With its additively manufactured gripper fingers, Schunk has opened a new chapter of online sales in the field of mechanical and plant engineering. Automotive supplier ROS from Coburg uses the Schunk eGRIP 3D design tool for diverse robot handling in assembly systems.

Just a few clicks are sufficient to upload the STEP or STL data, design the finger and trigger the order for the additively manufactured components. What sounds simple in theory is apparently also simple in practice. Christopher Lamprecht, production planner at the manufacturing facility of ROS, comes to this conclusion: “With just a little bit of background information on CAD, the program is very easy to use. It is ultimately a great modular design. You upload the STEP model, align it in the X, Y and Z directions, rotate the part how you want to grip it and then the fingers are automatically adjusted. It really is child’s play.”
Comparable with an online photo service, the operator configures the required gripper fingers by means of a few specifications with regards to material, gripper type, installation position and finger length. Once the basic information has been entered, the tool shows the delivery date and the exact price. Upon changing the material, the price changes automatically, making it very easy to compare the available materials with one another. Using a volume-based price model, Schunk can pass the cost benefits of cumulative production directly on to its customers: the smaller the volume, the more affordable the fingers.
With around 300 employees, ROS GmbH develops and manufactures precise tools and assembly systems at its Coburg and Ummerstadt plants for the production of functional and aesthetic plastic parts. In the field of seat systems, ROS provides a comprehensive portfolio of components for headrests and seat adjustments. Worldwide, in virtually all cars in the premium segment, guide bushings are fitted by ROS to lock the headrests.
ROS is extremely open to technologies like Schunk eGRIP. In two assembly plants for a Bavarian car maker, the company fully used the potential of the 3D design tool for the first time. Within two weeks, the additively manufactured gripper fingers were on Lamprecht’s table – additively manufactured, complete with the contour specified by him. Almost 20 different module variants are produced on the two fully automatic machines. Each achieves an output of several hundred parts per hour, so it is worthwhile if the gripper fingers are designed so universally that no conversion is required.

“By being able to additively manufacture the fingers, we always have the same gripper by which we can cover all variants,” says Lamprecht. “I don’t have to change any mountings and have neither maintenance nor retrofitting work. This is a huge advantage.
“All in all, the online tool has saved a great deal of work in device construction,” he continues. “From developing the idea, to the first tests, milling operations and co-ordination, two days would certainly have been needed. However, with eGRIP, the effort was half an hour maximum. When the fingers were delivered, they worked straight away. You mount the jaws, teach in your point, close them and that’s it.”
The effect of the world’s first online shop for individually designed gripper fingers is impressive. According to Schunk’s estimates, it enables the design time for gripper fingers to be reduced by up to 97%, while the production and delivery time is reduced by up to 88%. In addition, finger price is reduced by up to 50%.
Some eight to 10 different sleeve variants can today be produced for each machine: for this, the guide bushings are separated on one linear unit and delivered suspended. A camera records the rotational position and transfers the values to the robot, which grips and places the sleeve so that it is precisely aligned on the rotary table using a multi-tooth guided Schunk PGN-plus 64 universal gripper. At each station, springs, buttons and caps are then assembled. A second robot, which is also fitted with a Schunk PGN-plus gripper, serves to discharge NIO parts. In this way, secure access must be ensured, regardless of which components were fitted before and which ones were not. The gripper jaws of the two Yaskawa robots used differ accordingly.
So that the material of the gripper fingers can be precisely adjusted for the specific application, there are three materials on offer from Schunk eGRIP. Stainless steel fingers with a material density of 8 g/cm3, a tensile strength of
700 N/mm2, an elasticity modulus of 190 kN/mm2, an elongation at fracture of 34% and a tolerance of ±0.1 mm (coating thickness 30 µm) or ±0.2 mm (coating thickness 50 µm) are primarily suitable for sophisticated applications in machine manufacturing.

Fingers made of aluminum (AlSi10Mg) or polyamide 12 show their strengths primarily in dynamic assembly applications. The latter, with a density of barely 0.9 g/cm3, are extremely lightweight, resistant to chemicals, suitable for use with food products and can additionally be used reliably in connection with cooling lubricants and aggressive media. Schunk also offers top jaws made of FDA-approved polyamide 12 (PA 2201), specially for use in the pharmaceutical and medical sector.
For Lamprecht, the polyamide fingers also offer additional benefits: “While until now conventionally manufactured aluminum fingers had been used, we chose polyamide for the additively produced fingers. This will ensure that the sleeves are handled carefully.”
Looking forward, he sees excellent implementation possibilities for the 3D printed fingers: “When we have to tightly grip difficult parts in the future, we will certainly use eGRIP again.”
For further information www.schunk.com