Mobile spindle monitoring

"The spindle must turn" - as simple as the motto of Marco Popp, Managing Director of kptec service gmbh sounds, there is a lot behind it. The company repairs, overhauls and inspects machine tool spindles. The goal of the spindle service from Schorndorf near Stuttgart is to keep the customer's downtime as short as possible. When analysing and diagnosing spindles before dismantling, kptec uses the mobile spindle monitoring solution Portable SpindleControl (PSC) from Blum-Novotest.

A very important aspect of spindle service is the inspection of spindles in their installed state. If a company notices that a machine no longer achieves the usual precision or surfaces are not machined to the required quality, kptec service must first check where the problem lies. Until now, users only had the option of inserting a plug gauge into the spindle and manually recording the deviations of the spindle using a dial gauge. Since this measurement is made by contact and not under working speed, this is of course less meaningful in practice. In addition, the conditions on a spindle change greatly with the speed and running time. For example, the preload in the bearing assemblies varies over the speed range, the spindle heats up and expands - all these changes, which very much play a role during operation, cannot be recorded and taken into account in a manual measurement.

With Portable SpindleControl (PSC) from Blum, the Schorndorf-based company relies on a transportable, highly intelligent solution that enables measurement on the rotating spindle and in all operating states. Housed in a handy carrying case, the PSC consists of a laser measuring system that is attached to the machine's machining table by means of a magnetic holder, an interface unit and the LC-Vision PSC software that runs on a connected laptop. For the measurement, the machine operator positions the spindle with the clamped reference tool in the laser beam of the measuring system and starts a small NC programme, on the basis of which the machine runs through the previously defined speed steps. Parallel to the measurement, the software installed on the PC evaluates the measurement data and visualises it on the laptop screen.

The first measurement is usually a stability measurement. This is followed by a runout measurement over the entire speed range, during which the axial axial runout and radial runout are precisely measured and documented. This is followed by a vibration analysis and parameter measurements, including recording of various vibrations within the spindle bearings. In an application at a well-known automotive supplier, kptec service was able to show with the help of PSC that one of the two spindles on a machining centre with a double spindle was worn out, which led to expensive scrap and incorrect machining.

"The graphic visualisations with the help of which the LC-VISION PSC software displays the measurement results are of great advantage to us. The very precise non-contact measurements also make it possible to detect problems around the spindle that, strictly speaking, have nothing to do with it," explains Marco Popp. "These are, for example, worn ball screws or machine guideways that are worn because the same parts were manufactured on the machine for years and the slide always moved in the same places. As a plug & play solution that does not require a connection to the machine control system or any associated PLC adjustments for operation, PSC plays to its strengths especially in mobile use." This is one of the reasons why kptec service is now able to offer customers new services that were not possible before.

As one of the first users of the system, kptec was initially able to incorporate some suggestions for improvement from the field into the development of PSC. Blum-Novotest also rates the cooperation with kptec service as very successful and efficient for both sides. In addition, the measuring and testing technology specialist is very proud of PSC, because the system combines the know-how of the three business units measuring components, measuring machines and testing technology for the first time. Marco Popp also draws a positive conclusion: "We can optimally support our customers and ensure that the spindles turn. After all, we're not just talking about a spindle worth 35,000 euros or more, but about even more expensive machining centres that, in the worst case, stand still and the associated, often even more expensive production downtime. With Portable SpindleControl, we support customers so that they can rely on their machines at all times."