Building an Automated Assembly System

Manufacturers rely heavily on automated assembly machinery to meet two critical production requirements: speed and cost-efficiency. However, with today's extreme customization and shortened product life cycles, machine flexibility also rates high on the requirements list. Driving this demand are cost savings and time-to-market advantages inherent with ability to modify a production line without...

By Staff April 1, 2006


Micro controllers

Compact, modular design

Easy features, networking

Lower machine commissioning time

Manufacturers rely heavily on automated assembly machinery to meet two critical production requirements: speed and cost-efficiency. However, with today’s extreme customization and shortened product life cycles, machine flexibility also rates high on the requirements list. Driving this demand are cost savings and time-to-market advantages inherent with ability to modify a production line without purchasing and installing new custom machinery.

Desire to avoid machine obsolescence is at the core of Demco Automation’s approach to building assembly equipment. It serves small-parts assembly customers in industries including electronics, automotive, pharmaceutical, and medical devices. Demco’s flagship product, the Demco Wedge, is a modular, plug-and-play assembly system that allows manufacturers to customize and scale assembly operations—from manual bench-top product prototyping to full-scale automated assembly-line production.

Most Demco customers manufacture products with lifecycles of 12 to 24 months. To stay ahead of competition, they need to get to market quickly and cost-efficiently. Manufacturing and commissioning a traditional new assembly machine can take up to a year, which can lower sales and profits and increase manufacturing costs, unacceptable for Demco customers.

Flexibility challenge

Rotary dial assembly machines have been a mainstay of automation systems for decades. Despite their precision, durability, and reliability, these systems have lost ground in recent years to other assembly platforms that offer greater configuration flexibility. Thanks to improvements in size, cost, and power of distributed microprocessors, and high-speed plug-and-play networking systems, machine builders like Demco can offer more modular designs that increase machine flexibility and reduce development time for hardware and software.

Demco customers change product lines often in response to ongoing mass customization requirements. The company wanted to find a way to save customers the expense of frequent custom-machine purchases. It also wanted to help customers get products to market quicker by reducing machine delivery time from months to weeks, with a platform offering maximum configuration flexibility.

Building blocks

Patented in 2003, the Demco Wedge takes a building-block approach to automation with pie-shaped tooling plates, called Wedge stations, governed by a distributed-control architecture. Wedge stations work standalone on a tabletop or automatically by being plugged into a Wedge “base” chassis. Once in the base chassis, the control architecture recognizes the unit, automatically reconfigures, and begins processing.

The system allows the operator to easily swap a variety of Wedges, which can perform functions from pick-and-place to packaging and product inspection. Wedges easily can be disconnected, allowing operators to make a change in less than a minute. The operator can quickly gain access to the Wedge station by simply sliding it out of the base chassis for easy maintenance and troubleshooting.

Demco needed a flexible easy-to-operate machine and a compact, high-performance control system. On the base chassis is an Allen-Bradley MicroLogix 1500 controller, from Rockwell Automation, which coordinates workstation activities and controls the flow of parts as they transfer through the machine.

“Because of its compact, modular design and easy-to-use features, MicroLogix controller proved to be the ideal control platform for our Wedge system,” says Dave Duemler, founder and technology director, Demco. “Flexible architecture, combined with its high-performance processing capabilities, provides the functionality of a larger controller while maintaining affordability and a small size.”

At 5.19 x 6.62 x 3.43 in. (132 x 168 x 87 mm), the controller features an innovative two-piece design with a small footprint. The processor and base are independently replaceable, allowing users to maximize embedded I/O options and minimize inventory stocking costs. Modular and rackless I/O platform provides front accessibility for removal and insertion, lowering system cost and reducing maintenance time.

Distributed control architecture gives users advantages, such as easier programming and debugging capabilities. Normally, automated assembly systems are controlled by one large piece of controller code. A change in one portion of the program often affects another portion. By distributing intelligence to each Wedge, a program change in one part of the machine can occur independently of others.

“This is a huge advantage for regulated applications like medical-device assembly, because of all the ongoing analysis and validation required to prove the machine is reliable and predictable,” Duemler says. “With the Wedge system, customers can make a change in their process without revalidating the entire machine.”

Easy expansion

The system is designed to allow companies to purchase one station, and then expand their automation platform as their business changes. If a company decides to add an inspection station between two stations, it can slide the stations out, move them over one, and slide them back in.

“Our customers save the cost of developing and manufacturing machines since the plug-in components can be used in all phases of the product life cycle,” he continues. “Companies are able to achieve a greater return on investment, because a product can actually grow along with them.”

Manufacturers can swap out all stations and reassemble a different product. Or, assemblers can add stations as needed. If demand increases, existing stations can simply be replicated and plugged into the base.

“Because each workstation is controlled by its own microprocessor, it can operate independently on a bench-top,” Duemler explains. “This gives assemblers time to fine-tune processes off-line, while waiting for production volume to increase.”

Base chassis are available in in-line systems of two- and four-station configurations and in multiples of four. They are also available in rotary-dial configurations of six, 10, and 16 stations. For larger operations, stations can be linked to one another via standard conveyance systems.

DeviceNet communications add flexibility and help eliminate or simplify wiring. Instead of hardwiring every device to a central controller, DeviceNet network allows up to 64 nodes to be integrated on one wire, with all devices enabled to exchange messages with each other.

Each Wedge station is programmed with SuperWedge software, a graphical utility developed by Demco to communicate with the MicroLogix unit on each station. SuperWedge software allows communications and alarm handling to run in the background. The software allows end-users to program individual Wedge stations without extensive training. Most operators can learn the new system in less than a day, Demco says.

“Microsoft Windows-based programming utility helps simplify controller programming as well as machine debugging and operation,” Duemler says. “Wedge stations are programmed by simply checking boxes on a PC screen for a sequence of designated inputs and outputs to configure the Wedge station for your needs.”

Quick to market, fewer wires

Machines can be delivered and commissioned in weeks rather than months; Demco reports reductions of up to 70% in commissioning time. In addition, use of DeviceNet avoids repeating work during reconfiguration and addition of new devices without shutting down for extended periods of time.

The unique machine design of the Wedge has resulted in phenomenal advantages for Demco. “We are really enthusiastic about what the Wedge has done for us, and with the continued advancements being made in today’s communication and control technology, we’re even more optimistic about our future,” Duemler concludes.