- THE MAGAZINE
- FOOD MASTER
For years, the lights-out factory has been the holy grail of automation, the ultimate expression of production untouched by human hands. But as a practical matter, raw material variability and high-volume throughput make lights-out food production problematic.
A better goal might be grunt-free production, where machines do the heavy lifting and humans ensure product quality. In that case, Northeast Foods attained grunt-free baking with the opening of Automatic Rolls of North Carolina, Food Engineering’s 2012 Plant of the Year.
The Paterakis family owns Baltimore-based Northeast Foods, a commercial baking powerhouse with 13 production facilities either owned outright or in partnership. Five are part of the Northeast Foods group that stretches from Connecticut to Clayton, NC, where the newest plant began production in May 2011. Most of Northeast’s production is buns—rolls in East Coast parlance—bound for McDonald’s outlets. Meeting McDonald’s needs requires high throughput and few changeovers, an ideal scenario for lights-out manufacturing. But rather than turning out the lights, management hopes automation will better illuminate processes and their outcomes.
Two makeup lines push a continuous stream of oversized pans to a spiral proofer in Clayton, delivering 13,000 lbs. of raw dough an hour to an oven that bakes 1,400 hamburger buns a minute, or more than 2 million in an uninterrupted 24-hour period. Each shift has an operations team that borders on the skeletal. For any given shift, only a handful of workers are found on the 75,000-sq.-ft. production floor, and their responsibilities primarily are quality assurance, with a minimum of bending and lifting. Of the plant’s 63 employees, most are maintenance or sanitation personnel.
Only four products are baked and bagged in Clayton: regular buns, quarter-pounder buns, Big Mac buns and bakery-style buns. But specifications are extremely tight, and deviations barely perceptible to the naked eye are unacceptable. Therefore, the people who ensure quality standards are met may be more important to the plant’s ultimate success than the machinery. Engaging and involving them is critical, and the same has been true for others involved in the project, from the design stage through the plant’s first year of operation.
Northeast’s engineers believe they’ve achieved a new standard for rolls baking, though there are other distinctions in the Clayton facility as well. Two automatic storage and retrieval systems (AS/RS) were installed, including a lights-out freezer operation that was driven by supply chain considerations. The plant is Northeast’s first with ammonia refrigeration. The fatal Imperial Sugar explosion was fresh in engineers’ minds when design work began, and special care was taken to mitigate the possibility of such an event in Clayton. Sustainability considerations go beyond energy efficiency to include good neighbor practices such as a containment system that ensures any material spills are isolated onsite.
Satisfy the supply chain
Direct store delivery (DSD) typifies distribution for fully baked breads and rolls, and it works well for both retail and foodservice distribution, particularly in urban areas. But McDonald’s restaurants are found in rural hamlets as well, and the chain looks at suppliers to review DSD and deliver instead to distribution centers (DCs), where it makes logistical sense. Instead of a half-dozen suppliers’ trucks driving through the countryside, all the patties, chicken nuggets and other menu items can share the ride in a single delivery. Frozen buns are the choice if fresh bun deliveries are too far away to meet spec requirements on usable remaining days of shelf life at delivery.
Two other Northeast Foods plants use chlorofluorocarbon refrigerants to accommodate DC distribution, but the production volume in Clayton put ammonia refrigeration into the realm of possibility. The addition of Eric Mohrmann to the corporate engineering staff a year before planning commenced also eased qualms, given his previous experience with ammonia systems. Mohrmann served as project engineer for the Clayton plant.
For a 13,000-sq.-ft. freezer like the one used in the Clayton facility, a chlorofluorocarbon such as Freon typically is used, says Brian King, president of Charlotte, NC-based A M King Construction. “They chose ammonia refrigeration for all the right [sustainability] reasons,” King says. The decision did not go unnoticed by the plant’s customer: McDonald’s recognizes the Clayton facility in its 2012 Best of Sustainable Supply report, highlighting the climate/energy considerations of the project under the heading, “Building the Sustainable Bakery.” Despite the higher upfront cost, lower maintenance and operational costs make ammonia refrigeration more economical in the long run, and the existence of a municipal HAZMAT team addresses safety concerns. A key design consideration was to make sure peak load would be under 10,000 lbs., the threshold for process safety management requirements. A skilled technician and detailed documentation are ongoing requirements once that threshold is passed.
Despite its modest footprint, the high-velocity freezer boasts 702,000 cubic feet of storage. The installation of an AS/RS crane removed any height restrictions, and the freezer soars 54 ft. and accommodates 1,270 pallet positions.
Waste heat from the freezer’s compressors warms glycol that is piped through the freezer’s sub-floor, safeguarding against soil heaving and eliminating the need for electric heating. The ammonia system also chills glycol to 8°F and routes it to mixers and other process equipment.
Four ammonia compressors drive the system, though the fourth is redundant, reflecting a company philosophy of valuing uptime over lowest possible capital cost. Standby capacity also is engineered into boilers, air compressors and other infrastructure items. Two low-temperature compressors meet base demand, while a medium-temperature compressor outfitted with a variable frequency drive (VFD) ramps up and down, as needed.
VFDs are integrated into motor groups throughout the plant, including those powering freezer fans and condensers. The payback from those energy-efficiency investments was shortened thanks to King engineers’ early outreach to local utility Progress Energy. The annual electric demand of a base design was compared to energy consumption of an upgraded system. As efficiency improved, so did the rebate Progress would provide. The tiered rebates helped rationalize multiple upgrades, such as R-49 insulation instead of R-41 in the freezer’s metal panels. The cumulative affect is a freezer that draws 28 percent less electricity than a conventional design, or an annual reduction of about a 780,000 kWh.
“The incentives helped, but we’re in this for the long term,” says Dennis Colliton, Northeast’s vice president of engineering. While most improvements will produce a return on investment within three years, management supported some that stretched ROI to seven years or more, provided there were benefits beyond energy efficiency alone. A prime example is the backup diesel generators, also an outgrowth of the early discussions with the utility.
Nationally, electric utilities are pouring millions of dollars into efforts to shed demand during peak periods. A testament to those efforts are the three 1,000 KVA diesel generators positioned outside the Clayton plant’s western wall. The generators can meet all of the facility’s electric demand. In return for subsidizing their purchase, Progress Energy can request the plant to switch over to them when electric demand spikes. The power feed into the facility is synchronized with the grid, making the transfer seamless and imperceptible to equipment in the plant. Only a handful of requests were made in the plant’s first summer of operation, and when that occurs, the utility pays Northeast double the industrial electric rate for the generators’ output. Backup generators also allow Northeast to monitor severe weather conditions and effect a phase transfer when there is the possibility of a power interruption that could disrupt the facility’s electronics.
High throughput characterizes all the Northeast Foods facilities, with a previous high-volume mark of 1,000 rolls a minute. To raise the bar even higher necessitated an unconventional approach to conveying and a re-engineered system.
Typically, pans with pockets four rows wide and eight rows deep are fed to the oven. Northeast engineers specified pans with an extra row, in a five-by-eight configuration. They maintain the wide side of the pan as the leading edge, a technique they call conveying “the hard way.” Although line speed had to slow, the plant was able to set a volume standard 17 percent higher than the previous record rate.
The wide-side orientation means larger conveyor motors, wider turns and other modifications to the layout. The key change, however, was the introduction of an indexing conveyor where the two makeup lines are joined. In other plants, pans reached a T-shaped conveyor that altered direction 90° and lost the wide-side orientation. In Clayton, the lines come together at different elevations, with pans queuing on one level while an oscillating conveyor accepts pans on the other level. The oscillating conveyor alternates between the two levels and maintains the wide-side feed into the proof-box’s spiral.
For the rest of the process, the only personnel involved are the quality inspectors who watch for defective buns as they are fed into flow wrappers. After buns are baked and before they enter cooling racks, a vision inspection system automatically rejects product outside the parameters for color, shape, seed distribution and other specs. The high volume is a challenge for the machine, however, and the blotches and other flaws on some rejected buns are invisible to the naked eye. Slightly elevated waste levels are a price the manufacturer pays to assure customer satisfaction.
Carts usually ferry baking pans from the end of a production line to the start. That labor-intense and injury-prone activity was made obsolete in Clayton by a gantry robot and AS/RS. After baked buns are depanned, the pans enter either a recirculation loop or are detoured to the gantry system. Immediately before that juncture, the pans are rotated either 180° or 360° on an inline magnetic table while brushes and air knives remove any crumbs and other debris. The table’s capacity is 40 pans per minute, and it handles weights up to 25 lb. per pan, according to Ken Mentch, an electrical engineer with Workhorse Automation Inc., Oxford, PA.
Mentch designed a handful of similar magnetic tables for other bakeries, but the table used in the Clayton facility is the first to combine cleaning, inverting and diverting in a single station. “That is the fastest pan system in the US,” he says, with up to four pans being simultaneously handled.
Workhorse personnel fabricated both the freezer AS/RS and the pan system, including the AS/RS and gantry robot. When pans are fed to the gantry, they enter the robot cell upside down. The gantry maintains that orientation, and later the pans are stored on edge, a configuration that minimizes damages to the pockets that cradle the dough. Colliton anticipates damaged pans will become a thing of the past. The pan-handling system cuts changeover time in half and eliminates any worker involvement.
No workers interact with product after packaging until pallets are pulled from the freezer on a first in, first out basis. Filled trays are stacked 20 high automatically, then move on a 100-ft.-a-minute drag chain to a palletizer that combines four stacks and pushes the load into a stretch-wrapper. The completed pallet, with 4,800 buns, is then automatically delivered to the freezer AS/RS for inventorying.
The front of the production line is almost as hands off, though someone has to push a button to start the mixing process. After that, a recipe program takes over, metering in water, flour and other ingredients and delivering a sponge dough to a trough handling system that shuttles the dough into an adjacent fermentation room. The sponge room can accommodate 27 troughs; typical dwell time is about four hours. Based on data from the production management system, the dwell can be extended to seven hours, with the room’s temperature and humidity adjusted automatically to match hold time with production demand.
The human touch
Receiving is probably the most labor-intensive area of the facility, though the work is not too physically demanding. Once a day, a lift truck hoists a pallet loaded with minor ingredients, and someone must transfer those supplies to a pneumatic conveying system. The receiving staff also serves a QA function, locking in delivery trucks’ transfer hoses to the plant’s screens for flour, vegetable oil and liquid sugar and yeast. Receiving personnel compare delivery samples with the supplier’s certificate of analysis, then visually inspect the screens before unlocking the hoses and accepting delivery.
“We hired the best receiving crew I’ve ever seen,” says Corporate Engineer Andy Black. The silos and tanks that hold raw materials are positioned in below-grade depressions deep enough to hold the tanks’ contents. If an 8,000-gal. liquid sugar tank were to rupture or a 150,000-lb. flour silo were to fail, the crew would immediately close any storm water drains and call in a septic service company to vacuum out the spill.
Black is the architect of the production management program that integrates the multiple automation systems and ensures quality data are captured and analyzed. “After going through several canned software programs, we decided to build our own system that can grow with us,” he explains. “We’re on the cusp of all-digital data collection.” That, in turn, opens the door for more sampling and root-cause analysis of drift in product specifications.