As a result of receiving new and on-going business from a manufacturer of flow meters used in the oil, gas and food industries world-wide, the Leicester-based sub-contractor Nisan Engineering has bought an Akari four-axis horizontal machining centre. Built by Averex Automation in Taiwan, it is the first of its type to be installed in the UK.
The flow-meter contract involves the manufacture of a family of 10 cylindrical components, which at first glance look as though they should be made on a twin-spindle lathe with live tooling. However, on closer inspection it is evident that two operations on a twin-pallet HMC with a rotary table to provide a fourth CNC axis is the most efficient and cost-effective way to machine these steel parts.
Mukesh Prajapati, managing director of Nisan Engineering, bought the Akari from Kenilworth-based Whitehouse Machine Tools Ltd
(www.wmtcnc.com) — “one of our first ports of call when we need to invest in new plant. We have dealt with the company for more than 20 years, and they have always provided us with reliable applications engineering to get us started. The Akari, which we bought in January this year, has a working volume of nominally two-thirds of a metre cube. It is also a competitively priced 40-taper machine, and ideal for producing the new meter components economically.”
When Nisan Engineering took over the flow-meter component contract from another Leicester sub-contractor, Mr Prajapati talked to the customer about re-engineering the manufacturing process. This has simplified production and halved the previous 12-week lead time.
Design changes
A number of changes were made to the component design. For instance, a flat was re-sized so that a standard milling cutter could produce it in one pass, as a step-over was not allowed by the customer; this avoids the cost and delay associated with sourcing a special size of tool. The sides of the milled flat were also changed from vertical to 45deg, eliminating the need to deburr the edges. Another example of re-engineering was the introduction — during op 1 — of chamfers at both ends of the bore that runs right through the component, facilitating accurate clamping for op 2.
Tooling companies OSG and Seco were involved at an early stage to advise on the best tools for the various operations. One recommendation was to use a roll-forming tool in a synchronised tapping head to produce M3 threads, rather than a conventional holder and tap, as this arrangement broke taps frequently. At the time of interview for this application story, over 400 holes had been roll-tapped without any breakages.
The turn-key solution provided by Whitehouse Machine Tools also included Renishaw probing for setting workpiece datums, the design and fitting of an up-rated pump to increase coolant flow, and one of the supplier’s applications engineers spending two weeks at Nisan to set up the process. The result of all these measures was to reduce the economical batch size for each of the 10 components to 15 parts (between 30 and 50 of each type are currently delivered monthly to the customer, without the expense of having to hold consignment stocks).
Whereas each component was previously machined from carbon-steel hollow bar, it is now made from less-costly solid EN8 stock that has been turned to size.
As a result, the previous turning, boring and prismatic-machining operations, which required three set-ups plus separate deburring, have been condensed to two clampings on the two Akari pallets, parts coming off complete in a total cycle time of 25min. Interestingly, Nisan made 30 of one of the components ‘conventionally’ last December — before the new HMC was installed — to meet an urgent order from the customer during the change-over period. The batch took four weeks to complete; an identical run on the Akari in early February took just two days.
Special fixture
The flow-meter cylinders are machined from solid round billets that are 74.5-145mm in diameter and 270-557mm long. A bore between 34 and 65mm in diameter is machined during op 1, after which the part is held in a special fixture (made by Saluki, Leicester) that can accommodate all of the component variants for op 2, which involves drilling, tapping and milling.
Bores have to be accurate to 37µm total and other dimensions to between ±0.1 and ±0.2mm, while the faces of the component are ‘tied’ to the bore to within 50µm for concentricity and parallelism. The project has been so successful that Nisan Engineering has already started manufacturing a second component for the customer, this time on a twin-spindle turning cell with automation.
In conclusion, Mr Prajapati said: “We are pleased to be the first user in the UK of an Akari HS-450i. It is also the first horizontal machining centre that we have bought, and it adds to the capabilities and scope of Nisan Engineering. Although the Akari is manufactured in Taiwan, which keeps the price down, it is of high-quality construction and features, for example, hand-scraped surfaces for mounting the Tsubaki ballscrews; it also has THK heavy-duty roller guideways. We also like the Fanuc control with its nano interpolation, and the BIG Plus spindle.
Moreover, the machine can be expanded quickly and affordably, from two to six pallets and from 80 to 120 — or even 220 — tools, allowing the machine’s capacity to grow with the user’s business.