Numeric Control is operation of machine tools by the agencies of specifically coded instructions to the machine control system. The instructions are combination of the letters of alphabet, figure and selected symbols. The aggregation of all instructions necessary to machine a portion is called an NC plan, CNC Program or Part Program. The plan can be stored for a hereafter usage and used repeatedly to accomplish indistinguishable machining consequences at any clip.
The BASIC of adding NC ( Numerical Control ) is really simple that is add some electronic and actuator to command the place and replace the manus wheel by a placement motor. NC can mention to the automated machine tools which operate harmonizing to the abstractly programmed bids encoded on a storage medium or manually controlled via manus wheel or levers. Between the old ages of 1940 to 1950 the first NC machine which used clout tape was built. The accountant nowadays consist a simple computing machine with a special-purpose keyboard and a show for operator enter the sequence of motions ( the NC plan ) which was called CNC ( Computerized Numerical Control ) and utilizing this method to command the machine. An illustration coding for CNC is like “ G0X10Y20Z30 ” is for “ machine in a consecutive line from the current place to place ( 10, 20, and 30 ) ” . This is really labour intensive, and this is where CAM package comes in to ‘automatically ‘ generate NC plan files.
The CAD ( Computer Aided Design ) package assists applied scientists and interior decorators to plan and fabricate physical merchandises. CAD package is frequently referred to as CAD/CAM package ( Computer Aided Machining or Computer Aided Manufacturing ) .
Presents, the CNC machines had radically changed the fabrication industry. With the increased mechanization of fabrication procedures with CNC machining betterments in consistence and quality have been achieved. A series of CNC machines may be combined into one station in a production environment. CNC machine today are straight control from the file created by CAD package. That a portion or assembly can travel straight from design to fabrication without the demand of bring forthing a drafted paper drawing of the manufactured constituent.
Sing to Liu et Al. research on CNC construct was extended to ONC and DNC. ONC is unfastened numerical control which means that NC has a incorporate external criterion accountant interface. DNC ( direct numerical control ) hold legion component plans with one cardinal computing machine and can serve for assorted dissimilar machine and the informations can be stored if needed.
Besides come ining codifications, programming can be done besides by digitising or scanning. Digitizing is used in operations like sheet metal punching and hole boring. While, scanning is apply on complex free-form shaped by manually traveling a tracer over the contour of a theoretical account or pre-machined portion. The information for the motions are converted into tape by a minicomputer.
2.0 Position of CAD, CAPP, CAD/CAM and CNC Control Software in the Manufacturing Procedure
Presents, typically four different package plans are used in industry to fabricating a portion which are CAD, CAPP, CAM and CNC control package. Each of the package has different functionality and communicated between each other in the fabrication procedure. Figure 2.1 shows the place of CAD, CAPP, CAD/CAM and CNC control package in the fabrication procedure.
Figure 2.1: Position of CAD, CAPP, CAD/CAM and CNC Control Software in the Manufacturing Procedure
First, the CAD package is used to do the design of the portion. CAD package is a patterning tool used by designers and applied scientists to plan 3-dimensional objects. This package is used to make new merchandises or intensify the apprehension of bing merchandises. There are several types of computer-aided design and computer-aided fabrication package ( CAD/CAM ) that are listed as CAD plans.
Second, the CAPP ( Computer-aided Process Planning ) package is used to do basic determinations sing equipment to be used, tooling and operation sequence demand. If NC machining procedures are involved, CAPP package exists which will choose tools, provenders, and velocities, and prepares NC plans. CAPP is a span for CAD and CAM to do determination on the procedure choice, procedure sequencing, operation planning, coevals of instructions, etc ( Figure 2.2 ) . In other word, CAPP represents a transcriber or informations transformer ( Han, 2000 ) .
Figure 2.2: Function of classical CAPP ( Han, 2000 )
Next, the CAM package is used to cipher the tool waies based on the design, and set up machining operations such as counterbalancing for the cutter ‘s geometry, adding provender rate and spindle bids, etc. CAM allows interior decorators to import CAD files and control specific fabrication equipment. Typically, these tool waies are stored in cutter location ( CL ) format and exported to a postprocessor for transition to a NC plan.
Communication between the plans is done utilizing files. From CAD to CAM the design is transferred utilizing a file format for geometry informations exchange. The most widely used formats are IGES, STL and STEP for 3D, DXF for both 2D and 3D, and Postscript and HPGL for 2D applications. These are standard formats that in most instances can be used without any particular configuring needed. IGES ( Initial Graphics Exchange Specification ) is the most comprehensive criterion and is designed to interchange the full merchandise information between assorted CAD systems. STEP ( Standard for the Exchange of Product model Data ) is a method for interchanging merchandise theoretical account information. Measure defines the execution methods, geometrical form of a merchandise and others to wholly specify a merchandise throughout its full life. While, DXF ( Pulling Exchange Format ) was develop and support by Autodesk for usage with the AutoCAD drawing files.
CNC control package is used to read the tool waies and allow the machine really travel along these waies. CNC fabrication uses a particular coder to stipulate the machining operations. In bend, the CAM package creates the CNC plan.
Communication from CAD to Control package is done utilizing NC plan files, for which many formats do be. In most instances the format will be a ( minor ) fluctuation on the ISO / DIN G-code format. G-code is supposed to be a criterion ; nevertheless in pattern each maker chooses a spot different execution ( Lennings, 2001 ) . Hence postprocessor, a portion of the CAM package that translates the tool way informations into the right file format when economy is used to tune CAM end product so that it can run into the demands of the NC accountant used.
In some specific state of affairss one of the four plans ( CAD-CAPP-CAM-CNC Control ) can be ignored. For illustration some machines can be used without control package or in some apparatuss a secret plan file from the CAD system can be instantly sent to the control package, jumping the CAM measure ( Lennings, 2001 ) .
Types of CAD, CAPP, CAD/CAM and CNC control package
CAD is an application of computing machines and artworks package to assistance or heighten the merchandise design from conceptualisation to certification. CAD systems play an of import function in the mechanical design and geometric mold of merchandises and constituents. Existing CAD package availble in the market is AutoCAD, ProEngineer, Solidworks, CATIA, Unigraphics and I-DEAS. CAD possibly used to plan curves and figures in planar ( 2D ) infinite ; or curves, surfaces or solids in three dimensional ( 3D ) objects.
There are several grounds for utilizing a CAD system to back up the technology design map ( Ali, 2010 ) :
To increase the productiveness
To better the quality of the design
To uniform design criterions
To make a fabrication information base
To extinguish inaccuracies caused by hand-copying of drawings and incompatibility between drawings
CAM is defined as the effectual usage computing machine engineering in fabricating planning and control. CAM is most closely associated with maps in fabricating technology, such as procedure and production planning, machining, programming, direction, quality control, and numerical control ( NC ) portion programming ( Ali, 2010 ) .
Computer-aided design and computer-aided fabrication are frequently combined CAD/CAM systems. With this combination the information is transportation from the design into the phase of be aftering for the fabrication of a merchandise. The databases is stored foremost and so travel to CAM to treat the necessary informations and instructions for operating and commanding production machinery, stuff handling equipment, and automated proving and review for merchandise quality.
The 10 largest CAM package merchandises and companies, by terminal user payments in twelvemonth 2008 are ( Magenthran, 2010 ) :
CATIA from Dassault Systems
Cimatron from Cimatron Group
Edgecam from Planit ( Pathtrace )
Mastercam from CNC Software
NX ( Unigraphics ) , from Siemens PLM Software
Powermill from Delcam
Pro/E from PTC
Space-E/CAM from NDES ( Hitachi Zosen )
Tebis from Tebis AG
WorkNC from Sescoi
Software allows the human user to turn a hardware constellation into a powerful design and fabrication system. CAD/CAM package falls into two wide classs, 2-D and 3-D, based on the figure of dimensions are called 2-D representations of 3-D objects is inherently confounding. Equally job has been the inability of fabrication forces to properly read and construe complicated 2-D representations of objects. 3-D package permits the parts to be viewed with the 3-D planes-height, breadth, and depth-visible. The tendency in CAD/CAM is toward 3-D representation of in writing images. Such representation approximates the existent form and visual aspect of the object to be produced ; hence, they are easier to read and understand.
Applications of CAD/CAM
The outgrowth of CAD/CAM has had a major impact on fabrication, by standardising merchandise development and by cut downing design attempt, trial, and prototype work ; it has made possible significantly reduced costs and improved productiveness.
Some typical applications of CAD/CAM are as follows:
– Scheduling for NC, CNC, and industrial automatons ;
– Design of dies and casts for casting, in which, for illustration, shrinking allowances are pre-programmed ;
– Design of tools and fixtures and EDM electrodes ;
– Quality control and review — — for case, coordinate-measuring machines programmed on a CAD/CAM workstation ;
– Procedure planning and programming.
AutoCAD is a computer-aided drafting and design system implemented on a personal computing machine. It supports a big figure of devices and besides 2-D drafting and 3-D wire-frame theoretical accounts. The system is designed as a single-user CAD bundle. The drawing elements are lines, polylines of any breadth, discharge, circles, faces, and solids. Text and dimension symbols can be placed on anyplace on the drawing, at any angle, and at any size any founts.
Types of CAM package
A clear difference is present between CAM package for 2D and for 3D applications. With 2D is meant that the CAM system imports a 2D pulling file and calculates a toolpath with all motions taking topographic point on a changeless Z-level. Obviously several toolpaths on different Z-levels can be combined to make a 3D consequence, which is called 2.5 D machining ( note that more definitions of the impression 2.5D do be ) . In that instance to user has to come in the right Z-level to be used for each toolpath. A 3D CAM system in contrast imports a full 3D CAD theoretical account and calculates toolpaths to make a 3D consequence. Note that in this instance besides toolpaths on changeless Z-level may be used ( waterline machining ) , nevertheless these are automatically generated. Many CAM bundles do offer both 2D and 3D, nevertheless still have their clearly recognizable foundations in one of both Fieldss.
A 2nd differentiation is between simple and high-end CAM package. The high-end material is meant for professional toolmakers, which are adept and willing in commanding any machining parametric quantity for an optimal consequence. These excess high-end parametric quantities are ( Lennings, 2001 ) :
I ) support for a 4th axis, or for full 5 axis machining
two ) optimisation for high velocity machining ( changeless tool burden )
three ) particular sequences for nearing and go forthing the geometry ( ledes )
four ) automatic measure over computation
V ) a broad pick of machining schemes, like analogue, coiling, radial, pencil tracing, level surface acknowledgment, countervail machining, dip milling and automatic smoothing of about perpendicular surfaces.
six ) automatic sensing and remotion of remainder stuff
seven ) direction of undercuts
eight ) rendered machining simulations.
The NC system uses fixed logical maps, those that are constitutional and for good wired within the control unit. Theses map can non be changed by the coder or the machine operator. Because of the fixed wiring of the control logic, the NC control system is synonymous with the term hardwired. The system can construe a portion plan, but it does non let any alterations to the plan, utilizing the control features. All the needed alterations must be made off from the control, typically in an office environment. Besides that, the NC system requires the compulsory usage of punched tapes for input of the plan information.
Sing to Lennings ( 2001 ) , the NC Program besides can utilize for the ‘file that contains all toolpath information ‘ , exported by the CAM system and imported by the control package. The plan is average package ; sometimes the word “ NC plan ” is used for a ‘Program to cipher NC informations ‘ and for the CAM package.
The capablenesss of the machine must fit the demands of the CAM package. One demand should be checked is 3D line insertion. This means the possibility to go from point to indicate in a consecutive line in full 3D. This is hard to all three axes will hold to maintain up a different velocity. Some machines are merely capable of consecutive lines affecting 2-axes ( 2D line insertion ) .
Another of import machine capableness is online machining. Online scheduling is the act of come ining codification on the console of the CNC control. The capableness of machine to manage big NC plan files straight from the computing machine ‘s difficult disc. This involves some handshake between the Personal computer and the accountant, as in most instances the information transportation will be faster than the existent machining. However, there are many CNC machines can non be designed for NC plans that are wholly entered by manus, so see a 100 Kb NC plan file as really big. Those older machines require the complete NC plan file to be transferred before the machining can get down, restricting the file size to the 256 Kb of available internal memory.
Last, offline scheduling is the NC scheduling completed on a computing machine system, which is separate from the CNC control. NC portion plan is constructed and it must be typed into a computing machine at some point before we can utilize them. The codification is typed on a Personal computer, saved as text file and so moved to the machine tool. By and large talking, it is non really efficient to stand on the store floor and identify a plan into the machine tool. The keyboards and control are hard to utilize compared to modern and desktop personal computing machine. Furthermore, a typical control lacks the advanced redaction characteristics of a text editor or word processor. A more efficient method of making NC portion plans is to type them offline and so download the codification to the machine tool.