Automated internal deburring of high value components

At the recent METAV 2014, an innovative VG 25 vibratory finishing system for deburring & grinding the complex and delicate internal surface areas of high value components was presented by Walther Trowal.

The MV surface finishing machines have contributed to drastically reduce processing times for fine grinding and polishing. Now, with the new VG equipment and its closed loop media transport system, Walther Trowal goes one step further by practically eliminating the non-productive times for media and part handling.
The VG 25 finishing system effectively removes burrs from complex parts with difficult to reach surface areas including internal passages. It ensures that delicate part contours are not compromised and fragile ribs or cross-sections are not damaged. Even the inside of bore holes with diameters of less than 3 mm can be completely deburred.

Brand new is the closed loop system for transporting the grinding media. With this innovative and unique concept Walther Trowal could significantly reduce the non-productive times for loading and unloading the work pieces: After completion of the deburring process a suction pump removes the whole media batch from the work bowl allowing easy removal of the finished work piece from the magnetic fixturing plate and placement of a new raw part in the work bowl.  
The first VG systems have proven that the complex internal surface areas of aluminum or titanium components weighing 30 – 40 kg (66 – 88 lbs) can be automatically and efficiently deburred within 2 to 4 hours. In comparison, manual deburring of the same parts takes at least one week.

Lose burs in components used for the operation of complex systems, for example, hydraulic valve blocks for the aerospace industry, can cause system failures with catastrophic consequences. For this reason, such components require careful and complete deburring of all their internal passages.

The Walther Trowal MV finishing systems have demonstrated to be highly effective for such deburring tasks. And, compared to the Abrasive Flow Machining (AFM) with a grinding paste, or the ECM electrochemical deburring, the capital expenditure for the MV equipment with part fixtures and the operating costs (including consumables) are considerably lower.

In the MV machines the work piece handling had already been streamlined by simply placing the parts mounted to a special fixture on a magnetic plate in the work bowl where they are electro-magnetically clamped. With the VG systems Walther Trowal implemented further significant improvements.

However, the grinding medium, a mix of aluminum oxide and water, proved to be quite a challenge for the Trowal engineers. Because of its high abrasivity aluminum oxide is an excellent deburring medium but, at the same time, it can cause considerable wear on all machine components exposed to it during the finishing process, like for example, pumps piping and hose connections. To minimize the wear rate when pumping the corundum/water slurry Walther Trowal uses highly wear resistant materials and a special peristaltic pump.

After a raw work piece is placed onto the magnetic plate, the work bowl is flooded with water. Then the media/water slurry is pumped from a storage tank into the work bowl. Upon completion of the finishing process the slurry is pumped back into the storage tank. For removal of any residual abrasive particles from the work piece surface, the system is flooded with clean process water.

Technical highlights:
The work bowl of the multi vibrators, model range MV and VG, is equipped with an integrated magnetic plate. The work pieces, mounted onto a special fixture, are placed on this magnetic plate and held in a stationary position with an electromagnetic clamping device. This causes the clamped parts to vibrate at the same frequency as the work bowl generating a very fast relative movement between the work pieces and the grinding media and producing an intensive but, at the same time, gentle deburring/grinding effect. The result: Perfectly deburred and ground surface areas at significantly lower processing times.

At the center of these innovative finishing systems are three high speed vibratory motors which allow changing their rotational direction and RPM as well as their position. They are running at very high speeds but produce extremely low amplitudes. Since the directional effect of the induced vibrations is overlapping, the MV and VG vibratory systems produce excellent isotropic finishes on complex and/or delicate components, especially on surface areas which cannot be reached with conventional vibratory finishing methods.