Comparing Structural

Aug 16, 2023

With the Green Frame system, one bolt comes pre-inserted in each pipe end and is tightened with an Allen wrench. Photo courtesy Lean Factory America LLC

All pipes used in the Flexpipe system are 28 millimeters in diameter and plastic coated. Built structures include workbenches, reinforced shelving and flow racks. Photo courtesy Flexpipe Inc.

Light and medium-duty structures—like carts, workstations and flow racks—are frequently made with the Creform system. Some manufacturers also build complex multifunction AGVs and racks with pick-to-light error-prevention systems. Photo courtesy Creform Corp.

Many manufacturers use the MB Building Kit System to build typical material-handling carts and machine guarding. Photo courtesy item America LLC

Manufacturers and integrators use T-slotted extruded aluminum profiles for the upper sections of structures and small bases, as well as guarding, workstations and lean manufacturing requirements. Photo courtesy Bosch Rexroth Corp.

Lessons learned in childhood often last a lifetime. The same can be said of acquired skills, such as building things with Erector Sets, Legos and Lincoln Logs. Individuals who mastered and enjoyed these classic toys may very likely be the same people who use T-slot extrusion framing, pipe-and-joint and square-tube systems to build modular workstations, flow racks and other production structures for manufacturers.

"Modular systems’ main appeal is flexibility that extends over the life of a structure," says Keith Soderlund, vice president of sales at Creform Corp. Creform has been offering modular steel pipe-and-point systems in the United States since the early 1980s, although its parent company, Yazaki Industrial Chemical Co., first developed the Creform system in Japan in the mid-1960s. "Being able to easily move things around, and make small changes while the structure remains in place can be invaluable."

Flexpipe Inc. also offers a steel pipe-and-joint system, which was developed in 2009 to help Bombardier Research Products (BRP) improve the flexibility of its Spyder (three-wheeled motorcycle) production line. Before then, Flexpipe welded tugger carts that BRP used to bring parts from storage to the assembly line.

"BRP wanted to redesign its line with modular carts, workstations and flow racks," explains Julien Depelteau, co-founder and CEO of Flexpipe. "We worked closely with BRP's team leader and also met with the assemblers to discuss things like optimum component height and maximum weight capacities. Over a few months, we created our system that BRP then used to easily build the structures for its new assembly line."

Flexpipe and Creform are two of several suppliers that make pipe-and-joint products. An equal number offer systems based on T-slotted extruded aluminum framing or square tubing. All of these systems offer something beneficial to manufacturers, in general, and design engineers, in particular. Manufacturers are able to quickly and easily reconfigure a wide range of assembly line components (carts, workstations, display boards, etc.) with minimum capital outlay. Engineers can spend more time optimizing assembly processes rather than designing each assembly machine from scratch.

Back in the early 1980s, Bosch Rexroth AG regularly offered tours of its German plants to customers to showcase how the company made automotive components and other parts using general assembly production lines. Often times, the customers would ask about the aluminum framing Bosch used around its machines, notes Chris Lupfer, product sales manager at Bosch Rexroth Corp. (BRC). These constant inquiries convinced Bosch to begin selling the framing to manufacturers in Europe as a flexible alternative to welded steel.

BRC has been selling framing in the United States since the early 1990s. End-users include OEMs, Tier 1s and integrators that serve industries as diverse as medical devices, automotive, aerospace, white goods and consumer electronics.

"Some 25 years later, welded steel structures remain our main competition for heavy-duty applications, but aluminum framing has exploded for all other applications," says Paul Koziczynski, sales and distribution manager at BRC. "Most manufacturers and integrators use aluminum for the upper sections of structures and small bases, as well as guarding, workstations and lean manufacturing requirements."

Bosch's framing system consists of T-slot aluminum extruded profiles, connectors, components and accessories. Koziczynski says that more than 125 standard extrusion profiles are available, ranging from 20 millimeters square, to as large as 180 by 360 millimeters. Customers may cut each extrusion to length as required with a miter saw.

The square profiles feature a T- slot on each side that is 6, 8 or 10 millimeters wide. Smaller profiles feature narrower slots because they support less weight and require smaller connectors. The opposite is true for larger profiles.

Specialty profiles are offered for clean room and anti-static applications or others that require nice aesthetics. These profiles feature smooth sides to limit the accumulation of dirt or dust. Clean room applications are joined together with specialty hardware and gaskets made for low particulate and to resist acetones. To prevent static discharge, all plastic pieces are impregnated with carbon, and the metal nuts are serrated for conductivity.

More than 25 types of aluminum connectors may be used with this system, according to Lupfer. After a profile is positioned in the connector, the assembler inserts a Torx- or Allen-head screw, bolt or self-tapping screw, and tightens it with a handheld wrench to create a corner. This is done four times to create a frame. No other tool is needed to assemble and disassemble the system.

Tabletops, side panels, footrests and many other components are attached to the frame sides to create structures such as maintenance carts, machine guarding, assembly benches, flow racks, workstations and manual conveyors. Accessories range from casters and profile caps, to swivel brackets, adjustable mounts between two surfaces, and cable carriers.

Item America LLC's aluminum extrusion MB Building Kit System (MBBKS) can be traced back to Germanyin the early 1980s. The supplier's parent company, item Industrietechnik GmbH, had been building machines for assembly since 1976 before developing its extrusion system to increase customers’ flexibility in design and assembly.

Philipp Herrmann, CFO and executive vice president of sales and marketing at item America, says the U.S. distributors have offered MBBKS for the past 20 years. Currently, it includes nearly 3,500 extrusions, connectors and accessories. About 100 new components are added annually.

Extrusions range from 20 millimeters square to 160 by 320 millimeters, and come in five versions, called lines. Each line is numbered according to its slot width in millimeters. Lines 5 and 6 are economical extrusions designed especially for testing equipment and for the electronics industry. Line 8 profiles can withstand tensile loading of up to 5,000 newtons, making them robust enough for a wide range of applications.

Herrmann says that Line 10 profiles are used when heavy loads need to be supported but space is limited. These extrusions accommodate tensile loading of up to 7,000 newtons per screw connection. Line 12 is the strongest profile, with the ability to accommodate extraction forces of up to 10,000 newtons per connection. Also available are specialty profiles without grooves that are used as edge protection or grip rails.

Assemblers join the profiles to connectors and accessories with various screws, bolts and T-slot nuts that are positioned in the slots and tightened with standard hand tools. Threaded holes may be drilled in the core hole of the extrusion as needed.

Many manufacturers use the MBBKS to build typical material-handling carts and machine guarding. Other applications include interlinking and mobile workstations, assembly platforms (for aerospace companies), picking trolleys, cantilever racks and shelving units.

Both item and Bosch sell their components in four ways: uncut or precut profiles and components thatcustomers install; preordered, application-specific kits that end-users build; and fully assembled structures made and delivered by a local distributor. Lupfer says the latter approach represents a significant portion of Bosch extrusion-system sales. Herrmann points out that about 80 percent of MBBKS end-users in the United States request preassembly, compared to 30 percent in Europe.

The Toyota Production System (TPS) is well known in the assembly world as the initial model for lean manufacturing. One of the first companies to help Toyota implement TPS was Yazaki Industrial Chemical; first through its industrial plastic totes and then with the Creform (short for create a form) pipe-and-joint system.

"One of our strengths is the large number of parts users can choose from to build all types of structures," claims Soderlund. "We offer more than 700 parts, with 20 percent of them being used 80 percent of the time. A typical kit contains hundreds of parts, so the end-user can make whatever it needs."

Three sizes of steel pipe (28, 32 and 42 millimeters in diameter) and two types of joints (metal and plastic) are available. All the pipes feature a 0.5-millimeter-thick bonded plastic coating, but only the 42-millimeter pipe is recommended for high-strength applications. Assemblers may cut any size pipe with a chop saw, a band saw or a manual or electric pipe cutter. Creform does offer pipe precut to length for a small additional charge. This pipe is deburred on each end.

Pipe is clamped together with metal joints and glued to lower-cost plastic joints. Accessories clip on the pipe frame or attach with fasteners and include casters, extrusions, channels, feet, hitches, pipe clamps and mounts, label holders and roller conveyors. Fasteners are tightened with a 5-millimeter Allen wrench.

"Manufacturers have the taken the mild [i.e., simple components] and gone wild," says Soderlund. "Light and medium-duty structures are our niche, so we see lots of companies making basic carts, workstations and flow racks, as well as complex racks with pick-to-light error-prevention systems and multifunction AGVs [automated guided vehicles]."

Flexpipe's system differs in several ways. All pipes are 28 millimeters in diameter (with plastic coatings), all joints are metal (electroplated black or nickel-plated silver) and various fasteners (M6 and M8 bolts and nuts, and Torx-,countersunk- and square-head screws) are used during assembly. The fasteners are installed with a 5-millimeter Allen wrench or drill bit.

Main structural components include a wide range of conveyor roller tracks, deckings and casters. More than 35 accessories are available, such as leveling shims, pipe extensions, Y-shaped supports, hooks, drawer slides and tow bars.

Manufacturers in aerospace, automotive, white goods and medical devices are the primary users of the system, says Depelteau. He points out that company sales are split between customers who buy components and build their own structures, and those who have Flexpipe preassemble the structures.

A few years ago, representatives from racing-wheel manufacturer HRE Designs met with Depelteau to discuss their need for a system that keeps inner and outer rim sections of a four-wheel set near each other during production, which lasts an average of 13 hours. HRE workers and production managers had been spending a lot of time loading and unloading the sections to pallets, carts and shelving, or searching for sections on the shop floor.

Using the Flexpipe system, HRE developed a prototype black-pipe kitting cart on which perfectly fit a four-wheel set (with specific order number). Each order number had its own cart, creating a one-piece flow effect in the factory. The work order followed the flow cart on a simple hook that could not be removed. Rush order sets were handled on red carts, and return goods authorization orders on blue carts.

"Since incorporating this material handling system, HRE has reduced its lead time by 50 percent and work in progress (WIP) by 25 percent, while increasing floor space by 50 percent," explains Depelteau. "The carts offer better staging, flow, order tracking and visual management, thanks to their color code and FIFO floor marking. In addition, walking and handling times have been reduced because the quality control station, assembly line and packaging spaces are closer together."

Although WIP was reduced, the HRE production team initially followed the old WIP level and ended up building too many carts. They then dismantled some of them and used the parts to build an operator desk and other helpful structures.

The Green Frame system combines the benefits of pipe, with the growing acceptance of aluminum as a viable structural material, claims Kurt Greissinger, vice president of Lean Factory America LLC. He says that high-quality anodized aluminum pipe provides the same strength capacity as steel pipe with 40 percent less weight, further enhancing the flexibility of built structures.

Green Frame allows for the mixing and matching of more than 350 parts. There are three series of pipe, all of which have an external mounting feature at 90-degree increments. GF pipe comes 19, 28 or 43 millimeters in diameter and various shapes, depending on the application. These includeversions with functional T-slots, reinforced walls, the ability to telescope with each other, as well as double pipes for high-strength applications.

Die-cast zinc or aluminum connectors fit inside or outside the pipe. They come pre-assembled with all necessary hardware for quick tightening with an Allen wrench. The connectors, combined with 90-degree mounting features, ensure perpendicularity.

Panel holders, linear and rotary parts, door components and feet are the key components manufacturers use to build work tables, trolleys, carts, racks, production-status visual boards and clean booths. Accessories vary according to pipe type and include end caps, leveling feet, casters and snap-on strips to quickly and easily change the color of the pipe.

"The main reason Green Frame was developed was for karakuri applications," notes Greissinger. "Some customers new to karakuri bite off more than they can chew at the start. To overcome the learning curve, they need to be hands-on with the system and not be afraid to experiment."

The goal of karakuri is to increase efficiency and ergonomics by producing work with little energy input by assemblers. Ordinary forces, such as gravity, counterweights and springs, create extraordinary results that can minimize operator workload and improve ergonomic conditions. A single pull of a lever or step on a foot pedal can put the system into motion to exchange an empty tote for a full one, or stack and destack boxes in a FIFO manner.

One customer, an agricultural-equipment manufacturer, began using the system about 1.5 years ago strictly for simple carts and structures. The company is now looking to fully optimize Green Frame by adding karakuri components to build its own semiautomatic flow racks.

"Some [people] believe modular systems are not robust enough to handle the rigors of manufacturing, due to the friction-based joint used by [some suppliers]," says Jake Sparks, administration general manager and sales manager at Flex Craft LLC. "Advances in direct-bolt joints solve this problem and are capable of holding thousands of pounds."

Flex Craft has offered a direct-bolt steel square-tubing system since 2006. The perforated tubing is made of mild steel with a powder-coated finish (stock and coded colors), or anodized aluminum with a clear-coat finish. Tubes are supplied in standard lengths from 6 inches to 10 feet long, in 6-inch increments. Custom-cut lengths are available by request.

Common Grade 2 bolts and nuts are used with the system. Fasteners are tightened with a 0.5-inch wrench. Joints attach tubing at various angles and are made from 14-gauge mild steel with four strategic holes. Types include universal and edge, plus flush, inline, flat and offset gusset.

Accessories range from framing supports and plug-and-play components,to doors, drawers, towing hardware and specialty items. Rigid or swivel plate casters (with or without side brakes), footers and conveyors are sold separately.

Other modular configurations made with the system range from a pneumatic scissor lift to an ergonomic kickstand table. The kickstand table allows users to adjust work surface height by stepping down on a cross platform, and change table weight capacity by adjusting the fulcrum position.

Two recent ASSEMBLY Plant of the Year (POTY) winners use Flex Craft extensively to build and reconfigure mobile fixtures, flow racks, material-handling carts and workstations as needed. Polaris Industries Inc. uses the system at several facilities, including Spirit Lake, IA, which won the 2015 ASSEMBLY POTY. AGCO uses Flex Craft at both its Hesston, KS, and Jackson, MN, plants, the latter of which won this year's POTY award.

80/20 Inc. offers an extensive line of Ready Tube square anodized aluminum profiles for modular structures. Profile 9700 is 1.5 inches square with no predrilled holes. It lends itself to framing and other applications requiring an aesthetic look and a smooth clean appearance. Nylon connectors join the tubing.

Profile 9701 is also 1.5 inches square, but features predrilled holes at 1.5-inch intervals along each face. These holes accept fasteners and allow for applications such as conveyor tables, gravity racks and material-handling shelves. Nearly a dozen other profiles feature one or two flanges on each side, with or without predrilled holes, for extra weight capacity.

Jim is a senior editor of ASSEMBLY and has more than 30 years of editorial experience. Before joining ASSEMBLY, Camillo was the editor of PM Engineer, Association for Facilities Engineering Journal and Milling Journal. Jim has an English degree from DePaul University.