Gripper relates to a specific part incorporated in a robot arm used to carry objects and place them in a designated position.
Different types of grippers are available – e.g. grippers that resemble human fingers or rubber suction cups incorporated in the plate attached to the robot arm.
Grippers are designed to carry different objects and are frequently used during palletizing or handling of cartons or cardboards with suction plates when placing packaged goods on the pallet as programmed.
Grippers are commonly used in many industries and processes including:
- Palletizing and packing goods – EOLP (end-of-line-palletizing) and pick-and-place applications;
- Woodworking industry – handling of planed timber and panels;
- Construction industry – palletizing of bricks / hollow masonry units;
- Automotive industry – assembly lines.
LIGHTWEIGHT CARBON FIBER GRIPPERS FOR INDUSTRY PALLETIZING ROBOTS
Gripper weight is a factor that is crucial for speed of robot operation, arm operation range when under load, service life of robot arm bearing, as well as arm load capacity. The rule is very simple: the heavier the gripper weight, the poorer will be the performance. Therefore, it is crucial to seek out ultralight materials that also offer high stiffness.
Grippers/suction plates are most often made from aluminum. Aluminum weighs 3 times less than steel and provides for relatively easy CNC machining – set for soft metals.
However, the materials are now available with lower weight and higher stiffness than aluminum, for example carbon fiber.
Carbon fiber is about roughly 42% lighter than aluminum and offers very high stiffness. Note that stiffness of carbon fiber components depends on the type of material used.
Carbon fiber composite made with prepreg technology and 0/90 woven standard fabrics offers stiffness at the level of 90.5 GPa Stiffness (Young’s modulus), whereas aluminum has stiffness at the level of 69 GPa.
Standard carbon fiber composites have stiffness about 30% higher than aluminum and weigh 42% less.
High modulus aerospace one-direction (UD) carbon fiber parts are even 3-4 times stiffer than aluminum. This fabrics cost few times more than standard carbon fibers, but it ilustrate many possibilities for weight reduction and stiffness improvement.
HOW IS CARBON FIBER USED FOR GRIPPERS AND INDUSTRIAL ROBOTS?
Carbon fiber sheets are most often used for lightweight grippers / pneumatic suction plates manufacturing.
Benefits provided by carbon fiber grippers / machine parts compared to aluminum:
- weight reduced by about 42%
- stiffness improved by about 30%
- higher load capacity and operation range of loaded arm
- higher operation speed of arm – which improves robot performance (short cycle time)
- increased service life of gear/bearings
- an attractive appearance that gives an edge over the competition and is recognized as being a state-of-the-art engineering solution – shaping marketing also
The second area where carbon fiber is commonly used relates to robot arms for industrial purposes, designed to ensure ultra-light construction and outstanding strength.
OPINION ABOUT USING CARBON FIBER GRIPPERS
Lamela comany manufacture plastic elements for IKEA company.
We manufacture details using a mold and a Fanuc ARC Mate 120 robot. According to technical data, this robot offers load capacity up to 20kg. Our company purchased a second-hand robot specifically for this project. We designed and built a gripper for this robot to ensure automatic collection of moldings. Due to its spatial form we assembled the gripper from standard 30x30mm aluminum profiles, steel sheets for attachment, two actuators, two guides with linear bearings, standard elements attached to profiles and two aluminum sheets provided with compensators and suction cups. One 517x517mm aluminum plate supported 4 cavities within the mold.
A single plate weighs 1.7kg + 16 compensators, T-connectors, suction cups
Consequently, we have designed a beautiful gripper that weighs about 14kg.
In theory we were ready for production. But it was a surprise when we attached the arm assembly to the robot and the 5 axis dropped lifelessly when under load.
A quick analysis of the parameters indicated some design errors related to the position of the center of gravity of the gripper in relation to the attachment. Actually, due to the center of gravity being located 230mm from the attachment, our Fanuc robot’s load capacity dropped below 8kg.
PHASE I
Implementation of gripper ”weight reduction”:
- Dismantling of actuators
- Dismantling of guides and linear bearings
- Additional machining of aluminum plates
- Assembly of steel sheet instead of aluminum parts with quick fasteners
Inspection by the authorized service that confirmed that the Fanuc robot was in good condition, technically.
Following modifications, the gripper’s weight was below 10kg. Upon assembly and putting it back into operation, an improvement in performance was evident but 5 axis movement was irregular, preventing precise collection and handling of details.
PHASE II
Gripper ”weight reduction” continuation
Search for light carbon fiber based material
- Analysis regarding properties of carbon fibers in relation to aluminum
- Consultation with Dexcraft engineers
- Commissioning Dexcraft Company for delivery of two CNC machined carbon fiber plates that will replace aluminum ones
- Upon delivery of elements supplied by Dexcraft Company, we performed analysis regarding strength, stiffness and weight – and obtained promising results. According to measurements, aluminum sheets weight was reduced from 1.6kg to about 0.9kg. In all, the weight of two sheets was reduced by 1.4kg without any modification of shape and sheet thickness.
However, gripper weight was still excessive considering that it did not have the actuators used to collect details from the levels of mold at the same time. An irregular and delayed performance during operation was inevitable.
PHASE III
Further gripper ”weight reduction”
- Carbon fiber sheet thickness 1mm less than the aluminum ones
- Reduction of length of aluminum profiles used for carbon fiber sheet attachment
- Replacement of T-connectors and air adapters with lighter ones
Consequently, carbon fiber sheet weighed about 0,7kg each. Further modifications resulted in reducing the gripper weight below 7.5kg. However, use of carbon fiber parts allowed shifting the gripper’s center of gravity by 188mm, which increased the Fanuc robot load capacity from 8kg to about 10.5kg.
Thanks to using carbon fiber plate we:
- Reduced the total weight of the tool (gripper);
- Obtained the location of the center of gravity that allowed operation of the Fanuc robot we purchased;
- Obtained higher operation speed of robot provided with a gripper lighter than the original one (14kg) which meant it met the target objective (machine cycle time) without use of actuators;
- Reduced load, as well as wear and tear which improved reliability.
Paweł Bartosiak , R&D Head Lamela Sp z o o – supplier of plastic components for IKEA Company
PRODUCTION OF LIGHTWEIGHT CARBON FIBER GRIPPERS FOR PALLETIZING ROBOTS
Our Company delivers carbon fiber grippers for robots and industrial machinery. Actually, grippers are most often intended for so-called suction plates.
We offer series production or one-off production of customized grippers / suction plates according to the client’s individual needs.
Grippers / suction plates made from carbon fiber sheets to 4, 5, 6, 7, 8, 10, 12, 20, 25 mm thick.
Upon request we also deliver custom gripper thickness from 1mm to 25mm thick, to a precision of 0.05 mm, e.g. 6.05mm.
We have over 10 years’ experience in delivery of grippers for robots and industrial machinery. We provide services for thread and screw head slotting of carbon fiber grippers/suction plates.
To receive a quote for carbon fiber grippers /suction plates:
please send an inquiry to info@dexcraft.com, along with your design specification (.dxf, pdf, stp file) or call us: +48 797-775-826.
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