Thermal Mainstay Learns New Tricks

Despatch Upgraded Its Furnace to Bring More Reliability to Solar

By Aaron Hand, Managing Editor

Despite the relative infancy of the solar photovoltaics industry, it's not uncommon to find it populated with old-timers as well. Despatch Industries (www.despatch.com), headquartered in Minneapolis, will celebrate 110 years in business this year. It is applying its long history in thermal processing to solar PV manufacturing.

The machinery used to manufacture solar cells and panels is under pressure to drive down costs as low as possible. Despatch makes highly efficient thermal processing equipment for advanced PV production, including the CF Series metallization firing furnace.

The equipment maker sold its first metallization firing furnace to the solar industry in 2005, and by 2010 had sold its 1,000th unit. It is part of a complex manufacturing process that involves a long series of steps. After the metallization printing step, CF Series furnaces dry out organic final volatile materials in pastes and wafers, leaving behind metal components. The metals are then fired or connected to emitters to complete the circuits while enhancing the adherence of the metals to the wafer. After firing, the solar cells move through the cooling section and on to the next steps, cell sorting and testing. The special pastes involved in the process are developed for better solar conductivity and for bonding the layers of the solar cell together. The thermal profile and repeatable efficiency are key metrics during firing.

Two years ago, Despatch sought to upgrade the CF Series' industrial PC (IPC) and I/O hardware to improve performance and data collection while reducing required cabinet space. "Before IPCs, we were big PLC users, but they just aren't very well suited for the amount of data collection we must provide in our applications, so a modern IPC is required to properly manage this," says Ron Seger, lead engineer for Despatch. "However, the tower-style IPC we were using from our first vendor didn't quite live up to the 'industrial' promise."

The furnaces now use Beckhoff IPCs with 1.1 GHz Intel Atom processors. The IPCs run Despatch-developed software to manage the heater and conveyor controls, I/O, data logging, alarms, and interfaces to MES systems. "We've definitely traded up our IPCs with Beckhoff," Seger says, noting that the PCs are not only more reliable and durable, but also faster and more powerful. "These IPCs are also exceptionally resilient and can handle all the heat demands Despatch machines create."

A major need for the I/O system Despatch required was the ability to specify compact I/O devices. "We sought to move our I/O nodes closer to each device because we have numerous infrared heating lamps spread out over 40–60 ft of the CF Series firing furnace," Seger says. Despatch switched to Beckhoff's Bus Terminal solution. "The compact Bus Terminal I/O is fully compatible with not only Modbus, but essentially every other major fieldbus, so Despatch is covered if we need to change things for an application," says Brian Hajder, electrical engineer for Despatch.

Depending on the particular solution, the compact I/O and IPC combined provides space savings of 50-75% over Despatch's previous I/O and IPC solutions, Hajder adds.

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