CNC Engineering Case Studies
Perhaps more than any other machine tool group, sliding head lathe users tend to remain loyal to their respective supplier of choice. On the Star GB stand at MACH 2014, Dave Tudor caught up with two happy customers singing the praises of Star’s SR-20R IV – the latest incarnation of the company’s popular 20mm slider.
One good turn deserves another Perhaps more than any other machine tool group, sliding head lathe users tend to remain loyal to their respective supplier of choice. On the Star GB stand at MACH 2014, Dave Tudor caught up with two happy customers singing the praises of Star’s SR-20R IV – the latest incarnation of the company’s popular 20mm slider. Since its introduction some 12 years ago, the SR-20R series of sliding head machines has proven to be a solid performer with each new revision offering significant improvements over its predecessor. The SR-20R IV is the latest addition to the range and was initially introduced to the marketplace around 18 months ago. According to Star’s engineering manager Alec Warner, the new version has been positively received with a number of customers now ordering their second machines. Specification wise there’s a wealth of notable improvements on the SR-20R IV. It’s more power efficient; it can accommodate up to 41 tools to yield a variety of tooling options and features full programmable B-axis controlled power driven tools for varied machining operations – including full simultaneous 5-axis machining capability. It also offers double the amount of backworking tools (eight) compared to previous incarnations and modular stations across the yoke provide flexibility for different tooling arrangements and configurations. Interestingly, with the right accessories, it can actually handle workpiece diameters of 23mm. A welcome provision on the version IV is more muscle in the sub-spindle department which actually matches that of the main spindle. With both rated at 10,000rpm via 2.2kW motors, there’s plenty of power available to tackle challenging machining operations in either direction. (X Head) Guiding light New to the version IV however is the capability to swap between guide bush and non-guide bush mode. “This can make a significant difference in terms of material wastage especially on long production runs in exotic materials,” Mr Warner explains. “With the guide bush in place, a typical remnant length would be 250mm long but in non-guide bush mode this can be reduced to around 70-80mm. In non-guide bush mode however, the main limitation lies in the length to diameter ratio of the workpiece which maxes out at about 2.5 x D simply because the workpiece is unsupported. In real terms, this means that the workpiece length can’t practically exceed 50mm. “For short, thin diameter parts, non-guide bush mode can save a lot of material,” Mr Warner affirms, “but it would be true to say that most of our customers are running with the guide bush in place. With the ability to run in either mode, the SR-20R IV really does offer the best of both worlds. “We’ve also redesigned the yoke and platen on the machine so that in operation the tools are closer to the bar coming through the bush,” he adds. “Ultimately this means less idle time because the tools are in position ready to cut much quicker than with previous models.”
The SR-20R IV comes in two flavours – type A and type B. The former offers a manually positioned B-axis which, according to Mr Warner, is particularly suitable for 3+2-axis work and the latter is supplied with a fully programmable B-axis for full simultaneous 5-axis machining. On both types, control is courtesy of Fanuc with 31i-B5 on the type B and 32i-B on the type A. The type B also features Star Motion Control which, when run in optimised mode, analyses and reformats the program to reduce cycle times. “Both machine types have their merits but in terms of sales, customers are definitely leaning towards the programmable B-axis option for the additional operational flexibility they provide,” Mr Warner reveals. (X Head) Family values The machine is aimed fairly and squarely at the precision subcontract market and two Star customers that have purchased the new machine are Nick Groom, managing director at Hertfordshire-based Qualiturn and Phil Smith, a director at Wealdpark, located on Merseyside. Both companies are family run businesses, use Star machines extensively and both have two SR-20R IV’s after upgrading from previous versions. Wealdpark currently employs 23 members of staff at its St Helens facility (including two apprentices with third due to start later in the year) and was established in 1965. Up until 12 years ago, it operated as a traditional cam auto – then it bought its first Star machine, an SV32 J. Within a year the company had purchased a further two machines. “It was a real eye opener for us,” Mr Smith recalls. “With cam autos the process involved moving components around from machine to machine to complete separate operations but with our Star machines we can often produce finished parts in one hit. Today we have 12 Stars comprising SV16s, SR20s, SR32s and SV32s so there’s really not much in terms of turned part production that we can’t handle.” Nick Groom’s father Bernard started Qualiturn in 1974 so the company is celebrating its 40th anniversary this year. Like Wealdpark, Qualiturn is a progressive, forward thinking company that attributes a significant part of its success to the fact that it upgrades its machines on a regular basis to keep up with technological advancements. “We upgrade our machine tools as we would our computers,” Mr Groom explains. “Technology is advancing at such a rapid rate that ongoing investment is absolutely essential to compete in the marketplace.” (X Head) Spot the difference Whilst at first glance both companies may seem similar, from an operational perspective they reside at different ends of the manufacturing spectrum and it’s interesting to compare the two: Qualiturn has 19 sliding head machines and employs 14 setters whereas Wealdpark owns 12 machines and operates with only four setters. “Because of the variation in the work we undertake we find ourselves setting jobs frequently,” Mr Groom advises. “We’ll set a job and then run it overnight; next day we’ll do the same again.” A typical batch run for Wealdpark on the other hand could last an entire week.
This is reflected in the contrasting batch sizes that both companies undertake: Wealdpark regularly handles batch sizes of 5,000 to 10,000 whilst with Qualiturn, the average batch size last year according to Mr Groom was 1,100. “Our smallest job was a one-off and our largest was 200,000 so for us operational flexibility and the ability to be able to move rapidly from job to job is paramount. Shaving seconds off cycle times really isn’t a priority.” He continues: “That’s what’s so good about the SR-20R IV. With all the back and side working options available we can minimise the number of set-ups – and we don’t have to spend extra money on driven tooling because it’s all inclusive in the package. All we need to do is change the program.” For Wealdpark it’s a totally different picture: “We have two machines that run on the same brass component virtually all year,” Mr Smith says. “For us it’s all about cycle time optimisation.” (X Head) In for the long haul In the turned parts fraternity, demands can be particularly challenging simply because of the diversity of the work involved so with companies like Qualiturn and Wealdpark when it comes to selecting a machine tool supplier, you’ll often see high levels of brand loyalty – once a relationship between customer and supplier has been established, it tends to be long lasting. For both companies, the supplier of choice is Star GB. “For us it’s all about the quality of the machines and the exemplary service we get from Star,” Mr Groom enthuses. “I know that if I have a problem with a machine I can get on the phone and it’ll be sorted – often next day. The service side of a company is a hard thing for a salesman to sell, but as a long-term Star user, I can honestly say I’ve never had any problems. Another important point to note is that my operators are familiar with Star machines and this definitely optimises productivity. Changing over to another supplier would mean a pretty steep learning curve.”
Mr Smith echoes the sentiment: “Our business is fast moving and pretty relentless,” he says. “Even in the event of a breakdown, the longest I’ve ever had to wait for a service call is two days. Star understands our business and realises that we have to keep machine downtime to an absolute minimum.” For Mr Smith, the option to use the machine in non-guide bush and guide bush mode is by his own admission a ‘godsend’. “We regularly switch from one to the other,” he explains. We machine quite a lot of non-ferrous materials and the savings we can make through leaving a smaller remnant is significant. It does take an hour or two to swap over but this is time well spent in our opinion.” Star www.stargb.com