Pioneers in Machining Technology
Economical batch size is whatever is on a pallet
Dawlish-based control valve and marine steering system manufacturer, Hydraulic Projects (Hy-Pro), which is celebrating its 50th anniversary this year, is approaching the midpoint in a five-year plan to double turnover. The company is on target to do so, despite headwinds in the global economy.
A key resource in the successful completion of the plan will be the addition to the shop floor of a Japanese-built Okuma horizontal machining centre, a 400 mm pallet machine with BT40 / 15,000 rpm spindle, half-metre-cube capacity and 10-pallet pool, supplied in October 2015 by UK agent, NCMT.
The cell entered service quickly, within one week of installation, and was producing components unattended overnight within two weeks, thanks in part to the security provided by comprehensive collision avoidance built into the Okuma OSP control.
Hy-Pro’s managing director Elaine Slater commented, “We are an innovative company designing and producing hydraulic valves for mobile applications such as recovery vehicles and hydraulic pumps for autopilot systems on yachts and boats.
“We have to control manufacturing costs closely to compete with low-wage manufacturing countries and aim to replace at least one of our dozen or so machine tools every year to remain up to date technologically.
“This year we made our biggest ever investment in the Okuma flexible manufacturing cell. It has been operating for only a short time but has already revolutionised our productivity, allowing us to reduce work in progress and move towards kanban-style production, rather than for stock.”
Hy-Pro’s is mainly a series production business involving batches of 100- to 400-off, especially of standard valve components. Fixturing of multiple parts for six-sided machining is a priority, the aim being to reduce the number of set-ups to two. Three vertical machining centres with a fourth axis rotary indexing unit and a twin-pallet, 4-axis VMC have traditionally formed the mainstay of prismatic machining work at Dawlish.
The Okuma MB4000H is the first horizontal-spindle machining centre on-site. Three of the pallets are permanently set up for large batch production of 13 different core components, which is generally completed unattended overnight after production staff have left at the end of the single day shift. There is plenty of capacity for cutters and sister tools in the 218-pocket magazine to complete all of the parts fixtured on the pallets.
The remaining pallets are devoted to more labour-intensive production during the day. This has seen a major change, according to machine shop manager Kevin Saunders, in that batch sizes produced are now often much smaller than before.
He said, “A lot of lower quantities are needed for bespoke pumps and slow-moving items, for example. With the Okuma, economical batch size is whatever is fixtured to the tombstone on a pallet. A single part can be produced for a similar unit manufacturing cost as large runs.
“We regularly produce medium volumes of cast iron valve bodies, typically 32-off in a day shift, on one of our 4-axis VMCs. This quantity is doubled in the 10-pallet cell, however. It is because less time is wasted due to off-line set up, parts are presented to the spindle quicker and there is no need for retooling between jobs.
“A component that we now produce in-house from billet is an aluminium manifold, which we require in quantities of 3,500 per year.
“We previously had no capacity to produce these parts so were having them machined outside. We were paying twice what it now costs us to machine them overnight in the Okuma cell, 24 at a time.”
General tolerance held is ± 10 microns, which is well within the scope of all plant on the shop floor at Dawlish, but the Okuma is singled out by Mr Saunders as being “fantastic” in terms of its accuracy and repeatability. The production team adopts a policy of not wringing every last second out of cycle times, but concentrates instead on minimising handling, for example by incorporating extensive in-cycle component deburring.
Space is available on the shop floor to install a second, identical Okuma flexible production cell when production demands dictate. At that point, one operator will be able to run both cells, leading to even greater economies of production.