Topology Optimization Software Enhances Gripper Reliability

Preziosa Francesco SRL is a manufacturer of sheet metal cabinets, one which prides itself on the customizability of its standard line. To improve its workflow and stay competitive, the company invested in a robotic cell and an automated press brake bending machine.

This investment, worth hundreds of thousand euros, swiftly began running into problems because of a relatively cheap part: the robotic end effector’s gripper. The long lead times for CNC machining new, custom robot gripper sets for specific jobs created a bottleneck in Preziosa Francesco SRL’s process.

To solve this problem, the manufacturer partnered with design consultancy firm Additive Italia (also known as Add-It) to create a customizable part Preziosa Francesco could then manufacture in-house. Add-It was able to meet the customizability requirement — as well as improve upon other characteristics of the part — through creating reusable design workflows in nTopology.

Built-In Problems

Preziosa Francesco uses a FANUC M710-iC robotic arm to load metal sheets into its automatic press brake bending machine, orient and secure the sheets’ position during bending operations and remove the parts to the appropriate storage area. The two CNC-machined grippers traditionally attached to the arm created three technical challenges Preziosa Francesco and Add-It wished to overcome.

The original parts did not impose enough friction to ensure a good grip, especially when applications required precise positioning under high-load conditions. The parts were also too large for perfect agility, risking collisions with the machine at certain bending angles. Lastly, outsourcing to a CNC machining company meant slow, two-week lead times for manufacturing custom grippers — unacceptable, when Preziosa Francesco requires different grippers for different sheet thicknesses and blank sizes.

Designing Solutions Through nTopology

“We immediately decided to start this project with nTopology due to the variety of grips that we could make,” says Gianluigi Rossi, design engineer at Add-It and lead designer engineer of this project.

To enhance friction, Add-It designed a surface lattice and honeycomb-like perforation pattern on the gripper. The grooves of this traction pattern deform the softer aluminum sheets Preziosa Francesco uses, mechanically interlocking the parts.

Add-It also used nTopology’s topology optimization capabilities to reduce the gripper’s footprint without impacting performance. “We estimated the space that we needed to save in the volume of the clamps,” Rossi explains. “It was a matter of a few millimeters. Still, it was a few millimeters that counted in this application.” This small reduction in size enables the system to remain close to the press brake bending machine to perform more delicate robotic operations and handle smaller metal sheets without collisions or stoppages.

The design process proved swift, moving from concept to application within four days, rather than the two weeks previously required for production of a single gripper variant. With nTopology, the team automatically reconstructed and smoothened the topology optimization results. This eliminates a time-consuming manual step, and enables the generation of variations within a few clicks. “In one afternoon, we managed to make the component we needed,” Rossi says. “In a few minutes, we could change the type of grip and produce a part that was ready to manufacture.”

Ensuring Process Reliability with Reusable Design Processes

For Preziosa Francesco SRL, the redesigned gripper greatly improves process reliability, unlocking lights-out manufacturing and the full utilization of its robotic manufacturing system. The manufacturer also no longer needs to worry about supply chain issues from outsourcing, with its Desktop Metal Studio System able to produce parts on-demand. In-house AM production has also resulted in a 35% cost reduction for the part.

Preziosa Francesco and Add-It are looking into expanding their partnership to new parts, and continue to optimize the grippers. They are designing clamp replacements and spare parts for the company’s punching machine, while also attempting to design a version of the gripper that is twice as long to increase maneuverability and flexibility.