Mollart pushes boundaries of machining technology for oil exploration

Said managing director Guy Mollart: "Many of these parts are so complex they take certain areas of production right to the bounds of known machining technology and capability that is equal to or even exceeds aerospace machining standards. It is only by investing in very flexible, high quality machine tools and process equipment, the highest quality tooling and inspection techniques, coupled with a very knowledgeable skill base, that these parts are viable to be produced economically." Mollart Engineering won a series of contracts for a continuous supply of a range of "wireline" components from its Chessington, Surrey and Resolven South Wales facilities through its expertise in deep hole drilling. So demanding were the components, they had to meet almost perfect drilling standards for roundness and hole straightness while maintaining very close pitch centres and achieving very thin wall sections over length to diameter ratios on parts up to 140 mm diameter by 1.6 m long. To add to Mollart's problems and machining expertise, these ultra-expensive components are produced out of titanium which not only creates higher demands on tooling but also heavy financial risk associated with any rejection or scrap. Typical of the components produced for oil industry customers in Scotland, France and the US are extended cycle times, even though the latest turn-mill combined operation techniques are employed. Adds Mike Pragnall, operations director: "Producing one part can easily involve 40 operations and run to 120 hours – but you still need to add another 80 hours of processing time to deburr, clean and inspect each component. From material delivery to shipment involving batches of up to five parts, this normally takes eight weeks to process through the factories." Not only has Mollart to machine the components it has to take responsibility for outside specialist processes such as electron beam and TIG welding. Indeed, when one assembly of five parts is completed it is 3.4 m long! The components are used for collation and transmission of data from the drilling head back to the surface by fibre optic cable and also to carry hydraulic lines for manipulation of the unit. So critical is the function of these highly complex components that with correct and fast sample analysis they can quickly determine the quality of the crude sample which leads to a decision to continue drilling or abandon the well site and look elsewhere. Said Mr Mollart: "Quality is definitely the priority to our machining – you would never want to put a cost against failure when these units are well below the earth's crust." Mollarts' investment programme at the modern 20,000 ft² facility in Resolven soaked up almost £2 million with three Mazak Integrex 300-IIY turn-mill centres. To which Mr Molart adds: "When the machines were installed we spent an additional third on top of the capital outlay to add high quality tooling in order to achieve the levels of consistency from part to part." Also contributing to key processes on the titanium parts are three Takisawa turning centres, two very large capacity Weiler and Mori Seiki lathes giving a very flexible capacity up to 610 mm diameter by 4,500 m turned length. Four-axis machining centres were also installed from Haas, Cincinnati and Mori Seiki with capacities up to 1,500 mm by 645 mm by 700 mm and three in-house built Mollart gundrills to enable holes between just 1 mm to 60 mm by 1,500 mm deep to be drilled in a single hit. Indeed, Mollart has even developed its own process technology in zero point targeting when deep hole drilling parts that it is able to drill from one side to depth, index the part 180° and drill through to break into the original hole with absolute minimal mismatch. In addition to spends at Resolven, over £1.5 million was recently invested in the Chessington headquarters to provide combined machining centre and deep hole drilling capacity for holes between 1 mm by 60 mm by 2,000 mm deep and the installation of the largest depth to diameter ratio honing machine from Sunnen to be installed in the UK. This horizontal hone has a capacity to finish holes between 4 mm and 80 mm diameter and up to 1,000 mm deep. Due to the complexity of components with large numbers of internal intersecting feed holes, recesses, chambers and slots, processes also include extensive thread milling, reaming and precision boring with many critical seating and sealing faces. Mollart's also invested some £300,000 in large capacity ultrasonic cleaning and abrasive flow deburring. Not only does the abrasive flow automatically carry away rags and burrs at internal hole insertions it also acts as a blending agent to smooth the transition between features. Also in use at Chessington is fibre-optic camera technology to check out internal features deep in the body of the components. Said Mr Pragnall: "We are talking quality levels at least as high as aerospace industry in similar materials such as difficult to machine titanium. However, tolerances can be far stricter on some features requiring 10 micron to be achieved on size and between 5 and 10 micron on geometric tolerances – especially on concentricity. Surface finishes that are far more demanding than aerospace." For instance, even though gundrilled holes produce a very round and straight hole with a highly burnished finish, he explains that many holes have to be honed, purely to eliminate any indication of feed marks, pick-up or minute scratches. With Mollart's expertise in gundrilling it works very closely with its tooling partner Botek in order to perfect the balance between penetration rates, point angles and the critical support of the carbide wear pads for the drill point. But he maintains: "The spin-off in being able to drill small holes over 1 m deep, create a very thin wall section between the OD and hole without the drill wandering or swelling the outer surface, has led his company to become a world leader in this technology area."