By Bernd Busskamp
Sales Director, OEM Air Germany, Wheelabrator
Part geometries in Automotive are getting more and more complex – to cut overall vehicle weight and optimise the performance of each and every component.
The latest trend we’re seeing is the rise of parts with intricate internal areas. These can be engine blocks that resemble a Swiss cheese, or hollow torsion bars with multiple bends.
The challenge: these parts have to be shot blasted too – be it for cleaning and deburring or for precision peening. But how do you blast the inner walls of a long and winding cavity inside an engine block casting? And how do you do this efficiently?
Finding the answer to these questions has been the focus of a lot of R&D effort in recent years – and has led to new machine concepts for internal blasting.
Solutions to date fell into two camps: 1) blasting into a cavity by positioning airblast nozzles just outside the opening, and 2) using rows of rotating lances to insert blast nozzles into cavities and bores.
Both solutions quickly reach their limits when the inside geometry of a part gets more complex or when inside diameters get very small.
Blasting from the outside becomes more uneven with every bend, lances twist or get stuck and conventional nozzle heads are too big to navigate small diameters and sharp turns. The resulting problem: we can’t guarantee a thorough, even treatment across the full internal surface area.
Blast nozzle heads would have to become smaller, would ideally not need to be rotated (by a lance that could get stuck or stop turning) and would have to be able to reach into complex cavities in a controlled manner.
The solution we’ve found here at the Technology Centre in Metelen builds on the lance idea, but takes internal shot blasting into the realm of keyhole surgery.
Using a support structure for lances on the outside, thinner hoses for abrasive feed to the nozzles, and smaller-diameter, short nozzle heads, enables a controlled yet flexible journey of the nozzle inside the part.
But the key development was a nozzle head that can blast the full internal circumference without rotation, achieving both precise treatment and complete coverage. This was made possible by distributing nozzle openings evenly along the outside circumference of the nozzle head.
The first customer application of this new technology is the internal peening of stabilizers – hollow torsion bars of only 14mm internal diameter. Their three-dimensionally bent shape and changing profile could not have been peened with previous methods, but is now treated quickly, efficiently and reliably.
Turns out that taking a leaf out of the skilled surgeon’s book can open up new possibilities in automotive component design.