Just one sheet: sheet metal vacuum lifters with a special trick
When thin sheets are lifted from a stack, it is as if they stick together. To prevent this, Remmert uses various techniques in its laser automation.
The LaserFLEX loading unit for thin sheets has a suction matrix that is specially optimized for sheets less than 1 mm thick.
LaserFLEX automates the loading of laser cutting machines.
"It's like a pile of printer paper. If you only want to take one sheet from the stack, you have to lift one corner first, ideally with a lot of dexterity. And yet sometimes the second sheet still comes along," explains Fabian Gries, Product Manager at storage and automation specialist Remmert, describing the challenges.
This problem is also known in the field of sheet metal processing. "It looks as if the sheets are sticking together," says Gries. However, this is not "sticking" in the chemical sense, but rather a combination of several physical effects that together create the impression of adhesion. "The thinner and lighter the sheets are, the stronger these effects can be."
Technologies for the separation of sheet metal
Remmert offers solutions for the automation of laser cutting machines. For this purpose, sheets are transferred from a warehouse to an automation line. A removal unit picks up a sheet using vacuum suction cups and places it on the shuttle table - all automatically. "If a second sheet is lifted and falls off during transportation, this can lead to serious injuries with manually operated suction spiders. With automated solutions, it can still cause damage to the machine. If the next sheet simply slips on the stack, it cannot be picked up automatically in the best case scenario. It is even worse if it is so crooked that it becomes jammed when it is put back into the sheet storage system . In either case, material damage occurs and the process comes to a standstill," says Gries, explaining the problem.
To avoid this, the LaserFLEX automation system from Remmert is equipped with a number of mechanisms. "The vacuum cups for holding the sheets are activated one after the other, creating a slight wave motion in the sheet. At the same time, we blow air between the sheets to compensate for the negative pressure during lifting. For steel sheets, we also recommend using an expanding magnet to fan out the sheets. Finally, a pincer-like measuring device grips the sheet and compares the actual sheet thickness with the target value."
Special device for thin sheets
Thin sheets with a thickness of less than 3 mm are particularly affected by these effects, according to Fabian Gries. "Thin sheets are often processed from the coil. Nevertheless, we have customers in the heating and air conditioning sector who use stacked sheets less than 1 mm thick." Despite the features, problems with separation were experienced with the tried-and-tested automation that was used for sheets in the range from 1 mm to a maximum of 25.4 mm. "For this application, we modified the lifting unit with a special suction cup matrix to avoid deforming the thin material. Furthermore, we developed a special device that initially lifts only one corner of the sheet. The principle is very similar to the sheet of paper I mentioned, only better."