Inserts fed accurately to injection moulding machine
When a company manufacturing injection moulded parts needed a parts feeding solution for threaded inserts in order to fully automate production, it turned to DB Automation for a completely integrated insert moulding cell.
Where inserts are required in a plastic moulding, the two principle options essentially are for the inserts to be incorporated during the moulding process or as part of a post moulding operation. The right solution in any given application comes down to considerations of process speed, economic benefits and achieving the required accuracy.
For one manufacturer, the right solution was felt to be insertion as part of the moulding process, but this presented challenges of feeding the parts in the correct orientation so that a cartesian robot could pick them up and feed them into the moulding tool. To address this challenge, the company turned to DB Automation, not only for a parts feeding system, but also for the robot tooling, out-feed chute, machine framework and guarding - in short, a completely integrated moulding cell.
Each plastic moulding requires two threaded inserts. These are 6mm in diameter, with an 8mm 'top hat' flange and a length of approximately 10mm. The system requirements called for inserts to be supplied every 35 seconds, at a determined pitch for the finished moulding. The insert orientation requirement was for the 'top hat' flange feature to be uppermost.
DB Automation operations director Nick Parker comments: "The natural choice for this application was a 300mm diameter vibratory bowl feeder used in conjunction with a vibratory linear feeder, to offer a production buffer and adequate feeding. By utilising our standard range of vibratory drives for both the bowl and linear feeders we were able to manufacture a high quality feeding solution for use with this system. The feed rate requirements for this system were not high and the bowl was tooled in stainless steel on a cast aluminium top."
A simple concept, the bowl feeder design relied on the natural centre of gravity of the insert when hanging on the 'top hat' flange. The insert naturally 'swings' with the knurled diameter hanging downwards when supported under the flange. This enables inserts traveling either 'flange-leading' or 'flange-trailing' to be 'swung' into position.
"This assessment of the natural balance of a part always forms the basis of the tooling design for all bowl feeding applications," says Nick Parker. "In the applications we have addressed at DB Automation, we are faced with many different components, each having their own distinct characteristics, so we have extensive experience in providing feeding solutions and developing orientation tooling designs."
A further challenge for this application was the pitch that the inserts needed to be presented in to the injection moulding tool. It was essential that this position was repeatable and dependable and ultimately undisturbed by the vibration of the linear feeder.
"Our experience in automated solutions enabled us to design a robust solution for this problem," says Nick Parker. "A three position, pneumatically operated escapement unit was a perfect solution. Two of the three positions allow for inserts to enter the tooling plate within pockets provided. The third position allows for an undisturbed position and also ensures that trailing parts on the linear feeder are not affected when the inserts are collected." The robust design ensured that the equipment was suitable for use in a harsh repetitive environment. "The escapement slides are located and mounted on re-circulating linear bearing rails, all with end stop positions and dampers for the removal of inertia," says Nick Parker. "Every position is verified with sensors, and part presence is checked at each loading cycle."
A further requirement for the system was for the inserts to be raised from the escapement to enable collection by a Cartesian robot, with DB Automation tasked with the design and manufacture of the robot end-of-arm tooling. This had not only to grip the inserts, but also collect the finished moulded part from the mould tool and deliver it to the out-feed area. "With the added complexity of needing to rotate the end of arm tooling 90 degrees on the robot, the result was a relatively intricate tooling arrangement," says Nick Parker. "We used locator pins to ensure accurate location during collection, ensuring that the inserts were positioned to the required repeatability and that the accuracy of the robot was not the limiting factor."
Thus the finished machine was capable of feeding, sorting and orientating the inserts prior to loading, with the cartesian style robot loading the inserts into the mould tool and removing the finished moulding. DB Automation developed the full system, complete with out-feed chute, guarding requirements and machine framework, and integrated it with the existing injection moulding machine at the customer's premises.
"This project not only displayed a number of the different skills and capabilities that we possess but also provided a single source for our client in order that all of the system requirements could be fulfilled by the one supplier," concludes Nick Parker. "The robotic handling and integration elements of this project draw on our core skills in the injection moulding industry for which we have manufactured in excess of 250 systems worldwide."
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