Fast and precise to the best surfaces
When a well-known original equipment manufacturer of machines needed to replace an old vertical lathe, a new turning/milling centre now provides the necessary requirements and capacities for the complete machining of a wide range of large workpieces. For the manufacturing of the mostly customised products, zero-point clamping systems from AMF pulverise the clamping processes and set-up times. And precision as well as surface quality increase exorbitantly.
After more than 100 man-years of operation, an AMF customer has replaced an old vertical lathe with a new turning/milling centre. It works just as well in three-shift operation as the vintage predecessor. But it no longer needs seven clampings on three machines until the large and heavy housings are finished. The demanding production of the mostly customised products mainly includes the processes of turning, cutting and grinding. Up to 100 tools are used alone for machining the underside of such a housing.
Better surfaces thanks to lower vibrations
With the new machine, a zero-point clamping system has become the most important component. After the basic decision was quickly made in favour of hydraulics, the AMF zero-point clamping system won the comparison with competitors. This ensures significantly better surfaces and considerably longer tool service lives. For AMF Sales Manager Erik Laubengeiger, this is not much of a surprise. “With our extremely powerful hydraulic modules, we are repeatedly able to keep vibrations to a minimum during rough machining and finishing, which not only produces great surfaces but also serves precision.” The original equipment manufacturer for machine tools, which is used by numerous well-known machine tool manufacturers, requires an accuracy of 1/100 mm in three levels, namely the top and bottom of the housing and coaxially for bores.
Zero-point clamping modules pulverise set-up times
With pull-in forces of 25 kN and holding forces of 55 kN, hydraulically actuated AMF zero-point clamping modules of the type KH20 clamp large and heavy workpieces. The hydraulic actuation with 50-60 bar opening pressure makes it possible to install very strong springs inside that constantly re-tension without the medium being present. This high clamping force that is permanently active counteracts the entire system in which the workpiece could loosen due to the vibrations that occur during machining. Because AMF zero-point clamping modules ensure the best surfaces and the clamping processes are incredibly fast, the customer's decision is easy. In three to four minutes, a workpiece is now clamped ready for machining. In the past, with clamping arms, spacers and screw connections, this took 30 to 90 minutes, reports the user. The covers and pistons of the modules are hardened. The repetition accuracy in clamping is better than 0.005 mm (5 µ).
Powerful clamping significantly extends tool life
Eight modules are embedded in a spacer plate, which in turn is anchored to the rotary table of the machining centre. The base plate for workpiece clamping is placed on this. Four clamping consoles, each 200 mm long, are clamped on top of this, which AMF manufactures to customer specifications. AMF zero-point clamping modules are also integrated into the top and bottom sides, with which they are anchored directly to the pull-studs on the base plate on the one hand, and into which the workpiece is clamped on the other. This is also done by means of pull-studs that are directly integrated into the workpiece. This makes five-sided machining possible without interfering contours, and the underside can be machined in the same clamping operation as the other surfaces.
Clamping once increases precision significantly
Now, everything is much easier, faster and safer than before. The machine operator can concentrate more on the machining quality. And because the process for such a workpiece can take up to ten hours and extend beyond a single shift, it is all the more important that the component is correctly clamped. But most importantly, it's also about precision, which is greater when clamping is only done once. This also means that there is less tension in the part that would later require larger tolerances again.