A fine art

Perfect timing of an investment worth more than £3.5 million in multi-axis machining technology by Mollart Engineering at its two subcontract machining facilities has enabled the business to capitalise on the expanding demand for high technology components. 

Due to careful choice of equipment installed, both of Mollart's operational sites at Chessington, Surrey and Resolven, South Wales are geared up to meet demands for the manufacture of complex parts for the oil and gas industry. As managing director, Guy Mollart reveals, the components manufactured are continuously pushing technological boundaries.

“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,” he says. “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 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 close pitch centres and achieving thin wall sections over length to diameter ratios on parts up to 140mm diameter by 1.6m long. Added to the mix is the fact that the very expensive components are produced from titanium which not only creates higher demands on tooling but also heavy financial risk associated with any rejection or scrap. 

Total responsibility

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 3.4m 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 the 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. “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,” warns Mr Mollart.

Investment programme

Mollart's investment programme at the modern 20,000ft² facility in Resolven soaked up almost £2 million with three Mazak Integrex 300-IIY turn/mill centres. “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,” Mr Mollart adds.

Also contributing to key processes on the titanium parts are three Takisawa turning centres, two large capacity Weiler and Mori Seiki lathes providing a flexible capacity up to 610mm diameter by 4,500m turned length. Four-axis machining centres were also installed from Haas, Cincinnati and Mori Seiki with capacities up to 1,500mm x 645mm x 700mm and three in-house built Mollart gundrills to enable holes between just 1mm to 60mm by 1,500mm 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 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 1mm by 60mm by 2,000mm deep and the installation of the largest depth to diameter ratio honing machine from Sunnen to be installed in the UK. The horizontal hone has a capacity to finish holes between 4mm and 80mm diameter and up to 1,000mm deep. 

Aerospace and beyond

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 has 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.

Says Mr Pragnall: “We are talking quality levels at least as high as the aerospace industry in similar materials such as difficult to machine titanium. However, tolerances can be far stricter on some features requiring 10µm to be achieved on size and between 5µm and 10µm on geometric tolerances – especially on concentricity. Surface finishes can also be extremely demanding,” he continues. “For instance, even though gundrilled holes produce a very round and straight hole with a highly burnished finish, 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 Mr Pragnall maintains: “The spin-off in being able to drill small holes over 1m 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.”

Mollart
www.mollart.co.uk