Comparing and Contrasting Four Industrial Robot Pick and Place Techniques for Assembly

In today’s industrial landscape, automation plays a pivotal role in reducing labor demand / cost, enhancing manufacturing productivity and efficiency across most market sectors and applications. Among the numerous automation techniques in the engineer's arsenal, industrial robot pick and place operations stand out as crucial technologies in manufacturing and logistics processes that can be automated, reducing labor demand. These operations involve the movement of objects or parts from one location to another, often requiring precision and speed. In this comparison, we delve into four prominent pick and place techniques: flexible feeders, 4D bin picking, vibratory feeder bowls, and conveyor line tracking.

1. Flexible Feeders:

Flexible feeders utilize various mechanisms such as pneumatic, vibratory, or robotic systems to present parts to a machine vision system for robotic pick and place operations. These feeders are adaptable to different shapes and sizes of components, making them versatile in manufacturing environments with diverse product lines. One of the key advantages of flexible feeders is their ability to handle irregularly shaped objects and parts with complex geometries. But parts cannot be larger than 1/3 the width of the feed plate so that there is room for singulation and location by machine vision. Generally, parts must be from 1mm to 100mm in their longest dimension and must weigh less than 1kg (2.2 lbs) each

Beyond the size limits, flexible feeders also have other potential limitations. They can be slower compared to other part picking techniques, especially when dealing with intricate parts that require precise orientation. Additionally, the initial setup and calibration of flexible feeders can be time-consuming and may require skilled personnel with robotics and vision expertise. Parts must be rigid and cannot be soft or rubbery as they will not respond to the machine vibrations or oscillations required to singulate the parts.

One of the keys to a successful flexible feeder application is proper selection, calibration and integration of the machine vision system which identifies, qualifies and locates a part to be picked, sending the part coordinates and rotation to the robot controller. Along with this is proper lighting selection, top- or backlighting, selection of the feed plate design and extension of untended run time by bulk feeding options. Thereafter, the robot must be programmed to move to the part and pick it with an appropriate gripper. Once picked the part is placed in a custom fixture or a nest for further processing or assembly. The entire operation allows the picking, orientation and placing of 10 to 30 parts per minute.

2. 4D Bin Picking:

4D bin picking involves the use of advanced vision systems, including Artificial Intelligence (AI) and integrated robotics to identify and pick objects from a bin or container in all three dimensions: width (X), length (Y) and height (Z) plus lighting intensity. This technique is highly efficient in handling bulk materials and random and overlapping part orientations in even deep bins. By employing vision sensors and sophisticated algorithms, 4D bin picking systems can accurately locate and grasp objects, even in cluttered environments with highly variable lighting.

One of the main challenges of 4D bin picking is the computational complexity involved in processing large amounts of visual data in real-time. This is where AI (massive teaching of part orientation and lighting possibilities) comes into play, along with advanced math processing chips in the application server. Achieving reliable object recognition, in a variety of lighting conditions, and real-time generation of grasp planning algorithms requires significant computational resources and expertise. For 4D bin picking systems the cost is in the high-end GPU computation rather than in the cameras.

4D bin picking is an excellent technique for moderate feed rates. This approach can often solve irregular or larger parts where a flex feeder will be less effective or not even possible. Longer parts can overlap each other in a classic "pick up sticks" fashion but the vision is capable of discerning the best candidate to pick and directing the robot at the proper pose to pick and place the part at a rapid rate of 10 to 30 parts per minute.

3. Vibratory Feeder Bowls:

Vibratory feeder bowls utilize vibrations in a precisely fabricated bowl with a track for the parts to follow to orient and feed parts to a robot for pick and place operations. These bowls are particularly effective for small to medium-sized components that can be easily manipulated using vibration forces. Vibratory feeder bowls are known for their high-speed operation and reliability in maintaining part orientation during the feeding process. Photosensors and air blasts are used to detect parts incorrectly tracking and "blow them off" the track or otherwise purge them by strategic openings in the track.

Despite their efficiency, vibratory feeder bowls have limitations, especially when dealing with delicate or sensitive parts that may be susceptible to damage from excessive vibration. Additionally, the design and customization of feeder bowls for different part geometries can be challenging and may require specialized engineering and craftsman expertise. If there are frequent end-product changeovers requiring different parts for assembly, then a unique feeder bowl must be designed for those parts and all the bowls must be changed out and recalibrated. This is an expensive and timely operation making vibratory bowls most suitable for high production rates for fixed end-products with volumes in the hundreds of thousands or millions of parts per year. Vibratory bowls are capable of placing parts for picking at a rate of 60 to 200 parts per minute, with picking usually by dedicated "hard automation" as this rate exceeds the capabilities of most robot arms.

4. Conveyor Line Tracking:

Conveyor line tracking involves synchronizing the motion of a robot with a moving conveyor belt to pick and place objects as they travel along the production line. This technique is commonly used in high-volume manufacturing environments where continuous operation and rapid throughput are essential. By tracking the conveyor line, robots, usually "delta" robot designs from companies like Fanuc and ABB, can accurately position themselves to pick parts as they become available.

One of the key advantages of conveyor line tracking is its scalability and efficiency in handling large volumes of parts with minimal downtime. This technique is popular with food product packaging such as bakery goods, packaged snack foods or packaged clothing. Rates of up to 120 per minute can be achieved with a delta robot. However, this technique may not be suitable for applications requiring precise part orientation or dealing with irregularly shaped objects. The typical 4 axis delta operates only in one plane, does not have much "Z" or vertical motion, and so is best at picking flat objects and transferring to a packaging line. But there are hybrids available with a 3-axis wrist and gripper added to the 4 axis delta, such as the Fanuc M-1iA

Summary

Each industrial robot pick and place technique offers distinct advantages and limitations depending on the specific requirements of the application. Flexible feeders excel in versatility but may lack speed and precision for certain tasks. 4D bin picking is ideal for handling bulk materials but requires significant computational resources. Vibratory feeder bowls offer high-speed operation but may not be suitable for delicate parts. Conveyor line tracking ensures continuous operation but may lack precision for certain applications. Ultimately, manufacturers must carefully evaluate their needs and choose the pick and place technique that best aligns with their production goals and constraints.

Futura Automation provides components or complete solutions in each category of picking and placing for assembly applications. Futura Automation is the USA Representative for Flexfactory flexible feeders and is a Fanuc and Brooks Automation authorized robot dealer for complete systems. For vision components Cognex with our proprietary Feedware CX software for ease of integration, Fanuc IR Vision or Keyence vision systems are available and integrated into existing systems.

For 4D bin picking Futura works with Apera.ai which has a highly advanced system with rapid and error-free vision and robot path processing. Vibromatic is a good source for vibratory feeder bowls when that is the appropriate technique. For line tracking applications again Futura Automation can work with Apera.AI, Cognex or Keyence to solve the vision problem and Fanuc for the delta robots. Contact Futura Automation with your toughest pick and place problems and we will deliver an excellent solution for you. tech@futura-automation.com