Abstract - American Society for Engineering Education (ASEE ...

“INTEGRATION OF COGNEX VISION SYSTEM AND ROBOCYLINDER TO REDUCE THE REWORK AND PROCESS COST FOR RAW MATERIAL INSPECTION AND QUALITY CONTROL” Madhav D Patil Department of Electrical Eng.

University of Bridgeport [email protected]

Akash Sheth Department of Electrical Eng. University Of Bridgeport [email protected]

Prof. Jack Toporovsky Department of Electrical Eng.

University of Bridgeport [email protected]

Abstract: In any manufacturing and assembling plant, traditionally there is no specific method to inspect the raw materials in any industry when it arrives from the venders. If the raw material is not inspected then the end product may have a quality problem and it may be dumped or sent for rework, which increases the product cost as well as it’s a huge loss for the company, labor cost and power consumption increases, materials and time are wasted in vein. Generally, inspection of raw materials may be done manually using measuring instruments, or by machines based on laser sensor technology, using probes, weighing scales, etc. Manual process is too slow and meant to test only few batches out of the entire lot which is less effective. Dedicated machines are usually confined to a single type of raw material considering specific property of the component. This option can be expensive when several different raw materials are to be tested at in-feed line. The proposed inspection system is implemented in the PLC lab at University of Bridgeport. The paper start with the introduction of Cognex vision system then followed by ROBO actuator and then the wiring diagrams of camera with PLC as well as with the Actuator.

Proceedings of the 2011 ASEE Northeast Section Annual Conference University of Hartford Copyright © 2011, American Society for Engineering Education

Introduction:The goal of every production system or manufacturing industries is to produces the high quality product from the raw materials. Quality is an integral part of the process of design, manufacture and assembly which is defined as the degree of excellence or fitness for use or purpose by considering the most economical level [1]. The quality can be maintained by having different procedures and controls at various stages, but inspection at the raw material is the most useful for quality control and to reduce the scrap and reworks. Rework and scraps are the Major Industrial problems in United States. Any Industrial sector involve in manufacturing and later on assembling them always find loses when the ratio of rework and scrap rates go high, for example considering ‘Toyota Car Industry’[2]. The Shock & Struts manufacturing involves the use of around 100 machineries. If the raw Materials used are not properly inspected before sending to manufacturing phase then the end product will definitely have quality problems. As a result of which probably the final product is dumped or if possible send for rework. [3] have mentioned the strategies for rework of production rejects and there are lots of literature on control of rework and logistic planning, but no one had paid attention on the inspection of raw material. [4] developed an approach of the reduction in cost of defective part in serial assembly line and lots of production industries or manufacturing industries try to use the reject material by rework, but for that they have to spend huge amount of money, time, labor etc. [5] also mentioned in his paper, the different inspection methods such as gage inspection, judgment inspection by bell laboratory, statistical quality control method. But these methods are not autonomous or not for the raw material inspection. In this paper we will present a cost effective automated dynamic setup by which industry can eliminate this problem from their process cycle. We have integrated the latest vision system and multi positional ROBO-cylinder which enables inspection of the different types of raw materials on the same setup. Cognex vision systems are highly reliable and accurate in this regard. They have ‘path find’ technology by which they can first identify the object and then further analyzed it for defects. Cognex vision system uses the accurate and reliable tools for this inspection with the help of intelligent sensors. The ROBO cylinders are most precise in movements with built-in drive controller. They are easy to use and don’t need programming of large codes to perform different jobs. It gives real time display for all the operations being performed. Cognex Vision System: Vision System is the application of computer vision to production industry and manufacturing. Whereas computer vision is the general discipline of making computers see means understand what is perceived visually, machine vision, being an engineering discipline, is interested in digital input/output devices and computer networks to control other manufacturing equipment such as robotic arms and equipment to eject defective products. Machine Vision is a subfield of engineering that is related to computer science, optics, mechanical engineering, and industrial automation. One of the most common applications of Machine Vision is the inspection of manufactured goods such as semiconductor chips, automobiles, food and pharmaceuticals. Just as human inspectors working on assembly lines visually inspect parts to judge the quality of Proceedings of the 2011 ASEE Northeast Section Annual Conference University of Hartford Copyright © 2011, American Society for Engineering Education

workmanship, so machine vision systems use digital cameras, smart cameras and image processing software to perform similar inspections. Computers do not 'see' in the same way those human beings are able to. Cameras are not equivalent to human optics and while people can rely on inference systems and assumptions, computing devices must 'see' by examining individual pixels of images, processing them and attempting to develop conclusions with the assistance of knowledge bases and features such as pattern recognition engines. Although some machine vision algorithms have been developed to mimic human visual perception, a number of unique processing methods have been developed to process images and identify relevant image features in an effective and consistent manner. Machine vision and computer vision systems are capable of processing images consistently, but computer-based image processing systems are typically designed to perform single, repetitive tasks, and despite significant improvements in the field, no machine vision or computer vision system can yet match some capabilities of human vision in terms of image comprehension, tolerance to lighting variations and image degradation, parts' variability etc. The Cognex vision system has checker sensor with built in camera, processor, lighting, optics and I/O capable of detecting and inspecting up to 6,000 parts per minute. These checker sensors help to reduce the production costs and optimize quality. The new 3G Checker series of vision sensors from Cognex provides the easiest and most affordable way to verify the products you manufacture. Checker vision sensors offer extremely reliable part detection and inspection unattainable with photoelectric sensors. Inspecting the raw material received from vendor through Cognex system will definitely help in eliminating the scrap rate menace which becomes heavy loss for any industry[6]. Following are the major benefits that industries can own from this idea implementation. y Reduced Re-Work on Product. y Save Huge Electricity. y Save Labor Cost. y Save Material & Product Wastage. y Reduce Scrap Material Rate. y Improve Quality of Product. y Production and delivery on Time. All the problems such as labor cost, scrap and rework, electricity etc can be removed by Cognex Vision Camera if it is implemented to inspect the raw material parts before they even goes into manufacturing zone[7]. In this paper we have implemented the hardware in which Cognex vision system is integrated with ROBO cylinder and Programmable Logic Controller (PLC) for the inspection of raw material for the precise movements and very small parts. The vision sensor will be auto-handshaking with PC by USB port. A user can find the sensor on the connection list and create a new job. It can change the brightness and direction of parts Proceedings of the 2011 ASEE Northeast Section Annual Conference University of Hartford Copyright © 2011, American Society for Engineering Education

travel.It also can change the speed and trigger input delay. There are two personalities in the option, persence and meansurement. The basic idea is setup a image and decides it as a part at first. The sensor recives a part then compare the shape or length with preset image or scale. The vision sensor need installation with angle to get better result. The old tradition system didn’t have these features to verify the object is correct and then inspect it for further more levels to make sure that it is not defected. But now Cognex has all these features to take care. When this idea will be adopted in any industry especially the Automobile which I have tried to cover in this topic, they will have great benefits. They will get reduction in Labor cost, Electricity bills, rework etc. y Three things are checked by detect zone. y If there is anything triggers the photo-eye sensor, the relay 1 will send a signal to the sensor, than delay for 2 seconds to take a snap-shot. y If the mark of detect zone is passed, it will check the inspect zone. y After the detecting, the sensor will go to the inspect process immediately. ROBO Cylinder: ROBO Cylinders are the electrical actuator, electromechanical alternative to the Pneumatic actuator. These cylinders are more flexible than the Pneumatic actuators, intelligent in nature and also economical. The ROBO Cylinder which we are using for this application is from the IAI Inc. This actuator has the following characteristics over the pneumatic actuators, • Uses low power consumption • Used for multiple positioning with precise movements • ± 0.02 mm repeatability • Easy programmable velocity control • Also programmable acceleration and deceleration • Also present with push torque function control mode • With wide range of Stroke length – 50mm to 1000mm • With different speed depend upon the different model • Serial input/output linking up to 16 different axes These actuators are available with wide types of configuration to fit your application. We are using ERC2 type of actuator for this application. The actuator has build-in controller with stepper motor for position, torque and speed control mode. The build-in controller reduces the wiring to connect with PLC as well as reduces the panel board size i.e. no need to be install the controller separately. The ERC2 actuators are operated inside the shaded area as shown in the following graphs. The following graphs are provided for reference only. Check the exact values of maximum speed and load capacity for each model using the ROBO Cylinder General Catalog 2006. Proceedings of the 2011 ASEE Northeast Section Annual Conference University of Hartford Copyright © 2011, American Society for Engineering Education

Figure - 1 ERC2 Operating Graph The ERC2 slider type actuator which we are using for this application has the following Specification,

Table 1 Specification of ERC2 - SA6C Series Item Description Drive Method Ball Screw ? 10mm, rolled C10 Positioning Repeatability ±0.05mm Backlash 0.1mm or less Allowable Load Moment Ma: 8.9N ? m Mb: 12.7N ? m Mc: 18.6N ? m Overhang Load Length Ma direction: 150mm or less, Mb:/Mc direction: 150mm or less Ambient Operating 0-40 °C, 85% RH or below (non-condensing) Temp/Humidity The speed and the load capacity of the ERC2 series actuators are inversely proportional, due to the pulse motor is used. The comparison of annual power consumption between the ROBO Cylinder and Air Cylinder (taken from IAI Inc.) is shown in fig. 2.


Figure 2 - Power Consumption bar graph. Hardware Design: The key elements of this project Programmable Logic Controller (PLC), which is the brain of the project. This application is implemented in the PLC Lab at University of Bridgeport. The project is made up of the following components, 1. Programmable Logic Controller – Allen-Bradley (Micro-logix 1000) 2. Cognex Vision System 3. ROBO Cylinder (Actuator) 4. Power Supply The basic block diagram of the project is as given below,

PLC

Power Supply

Cognex Vision System

ROBO Cylinder – ERC2 slider type actuator

Figure - 3 Basic Block Diagram

As shown in above figure 3, PLC is connected to Cognex Vision System and Actuator through I/O, the Cognex vision camera has two outputs one for the good part and another is for the bad part. These outputs of the camera are connected to the inputs of the PLC and the trigger signal of camera is connected to output of the PLC. The Cognex vision camera operates on the 24 VDC power supply. To set the good/bad part images into camera, Checker software is used. By using Proceedings of the 2011 ASEE Northeast Section Annual Conference University of Hartford Copyright © 2011, American Society for Engineering Education

this software we can set the images inside the camera to determine the good/bad part. PLC perceives the signal from these two outputs of camera and performs the respective action on the actuator. The wiring diagram of the PLC and Cognex vision camera is as given below,

Figure 4 Wiring Diagram of PLC - Cognex Vision The ROBO cylinder also connected to PLC as shown in figure 5. The actuator has build-in controller and it moves to different user defined positions, as the actuator is very precise in movement. In this paper we have set the parameter on pattern 0 i.e. for 8 different positions. These positions can be feed through the PC interface software into the actuator and it will be stored into it. These actuators are very precise in movement, so they can be used inspection of very small part production companies such as IC design, PCB designs or also in automation assembly units. When we push the start button, the actuator will perform the home return command and it will come to home position which is defined by the user/by-default. As soon as the actuator will reach the home position, HEND (Home return completion) flag will be initialize to the PLC. Then the PLC will give the command to the actuator to move toward the 1st position (PC1), on this position the Cognex vision camera will inspect for the good part detection, if the part is detected and it is good part, then it will gives signal to the PLC and the actuator will move toward the 2nd position (PC2). If the bad part is detected, then Cognex vision will give signal to the PLC and the PLC will move the actuator for the rejection position. In this way if there is any bad part in the raw material before the assembling operation or in the production line, then it will be removed from the line and we can save the time as well as the scrap work and money. From the Checker software, we can determine the good part and bad part detection ratio.


Figure 5 - Wiring Diagram of PLC and ROBO Cylinder Conclusion: This paper presents the new concept of the inspection of raw material and to improve the quality of the product in the manufacturing industries as well as assembly industries. The Cognex vision system is used for the inspection of parts or the material while the ROBO actuator is used for the very precise movement or the displacement. These two different systems are integrated with each other as well as to the Programmable Logic Controller too. The major advantage of this implementation is to maximize the production ratio with good product quality. The inspection of the raw material or for very small parts is improved by these equipments, which are not that much costly.


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