Even though CNC machining centres are now often used in manufacturing, standalone systems can be a sensible and economic addition as reliable thread production is certainly easier to achieve with integrated torque monitoring.
Many companies currently resort to modern CNC machining centres to machine components. However, separate thread cutting machines can be a sensible and economic addition. With the Gewindequick torque-monitored thread cutting machine from dk Fixiersysteme, reliable thread production is simple. What’s more, the Gewindequick performs extremely well with small thread diameters, blind hole threads and materials which are difficult to machine. Precise threads are required to optimise balancing systems for grinding machines. The company Dittel Messtechnik, which recently joined the Marposs Group and has 120 employees based in Landsberg am Lech (Germany), manufactures process monitoring and balancing systems for machine-tools.
Grinding machines from renowned manufacturers are being fitted with Dittel systems to effectively compensate for the imbalance of grinding wheels. Hundreds of different versions of these balancing heads are produced depending on the mounting dimensions of the grinding machines and the specific requirements of the customer in question. At Dittel, the components for the balancing systems are produced on the very latest generation of turning and milling centres.
These machining systems cut large threads from M4 directly in the component. However, with smaller examples, the tap can get stuck when machining centres are used; this is particularly annoying if it happens with expensive workpieces. In the Dittel production facilities, smaller threads between M2.5 and M3 are therefore produced using special thread-cutting machines – a reliable way to avoid the problem. Thread-cutting machines are compact table systems which are placed immediately next to the CNC machining centres in the production facilities to keep distances to a minimum. Dittel Messtechnik uses several cutting machines, some of which have been in operation for more than 30 years.
All machines come from the dk Präzisionstechnik production facilities in Reutlingen (Germany) and are primarily used for making blind hole threads in stainless steel. The torque monitoring function does not just prevent the tap from breaking – it also means that the machine can detect if tools have become blunt and need to be replaced or re-sharpened in good time. As these machines were being used at full capacity, Dittel decided to buy a fifth thread-cutting machine. The company chose the current version of the Gewindequick from dk, which was released in autumn 2012 as a fully revised and optimised third-generation model. With an improved motor and control technology, it is now possible to produce thread sizes from M0.8 to M6 with the smaller Gewindequick GQ-6 and thread sizes from M2 to M10 with the larger GQ-10 version. Machine-tools are not the best choice in every case. The experts from dk repeatedly emphasise that many users often wrongly believe that a modern and expensive machining centre must be able to carry out all necessary cutting processes – including thread production. This is certainly understandable. However, in many cases, it is possible to prove that it is more economic to produce threads separately, with the Gewindequick, for example, rather than on a milling machine. On closer inspection, it makes more efficient use of the machine time as a Gewindequick only costs a fraction of the machining centre and the machine personnel can often cut the threads and operate the machining centre in parallel. However, the major advantage is the extremely high level of process reliability, which the user cannot always achieve with a CNC system. Conversely, a broken tap can cause downtimes and result in high costs due to damage to both the workpiece and the tool itself. In every case, the process has to be stopped. Cutting without forced feed using a counterbalance system. The dk Gewindequick thread production machine is ready for use once the maximum permissible torque, required speed and thread depth have been entered. Using the machine, it is possible to cut or form all types of thread – including fine threads and UNC/UNF threads – easily and reliably. The tap pulls itself into the workpiece being machined during the process without forced feed.
Lead spindles and guide heads are not required. This is made possible thanks to a counterbalance system which holds the drive spindle in a kind of floating state during machining. The torque is monitored constantly and the cutting process is stopped within milliseconds if it is exceeded, which reliably prevents the drill from breaking. The Gewindequick is suitable for the production of both internal and external threads and is flexible in use and portable as a compact table system. As it is so easy to use, employees at different levels can handle the Gewindequick devices without needing extensive training – virtually nothing can go wrong. The decision-makers at Dittel agree that using the Gewindequick systems ensures that the necessary precision threads are produced efficiently and also fulfils all of the quality requirements in production. Practical experience has also shown that for batches of 10 to 200 items, the threads can be implemented quickly and therefore efficiently in the balancing head components as no clamping or aligning is required. As a result, a workpiece can be machined in a matter of seconds.