Signal Cable Connections

Signal Cable Connections  

   The chain must be completed and have high integrity to provide the communication path for control signals to pass over. Depending on the specific design of the programmable control system, loss of communication to the I/O system will cause a critical failure, stopping the CPU scan .cnc machining parts In other systems, configurations can be accomplished that allow the unaffected portions of the programmable controller system to continue to operate.  

   As we saw earlier, communication between chassis can either be parallel or serial. Parallel communication uses multiple conductors to pass all bits of a byte or word of data simultaneously. Serial communication provides a method for single bits of a byte or word of data simultaneously. Serial communication provides a method for signal bit of a byte or word to be transmitted sequentially. The difference this has on cable design and selection is significant. Parallel cables are made of as many as 16 or more pairs of twisted individual conductors, protected by a shielded external jacket. cnc machining parts Multiple pin connectors are connected to one or both ends of the cable. The "D" type is popular, providing 25 or 39 pins in a standard configuration. Earlier design used a round type positive contact threaded design and certain manufactures still use this type of connector, although most have found the "D" type satisfactory.

 This cable is normally made available by the programmable controller manufacturer, and while it may seem expensive, the assurance of having a well-designed and thoroughly tested cable is worth almost any price compared to tracking down an intermittent problem later during a critical production period. The programmable controller manufacturer will provide parallel cables designed to operate with its equipment in various lengths, from 2 ft (feet) up to as much as 500 ft. Serial cables on the other hand are generally easier to use and less expensive to purchase or build. Manufacturers may or may not provide these as an item to purchase, and may just refer the purchaser to a third party source. Serial signal cable is normally a single or dual twisted pair of conductors, and is often just connected directly to the I/O driver or receiver with screw terminals. The only major reason to use parallel over serial is the great communication speed available with parallel, which can be a factor of 10 to 1, or more.

   Troubleshooting and Repair   

  Even the best of today’s well-designed and manufactured programmable controllers require occasional preventative maintenance and repair. This section looks at some of the tools provided by the manufacturer and techniques for general maintenance.  

   Most of the medium- and large-sized programmable controller systems available today are designed to be maintained by individuals with a wide variety of skills, without the benefit of in-depth formal training of this piece of equipment. This is accomplished in the design by providing individual modules of functionality installed in a chassis serviced from the front (all module types including power supplies). Front access is critical to proper maintenance. This allows easy inspection and replacement of the suspected bad module. Module health is determined by inspecting the LED indicators normally provided on the front of each module. Typical indicators will be on or off depending on the design and individual condition of the module in question. Various CPU and I/O modules will have indicators showing I/O control communications status, memory integrity, power supply tolerance check, scan integrity, and others. On future controller designs, and even today on a few systems, it is likely that English language messages will be displayed on the controller advising the user or maintenance personnel that a particular failure has occurred and recommended actions to take.

 The modular design and diagnostic indicators are, of course, important, but would be quite useless without well designed documentation provided by the manufacturer for the programmable controller system in question. Proper documentation will have sections dedicated to each major subsystem including CPU, I/O, and programming device. Each should explain in depth the stop-by-stop inspection of the system. All possible combinations of failure mode should be listed, along with suggested actions for repair. This will most often involve only the substitution of a re- placement board for the suspected failed unit. The user is urged to purchase a set of spare modules for the system in question as recommended by the manufacturer. This is normally, at a minimum, a single replacement module for each CPU and programming device serviceable module, and spare I/O modules equal to 10% of the number in the system.   

  While the design of system and documentation provide an easy vehicle for system maintenance once trouble is detected, it is always better to perform preventative maintenances where possible. Some systems available today provide levels of predicted failure detection that allow excellent preventive maintenance.

 This can range from automatic singling of low battery conditions on the memory modules to predicting an output circuit failure before the circuit is energized. This particular phenomenon can be extremely valuable in performing predictive maintenance on critical systems. Examples of this would include emergency circuits for rapid shutdown of a machine sequence or plant process. Outputs that fail prior to their need may not be detected in time to provide this critical service.

 The documented ladder logic diagram is a very useful tool for troubleshooting, especially on a complex system. It allows maintenance personnel or "walk through" the I/O segment in question, forcing transitions in specific inputs and outputs, while watching the system's reaction. cnc machining parts Many times this can ferret out a tough system problem, and may help isolate problems external to the controller such as an open sensor wire.  The major manufactures of programmable controller systems maintain 24 h telephone service numbers for users requiring emergency, service. Their highly trained personnel can normally walk the user through his problem and determine what action he should take for repair.

  

Installation and Maintenance of PLC

Installation and Maintenance of PLC

  Today’s programmable controller, properly installed, will provide a maximum of productivity with a minimum of maintenance. Cnc machining This section will cover the strength forward but critical areas of installation and maintenance of the programmable controller. It is intended to serve only as an overview on the subject, with the best guide for use being the documentation provided by the programmable controller manufacturer. This section will include rack installation for the CPU and I/O racks involved, line power, grounding, and signal cable consideration. Troubleshooting techniques as well as repair situation will be examined, and finally, training options will be presented.

   Rack Installation

   Depending on the size of the programmable controller being considered, the installation of the racks or chassis can be a simple or very complex task. Since most controllers are of open or particular application area. Many times this is a NEMA 12 type enclosure. Cnc machining It provides an environment in which the controller can operate without exposure to the grime outside the enclosure. Most racks can be mounted in either a panel type mounting arrangement, or a 19 in rack mounting. This is not true of controllers of the very small variety, as they are normally a panel mount only design. Rack mounting is generally used where the equipment is otherwise controlled. This type of installation is common where many instruments are mounted and used along with the programmable controller equipment. In either case, wire conductors must be routed in the rack; this is done with commercially available conduit that provides a means to bring in and out as many as 100 to 200 individual conductors from input and output points to real-world sensors and actuators. It is important that this phase of the design and installation be handled with care as it will dramatically affect the ability to maintain the systems. In addition to allowing any required system maintenance, this early care will make any system additions or modifications much easier.

  Line Power and Grounding     

    Proper power to the programmable controller is critical. Today’s systems are available in a wide variety of electrical configurations. Virtually all are designed for use in single-phase power systems, and most are now beginning to be offered with the optional ability to operate in a DC supply environment. AC designs are offered in either single voltage supplies, Cnc machining such as 115 or 230V AC; while some can be configured as either through a selection made on the power supply. Proper grounding of the power supply connection is required for a safe installation. Some programmable controller designs have individual grounding connections from rack to face- plates and other system components, so care must be taken to follow well electrical practice in system grounding during electrical installation. In certain applications, a 24 or 120 V DC power supply is required. This is common for installations that axe made where no AC power is available, such as remote electrical generation stations. It is also found where AC power is unreliable and where loss of control is considered an unacceptable situation

Tactile Sensory

Tactile Sensory  

  Next to vision in importance is tactile sensing or touching. Imagine the blind can do delicate jobs relying on his/her sensitive tactile.Cnc machining  A blind robot can be extremely effective in performing an assembly task using only a sense of touch. Touch is of particular importance for providing feedback necessary to grip delicate objects firmly without causing damage to them.   

  To simulate tactile in human hands, a complete tactile-sensing system must perform three fundamental sensing operations: (1) joint force sensing which senses the force applied to the robot’s hand, wrist and arm joints; (2) touch sensing which senses the pressure applied to various points on the hand’s surface or the gripper’s surface; (3) slip sensing which senses any movement of the object while it is being grasped.

  The joint forces are usually sensed using various strain gauges arranged in robot wrist assembly.Cnc machining  A strain gauge is a force—sensing element whose resistance change in proportion to the amount of the force applied to the element. The simplest application of touch sensor is a gripper equipped with an array of miniature microswitches. This type of sensor can only determine the presence or absence of an object at a particular point or an array of points of the robot hand. A more advanced type of touch sensors uses arrays of pressure-sensitive piezoelectric material (conductive rubber or foam, etc.). The arrangement allows the sensor to perceive changes in force and pressure within the robot hand. Since the force at each point can be determined, the force on its surface can be mapped and the shapes of objects grasped in the robot hand can be determined respectively. Slip sensing is required for a robot to create the optimum amount of grasping force applied to be picked up without the danger of being dropped. The gripping force is increased step by step until the object has been firmly grasped and no more slip occurs

 The integration of tactile sensing and vision sensing can dramatically enhance robotic assembly task. An example of this type of sensors would be a vision sensor used to locate and identify objects and positing of the robot itself, combined with a tactile sensor used to detect the distribution of force and pressure, and determine torque, Cnc machiningweight, center of mass and compliance of the material it handles. The hand-eye coordination for general-purpose manipulation will be extremely powerful in the industrial world.

  

Intelligent Robots and Visional Sensory

Intelligent Robots and  Visional Sensory      

    A new phase in robot applications has been opened with the development of “intelligent robots”.Cnc machining  An intelligent robot is basically one that must be capable of sensing its surrounding and possesses intelligence enough to respond to a changing to a changing environment in much the same way as we do. Such ability requires the direct application of sensory perception and artificial intelligence. Much of research in robotics has been and is still concerned with how to equip robots with visual sensors—eyes and tactile sensors—the “fingers”. Artificial intelligence will enable the robot to respond to and adapt to changes in its task and in its environment, and to reason and made decisions in reaction to those changes

 Visional Sensory    

 Much effort has been made to simulate similar human sensory abilities for intelligent robots. Among them, vision is the most important sense as it is estimated that up go 80% of sensory information is received by vision. Vision can be bestowed on robotic systems by using imaging sensors in various ways. For improving accuracy of performances,Cnc machining it can help precisely adjust the robot hand by means of optical feedback control using visual sensors. Determining the location, orientation, and recognition of the parts to be picked up is another important application

 Among the vision system, one of the key components is imagery sensor. The imagery sensor of a robot system is defined as an electro-optical device that converts an optical image to a video signal. The image sensor is usually either a TV-camera of a solid state sensory device, for example, charge-couple devices (CCD). The latter device offers greater .sensitivity, long endurance and lightweight, and is thus welcome when compared with the TV-camera. The camera system contains not only the camera detector but also, and very importantly, a lens system. The lens determines the field of view, the depth of focus, and other optical factors that directly affect the quality of the image detected by the camera.

 Either TV-camera or CCDs produce an image by generating an analogue value on every pixel, proportional to its light intensity. To enable a digital computer to work with this signal, an analogue-to-digital (A/D) converter is needed to transfer analogue into digital data, then store in random access memory (RAM), installed in computer. The computer analyzes the data and extracts such imagery information as edges, regions, Cnc machining colors and textures of the objects in the image. Finally, the computer interprets or understands what the image represents in terms of knowledge about the scene and gives the robot a symbolic description of its environment.

  

The Robotics Application

The Robotics Application

  Many of the robots in use today do jobs that are especially difficult for human workers. Cnc machining These are the types of jobs that require great strength or pose danger. For example, robots are particularly useful in the auto-manufacturing industry where parts of automobiles must be welded together. 

 A welding tool used by a human worker weighs about 100 pounds or more and is difficult to handle. Cnc machining As mechanical supermen, robots may be called upon to do anything from moving heavy components between workstations on a factory floor to carrying bags of cement.    

 Spray painting is another task suited to robots because robots do not need to breathe. Unlike human painters, they are unaffected by the poisonous fumes. Robots are better at this task, not because they are faster or cheaper than humans, but because they work in a place where humans cannot. 

 Third in the list of useful jobs for robots is the assembly of electronic parts. Robots shine at installing chips in printed circuit boards because of a capability that robots have that people don’t. A robot, Cnc machining once properly programmed, will mot put a chip in the wrong place. This automatic accuracy is particularly valuable in this kind of industry because locating and fixing mistakes is costly

Renoho Precision Machinery Technology Co.,Ltd: Controller and Power supply

Renoho Precision Machinery Technology Co.,Ltd: Controller and Power supply: Controller and Power supply   The controller in the robotic system is the heart of the operation. cnc machining parts  The controller sto...

Controller and Power supply

Controller and Power supply 

 The controller in the robotic system is the heart of the operation.cnc machining parts The controller stores preprogrammed information for later recall, control peripheral devices, and communicates with computers within the plant for constant updates in production   The controllers is used to control the robot manipulator’s movements as well as to control peripheral components within the work cell.

 The user can program the movements of the manipulator into the controller through the use of a hand-held teach pendent. This information is stored in the memory of the controller for later recall. The controller stores all program data of the robotic system. It can store several different programs, and any of these programs can be edited。

 The controller is also required to communicate with peripheral equipment within the work cell. For example, the controller has an input line that identifies when a machining operation is completed. When the machine cycle is completed, the input line turns on, telling the controller to position the manipulator so that it can pick up the finished part. cnc machining parts  Then, a new part is picked up by the manipulator and placed into the machine. Next, the controller signals the machine to start operation.

 The controller can be made from mechanically operated drums that step through a sequence of events. This type of controller operates with a very simple robotic system. The controllers found on the majority of robotic systems are more complex devices and represent state-of-the-art electronics. That is, they are microprocessor-operated. These microprocessors are either 8-bit, 16-bit, or 32-bit processors. This power allows the controller to be very flexible in its operation.

  The controller can send electric signals over communication lines that allow it to talk with the various axes of manipulator. This two-way communication between the

 8  robot manipulator and the controller maintains a constant update of the location and the operation of the system. The controller also controls any tooling placed on the end of the robot’s wrist.   The controller also has the job of communicating with the different plant computers . The communication link establishes the robot as part of a computer-assisted manufacturing (CAM) system.

  As the basic definition stated , the robot is a reprogrammable , multifunctional manipulator . Therefore , the controller must contain some type of memory storage . The microprocessor-based systems operate in conjunction with solid-state memory devices . These memory devices may be magnetic bubbles , random-access memory , floppy disks , or magnetic tape . Each memory storage device stores program information for later recall or for editing。

Power supply

  The power supply is the unit that supplies power to the controller and the manipulator . Two types of power are delivered to the robotic system . One type of power is the AC power for operation of the controller . The other type of power is used for driving the various axes of the manipulator .

  For example , if the robot manipulator id controlled by hydraulic or pneumatic manipulator drives , control signals are sent to these devices ,cnc machining parts   causing motion of the robot .  For each robotic system , power is required to operate the manipulator . This power can be developed from either a hydraulic power source , a pneumatic power source , or an electric power source , These power sources are part of the total components of the robotic work cell。

Renoho Precision Machinery Technology Co.,Ltd: The robotic system has three basic components

Renoho Precision Machinery Technology Co.,Ltd: The robotic system has three basic components: The robotic system has three basic components : the manipulator , the controller , and the power source   Manipulator    The manipulato...

The robotic system has three basic components

The robotic system has three basic components : the manipulator , the controller , and the power source

  Manipulator

   The manipulator , which does the physical work of the robotic system , consists of two sections : the mechanical section and the attached appendage .

   The manipulator also has a base to which the appendages are attached .

 The base of the manipulator is usually fixed to the floor of the work area . Sometimes , though , the base may be movable . In this case , Cnc machining the base is attached to either a rail or a track , allowing the manipulator to be moved from one location to another .

 As mentioned previously , the appendage extends from the base of the robot . The appendage is the arm of the robot . It can be either a straight , movable arm or a jointed arm . the jointed arm is also known as an articulated arm .

 The appendages of the robot manipulator give the manipulator its various axes of motion . These axes are attached to a fixed base , which , in turn ,Cnc machining  is secured to a mounting . This mounting ensures that the manipulator will remain in one location。

 At the end of the arm , a wrist  is connected . The wrist is made up of additional axes and a wrist flange . The wrist flange allows the robot user to connect different tooling to the wrist for different jobs

  The manipulator’s axes allow it to perform work within a certain area . This area is called the work cell of the robot , and its size corresponds to the size of the manipulator . Fig.2 illustrates the work cell of a typical assembly robot . As the robot’s physical size increases , the size of the work cell must also increase .

   The movement of the manipulator is controlled by actuators , or drive systems . The actuators , or drive system , allows the various axes to move within the work cell . The drive system can use electric , Cnc machining hydraulic , or pneumatic power . The energy developed by the drive system is converted to mechanical power by various mechanical drive systems .The drive systems are coupled through mechanical linkages .These linkages, in turn , drive the different axes of the robot . The mechanical linkages may be composed of chains , gears ,and ball screws.

The Robots

                The Robots

 The industrial robot is used in the manufacturing environment to increase productivity . It can be used to do routine and tedious assembly line jobs , or it can perform jobs that might be hazardous to do routine and tedious assembly line jobs , or it can perform jobs that might be hazardous to the human worker . For example , one of the first industrial robots was used to replace the nuclear fuel rods in nuclear power plants . A human doing this job might be exposed to harmful amounts of radiation .Cnc machining  The industrial robot can also operate on the assembly line , putting together small components , such as placing electronic components on a printed circuit board . Thus , the human worker can be relieved of the routine operation of this tedious task . Robots can also be programmed to defuse bombs , to serve the handicapped , and to perform functions in numerous applications in our society

 The robot can be thought of as a machine that will move an end-of-arm tool , sensor , and gripper to a preprogrammed location . When the robot arrives at this location , it will perform some sort of task . This task could be welding , sealing , machine loading , machine unloading , or a host of assembly jobs .Cnc machining  Generally , this work can be accomplished without the involvement of a human being , except for programming and for turning the system on and off .

 The basic terminology of robotic systems is introduced in the following :

  1. A robot is a reprogrammable , multifunctional manipulator designed to move parts , materials , tools , or special devices through variable programmed motions for the performance of a variety of different task . This basic definition leads to other definitions , presented in the following paragraphs , that give a complete picture of a robotic system . 

  2. Preprogrammed locations are paths that the robot must follow to accomplish work . At some of these locations , the robot will stop and perform some operation , such as assembly of parts , spray painting , or welding . These preprogrammed locations are stored in the robot’s memory and are recalled later for continuous operation . Furthermore , these preprogrammed locations , as well as other program data , can be changed later as the work requirements change . Thus , with regard to this programming feature , an industrial robot is very much like a computer , where data can be stored and later recalled and edited .

  3. The manipulator is the arm of the robot . It allows the robot to bend , reach , and twist . This movement is provided by the manipulator’s axes , also called the degrees

  6  of freedom of the robot . A robot can have from 3 to 16 axes . The term degrees of freedom of freedom will always relate to the number of axes found on a robot . 

 4. The tooling and grippers are not part of the robotic system itself  rather , they are attachments that fit on the end of the robot’s arm . These attachments connected to the end of the robot’s arm allow the robot to lift parts , spot-weld , paint , arc-weld , drill , deburr , and do a variety of tasks , depending on what is required of the robot . 

 5. The robotic system can also control the work cell of the operating robot . the work cell of the robot is the total environment in which the robot must perform its task . Included within this cell may be the controller , the robot manipulator , a work table , safety features , or a conveyor .

  All the equipment that is required in order for the robot to do its job is included in the work cell . In addition , Cnc machining signals from outside devices can communicate with the robot in order to tell the robot when it should assemble parts , pick up parts , or unload parts to a conveyor.