A leading subcontract supplier to the healthcare, medical and scientific sectors has seen cycle times cut by 80% in some instances as a result of investing in its first sliding-head turning centre – a seven-axis Tornos Swiss DT 26. Previously relying on fixed-head turning centres, the introduction of the Swiss DT 26 has also eliminated the need for second operations, leading the company to anticipate a rapid return on its investment.
In 1989, some 12 years after completing his apprenticeship with a scientific instrument manufacturer, Mildenhall-based CTPE Ltd was formed by the current Managing Director Mr. Chris Taylor. Specialising in components manufactured from plastic and non-ferrous metal, the company has recently been adding to its machine tool portfolio, currently running with five CNC vertical machining centres and three fixed-head turning centres. However, when one of CTPE’s multinational healthcare customers began to introduce JIT manufacturing, complete with weekly scheduled deliveries and monitored performance (quality and delivery), the company decided to look at technology that could take it to the next level, namely its first CNC sliding-head.
“To meet demand we were setting up the same batch of say 200 plastic turned parts on our fixed-head machines perhaps twice a month, simply because we didn’t have the time to produce larger, more economical batch sizes,” explains Mr. Taylor. “As a result, we started to look at sliding-head machines as a way of increasing our capacity and throughput.”
CTPE looked at four major suppliers of sliding-headstock machines, conducting what the company describes as “an in-depth evaluation”. The results shaped a clear purchase decision in favour of the Tornos Swiss DT 26.
“One of the major issues related to our historical use of water-based soluble cutting fluids, which we find never give any problems with cleanliness, carryover or adverse effects on our plastic materials,” says Mr. Taylor. “However, we found that the major competitors to Tornos did not want to run their machines with soluble coolant, only neat cutting oil. We were told there would be restrictions to the warranty if we wanted to use soluble coolant, as the machines are not designed for that purpose. Conversely, the Tornos Swiss DT 26 has been developed for use with either soluble coolant or neat cutting oil.”
Another attributes that impressed Mr. Taylor and his team was the capacity of the machine. At 26mm, CTPE discovered it could cover a large proportion of its current job profile, at a very competitive price.
“It was apparent that we could buy the Swiss DT 26 from Tornos for around the same price as most 20mm capacity machines from other suppliers,” says Mr. Taylor. “We could have gone for a 32mm machine, which is the next size up offered by most Tornos competitors, but found that the price rose by around 50%.”
CTPE also admired the fact that the Swiss DT 26 offers 10kW of power on both the main and sub-spindles, which contrasts greatly to competitor machines, where lower-powered sub-spindles are commonplace. Although most of the parts completed by the company on the Swiss DT 26 to date have been machined from plastic, it won’t always be that way. CTPE has already introduced a number of aluminium components to the machine since it was installed in October 2016, where high-powered spindles help remove stock quicker, and facilitate the use of larger drilling and boring tools.
Guide Bush to Non- Guide Bush machining
“We also like the ease and speed with which the Swiss DT 26 can be switched from guide bush to non-guide bush mode,” says Mr. Taylor. “A lot of our parts are short and so the ability to switch in just 15-25 minutes is very useful and saves money on tooling and bar wastage. In guide bush mode the bar end is generally longer, but in non-guide bush mode this is reduced to around 65mm, increasing the number of parts we can machine from a bar and gives a significant saving if we are turning expensive plastics such as PEEK™.”
Aside from PEEK™, the company also uses its DT26 to machine acetal, PTFE, PVC, nylon 66 and Rulon®, as well as 2024 aluminium, with some parts demanding tolerances in the region of 10µm.
“The Tornos machine will hold 5µm all day long, so dimensional accuracy is not an issue,” says Mr. Taylor. “We have found the machine to be far more sturdy and repeatable than our fixed-head machines, which means – for the first time – we can run unmanned whenever demand dictates, safe in the knowledge that parts will be produced to specification while we are not here.”
The Tornos Swiss DT 26 can produce components up to 200mm in length and is paired with a Tornos Robobar SBF 326 (3.2m capacity) barfeed for unmanned production. Inside the machine, as standard can be found six turning tools, four driven radial tools, an angle tool post that enables the installation of four tools each for front and back machining, and four independent positions for use with the counter-spindle, all with the ability to use live tools. The modular concept of the Swiss DT 26 means the machine configuration can easily be adapted to meet requirements.
At CTPE, the machine has been set to work producing parts typically in batches of 1000 to 2000-off. However, due to the ease and speed with which the machine can be set up, Mr. Taylor says it is equally economical to run batches as small as 300 to 400-off. On average, parts produced by CTPE are around 20mm long and 15mm in diameter, while some feature complex features such as end barb fitting for hoses, as well as side port holes. A typical cycle time on the Swiss DT 26 is 20 seconds, or up to 50 seconds for more complex components.
“Compared with our fixed-head turning centres, we’ve seen some cycle times reduce from 150 seconds, to just 30, which is an 80% reduction,” states Mr. Taylor. “Moreover, some of those fixed-head parts will still require a second operation, not to mention deburring and picking-out. We have none of those tasks with our sliding-head. Without doubt, we should have bought one years ago.”
Effective swarf management
Another advantageous attribute of the Swiss DT 26 is its kinematic design, which promotes both rigidity and swarf evacuation, particularly in combination with the standard 20 bar high-pressure coolant delivery, as Mr. Taylor can testify: “Effective swarf management is vital when machining plastics, as it is easy for issues like swarf wrap-up to develop, not to mention component burning. However, I’m pleased to say we have not encountered any such problems with our new machine.”
The Swiss DT 26 at CTPE was also supplied with the Tornos TISIS 2.0 programming and machine management software, which Mr. Taylor describes as “easy and quick to use”. Designed for all Tornos products working in ISO mode, TISIS has been continuously expanded to provide the users with a steadily increasing number of features, such as program optimisation, to ensure the minimum cycle time, program wizard, which simplifies programming and helps prevent errors, machine production monitoring and Industry 4.0, giving users access to production output in real time wherever they happen to be.
CTPE is currently enjoying a spell of continued year-on-year growth, and it’s easy to see why. The introduction of the Tornos Swiss DT 26 is the company’s fifth CNC machine tool investment in the past five years, helping to assure the future of this progressive precision machining specialist.
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