Every sheet of metal contains internal stresses going in different directions, some competing and some neutralizing each other. The higher the stress, the more likely it is that these forces become visible when the sheet is processed on a laser cutter. After cutting, a flat part that previously seemed acceptable might now appear to be twisted or bowed.
If that metal sheet is then sent to a secondary operation, such as bending or stamping, the internal stresses that created the twisting or bowing will cause it to be more difficult to process and even more stress could be added to the material.
More often than not, service centers that provide fabricators sheet metal run cut-to-length metal through a leveler to ensure their customers receive flat material with minimal internal stress. There are, however, situations in which a fabricator may want to employ its own leveler – especially if the operations involve laser cutting followed by further downstream processes.
Whenever a piece of metal is fabricated, be it by laser cutting or bending, heat is injected into the material, which can result in thermal stress near the cut edges or bends. The higher the temperature and the longer the metal is subjected to heat, the more significant the thermal stress can be. In regard to laser cutting, the degree of the resulting deformation is dependent on the cutting speed, laser power intensity and type of metal being processed.
If that laser cut part has incurred enough heat-induced stress, bending it can be tough. Imagine trying to hold a distorted part up against a press brake’s backgauge. Then, imagine trying to weld or assemble a part that wasn’t properly bent in the first place. What started out as a minor issue has now snowballed into something much worse.
There is, of course, a threshold for how much internal stress a sheet of metal can have before it becomes an issue. Therefore, many fabricators don’t require a leveler.
Whether one is necessary depends on the initial quality of the sheet metal received as well as the end product being produced. Some fabricators require a leveler for robotic welding, which requires consistent gaps that sometimes aren’t possible if the original sheet metal had any warping and others need it for a tight fit for shipping and packaging that sometimes isn’t possible if the parts are warped and can’t be tightly stacked.
On the hunt
For USG Ceilings Plus, quite a few factors led to the investment in its leveler, a Peak Performer from Kohler Maschinenbau GmbH. Those factors primarily revolved around aesthetics and the need to relay the utmost in perfection to customers to outweigh the competition. Additional factors that lead to the investment in a leveler include bowing of metal sheets after laser cutting and the difficulties that warped material introduces in downstream operations.
When Ceilings Plus opened its doors, a handful of skilled employees were making sheet metal parts for suspended ceiling systems with a notcher and a mechanical press brake. Today, the company has a comprehensive fleet of the most cutting-edge metal fabricating equipment available on the market.
When Nancy Mercolino, general manager of USG Ceilings Plus LLC and her team first started their hunt for a leveler, they were looking to replace the unconventional – and inefficient – method in which material was being leveled at their facility. She knew there had to be a better way to do it.
As Mercolino learned while working with Condor Technology Services, a sheet metal fabricating equipment consultancy firm, several manufacturers produced the type of equipment that her company needed. So, they looked at every aspect of every leveler available, including ease of operation, ease of accessing the rollers for cleaning, level of maintenance required and power consumption.
After doing thorough due diligence, Mercolino sent Kohler some of the most difficult parts she’d encountered to date. Kohler leveled the parts, Mercolino verified the results were acceptable, and she placed the order for the Peak Performer. Since then, every part that leaves the facility has been perfectly (flat and) stress free.
What makes it work?
The overall goal of leveling with rollers, which is the common approach to leveling, is that internal stress is balanced and reduced to a minimum. It’s achieved through a top and bottom set of offset rollers that alternately bend the metal and remove the stress points. When metal parts or sheets are run through a leveler’s rollers, they stretch and compress the metal, and it is these alternating bends that relieve the internal stress. Most leveling equipment includes the ability to set the parameters to a desired flatness.
In regard to the Peak Performer, a tight inlet gap forces the material into the machine to bend and erase any memory in the material that was caused by the internal stress. By the time the material gets to the outlet side of the machine, the internal stresses become more balanced and, by then, the part or sheet is flat.
When processing complex parts, especially high-strength metal that has varying cross sections, different forces can act adversely on the leveler. The forces can change the pre-set leveling gap and negatively affect the leveling result.
Kohler’s electromagnetic leveling control unit, however, can act against these varying forces and maintain the pre-set leveling gap. As a purely electromechanical machine, the Peak Performer doesn’t require any of the heavy costs associated with hydraulics.
Furthermore, the level of maintenance required for the leveler is incredibly low. As just one example, cleaning the rollers is easy thanks to quick-change leveling cassettes that can be smoothly driven out of the machine for easy access.
When perfectly flat material is the goal – at all stages of processing – a leveler can be an essential tool. Whether it comes down to easier work at the laser cutter or press brake, better fit-ups for welding or maximizing the space in a box for shipping purposes, material that has been leveled offers a major competitive edge.