Following thread milling trials using Vargus Tooling&rsquos &lsquosuper fast&rsquo Multi-flute Indexable Thread Mills (MiTM), BIS Valves has slashed machining times by almost 25 minutes in the production of 1¼ x 12 UNF threads in valve body manifolds - reducing the previous time from five minutes to just two minutes and 20 seconds per thread!
The change in the thread milling process and the switch to the use of the Vargus MiTM with its long (40 mm) s and multiple flute holders coincided with the installation of a Dahlih MCH 630 twin-pallet horizontal machining centre at the company&rsquos newly-acquired 3,000 ft2 of additional production facilities in Wimborne Minster, Dorset. The installation provided the additional spindle capacity to not only meet a significant rise in the order book but also to provide further growth potential scheduled during 2013.
Calling in Vargus Tooling UK to advise on possible improvements in thread milling &ndash a process that involves up to eight ports being produced on three faces of seven variants of the 316 stainless steel manifold blocks &ndash Vargus&rsquo latest multi-fluted thread milling system was put forward. And since the initial trials that saved over three minutes per hole, the tool still showed no signs of wear even after more than 500 cycles. It also delivered improved finish on the class 2B fit thread form that has to accommodate pressures of up to 10,000 psi.
The largest of the BIS Valve manifolds are 100 mm square by 330 mm long with up to eight ports on each of three faces, as well as a variety of feed and connecting holes on all six faces. Smaller versions within the component family are 100 mm square by 127 mm long and 75 mm square by 300 mm long. These variants also have up to six ports to the same specification with a 26.7 mm depth of thread. These are used to control hydraulic systems mainly installed in the oil and gas industry for topside, subsea and down-hole applications.
By moving to a horizontal machining strategy, one face and both ends of each block are initially milled. The part is then located on the datum machined faces and the other three faces are skimmed square and flat. The part is then gundrilled as a separate process and returned to the machining centre, where the multiples of different drilled and threaded features, including the port holes, are incorporated in the same setting.
Previously using vertical spindle methods, these were all separate cycles and this process extended lead time and involved additional lost time with the resetting of batches that are no bigger than 60 but more likely under 10.
The porting cycle using Vargus&rsquo MiTM uses an initial U-drill to hog out the material followed with another U-drill carrying a formed to finish the form in the part, create a chamfer and produce a 60 deg cone. As part of the proving trials, Vargus also supplied its TM Gen Software to provide optimised machining data and G-codes that are acceptable to most machine control systems. The toolholder supplied was a RTMC 2522-43L3 with TiCN coated s R40I12UNTM VBX that incorporate two cutting edges.
The design of the MiTM toolholder uses three equi-pitched s that can be either 25 mm or 40 mm in length (as in the BIS Valves application) and enables a significant increase in feed rate and provides for longer uninterrupted &lsquoin-cut&rsquo life to be applied as well as reducing the number of machining passes. This effective increase in the number of available cutting edges not only reduces cycle times but also leads to reductions in tool costs and improvements in finish-machined quality.
MiTM holders have cutting diameters from 13.6 mm to 58 mm and one to eight flutes. The s are supplied with varying numbers of teeth in a variety of pitches and are offered in a range of threading standards. Conical and Shell Mill holder styles are available to suit the thread and pitch size required.
At BIS Valves, the previous incumbent tool and single was run at 129 revs/min and a feed rate of 69 mm/min while the Vargus MiTM tool is rotated at 2,400 revs/min and at a feed of 188 mm/min - 36 per cent faster. Workshop Team Leader, Adrian Booth commented: &ldquoWe could increase the speeds to cut even faster but have a policy of &lsquoinsurance&rsquo and tend to throttle back to maximise tool life and process security. The reduced speed also helps with swarf control in the 316 stainless material.&rdquo
The thread milling process involves the tool feeding in rapid traverse from Z-zero position to the bottom of the hole. It then arcs using the machine&rsquos three axes at a third of the overall feed rate in order to initially load the before the full thread form is engaged. The tool is then rotated by one revolution and arcs out to the Z-zero plane ready for toolchange.
BIS Valves was originally set up in 1964 and it adopted the name, Bournemouth Industrial Supplies, in the early 1970s when it became involved in supplying valves to the offshore oil and gas industry. Following a management buyout, in 1994, the business &ndash which changed its name to BIS Valves in 1998 - had three operational directors: Paul Gardiner as Managing Director, Matthew Smith as Production Director and David Kelly as Technical Director &ndash who joined the business in 1991 as a Design Engineer. In 2002, Paul Gardiner departed the company, and Matthew Smith and David Kelly became Joint Managing Directors but in 2007, regrettably Matthew succumbed to illness and David became sole MD.
Continuous growth based on a self-funding policy saw sales top £4.3 million in 2011 and this year it is well on target to exceed £5 million. It was on the back of a growing forward order book that the decision was made to take the additional facility and install the horizontal machining centre. The business employs 62 people and is currently recruiting. It has four apprentices.
The company&rsquos headquarters and main production centre in West Moors, Dorset, houses design, development and the mainstay of production with 80 per cent of product dedicated to oil and gas sectors and the remainder to pharmaceutical, power generation, water hydraulic and fuel system customers. Half of production is exported direct to Norway, Europe, Far East, Australia and the USA while a further 30 per cent is exported indirectly through incorporation within customer products.
Explaining the continued growth and success, Mr Kelly said: &ldquoWe have our own product and our own hydraulic design specialists, which means we can adapt quickly to customer requirements. We also have a fairly small but dynamic operation with our own machining facility, which gives us the flexibility to respond promptly - a factor which customers are very keen to take maximum advantage of.&rdquo
Concluding, Mr Booth added: &ldquoSo pleased are we with the Vargus thread milling system that on the next batch of components will be carrying out face milling trials and introducing Vargus thread milling to manifolds that have smaller, ½&rdquo BSP threads. Looking at the projected cutting data for both projects, we should be able to add to our productivity gains and further improve spindle uptime.&rdquo