Theory and Design of CNC Systems Part 9 potx

7.7 PLC Configuration Elements 267 void CPLCStack::ANDS(char symbol, int AddNum, int BitNum) { if(m stack[1] && m stack[0]) m stack[1] = true; else m stack[1] = false; RShift(1); } l) ORS (OR STACK) • This command carries out the logical summation of SR0 and SR1 and sets the result to SR1. It also shifts the value stack register one place to the right. • Program structure - Ladder diagram - Coding sheet and operation result 268 7 Programmable Logic Control void CPLCStack::ORS(char symbol, int AddNum, int BitNum) { if(m stack[1]  m stack[0]) m stack[1] = true; else m stack[1] = false; RShift(1); } As mentioned above, the PLC executor performs the bit operations by using stack registers and, therefore, the execution time is very short. In general, it takes several tens of milliseconds to execute a PLC program with hundreds of lines. Depending on the performance of the PLC processor, the time for execution can be even shorter. 7.8 Summary A PLC system consists of a programming tool that is used for editing and loading a PLC program, Input unit, Output unit, processor unit, memories, and auxiliary units. AC and DC can be used for the input signal and output signal of a PLC system. Various inputs and outputs, such as On/Off signals and timers/counters, can be used. Textual language such as mnemonic and graphical languages such as the ladder diagram are used as PLC programming languages. Each programming language has a different structure and command list depending on PLC makers. This makes it im- possible to exchange PLC programs between different systems. In order to overcome 7.8 Summary 269 this problem, IEC1131, the international standard for PLC systems, was established. The programming languages specified in IEC1131-3 have come to be widely used. To satisfy the openness and compatibility of PLC systems, hardware-based PLC systems have come to be replaced by software-based PLC, the so-called Soft PLC system. A Soft PLC system is regarded as a software-oriented PLC system that is based on PC hardware. The behavior of the executor, being the key module of PLC system, is as follows. First, the PLC processor reads the input contacts and saves the values in the appro- priate input memory. Next, the PLC processor executes the operation and stores the operation result in the output memory. Finally, the PLC processor sends the values from the output memoryto the output module. Consequently, the PLC executor plays the role of performing bit operations based on the data in input memory according to the PLC program and saving the result in the output memory. Chapter 8 Man–Machine Interface The Man–Machine Interface (MMI) provides the interface that enables a user to op- erate a machine tool, edit a part program, perform the part program, set the parame- ters, and transmit data. In this chapter, the function and components of the MMI will be addressed, and programming methods such as CAPS (Conversational Automatic Programming System) will be described. In addition, for designing CAPS, the main functions and components of CAPS will be described. 8.1 MMI Function In order for a user to operate a machine effectively and to use the function of the machine optimally, it is necessary to design the operation panel for usability accord- ing to the machine–tool characteristics. In other words, an operation panel should be designed from the point of view of ergonomics, operation error prevention, key grouping and key allocation for specific machine tools with regard to user conve- nience. Figure 8.1 shows a typical operation panel and, in general, the operation panel can be divided into four areas. 8.1.1 Area for Status Display This area displays the machine status and NC parameters. It provides the graphi- cal user interface (GUI) for interaction between the CNC and the user. Figure 8.2 shows a typical display of this area and the functions related to the numbers shown in Fig. 8.2 are as follows. 1. Machining information: Displaying information related to the current machine status including the coordinates of machine tools, current part program, cutting tools and machine parameters. 271 272 8 Man–Machine Interface Status display area Data input area Machine operation area MPG operation area Fig. 8.1 Typical operation panel 2. Operation Mode: Displaying the operation modes of machine tools, such as zero position return mode, JOG mode, Automatic mode and MDI mode. 3. Program name: Displaying the name of the program that is currently loaded in the memory for machining. 4. Alarm window: Displaying the warning and alarm messages. 5. Key input window: Displaying the strings that are typed by a user. 6. Window for displaying user interface relevant to operation mode and function: • Machining status (POS): operation status such as axis position, spindle speed, feedrate, modal G-codes, and tool number is displayed by this function. • Program (PROG): the GUI for editing a part program, managing the program folders, graphical simulation, and CAPS is provided by this function. • Tool management: the GUI for managing tool compensation, tool life, and tool offset is provided by this function. • Parameter and system: the GUI for managing the NC parameters, system pa- rameters for servo and spindle is provided. • Auxiliary application: the GUI for monitoring PLC, displaying alarms, per- forming DNC, and compensating pitch error is provided. 8.1 MMI Function 273 7. Function keys: these keys are horizontally placed in the bottom or vertically on the right-hand side of the display and are mapped to the particular functions. There- fore, to effectively design the menu structure, it is important to classify the func- tions into the appropriate group and enable the necessary keys to be displayed in one display. It is necessary to consider that the number of hierarchical layers in- creases if CNC functions are grouped and are designed as a hierarchical structure. Therefore, if the user wants to select a particular menu at the bottom of the hier- archical structure, the user has to select a sequence of menus from the top menu to the bottom menu. Also, the user has to remember the hierarchical structure and the menus located in each layer. This problem makes the user interface inefficient. To overcome this problem, it is necessary to design a ring menu structure of menu trees where, by selecting the displayed menu tree, the user can carry out the de- sired task from the function keys displayed on one screen as much as possible and each function keys is connected with the various modes. In this type of menu structure it is not necessary to remember the menu structure. However, the menu structure may be inconsistent and many function keys may be required. 8.1.2 Area for Data Input As this area is the keyboard for inputting user data to the CNC system, it consists of alphanumerical input buttons and hot keys for executing the functions of CNC. 8.1.3 Area for MPG Handling This area consists of the MPG (Manual Pulse Generator), the MPG handle ON/OFF switch and the feed ratio selection key that are used for the user to move each servo axis manually. In addition, the Chuck CLAMP/UNCLAMP key for manually loading and unloading tools to the spindle and the emergency stop button are located in this area. 8.1.4 Area for Machine Operation This area consists of many kinds of switch and lamp that provide various functions as follows. 1. Mode selection switch: for selecting Auto mode, MDI mode, Teach-In mode, Re- turn mode, JOG mode, Handle mode, Incremental Moving mode, and Rapid Mov- ing mode. 274 8 Man–Machine Interface Current Coordinate X 123.999 Y 246.000 Z 000.000 U 000.000 W -40.100 Feed Actual 19.99 mm/min Set 20.00 mm/min Override 100% Spindle Actual 3000.02 RPM Set 6000.00 RPM Override 50% Machine Coordinate X 111.000 Y 000.000 Z 120.000 U 000.000 W 110.100 Distance to Go X 3.999 Y 6.000 Z 0.000 U 0.000 W 10.100 Tool# 7 Work Counter 125 Running Time 08:35 Input Feed Rate? Machine Program Parameter Tool Service PG EDIT Test Save Light Machine Auto Prog. #1 Emergency Stop ON (1) (2) (3) (4) (5) (7) (6) Fig. 8.2 Typical machine status and NC parameters display area 2. Rapid Override button: by using this button, rapid feed can be adjusted in scale to 10%, 50%, and 100%. 3. Feed override switch: by using this switch, the commanded feedrate can be ad- justed from 10% to 150%. 4. Spindle speed override switch: using this switch, the commanded spindle speed can be adjusted from 50% to 150%. 5. Spindle handling buttons: these buttons consist of the spindle start button, the spindle stop button, rotation direction selection button, and the spindle orientation button, inverse. These buttons are used in MDI mode. 6. Cycle Start button: This button is used for starting the auto-execution or resuming the execution of a part program during feed hold state. 7. Feed Hold button: This button is used for temporarily stopping the axis move- ment in automatic machining. When the button is pushed, the spindle continues to rotate. If any axis of the machine tool is moving, that axis is stopped after deceleration. 8.2 Structure of the MMI System 275 8. Single Block Button: Single block execution means that in auto mode or MDI mode, the execution of a part program is stopped after the execution of one block has been completed and the next block begins only after the Cycle Start button has been pushed. The single block button turns on or off single block execution mode. If this button is ON during the execution of a part program, the CNC system goes into the idle state after completing the executed block. If this button is OFF, the remaining blocks are executed. 9. Zero return button: This button is used for making each axis return to the zero po- sition. All axes can be returned to the zero position simultaneously. Feed override is validated during zero return. 10. Emergency Stop button: This button is used for stopping the machine in an abnor- mal state as soon as possible. 11. Part program modification Lock/Unlock key: This key is used for preventing an unauthorized user from modifying, editing, or deleting part programs or prevent- ing unintended modification of a part program due to incorrect operation by a user. 12. Door Interlock key: In the case that this key is ON, if a door is opened while the spindle is rotating, the emergency stop is invoked. 13. In addition, there is an OT (Over Travel) cancel button that temporarily cancels safety mode when an axis moves beyond its set limit, a power switch, and a reset button that initializes the CNC system. 8.2 Structure of the MMI System The ultimate design goal for the MMI system is to provide ease of operation and various functions for users. Following this trend, MMI has advanced to become PC- based MMI that is operated by an individual processor and allows various functions and advanced functions to be invoked from a single panel whereas traditional MMI only allows simple operations. PC-based MMI allows the usage of a graphical user interface that replaces the earlier simple textual user interface. It also allows a CAM system to be used on the CNC system itself and enables the CNC system to communicate with external equipment. Furthermore, the user can use the various functions normally found on a PC. In recent times, the majority of PC-based MMIs use Windows OS from the Microsoft Corporation as an operating system, which makes third-party development and deployment of MMI applications relatively easy. Accordingly, the MMI system of PC-based systems are developed continuously to meet various user requirements. The details of PC-based systems will be addressed in Chapter 9. As shown in Fig. 8.3, the structure of the MMI software can be divided into three layers; Application layer, Kernel layer, and OS layer. The application layer is composed of the applications with which the user inter- acts. The following MMI functions belong in this layer and each application is made in stand-alone executable file format. 276 8 Man–Machine Interface Operation system Keyboard Communication Alarm Task manager Boot-up Display File Part programming Cycle programming Dialog programming PLC mointoring Error history management Serial communication Parameter setting for machine, programming and user Tool offset Tool monitoring Tool data Graphic simulation Manual operation Automatic/M DI operation Kernel layer OS layer Application layer Fig. 8.3 MMI software structure 1. Machine Manager: This program monitors the machine status and displays the real-time tool path during machining in Auto mode or MDI operation mode. 2. Parameter Manager: The user can edit NC parameters and system parameters using this program. 3. Program Manager: This program provides the functions for editing G-code pro- grams and managing part programs such as saving and deleting. 4. Tool Manager: This program is used for editing and managing the tool informa- tion, such as tool offset, tool life, and tool geometry. 5. Utility: Service functions of the CNC system such as alarm history management, PLC monitoring, DNC, and communication with external systems are provided. The functions provided in the application layer may be added, deleted, or replaced according to the user’s needs. Therefore, in order to make this possible, openness should be considered when the kernel layer is designed. As the kernel layer is the core of the MMI software, it plays the role of linking the applications and the NCK. It sets environment variables during system boot-up, links application modules with key input and alarm/help file, and transfers files and parameters. The binary modules for executing the following functions are placed in the kernel layer. The modules are automatically linked with the applications while the CNC system is running. 1. System boot-up: This function initializes the variables of the operating system and system boot manager for setting the language type of MS Windows, machine parameters, etc. 8.2 Structure of the MMI System 277 2. Communications interface: This carries out communication and data exchange with the NCK and PLC. It manages the services for sending the data required by the user to the MMI for display. 3. File management: This provides the services for managing folders and files, such as copying, saving, deleting, and changing part programs and PLC programs. 4. Alarm: This displays alarm and error messages from the machine, PLC, and MMC in the alarm window. It manages the history and displays the help information. 5. Key input: This transmits the key input from soft keys, keyboard, and dialog boxes to the applications and the CNC system. 6. Screen Display: This handles the horizontal or vertical function key window that is shared by all applications and connects the function keys with particular appli- cations. In addition, it provides the interface for handling MMI soft keys. 7. Task manager: This executes the programs registered in the application layer and provides the function for calling and switching them. It registers the applications as a program list in a text file format and executes the applications sequentially when the task manager begins. When the task manager is terminated, it termi- nates the applications in reverse order. The basic functions can be summarized as follows. • Registering/terminating applications • Defining the execution sequence for applications and initializing them while booting up. • Switching applications while they are executing. • Monitoring system resources. An MMI system based on PC hardware typically uses a PC operating system as OS. MS Windows or Linux have both been used (recently, Windows embedded XP and Windows CE have become widely used) However, these operating systems cannot provide the real-time capabilities required by a CNC system. Generally, an MMI system requires a non-real-time environment, whereas an NCK system needs a real-time environment. Therefore, when the overall architecture of the CNC system is designed, techniques to overcome the non-real-time capabilities of the PC operating system must be considered. One simple solution is to use two operating systems, using a PC operating system (non-real-time OS) and a hard real time OS for the MMI and NCK systems, respectively. In this case, it is very important to regard the execution of the MMI system as one specifictaskintheNCKsystem. In the MMI, various applications are executed based on the kernel and the user interface for editing a part program, which is one of the key applications in MMI. In general, the machine tool operator spends a lot of time learning how to generate a part program. So, from the MMI designer’s point of view, the MMI should be designed for the MMI to be able to provide the most efficient method for generating a part program. In the following sections, the advantages and disadvantages of various programming methods will be discussed. The design of an efficient programming system will also be addressed. [...]... Interface 8.3 CNC Programming In order to machine the part in a drawing by using CNC machine tools, it is necessary to generate a series of instructions for activating those CNC machine tools This task is called CNC programming 8.3.1 The Sequence of Part Programming Roughly, CNC programming is composed of the generation of a process plan from a part drawing and the generation of the part program The... within CNC equipment but also outside the CNC equipment Due to the differences in terms of function and design concept between CNC makers, each CNC system has a slightly different programming instruction set compared 280 8 Man–Machine Interface with other CNC systems, although the EIA/ISO standard for programming instructions exists This makes it difficult for a programmer to use a variety of CNC systems. .. in APT The part program consists basically of four parts; 1) the shape definition part where the shape for the machined part is specified, 2) the motion definition part where the tool paths are specified, 3) the post processor part where cutting conditions and the characteristics of the CNC system are specified, and 4) the Auxiliary part where auxiliary data such as tool size, workpiece number, and so on... examples of this type of system, such as CATIA, MasterCAM, EdgeCAM, so on As the above-mentioned conversational programming system is an of ine system, a part program is generated on an external computer rather than on the CNC system Because of this, the part program has to be transferred to the CNC system via a DNC system Therefore, the creator of the part program and the operator of the part program... operations and cutting conditions, it is easier to use than APT However, the kinds of machineable part shape that can be handled are more limited than with APT • FAPT FAPT was developed by FANUC and is similar to APT FAPT can be used in carry-on exclusive programming equipment By using particular programming software such as FAPT Turn, FAPT Mill, and FAPT DIE-II, part programs for turning, milling, and die and. .. tool interference, overcut, undercut, and aircut, and determining the operation sequence that minimizes the cutting time and tool change 2 A unique method for specifying the part shape is needed In order for an operator to generate a part program quickly at the machine, a simple and easy way of specifying the part shape is needed instead of an of ine CAD system  296 8 Man–Machine Interface 3 In addition,... complicated parts is restricted The shopfloor programming system in CNC can be widely used for generating a part program on a variety of machine tools In particular, when this programming system is applied to machines that produce parts with simple 2D, 2.5D, and primitive 3D shapes, it is possible to improve productivity and flexibility Considering that an operator edits the part program at the front of a machine,... EDG MTR 294 8 Man–Machine Interface 8.5 Conversational Programming System Design As the shapes of parts have become more complex and their accuracy has increased, so has part programming become more difficult At the same time, on the shopfloor, the number of expert programmers has decreased Because of this, a conversational programming system has become an essential function of an advanced CNC system... 8 9 To analyze the part drawing To decide on the removal volume and to select the machine To decide on the jig and chuck To decide on the setups, machining sequences, cut start points, cut depths for roughing and finishing allowance To select tools and tool holders and to decide on the tool position To decide on the technology data such as spindle speed, feedrate, and coolant on/off To generate the part. .. interface The majority of CAM systems have CAD functions as methods to specify the part shape and features However, 8.5 Conversational Programming System Design Categories File type Work material 297 Contents Main Program / subprogram Workpiece material is classified in terms of the hardness of material Unit, Length, Width, Height, Face-off Work Size Initial point - Z The Z position where tool and workpiece . programming. 8.3.1 The Sequence of Part Programming Roughly, CNC programming is composed of the generation of a process plan from a part drawing and the generation of the part program. The detailed. than on the CNC system. Because of this, the part program has to be transferred to the CNC system via a DNC system. Therefore, the creator of the part program and the operator of the part program. mode, Handle mode, Incremental Moving mode, and Rapid Mov- ing mode. 274 8 Man–Machine Interface Current Coordinate X 123 .99 9 Y 246.000 Z 000.000 U 000.000 W -40.100 Feed Actual 19. 99 mm/min