding wheel and an internal grinding spindle. With high precision, the user can manually (2.5°) index the turret

The machine’s Fanuc 0i CNC control, with an active flat colour monitor (10.4”), is both reliable and optimally matched to the favorit’s drive elements. A manual control unit facilitates setup close to the grinding process, while a special electronic contact detection sensitron function (optional), enables downtimes to be reduced to a minimum.

The high-specification mechanical engineering concept of the favorit is complemented by a grinding software program developed in-house by Studer. Based on pictogramming, the operator strings the individual grinding cycles together, and the control system generates the ISO code. Grinding and dressing process sequences can be programmed freely to optimise the grinding process.

Cox Powertrain’s head of DFM & Manufacture Colin Stapley concludes. “The decision to purchase a Studer favorit and to install it at the premises of Delta Tooling has proven to be a highly successful one.”

Advanced Grinding Supplies


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