By Karen Knapstein
Carport components seem like simple things, right? Perhaps you may believe your components should cost less. But there’s more to the manufacturing process than you may realize. It’s important to remember you’re not just buying some steel from your component supplier. They’ve invested a lot of money in their equipment, and they continue to invest in the equipment’s maintenance. Here, with the help of Ralph Girkins of Universal Tube & Rollform Equipment, we will look at the process of making tube from coiled steel.
Girkins, who has “made this business his business for 40 years,” founded Universal Tube & Rollform Equipment of Perrysburg, Ohio, in 1984. In 2005, he, along with Ken Metzger and Laura Smirin, formed Universal Controls Group (UCG) to offer their customers more options when buying metal-forming machinery. Today the company offers one of the largest in-stock metal-working machine inventories, machine reconditioning, on-site field services, new controls, drive systems, and buying and selling options for surplus machinery.
Girkins said, “We have 15 tube mills in stock and about 45 roll-forming machines, including used and rebuilt equipment. A lot of new guys want used equipment to get started. Once they start making money with it, then they want a new machine because they want to go faster. We can supply all the machines and equipment you need for a tube mill.” He said the typical cost for a new tube mill is about $600,000-$800,000, depending on the machines and tooling included in the lineup. A used machine is about half the investment.
How It’s Made – Coil to Cut
Carport framing members, supports, panels, and trims are made by roll forming coils of galvanized steel. (Trims can also be made by folding metal; watch for an article addressing this method in a future edition.) Hat channel, commonly rolled from 26- and 29-gauge steel, is used to support roof and wall panels. U channel, used for braces and supports, help reinforce the structure. Panels and trims are rolled quickly and easily from 24-gauge to 28-gauge coil steel. Companies like ASC Machine Tool, Metal Rollforming Systems, and The Bradbury Company manufacture machines that roll form several profiles, eliminating the need for multiple trim machines.
Roll forming tube steel is a bit more complicated than roll forming panels and trims. The gauges used for carport framing are heavier — primarily 12- and 14- gauge steel. Tubing usually measures from 2” to 2 ½”. “The gauge you use depends on the size of the structure you’re building. The bigger the structure, the heavier the gauge of framing you need to use,” explained Girkins.
There are more steps to the process and more equipment is involved in making steel tube. The high-speed equipment runs at a rate of 150-250 ft. per minute, although Girkins said they manufacture some mills that run at up to 1,000 ft. per minute.
Roll Forming Steel Tube
There are several steps involved in turning a flat coil of steel into a round or square tube. If the tube will need holes or slots, they are punched into the steel before it’s formed into tube. Universal Controls Group manufactures machines that measure the flat coil steel and punch holes and slots in it. “It’s a lot easier to punch holes in the material while it’s still flat,” said Girkins.
The steel coils are butt welded to make a long, continuous strip and loaded onto an accumulator. Welding the butt ends together eliminates the need to rethread the machine, it reduces waste, and reduces changeover time between coils. It also reduces the risk of damaging the dies because of mis-threaded steel.
From the accumulator, the coil is fed into the mill into a pinch roll. “The mill never stops,” he explained. “The theory is you never shut the tube mill down. You use the accumulated material to keep it going until you’re done for the day.”
As the flat coil runs through the machine, it’s formed up and around until it makes a tube. It is like pulling the strip thru a funnel. Before it’s cut, the tube goes through a high-frequency welder. “A high frequency weld isn’t welded with a torch,” Girkins clarified. “The welder heats up the edges and the edges are squeezed together. It’s more forged than welded.”
The edges are heated up to approximately 1800 degrees, which is so hot the pre-galvanized protective zinc coating burns off the heated area and it creates an upset. A lathe tool is used to scarf off the upset material, making the area smooth again. A torch and automatic spray welder are used to reapply the protective zinc layer on the top of the seam.
After the zinc coating is reapplied, the round tube runs through a 20’ cooling trough where it’s sprayed with coolant (water). The standard way to create the square tube used in framing carports is to make a round tube and then squeeze it into its square shape.
It usually takes three passes through the sizing mill to get the square shape. After it goes through the turkshead unit, where it’s straightened and squared (if desired), it runs through an encoder where it’s measured. Then it’ll go through either a flying saw or a cutoff. “Many carport people use flying cold saws now; it’s a nice, clean, easy way to cut,” he said. “There’s no deformation in tubing when the blade goes through and there’s no burr.” Neither the material nor the machine stop to make the cuts. A die travels along the tube at the same speed as the tube and makes the cut when it receives the signal from the encoder.
It’s at this point that the lengths are run through a swager, as a secondary operation, if needed. If the tube is going to be used for slip-fit construction, the lengths are put through a swager to squeeze one end of the tube enough that it will slip inside the end of another tube.
At this point, the framing components are finished and waiting for you.
Now that you’ve learned a bit about the process, you can appreciate the effort — and understand the cost — that goes into making the components. Tube mills are a major investment. But if you’re ready to invest in a mill of your own, either new or used, there are plenty of companies that are ready to help guide you. GSCB