Good health

Previously relying on fixed-head turning centres, the introduction of the Swiss DT 26 machine at Mildenhall, Suffolk-based CTPE has not only improved cycle times but also eliminated the need for second operations, leading the company to anticipate a rapid return on its investment.

In 1989, 12 years after completing his apprenticeship with a scientific instrument manufacturer, precision engineering operation CTPE was formed by the current managing director Chris Taylor. The company, which specialises in components manufactured from plastic and non-ferrous metal, 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 multi-national healthcare customers began to introduce Just in Time 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 turning machine.

“To meet demand, we were setting up the same batch of around 200 plastic turned parts on our fixed-head machines 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,” comments 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 factor 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,” he says. “We could have gone for a 32mm machine, which is the next size up offered by most Tornos competitors, but we found that the price rose by around 50%.”

Double spindle power

CTPE also liked 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.

“We also like the ease and speed with which the Swiss DT 26 can be switched from guide bush to non-guide bush mode. 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 giving 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. 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,” Mr Taylor affirms.

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) bar feed 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.

Flexible batches

At CTPE, the machine has been set to work producing parts typically in batches of 1,000 to 2,000-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 an 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. 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.”

Another advantage 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.

Mr Taylor explains: “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, but 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 Tornos Tisis 2.0 programming and machine management software, described as ‘easy and quick to use’. Designed for all Tornos products working in ISO mode, Tisis has been continuously expanded to provide 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 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 the progressive precision machining specialist.

CPTE www.ctpe.co.uk

TORNOS www.tornos.com