Punching parts, injection molding and assembly in a single cell

TASK

Production of oil level sensors

Picking up punched parts and connectors, inserting delicate metal pins into a mold cavity, removing injection-molded casings from the cavity and clearing away the sprue. This whole complex operation is performed by four Stäubli robots during the production of oil level sensors.

Copper strip in rolls and plastic granulate are the basic materials. The final product is the sophisticated housing for the oil level sensor in a car. The housing is extremely thin-walled and 12 pins in five different versions have to be inserted in the injection mold. These protrude from the bottom of the component and differ both in their coating and in their shape. Three of the pins are diverted into the side connector, which requires them to be bent four times and cut. In addition, there are three sockets for mechanical attachment to the oil sump.

SOLUTION

Three robots on a rotary tablet

The ready-to-connect housing is produced in a compact manufacturing cell that have been integrated into a plastic injection molding system with three servo eccentric presses, a rotary table and four Stäubli TS60 SCARAs.

Preparation and feeding of the inserts are synchronized by means of a central rotary table. Three of the SCARAs populate a four-cavity mold with inserts. These ultra-fast machines have to handle 60 metal inserts per cycle. In doing so, they directly access the belts issuing from the punching and bending unit, gather up the individual contacts there and insert them into the four cavities on the rotary table. For each of these, they required 15 inserts per housing and are pre-sorted so that the sophisticated gripper can pick them all up at the same time and place them accurately in the mold. Prior to placement, the camera system checks the pin set for completion so that, in the event of a fault, rejects are avoided.

The fourth Stäubli TS60 manages the insertion and removal of the finished housing from the cavity in an extremely short cycle time. In order to remove four housings simultaneously while also clearing away the sprue, it is equipped with an intricate gripper that was designed and built according to the principles of lightweight construction using carbon-fiber composite. This creates the right conditions for fast and precise handling required.

CUSTOMER USAGE

High level of efficiency thanks to processes running in parallel

With each cycle, a high-precision gripping operation with very small and differently shaped inserts has to be performed. This is a task for which the Stäubli TS series robots are ideally suited thanks to their speed and precision. Population of the mold takes place parallel to the injection molding on the underside outside the clamping unit. Taking place in parallel to this are the extensive, fully automated quality controls and laser marking.

Production plants in the automotive industry have to operate with very high availability, usually 24 hours a day and seven days a week. This is another aspect in which the system supplied by Engel Austria as a turnkey provider performs exceptionally well. It has been in operation since the end of 2013 and is working with a high level of efficiency, process stability and reproducible quality – and tolerances are consistently between 0.05 mm and 0.1 mm.