Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Robot cell adds polish to pump manufacturer's operations
Robot cell adds polish to pump manufacturer's operations
ABB, has designed and developed a robot-based application solution for pump manufacturer Alfa Laval Ltd, of Eastbourne, East Sussex, UK which is both labour saving and cleaner than the previous, manually intensive production methods that were employed.
Alfa Laval is a leading global provider of specialised products and engineered solutions, and the Eastbourne plant has established itself as a centre of excellence for the design and manufacture of positive rotary lobe displacement pumps.
The plant, and indeed the whole Alfa Laval Group, is working towards world class performance in line with “Six Sigma” and “5 S”s' philosophies, and intends to have this completely rolled out by 2008. In line with this initiative, Alfa Laval has made significant investment in the Eastbourne plant in recent years. A key investment has been the introduction of a two-tier, flexible manufacturing system – incorporating a rail guided vehicle and a series of Mandelli “5” and Mandelli “7” Horizontal Machining Centres – for the production of rotors, rotor cases and pump end covers.
A further investment has been the development of a robot-based, flexible automation cell to replace labour- intensive fettling and blending operations on rotor case inlet and outlet ports.
The ports are attached to the rotor case by means of orbital TIG welds – the exact port size, configuration and location being dependent on the requirements of individual end-users.
The semi-automatic TIG welding process leaves significant penetration into the port internal diameter, which, particularly on aseptic applications, must be removed, as imperfections in surface finish can become a breeding ground for bacteria.
Previous manually intensive methods for removing weld build-up were dirty, exhausting and painstaking tasks, which carried with them possible risk of repetitive strain and white finger complaints, plus the unpleasantness of working in cumbersome protective clothing and face mask to protect against the dust-laden environment.
The new robot-based cell, designed and supplied as a turnkey project by ABB Robotics, Milton Keynes, was installed in 2005 and its introduction has made a significant step forward in enhancing workplace ergonomics within the port welding and finishing facility. The introduction of the robot cell has also saved on labour. It is staffed by a single operator who can conduct welding operations while the robot cell carries out its cycle. The only manual input is the loading and unloading of rotor cases onto a two-way rotary table that feeds the cell.
Discussing the rationale for opting for an ABB-supplied cell, Alfa Laval Production Engineer, Bill Boniface comments: “The final choice of supplier came down to ABB and one of its leading competitors. ABB was chosen because we thought they offered a better overall package and they assured us they could carry out the complete installation themselves. Added to this, we were reassured by the fact that our parent company in Sweden has operated ABB robots for a number of years.”
The cell incorporates: an ABB IRB 6600 “FoundryPlus” six-axis robot and control system; pneumatically operated grippers; rotary table with adjustable fixtures for five rotor cases per side; pneumatically operated touch probe; bar code scanner; Renishaw probe; eight internal and two external, electrically powered abrasive wheels; as well as a dust extraction system with inlet ports stationed at each set of wheels.
The cycle, which on average takes 20min to complete, starts with the robot gripper using a pneumatically operated touch probe to search each fixture nest for a rotor case. Once found, the robot gripper picks up the rotor case and then transfers the workpiece to a bar code scanner station. The bar code scanner reads a standard product bar code label affixed to the rotor case, so that the specific pump type can be identified, and thus the port configuration and dimensions ascertained, and the relevant robot program and abrasive wheel set-up correctly assigned.
At the next station, the robot manipulates the workpiece so that both rotor case ports, in turn, are inspected by the Renishaw probe for correct alignment with the rotor case. The “standard” product dimensions derived from the bar code are then crossed checked against the “actual” dimensions measured by the probe. Should the dimensions differ minutely, the robot program can be amended accordingly and thus robot positioning at the relevant abrasive wheel, dimensionally offset, to take the difference into account.
The robot then transfers the rotor case body to the weld finishing area for grinding and finishing of each port in turn. Internal weld grinding is carried out using cotton bonded abrasive wheels before the workpiece is transferred; first to a semi-finishing abrasive flap wheel, and finally to a finishing abrasive flap wheel, to achieve final surface finish levels of Ra 0.6mm or better. A further station, incorporating a pair of bristle brush wheels, removes heat discolouration around the external weld circumference of the port.
When dressing is complete, the robot returns the rotor case to its original fixture on the rotary table and then probes the next fixture nest to start a new cycle. When all five rotor cases have been processed, the two-way table is rotated through 1808 degrees by operator command to reveal the next batch of units.
Having worked-up the cell and refined the process through the latter part of 2005, satisfactory operating levels were achieved around Christmas last year, and payback is expected in four years.