Forming Different Types of Metal

HARD VERSUS SOFT

Dave Greene, vice president of manufacturing at Americlad LLC, Rogers, Minn., explains that most metals form in a similar way in conventional press brakes, but the softer the material, the less effort it takes to bend. “Keeping this in mind, we can achieve shorter minimum flange dimensions on softer metal.

Also, we can use smaller tooling that is under less stress. Using smaller tooling on softer materials helps us achieve even smaller minimum flange dimensions. Copper and zinc are even softer than our typical 3000 series aluminum so the minimums get even smaller.”

The single most common issue Greene says Americlad runs into with customer-designed parts is the minimum forming dimensions. There are physical limitations to machinery and tooling that prevent forming extremely short flanges on most metal, and he explains this is typical for all different material types. “Unfortunately, those dimensions are different for every material thickness; the thicker the material, the greater the minimums are. In house, we have a small forming chart that shows our engineers what our minimums are; that being said, it is more of a guideline as to what is capable with our typical operations. We do our best to try to figure out a way to achieve what the customer is looking for.”

Steve Kovach, president of Kovach Inc., Tempe, Ariz., agrees that zinc, copper and steel up to 18-gauge bend very similar on press brakes and folders. Also, “Assuming aluminum has been painted, it does need to be scribed if its thickness exceeds 0.090 inches. Flange depth is typically limited by the machines not necessarily the metal. However, flange depths never go below 3/8 inches. For strain rates, copper and zinc are very malleable and this is not an issue. Steel and aluminum strain rates vary by thickness.”

STEEL

It’s important to remember that perforated steel panels need to be post painted. “The exposed pores with the perforations will, of course, lead to rust,” Kovach says. “Steel is a stronger metal so you can use a lighter gauge than other products for flashing and wall panels. Press brakes and folders can usually handle all paint systems without crazing or cracking. Galvalume-coated steel is the best for roller-coated paint applications.”

ALUMINUM

Generally, when fabricating metal systems with aluminum, a thicker gauge, such as 0.040, is required since aluminum is not as strong as steel. ”Aluminum has a higher coefficient of expansion and contraction compared to steel,” Kovach says. “Thicker aluminums, above 0.090, must be scribed prior to bending or you risk stretching the paint and having a large end radius. Aluminum should be isolated from any steel products since they are dissimilar metals. To that point, stainless steel fasteners must be used with aluminum attachment systems. Another difference between the two metal types is that aluminum panels cannot expand as much as steel in the same profile.”

ZINC AND COPPER

Both zinc and copper are very similar in fabrication, handling and strength, but have very different properties. “When handling zinc or copper you must use gloves to prevent the transfer of oils from handling during fabrication,” Kovach says. “Both products cannot have moisture between the sheets, otherwise staining can occur. Both metals also require stainless steel fasteners.”

Copper panel widths are limited by coil sizes, which typically do not exceed 48 inches; however, there are larger customized solutions available. “Due to its high level of strength and malleability, copper panels respond very well to custom bends and perforations, making design options virtually endless,” Kovach says. “Architectural zinc is 99.995% pure. Small amounts of copper and titanium are added to zinc to increase malleability and ductility, which aids in forming shapes and panels.”

BRITTLENESS

Brittleness is the property of a material by virtue of which it breaks without significant plastic deformation, when subjected to stress. The more brittle a material is, Greene cautions the higher the chance is that it will crack or craze.

“When aluminum gets anodized, there is a coating embedded into the material that does not bend or stretch with the aluminum as it is formed,” Greene says. “When you bend anodized aluminum, the aluminum stretches around, but the hard anodize coating does not and it can craze or crack leaving the raw aluminum exposed. This crazing can also happen on the raw aluminum but is much less noticeable as there is no color difference. The thicker the aluminum, the better chance of crazing or cracking.”

Tom Laird, senior account manager at New Tech Machinery (NTM), Denver, explains zinc is brittle and is only specified in NTM machines when running mechanically seamed profiles. “If you bend it too much like on many snap-lock panel profiles you could fracture the material.”

Kovach believes brittleness mostly applies to rollforming except when press breaking thicker, painted aluminum. “When rollforming material with different metal tensions, machine speed and spray-applied lubricants that do not affect finishes are applied to ease strain on material. For softer metals like zinc and copper machines roll slowly to avoid cracking and warping.”

OVERALL APPEARANCE

Americlad’s metal arrives from its distributor with a poly masking on the finish side of the sheet. This remains on the metal until it is installed on the building or it is peeled off for a finishing operation. “The softer the metal, the more prone it is to showing tooling marks, [which are] indents from the tooling,” explains Greene. “Whenever this is a concern, we can wrap the press brake tooling with a polyurethane sheet to protect the material past the point of the poly masking. If we are forming the metal in a folding machine rather than a press brake, the tooling marks are less of an issue due to the way the machine folds the metal rather than forcing it into a v die like in the press brake.”

Laird explains thicker materials tend to form better and show less oil canning than thinner materials. “Using ribs such as striations will help in hiding oil canning or material/installation defects once the roofing panels have been installed. [Also,] our machine specs call out the materials recommended for each machine, and clients can contact us if they aren’t sure. For example, I’m familiar with some Canadian companies that use Grade 80 material, and we only recommend that in 26-gauge steel—otherwise heavier gauges may not bend properly or cause damage with the rollers in the machine.”