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The VG 25 finishing system shown with a peristaltic pump abrasive media storage tank and vibratory work bowl

Automated Internal Deburring

March 17, 2014
Closed-loop media handling Vibratory work bowl Magnetic fixturing plate Corundum/water slurry

WALTHER TROWAL’s VG 25 vibratory finishing system effectively completes deburring and grinding for complex and delicate internal surface areas of high-value components, including internal passages. It ensures that delicate part contours are not compromised and fragile ribs or cross-sections are not damaged. Even the interior surfaces of boreholes 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 concept Walther Trowal indicated it would significantly reduce the non-productive times for loading and unloading the workpieces: After the deburring process is complete a suction pump removes the entire media batch from the work bowl, allowing easy removal of the finished workpiece 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 Abrasive Flow Machining (AFM) with a grinding paste, or the electrochemical (ECM) deburring, the capital expense is considerably lower than for its previous MV series equipment, including part fixtures, consumables, and operating costs.

In the MV machines, workpiece handling was streamlined by mounting the parts 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 improvements.

For grinding medium, the MV machines’ mix of aluminum oxide and water proved to be a challenge. Because of its high abrasiveness, aluminum oxide is an excellent deburring medium but it can cause considerable wear on all machine components exposed to it. To minimize the wear rate when pumping the corundum (Al2O3))/water slurry Walther Trowal uses highly wear resistant materials and a special peristaltic pump.

After a raw workpiece 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. To remove any residual abrasive particles from the workpiece surface, the system is flooded with clean process water.

In both series the work bowl is driven by several vibratory devices, and equipped with an integrated magnetic plate. The workpieces, mounted onto a special fixture, are placed on the magnetic plate and held in a stationary position with an electromagnetic clamping device. This causes clamped parts to vibrate at the same frequency as the work bowl, generating a very fast relative movement between the workpieces 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 that can change rotational direction, RPM, as well as position. They run 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 that cannot be reached with conventional vibratory finishing methods.