DEVELOPMENT OF STEP-NC CODE GENERATOR FOR MILLING BASED ON

INFORMATION

PRESENTED BY

ABHILASH SINGHBranch-CAD/CAM

2012CC11

THESIS SUPERVISOR

Dr. V.R. KOMMA MED, MNNIT

INTRODUCTIONWhen a CNC machine appeared on the market people have followed a dream of automatically manufacturing products.

In the last 50 years CNC machines have evolved from simple, perforated paper belt controlled machines to today’s high-end machines controlled by multiprocessor workstations.

The people do something with the drawing & what they do is usually on a CAD system. This can introduce a new problem. If the CAD systems are from different vendors they may, & usually do, represent the same information in different form.

The CAD, CAPP and CAM software vendors realized that they need to have a standardized and open format to transfer information in the process of product and manufacturing planning.

During 1980s many different data formats for geometry transfer were proposed.

IGES(Initial Graphics Exchange Specification ) but none of them satisfied all the needs of software developers and users.

Some problems related to IGES are- Poor pre-processors & postprocessors. The size of the IGES file & the time it took to process them. Inability to translate all the information stored in the sending CAD system.

introduction

The international community started to develop the ISO 10303 group of standards which are today known under the name STEP.

Standard for Exchange of Product Model Data(STEP) is a large & powerful set of ISO(International Organisation for Standardization) standards, all under ISO 10303. STEP provides both broadly useful data modelling methods & data model focussed on specific industrial uses.

STEP is its ability to support many different application protocols which can be used in wide range of applications.

STEP-NC is one of the application protocols of the STEP standard. Its main goal is to support the interchange of geometry and technological data between CAD, CAM and CNC controls.

introduction

e-Manufacturing for DA-BA-SA

What is STEP-NC System ?

What is STEP-NC System ?

A designer, “A” makes a 3D design by ANY CAD system in Korea. A CAM specialist “B” in the USA generates a process plan by ANY CAM system for manufacturing the design transmitted through the internet. Operator “C” in South Africa downloads the design and its process plan and executes the ANY CNCFRONT simulator, followed by machining with ANY MACHINE controlled by INTELLIGENT CNC.

When the operator clicks on “Cycle Start” button, machining isstarted. During the machining operation, the INTELLIGENT CNC controls the machining operation precisely in an optimized way. With adaptive capability in handing unexpected situations such as tool wear/breakage/unavailability.

HISTORY OF STEP STEP evolved from earlier effort in building data standard for CAD, particularly Initial Graphic & Exchange Specification (IGES) the first version of which was released in 1981.

Many of the organisation & people who worked on IGES were aware of its weakness collaborated in building the next generation product data standard, PDES , the Product Data Exchange Specification, which first appeared in 1984. IGES & PDES were U.S national effort, but similar work was being done in France, Germany, & U.K. in 1984.

ISO TC 184/SC4(Technical Committee 184, Sub Committee 4) resolved to try build a standard for computerized product model data. Much of the expertise that has gone into building IGES & starting PDES were transferred to the new international effort that become as STEP.

The first version of STEP to become ISO standard was adopted in 1994 & companies such as GE, Boeing, & GM began announcing commitment to using STEP in 1995.

WHY STEP-NC? Programming with G-code. results huge programmes which are difficult to handle.

Problems with G&M Codes (Information loss, Difficult traceability)

last-minute changes or correction of machining problems on the shop floor are hardly possible and control of programme execution at the machine is severely limited.

Due to many different vendor-specific additions to the programming language, part programmes are not interchangeable between different controls. As a result, porting programs between machines is difficult.

NEED FOR STEPThe manufacturing environment has been changing, with more collaboration & intelligence since 1990s. High speed machining, high-precision machining & multi-axis complex machining have extensively enhanced the productivity & quality of manufacturing.

DA-BA-SA(Design anywhere, Build anywhere, Support anywhere) can be realized via the collaborative scheme of distributed manufacturing system & CIE.

OBJECTIVES OF STEP To provide a mechanism that describes a complete & unambiguous product definition throughout life cycle of product (i.e. design, manufacturing, utilization & disposal).

It permit different implementation method to be used for storing, accessing, transferring & archiving product data.

Exchange & sharing. To create a single international standard covering all aspect of CAD/CAM data exchange.

Objective of STEP-NC Providing an information bus for manufacturing running in the world via the internet and that realizing seamless DA-BA-SA.

To cover the current and expected future needs for data exchange.

To use standard, modern languages and libraries for the implementation of the data model.

To create an exchangeable, workpiece-oriented data model for CNC machine tools.

STEP TOOLS STEP uses a formal specification language, EXPRESS, to specify the product information to be represented. The use of formal languages enables precision & consistency of representation & facilitates development of implementation.

STEP uses Application Protocols (APs) to specify information for one or more application.

IMPORTANT AP’sAP 203: “Configuration controlled 3D design

of mechanical parts & assemblies”.AP 219: “Manage dimensional inspection of

solid parts or assemblies”.AP 224: “Mechanical product definition for process planning using machining feature”.AP 240: “numeric control process plan for

machined parts”.AP 238(STEP-NC): “Application interpret

model for computerized numeric controller”.

STEP tools...

AP’s HARMONIZATION IN INTEGRATED MANUFACTURING ARCHITECTURE

STEP tools...

AP 203It is used for data exchange for different CAD/CAM systems.

It forms a neutral format based on boundary representation technique using geometry of the parts.

STEP tools...

AP 224AP224 was the first AP to define & use machining features within ISO 10303. The purpose of AP224 is to bridge gap between design & manufacturing by providing machine part information that ensures design information is 100% complete, accurate, computer interpretable & reuseable.

STEP tools...

AP 240 It defines macro, high level, process plans for machining parts.

AP240 process plan defines the sequence of machine process.

Each machining process identifies the machines tool, the machine setup, clamping, a list of machine operations, & a list of machining feature that are eligible to be machined per process.

STEP tools...

AP 238(STEP-NC)(ISO-14649)It is the next step in manufacturing after AP240.

This AP defines micro process planning function.

AP238 defines setup, sequential worksteps, cutting tool specification for tool like drill, tap, boring tools & reamer.

AP238 defines how to make geometry from a piece of stock by removing metal volumes defines as AP224 in a sequential order with specific tolerances with tools that meet all engineering & design requirement.

STEP tools...