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Streamlining EV Battery Assembly Layout

By Bosch Rexroth Contributed Article
The MTpro software is a free, electronic catalog of the Bosch Rexroth portfolio that is available to all users. (Photos provided by Bosch Rexroth)

Designing a manufacturing assembly is not unlike creating a story. And just like every story starts at the beginning, every assembly line starts with layout design, which is an often overlooked chapter yet is central to the project narrative.

The design phase is the first touchpoint in determining a project’s success. If executed inefficiently, team members have a rocky road ahead of them. If executed well, the result is a more streamlined process from start to finish. That’s why when Eagle Technologies was presented with a complex design challenge, the company penned the lede with ink from Bosch Rexroth Corp.

Top of the Line

An automated manufacturing machinery supplier, Bridgman, Mich.-based Eagle Technologies was an early participant in the electric vehicle market with battery and powertrain assembly systems. It faced an aggressive timeline for a complex product, needing a turnkey battery module assembly system for cylindrical lithium-ion cells. The time constraints, along with floor space and throughput challenges, meant the initial proposal was going to be critical. The new line required several parallel processes and a conveyor capable of handling complex routing and variations driven by the build schedule. There were two basic module types and three cell manufacturers involved, resulting in 12 different part numbers that would be produced on the final line.

“The complexity affects two areas of the line,” explains Earle Cooper, Eagle Technologies senior key account manager. “The production process of the module is very similar for all 12 models. There are two module geometries, and different cell manufactures and cell quantities make up the variation within the two types.”

A large EV supplier needed a turnkey battery module assembly system for cylindrical lithium-ion cells with an aggressive lead time. The new line required several parallel processes and a conveyor capable of handling complex routing and variations driven by the build schedule. The overall layout went through 15 revisions before converting to an order.

From a production and test standpoint, this is fairly straightforward. At the end of the line, modules are stored in a buffer system.

“We must pull modules by part number in sequence based on the pack build recipe,” Cooper continues. “Modules are delivered to three different automated module load stations in the pack assembly line (supplied by others). The sequencing and timing of these deliveries is critical, and easily the most complex problem created by the various module types.”

Design Professionals

Since 1978, Eagle has partnered with Bosch Rexroth, which is part of German engineering giant Robert Bosch GmbH. By combining its experience in the EV market with Bosch Rexroth’s technologies, Eagle was able to tackle this application head-on.

Using Bosch Rexroth’s free design engineering tool MTpro, and its extensive knowledge of Bosch Rexroth’s conveyance and aluminum framing products, Eagle says it was able to generate a highly accurate system layout at the quoting stage.

Using Bosch Rexroth’s MTpro, Eagle generated a highly accurate system layout at the quoting stage. The proposal layout was so close to the final project, months were saved at the design phase.

Developed in 2010 as a digital sales tool in response to industry demand for computer-aided design (CAD), MTpro is a software tool for planning assembly systems that assist users in everything from selection and configuration to ordering components. MTpro is used to plan, calculate and document assembly systems in just a few steps. From a transfer system or profile frame to a manual production system, the operating concept of the layout designer can create even complex designs and system layouts.

MTpro is an electronic catalog of Bosch Rexroth’s products, including MGE, MPS, TS and VF. All of the Assembly Technology division’s products can be found in the catalog, according to Gerald Berzins, application engineering supervisor for Bosch Rexroth.

MTpro software is free to all users and everyone has immediate access to all the features of the package. Customers that purchase a conveyor from Bosch Rexroth receive a copy of its line layout that identifies all of the modules used.

“Because of the lead time for most projects, we build the line based on our proposal drawings, which we can do because of MTpro,” Cooper says. “If we didn’t have that tool, we wouldn’t be able to do that and meet the needs of the customer.”

MTpro impacted Eagle’s project in two ways:

It enabled the design team to develop a robust layout at the onset.

It allowed Eagle Technologies to kick off the project with an accurate bill of material (BOM) that could be submitted as an order within weeks, instead of months.

To meet the lead time for such a robust line design, modules had to be ordered early, even before mechanical engineering was completed. This made the accurate BOM essential to the successful execution of the project.

Cooper cites MTpro’s complete library of configurable 3D models for Bosch Rexroth’s Assembly Technology components as a key factor in the speed of the design process. Single models, as well as whole layouts, can be exported in various file formats or directly inserted in common CAD systems.

“The Bosch product line features a very large array of product configurations based on the weight and size of the application,” Cooper explains. “Being able to use this tool to configure the modules and then download CAD models in various formats enables us to rapidly design the system, generate a BOM and release these requirements to purchasing much faster than with other vendors.”

From the conveyor standpoint, a common challenge Eagle Technologies encounters is that other suppliers don’t provide CAD blocks before an order is placed, preferring to provide complete design support afterwards. This exposes unnecessary risk by not having detailed information in the quote stage, and can slow down the transition from the 2D proposal to a complete 3D-line layout, the company says.

With MTpro, paired with a quoting tool from Bosch Rexroth, Eagle was able to provide a detailed BOM, as well as an accurate cost and comprehensive layout.

Seamless Execution

The overall layout went through 15 revisions before converting to an order. During the process, Eagle Technologies says it had quick access to CAD blocks for all of Bosch Rexroth’s TS 2plus conveyor modules, aluminum structural framing and other components needed to complete the layout.

The completed systems produce a module every 7.4 seconds, starting with automatically depalletizing and deboxing the incoming cells (130/box). At the end, assembled and tested modules are handed off to the battery pack assembly line.

Because the final project was so close to the proposed layout, months were saved at the design phase, according to the partners. The final system was too large to fit as a singular unit in any of Eagle Technologies’ 150,000-sq-ft (13,935-m) facilities. To meet the customer’s timeline, the project was broken into three phases to accommodate runoff, installation and built-in redundancy.

With the installation of all three phases of the line, Eagle Technologies met the customer’s timeline. And by utilizing an effective and efficient design process, the project was set up for success before construction began.

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