Following the installation of a new turning centre, it took Blackburn-based scuba-diving specialist Apeks Marine Equipment just eight weeks to record production cost savings of almost £4,000, compared with the original well-proven turn-milling methods. Moreover, the machine has allowed setting times to be halved.
The machine in question is a Miyano BNE-51MSY, which was bought from Bushey-based Citizen Machinery UK Ltd (
www.citizenmachinery.co.uk) following four months of in-depth investigation that involved four machine suppliers.
Machine shop supervisor Stuart Davis says: “Each supplier was asked to provide cycle times and change-over times for two very complex multi-featured breathing apparatus components, highlight the advantages of the machine they were proposing, and give a price for a turn-key project.
“Our initial assessment favoured the Miyano machine, so we gave Citizen a part drawing, tooling sheet and program from the existing turn-mill machine so that the company could undertake production prove-out trials on a BNE-51MSY at its headquarters.”
Apeks Marine was founded in the 1970s by Ken Smith Ainscough and Eric Partington (the initials form the company name), both keen divers and precision engineers. They started in a small garage in the north of England and now employ 150 people. The company is part of Aqua Lung International and sells a range of scuba-diving regulator units — plus bladders, instruments and a wide range of accessories — to over 50 countries.
Sales are not only to diving enthusiasts, but also to professional divers — including those in the military and emergency services. Indeed, the company has a hard-won world-wide reputation; it has also provided equipment used to explore some of the deepest, coldest and most hostile diving environments on earth. For instance, its MTX military-based regulator is claimed to be the only one in the world that will not freeze when used in ice water.
Any regulator failure in use could lead to lives being put at risk, which is why the business ensures total control over every manufacturing process, in order to guarantee quality and performance.
Furthermore, based on the reputation gained in diving-equipment circles, it is now expanding its product range to include ‘first response’ systems (used to neutralise the effects of chemical spillages) and compressed-air chargers that allow the likes of spear guns and paint-ball guns to be recharged on site.
Combined operations
While the new Miyano replaced existing machines, key to the installation was its ability to combine operations on a range of CZ121 brass components into a single cycle. These included: the finishing of a critical valve seating to 0.2µm CLA; maintaining a 0.05mm tolerance on the depth of key porting features; achieving a 0.02mm tolerance on a special internal radius, which also has a 0.04mm positional tolerance taken from a 45deg angle intersection point; and holding various concentricity requirements within 0.08mm TIR.
Mr Davis said: “The Miyano runs from 6am to 10pm Monday to Thursday and from 6am to 7pm on Fridays — and to date it has never missed a beat. The control is very familiar to us, as it is similar to the one on the Citizen A32 sliding-head lathe we installed in 2012. This helps with operator familiarity, plus it offers very fast data processing. We also use the control’s highly flexible and time-saving overlapping cycle capability, while being able to have three tools in cut simultaneously provides major cycle-time reductions.”
Comparing the current machining of a four-port regulator body (that formed part of the initial trial and is run in batches of 1,000 parts) with the previous methods, Mr Davis says: “We have seen setting times reduced from 4hr to just 2hr, while the cycle time has been cut from 4.93min to just 2.9min. We are using 28 tools, which are mounted on both the Miyano’s 12-station turrets, along with some special tool-holders.”
The regulator body, which regulates air from the tank, is made from 42mm-diameter brass and is 45mm long. On the front face, the machining cycle includes the production of features such as bores that are 38 and 30mm in diameter, as well as undercuts, grooves, chamfers and an M38 x 1.5 thread.
A 3.5mm-diameter hole is drilled through, and a 45deg angular form with a 2mm outside radius is created in the bottom of the bore. In addition, four slots are milled in a cross form in the centre section at the bottom of the bore, and two 2.5mm-diameter holes are drilled 41mm deep to break into two of three port holes that are produced from the outside diameter.
On the rear face, stepped bores of 18, 14 and 11mm are drilled. Also machined are a 1.5mm-wide undercut and two 3.5mm-diameter bull-nose forms 1.4mm deep and at 90deg to each other, while a 0.3-0.5mm radius 0.08-0.12mm from a 45deg form is generated at the bottom of the bore.
Two connector ports are radially drilled, counter-bored and tapped 3/8 UNF from the outside diameter, and a third 7/16 UNF port with a 1mm breakthrough to the central bore is produced.
Each part is then individually engraved with consecutive serial numbers to confirm the month and year of manufacture; CE and EN numbers are also added.
The eight-axis Miyano BNE-51MSY features a rigid single-piece bed casting with scraped square guideways that allow full advantage to be taken of the 15kW main spindle and 7.5kW second spindle; both offer a maximum speed of 6,000rev/min. Meanwhile, the two 12-station all-driven turrets have 2.2kW motors developing 20Nm of torque and 6,000rev/min.
Overlapped machining can be carried out on both end faces of a part simultaneously, such as drilling with the main turret (which has three axes X1, Z1 and Y1) at the main spindle while the second spindle feeds forward with two axes (X3 and Z3) to engage the same turret. In addition, the second two-axis turret (X2 and Z2) can be independently engaged to produce outside features at either the main spindle or second spindle.
Mr Davis says: “Without doubt, the Miyano specification and build ticked all our boxes.The machine was also mid-range on price when compared with those offered by the other suppliers considered; and it has contributed to our drive to achieve ‘cost down’, while at the same time assuring us of machining a quality product that meets our strict safety demands.”