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 clever 3D design tool SCHUNK eGRIP for diverse robot handling in assembly systems.
The contour of the gripper fingers was generated fully automatically based on the STEP data in SCHUNK eGRIP
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 automotive supplier ROS in Coburg, 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”, Lamprecht highlights. 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 each other. Using a volume-based price model, SCHUNK can pass the cost benefits of cumulative production directly onto its customers: the smaller the volume, the more affordable the fingers.
Significant time savings
With around 300 employees, ROS GmbH & Co. KG develops and manufactures highly precise tools and plants in the Coburg and Ummerstadt plants for the production of function and visible parts from the plastics Duroplast and Thermoplast. 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 innovative technologies like SCHUNK eGRIP. In two assembly plants for a Bavarian car maker, the company has fully used the potential of the 3D design tool for the first time. Within two weeks, the additively manufactured gripper fingers are on Christopher Lamprecht’s table – additively manufactured, with the contour precisely specified by him. Almost twenty 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. I don’t have to change any mountings and have neither maintenance nor retrofitting work. This is a huge advantage”, Lamprecht explains. With minimum effort, he adjusted the gripper fingers to the optimum contour. “All in all, the online tool has saved a great deal of work in device construction.” >From developing the idea, to the first tests, milling operations and coordination, two days would certainly have been needed, he estimates. “But with eGRIP, the effort was half an hour max.” When the fingers were delivered, they worked straight away: “You mount the jaws, teach in your point, close them and that’s it. Awesome.” 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%. The production and delivery time is reduced by up to 88%. In addition, the finger price is reduced by up to 50%.
A lot of variants
Eight to ten different sleeve variants can be produced for each machine today: 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 precisely aligned on the rotary table using a multi-tooth guided SCHUNK universal gripper PGN-plus 64. 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. For this, 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 differed accordingly.
Christopher Lamprecht (right) was assisted with this project by SCHUNK Area Sales Manager Harald Jörig
Polyamide, aluminum or stainless steel
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 +/- 0.1mm (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 however 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 also 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 Christopher Lamprecht, the polyamide fingers also offer additional benefits: “While until now usually conventionally manufactured aluminum fingers had been used, we chose polyamide for the additively produced fingers. This will ensure that the sleeves are handled carefully.” With respect to the durability, Lampert is confident: “Up until now, the plastic fingers only exhibit minimal wear, which is very good news.” Looking forwards, he sees excellent implementation possibilities for the 3D printing fingers: “When we have to tightly grip difficult parts in the future, we will certainly use eGRIP again.”
Convenient operation
SCHUNK has provided the order process with all sorts of options: If you don’t want to order the gripper fingers immediately, you can recall the automatically saved offer later using the configuration number, continue processing it or request it via email so as to submit it to the purchasing department later. The external contour of the generated modules, consisting of gripper, top jaws, and workpiece, can also be downloaded free of charge as an STL file and used directly for the construction of the system. Follow-up orders are just as easy, because all orders can be recalled again, activated again or adjusted at any time. The intelligent web tool, for which there is a user guidance in German and English, is available for the SCHUNK PGN-plus universal gripper 40 to 125 (polyamide) or PGN-plus 40 to 80 (aluminum and stainless steel), for the pneumatically controlled SCHUNK MPG-plus 20 to 64 small-components grippers, and for the electrically controlled 24V SCHUNK EGP 20 to 50 small-components grippers. Orders can also be placed from EU countries and Switzerland.
