Please click on the cover to view
Laser & Waterjet Profiling
Register here for a free monthly edition of the magazine
Subscribe here to receive our free newsletter for a monthly round-up of the latest news and features
Stainless steel is a material valued for its corrosion resistance but it does create challenges for machinists.
The main problem associated with the material surrounds in-process work hardening, which can inhibit successful chip formation and edge build-up. This can lead to premature tool wear, breakages and a poor quality finish.
Scunthorpe-based JCF Engineering has enjoyed success using Horn’s broaching, face grooving and boring tooling in the manufacture of marine grade 316 stainless steel products. Many of these are used on undersea systems for the oil, gas and telecommunication industries.
Since its formation in 2008, JCF has specialised in machining stainless steel. CEO John Felton established JCF with a 2-axis CNC lathe and a machining centre but the success of the venture has seen the number of machines rise to five (three CNC lathes and two machining centres). As a result, the company has expanded into the industrial unit adjacent to its start-up premises and is considering taking on an engineering apprentice.
“We elected to specialise in machining stainless from the outset because it’s generally more demanding work,” explains Mr Felton. “Quite a few companies are reluctant to take it on which works to our advantage as we can bring our expertise to bear. The overriding necessity is to work to a high standard consistently and in order to achieve that end we work closely with our customers and suppliers which seems a successful formula.”
A significant proportion of the company’s customers provide components and systems for subsea applications where quality and reliability is paramount. Batch quantities are generally modest – in the 50-150 component range – but JCF also has the technical capability needed to participate in production design during prototype product development, optimising component suitability for manufacture.
“We engaged with Horn at an early stage in the company’s development,” Mr Felton continues. “We had a contract to supply stainless steel connector body components and this was based on our ability to improve quality and productivity compared with existing methods of manufacture. A common, critical feature of all the connector variants is a pair of axial keyway slots radially spaced at 120° to align the male and female components. Horn’s broaching tooling appeared to offer the ideal solution to produce these features if the part could be positioned accurately and the tooling would last long enough for economical production.”
Machining of the components is split between a machining centre and a 2-axis CNC lathe. Initially the broaching operation was carried out using the machining centre – using the fourth axis for positioning with the broaching tool mounted in the spindle. This proved the basic capability of the broaching process but it was apparent that the balance between the lathe and the machining centre was far from ideal.
Mr Felton elaborates: “Although the lathe has no C-axis it does have a servo clamping facility on the spindle. This proved to be capable of achieving the radial positioning accuracy and repeatability that we needed and it has been very successful.”
Having established the process, JCF then worked to refine the cutting data for the broaching operation to optimise finish and swarf control and maximise tool life. This has hinged on reducing the depth increment during broaching to form a weakened chip which separates reliably at the end of the stroke. As a result, the broach tooling now lasts for up to 1,000 components or 2,000 slots before replacement is necessary. Also, the need for deburring is minimised.
“A key aspect of machining stainless steels – particularly 316 – is patience,” Mr Felton says. “If we tried broaching with heavier increments we would make marginal savings on cycle time but we’d probably lose on process reliability and tool life. As Horn’s broach tooling is custom made to achieve the correct dimension it can be initially expensive but because it lasts so well, the return on investment is soon realised. From our customer’s standpoint the fact that we have developed a reliable high yield process smooths their workflow.”
As well as the broaching tooling, JCF also uses Horn System 114 face grooving and Horn System 108 boring inserts to produce features on the bodies. In all, three sizes of connector body are produced with a number of feature variations within each size band.
“Overall the association with Horn has been very successful.” Mr Felton concludes. “We’ve demonstrated the ability to provide a reliable service which has generated more business – several of our contracts now require the production of splines and keyways. Much credit goes to Horn as the tooling has proved absolutely fit for purpose and its ability to supply customised tooling remains an important resource for us.”
Horn Cutting Tools