Metal Forming
Monday | 06 October, 2008 | 7:58 am

Rollforming just sounds round

By Sue Roberts

When describing a rollform application, the first thought typically is a coil strip feeding through a series of progressive form rolls in a single pass-through operation. But as many manufacturers of large fans, venturi tubes and damper housings are finding, rollforming can be a profitable process for round shapes.

Custom Rollform Products Inc. combines a broad variety of fabricating capabilities into its lines including curling and roll-spinning operations helping customers with cylindrical parts to reduce production costs.

"We not only build rollform machines but the whole gamut of sheet-metal fabrication equipment," says Larry Slavik, company president. "What we can do with hydraulics in our lines can be very costly to do using large presses or other processes."

As an example, Slavik discusses how a drum fan manufacturer went from a multi-step process to one-step manufacturing for fan housings. They reduced production costs, operating personnel and material handling and achieved just-in-time (JIT) capability.

Before talking with Custom Rollform Products, production flow for the fan housings began by feeding pre-cut blanks to a rollform line. From there the blanks went to a three-roll bender for the curl operation. Next came a re-trim of lead and tail ends, before moving on to the welding process. Finally, the housings were sent to the paint line. Mounting and hardware holes were punched or drilled as the fan housings were assembled.

Weeks of inventory at various stages, plus a large stockpile of finished housings, were maintained to assure meeting daily production requirements.

Capabilities to produce housings in three different widths and five different diameters, ranging from 17-in. to 42-in. diameters, all from 22 gauge, were needed.

A combined coil-feed rollform and curl system improved the manufacturing, scheduling and ultimately the profits of the product line. Changes began at the front end, switching from pre-cut blanks to pre-painted coil. Savings started with the reduced cost of material combined with the elimination of the paint process and moved through reduction of work-in-process and inventory.

Eliminate steps
"Basically we eliminated all the processes," says Slavik. "We punched and notched the parts before we rolled them. Then we rollformed the parts and curled them into big housings. We made some assembly equipment for them to join the housings together."

Multiple processes were built into one automated line, engineered to adjust to the various widths and diameters of the housings. JIT production became a reality.

Chris Pleiman, vice president and general manager, adds, "The line draws from different coil beds, a JIT operation where they program in whatever part they’re looking for. They roll the part out with all the different punching and notching that goes along with it, curl it, seam weld it, then it goes into a secondary off-line beading unit that makes it perfectly round."

That is just one example of how a rollforming process can change manufacturing and profitability for round parts. Since each piece of rollform machinery and each line is designed specifically to the customer’s needs, there are an unlimited number of solutions to the challenge of producing parts with a diameter.

Virtually all machines are designed and built at Custom Rollform Products with each unit engineered for specific applications.

Rolling, spinning combination
Combining rolling and spinning operations, known as bead rolling, forms contoured cylinders with very accurate diameters. In this process, strip stock is curled into a ring with the two ends of the part seam welded or overlapped and spot welded. Since the parts are seamed or joined together before the rolling, spinning process, there is little or no end condition. Roundness problems are greatly minimized.

Parts are placed between matching male and female contoured form rolls. A contoured pattern or edge flanges are grad­ually and progres­sively formed as the roll feeds and clamps the round strip.

Venturi flange machine
Roll spinning flange units, whether automated or manual load/lunload machines, perform identical functions.

A variety of ring diameters can be formed without setup or changeovers by easily changing center spacers. Once the part is positioned and centered, the rolls feed, clamp and engage the ring to stretch and form the edges. As material is drawn in on both sides, it is progres­sively stretched and formed in a continuous feed-form cycle. Feed and clamp cycles vary based on the diameter of the ring being formed.

Greater flange lengths can be achieved by using this process rather than curling or expanding. Flange configurations and length limits are directly related to the type of material, thickness, and draw and stretch qualities.

Selling the process
Repeat customers and word of mouth keeps Slavik and his 20-year-old company prospering. Pleiman says, "It’s funny because we might get into a certain field or market like those fan housings, then within three or four years, we’ve built a lot of these systems for competitors. We have customers we’ve built 10, 12, 15 machines for. They know we’re the Chevy of the industry: reliable, affordable and long lasting."

"You’ve got to educate companies and enlighten a lot of people. Industry has a hard time understanding what we do," adds Slavik. "They’ve grown up with the fact that you buy a big reel and a great big press that stamps out parts. Rollform is a hard sell for the first one, because everybody’s mindset is on big dies, big presses, big feeds. The second time around, it’s a shoo-in."

So when is a good time to consider automated rollform equipment? According to Slavik, a great time is when accurate, round, contoured parts up to 12 in. wide, from 7-gauge material need to be produced. A roll-form unit will take minimal floor space, require little setup and change­over, and help inventory. FFJ


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