Taking the heat out of brake servo production

Citation

(2000), "Taking the heat out of brake servo production", Aircraft Engineering and Aerospace Technology, Vol. 72 No. 5. https://doi.org/10.1108/aeat.2000.12772eab.001

Taking the heat out of brake servo production

Taking the heat out of brake servo production

Keywords Jones & Shipman, Dunlop Aviation, Grinding, Braking systems

Dunlop Aviation Braking Systems of Coventry has installed a Jones & Shipman 1300X universal cylindrical grinder (Plate 1) in the match grind cell of its brake system manufacturing module to replace outdated machinery and to "gear up" the cell for increased production as new braking systems come on-stream.

Plate 1 Jones & Shipman 1300X universal cylindrical grinder at Dunlop Aviation Braking Systems

The brake system module manufactures complete aircraft braking systems including electronic controllers, dual-servo units, master cylinders, emergency parking brakes and various supporting assemblies, while its climate-controlled match grind cell is responsible for precision grinding of stainless steel brake servo valves and corresponding housing bores, before selectively "matching" the two components.

After initial CNC turning and then precision grinding operations to surface finish tolerances of 2-4 inch, and straightness and roundness to 0.00004 inch, selective matching is carried out between servo valves and control housing bores to achieve working clearances of 10-15 inch. This design clearance is vital – allowing controlled, metered leakage of brake fluid past the servo valve when installed. Once "matched", the two components are non-interchangeable.

Some time ago manufacturing team leader Kevin Dunnion identified an urgent requirement to replace, or refurbish and upgrade, a stand alone internal grinder and a grinding centre, both 25 years old. The two grinders were employed on intermediate grinding operations in preparation for final match grinding using a fully automated Jones & Shipman Series 10 CNC production cylindrical grinder.

If the replacement option was to be taken, the new machine needed to have an internal/external grinding facility, a modest price, quick set-up time, be able to increase productivity through simple automated operation, and have the accuracy to achieve a limited match grind capability. After lengthy deliberation Mr Dunnion decided to re-equip rather than refurbish, opting for the microprocessor-based Jones & Shipman 1300X, satisfying both the rigorous specification and tight budgetary constraints demanded by Dunlop.

Mr Dunnion comments:

Although the new acquisition had to meet a wide range of production parameters we still needed to remain extremely cost-conscious at all times. Another important consideration was service back-up. The after-sales and service support for our Jones & Shipman Series 10 has been excellent, while the machine itself has been very reliable and performed very well. Downtime has also been minimal over the nine years we have operated it. Therefore, after a long and considered appraisal of all suitable machinery, the 1300X from Jones & Shipman appeared to be the most cost-effective solution by far.

To satisfy Dunlop's extensive requirements the 1300X, which was delivered in March this year, features a universal wheelhead for rapid transfer between external and internal grinding formats, diameter callipers to assist its match grind capability, and a high speed internal grinding spindle essential for close tolerance grinding of small diameter holes.

The 1300X has impressed Kevin Dunnion and his team both with its unerring accuracy and its range of facilities, for a relatively modest cost. Time-served operator Steve Richings says:

I was pleasantly surprised to find that the 1300X consistently achieves surface finish levels of 4-8 inch – which compare favourably with final match grind standards – even on the hardest, heat-treated stainless steels which hard turning just wouldn't touch, while the set-up between internal and external grinding is quick and easy.

Mr Richings has found grinding cycles on the 1300X very easy to program, using step-by-step parameter prompting with default values which can be accepted or amended as required. At the end of a cycle the wheel retracts automatically. For manual operation, precise control of table traverse and wheelfeed is by hand pulse generators and the position of each axis is clearly indicated on digital read-outs, which also display parameters.

Mr Dunnion notes: "The 1300X has already brought considerable benefits in reduced cycle times, particularly in automatic dressing modes, and has had a major impact on the cell's machining ability".

Already in use several hours per day, the coming months will see work load increase dramatically as brake systems for the Dornier 328, Eurofighter, CASA 295 and Nimrod update all reach production status. The microprocessor-based 1300X universal cylindrical grinder from Jones & Shipman has made an important contribution in preparing the way.

Details available from Jones & Shipman International. Tel: +44 (0)116 289 6222; Fax: +44 (0) 116 289 2945; E-mail: mfranckel@js.renold.com