Mollart cuts an edge to add value to its deep hole subcontract services

Based on its branding of the business under 'The Hole Solution' the investment builds on its deep hole expertise that spans machine tool development and build, process development and supply of tooling that can be applied to subcontract production of customers components. With the installation in place, Mollart is now providing an independent deburring and component cleaning service and so extends the subcontract capability of Mollart Engineering that following its recent acquisition of Bencere also provides a source of mechanical deburring and superfinishing solutions that can be applied to a wide range of components. Explains managing director Guy Mollart on the background of his company's attention to removing burrs. "Some of the components we produce for customers in the aerospace, oil and gas, medical, nuclear, telecoms and marine sectors are so complicated. Many have numerous and intricate intersections of a variety of different sized deep holes, internal galleries and chambers with the added burden of very deep cavities, so precision deburring and high standards of final cleaning are a resource we have to provide to customers to meet strictly controlled requirements." As a supplier, he adds the removal of burrs and sharp edges is very skill dependent and labour intensive to achieve the standards demanded. It is not uncommon for deburring to add up to 15 per cent to the price of a job. "In some cases we have spent over 100 hours finishing time on certain highly complex, multi-featured components," he says. From a management perspective he maintains that deburring results are always subjective based on 'remove sharp edges' on a drawing and can, even despite the best will in the world, be inconsistent. He said: "The task can also be very unpleasant, you have to be very aware of health and safety issues and be extremely careful not to mark, or damage these high value parts at the end of the production cycle. So by automating the process you have an important advantage to offer customers." As part of Mollart's production engineering expertise in applying deep hole drilling technology, debate and discussion often ensue about controlling a burr, especially on the intersection or break out point of a hole – the best shape of the burr in its creation for easy removal, its position and the direction of the sharp edge and where and when it is best removed. It can be as simple as passing another drill down one of the holes but it is always imperative that the burr must never be missed, deformed or bent. The Micro-Technica MicroStream Duplex 250 abrasive flow system now installed in a purpose extended shop area at Chessington is the largest ever built by the German specialist and was tailor engineered to Mollart Engineering's requirement. It is a twin-spindle machine with independent vertical and horizontal heads and has the capability to handle components up to 1.6 m by 2.0 m in its working envelope. Important in Mollart engineers eyes were its ability to deburr, using the abrasive flow technique, holes as small as 0.8 mm and up to 50 mm dia and up to its 2 m maximum length of processing. The process uses a putty-like polymer visco elastic base material that acts as a flexible carrier for abrasive particles. Here, the application expertise is key as the media has to be formulated to suit the material being processed and production requirement. During the process the media is pushed forwards and backwards through the workpiece under hydraulic pressure with the abrasive particles carried just below the surface. As the media flows under pressure in the component when the flow characteristics change, for instance when encountering an edge or burr, the grit rises to the surface and the edge or burr is 'machined'. The action does not infringe existing tolerances and the frequent changes of direction of flow result in the removal of any sharp edge and the imparting of a very smooth precise radius to the corner. The Micro-Technica abrasive flow machine is able to process materials as diverse as hard plastics to high grade alloy steels and through special media concentrations, is also suitable for soft materials such as aluminium without degrading surface finish. As Operations Director Mike Pragnal explains: "The decision to install a twin-head machine was based on providing us with total flexibility, so we can process two completely different components simultaneously – one under the vertical head and the other using the horizontal media flow head. We can even process the same part, with suitable fixturing from the vertical and horizontal head and have the flexibility to apply different media from each head to suit the type of deburring required." An important area, he maintains, is where we are required to drill from each end of a component working to a large hole length to diameter ratio. We can now pump the abrasive through the bore which will blend any step or misalignment into a smooth profile and remove any burr at the breakthrough position. As part of this capability Mollart has invested in a borescope measurement device able to accommodate holes as fine as 3 mm dia and fibre-optic vision probing with CCTV to inspect the quality of the hole intersections. Having deburred the component, Mollart had concerns that the abrasive media could be captured within the component with dire consequences so the decision to install the Hilsonic IST 3510 twin-stage ultrasonic washing plant was made to ensure components up to 140 mm dia by 3 m long that have been deburred are cleaned to customer requirements. The installation would also provide a highly effective cleaning process for other parts that have been machined at Chessington prior to final despatch and as a subcontract service for high precision machined parts. Central to this machine specification, like the abrasive flow machine, is that it has been tailored to meet Mollart's requirements such as the inclusion of a programmable 30 bar high pressure wash jet and the ability to hold multiples of small components in a rotating basket. Due to its machine tool build and design and development capability, Mollart Engineering already has a strong design team using SolidWorks CAD to CAM and a fully operational toolroom. Here, Mr Mollart explains how the tooling up of both deburring and cleaning processes can be totally managed in-house as part of the deburring and cleaning service. However, he maintains that most important is the team of quality engineers who are highly experienced in the inspection of very complex internal features typically involved in the deephole production process: "They have the understanding and the equipment available to certify full compliance to customers' requirements," he says.