02 Oct 2019
Laser-based process to shape glass sheets could be used in medical technology and industrial design.Fraunhofer IWM has been developing a laser-based technique to bend glass for some time, and has recently announced its latest project milestones. The project is now seeking industrial partners with which to collaborate while scaling up the process and producing larger format items.
"We’ve already had lots of positive feedback from architects," said Tobias Rist, a specialist in glass forming at Fraunhofer IWM and head of the Glass Forming and Machining group.
"A lot of them are now keen to know when this corner glass will be available. But our lab system only processes sheets of glass one square meter in size, so we’re only able to produce prototypes."
Lasers offer the prospect of forming glass sheet into narrow curvatures and clean-edged bends of 90 degrees, which are problematic for conventional glass bending techniques. Traditional methods also tend to impair the optical properties of the glass, closing off several potential end-uses.
Applying lasers to the task is a complex prospect, however. The ability to focus a laser onto a small area can potentially help create sharply angled geometries, but material thickness and thermal expansion coefficients must be accounted for. Mechanical stresses created by the forming operation are a further consideration.
Describing its glass-bending procedure in earlier research, Fraunhofer IWM commented that it involved directing a laser beam onto glass pre-heated in a specialized kiln to around 500-degrees Celsius, just below the temperature at which glass begins to melt. Only the area of the glass where the actual bending is to take place is heated to that point, rather than the entire sheet, so the laser needs to heat the relevant area by just a few more degrees for it to reach the glass transition temperature and become formable under the action of gravity.
Industrial, retail and medical uses
"The glass softens at the points heated by the laser and gravity bends the material into the desired shape," stated the Glass Forming and Machining group in its project literature. "Once the desired form has been achieved, the laser is switched off and the glass solidifies. The result is a shape with bends featuring small radii, waves and round protrusions."
The technique's complexities include defining exactly how long the material will be heated and precisely where, and then creating a control program to ensure that the laser duly does what is required. Fraunhofer's protocol also allows for the laser to momentarily stop, heat a single point multiple times, or change the intensity of the beam.
"We now know how to control the laser in order to bend glass of the required thickness to achieve the exact angle or bend radius we want," said Rist. "We’re the first to be able to produce a 90-degree bend like this. Furthermore, the process can also be used to bend a series of glass sheets to specific, graduated radii so as to produce sandwich structures and sheets of laminated, safety and insulating glass."
Other uses for formed glass sheets created by the Fraunhofer method could include retail store fittings such as display cabinets and refrigerated counters. With a wide variety of possible applications now opening up, Rist and his team are keen to work with manufacturers from a wide variety of sectors.