Mechtek’s latest project was to design and build an automated battery assembly line for one of the largest battery manufacturers in the world. The application is assembling large lead acid battery packs used to power electrically operated vehicles such as forklifts, pallet jacks and aerial lifts. Lead is a major health risk and exposures are controlled by automating the process, thus removing the workers from the hazard. Increasing production was also key focus for Mechtek designing the system.
A fully automated assembly line, with a number of different stations and processes, this turnkey solution requires numerous low maintenance products that can withstand the harsh environment of battery production and operate 24/7. Based on recommendations, Mechtek turned to linear motion specialist HepcoMotion to specify multiple products for this application. Hepco worked extensively with Mechtek to assist with the design, specification, load/life calculations and CAD models.
Mechtek employed a modular approach with this detailed assembly line by subdividing the system into stations that could be independently created.
“With a strong working partnership we were able to overcome many design challenges by providing fully modular Hepco linear systems. We were able to draw upon our wide product range to provide specification to meet the requirements for each of the linear applications involved in the process.”
The assembly line begins with the formation of positive and negative plate stacks. There are three loading sections, loading the positive, negative and double-negative plates onto the line. Each conveyor moves its stack of plates forward to the end of the line where they are lifted 100mm by a ZIMM Screw Jack to reach a pick and place process that picks one plate at a time and places it onto the next conveyer belt. HepcoMotion offers a range of Screw Jack systems by ZIMM. With a cubic compact design, these systems ensure ease of mounting and are built with quality components ensuring maximum operation lifetime.
The plates are picked in sequence, alternating between positive, negative and double negative. As a plate is picked, ZIMM Screw Jacks raise the stack of plates by one index to compensate for the reduction in height of the stack due to a plate being picked. The ZIMM Screw Jack continues to raise the stack as each plate is taken – indexing a total of 100mm over 6 indexes. This cycle is repeated every 22 seconds.
The plates are then moved via a conveyer belt to the separator pick and place system where a sheet of paper is added to the top of each plate. The paper acts as a separator between the positive and negative plates preventing short-circuit through physical contact.
Two PDU2 belt driven actuators on X axis support the Z axis pick and place. These compact, low maintenance actuators save time in specifying as they are ready to mount and designed for simple fitting of stepper or servo motors; a key benefit for Mechtek. PDU2 also offers a long service life, again of particular interest for this application.
The payload here is only 10g and the two grippers approximately 2kg each. The X axis beams are 1000mm long, with beam centres of 1800mm. The conveyer then moves the plates to the stacker assembly drive unit where the plates are stacked with the sheets of paper between each plate.
Hepcos HDCS heavy duty ball screw actuator provides the necessary Z movement; dropping down in 10-20mm increments as plates are added to the stack. When the stack is full, the stack is released to the conveyer belt, and the HDCS returns to the top of the stroke to collect the next stack, moving down as plates are added. The cycle time is approximately 1 minute, although the number of plates in the stack will vary depending on the product. The HDCS is particularly suited to this application as this heavy duty actuator can cope with high moment loads; in this case 70kg at 300mm offset. Bellow covers protect the HDCS from the harsh and dusty environment.
The new automated assembly line will have a profound impact on productivity. Mechtek anticipates the line will produce 1200 batteries per shift; effectively tripling current production rates and removing up to 40% of the manual handling from the operation. Furthermore, the new machine produces less dust, making it environmentally safer.
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