Robot unload system ups grinding cell utilisation

When a bearing manufacturer moved three independent grinding operations into one cell it was able to justify a robotic machine unload system.

When bearing manufacturer SKF recently moved three independent grinding operations into one purpose built cell it created a justifiable need for a robotic machine unload system.

The cell comprises three grinding operations, finish grind the outer ring faces, rough grinding of the outer ring outside diameter, and another centreless grinding operation to finish the outside diameter.

Putting the cell together has enabled it to be fully automated from input on the first operation to output of the finish operation.

Initially the cell was manually unloaded with the intention to automate at a later date.

The SKF engineering team trawled the robot systems houses and manufacturers to explain their need to place 10,000 components - average weight.75kg and 50 different types - over 16 hours per day into stillages.

"This is where most suppliers faced the first problem," explained Roy Covington, an SKF Process Development Engineer.

"We use a non-standard pallet which has sides that taper in and an overhang on the opening.

Although this would make placing the outer rings into layers more complex, most suppliers were able to work around this." Expanding on this, Roy Covington said: "What became more of a problem was picking up separators to lay on top of each layer.

To allow oil drainage we use a plastic lattice type separator which meant vacuum pick-up was out of the question." FANUC Robotics (UK), who was selected to supply the system, specified a FANUC M420i robot to do the unloading and engineered a gripper to pick two rings at a time - gripping them internally - and place them into the stillage.

They also engineered a gripper to pick up a standard SKF lattice separator as required and place it onto the layer of bearing cases.

A standard auto tool changer system was specified to enable automatic changeover of grippers.

The M420i is FANUC's latest generation, high performance, high-speed robot.

A four axes 'arm' capable of lifting up to 40kg.

The robot's large working area - the largest in its class with a reach of 1855mm - accommodates two stillages in the cell which allows either to be changed without interrupting operations.

Overall the cell has provided many benefits to SKF, but in particular running the grinding machines as a cell has enabled their utilisation to be increased.

The payoff has seen greatly increased consistency on the finished diameter, which is machined within 10 microns.

Other benefits include the elimination of handling damage, and the release of skilled operators from the mundane handling operation to the more productive setter operator tasks.

Roy Covington continued, "One reason we went with FANUC is they gave us the confidence they would deliver what we - the customer - wanted.

We felt they accepted, and its proved to be the case, that the concept would change as the project developed." He added: "We're certainly used to automation at SKF, but this was to be the first robot to be installed on a UK SKF site - it had to be right and it had to be accepted by the operators.

FANUC took all the cell personnel to its factory during system build and undertook system training before it arrived in our factory.

This really did help the implementation process." Since system commissioning, SKF has placed an order for a bearing assembly machine using a further two FANUC robots.

The new equipment will be delivered shortly to SKF's spherical roller bearing manufacturing operation at Luton.

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