STEP NCTool path programming in an intelligent Step NC Manufacturing Context

Adopted and edited from a presentation made by:Raphaël LAGUIONIE - Matthieu RAUCH – Jean-Yves HASCOET

Institut Recherche Communications Cybernetique Nantes (IRCCyN) France.

Scope

Introduction & Applications

Step_NC: A new approach– Lacks of curent G-code– A new vision: Step_NC– Machining strategies in a Step_NC file– The Korean Step_NC prototype

Pattern strategies– A new method to build toolpaths– Proposition of integration in Step_NC standard

Validation of the proposition– Implementation in PosSFP (Shop Floor Programming System)– Development of a Step_NC numerical chain– From the CAD model to the machined part…

Conclusion

IntroductionThe STEP-NC AP238 StandardThe STEP-NC AP238 standard is the result of a ten year international effort to replace the RS274D (ISO 6983) M and G code standard with a modern associative language that connects the CAD design data used to determine the machining requirements for an operation with the CAM process data that solves those requirements.

Enabling e-Manufacturing for Mechanical PartsSTEP-NC allows manufacturing organizations to seamlessly share machining and measurement information between machines and over the Internet. The emerging STEP-NC technology is yielding process improvements including a 15% reduction in machining time. The automated measurement and compensation enabled by STEP-NC promises to yield parts that meet higher accuracy requirements for less cost. The integrated simulation and verification enabled by STEP-NC promises to guarantee that every part will be made correctly and that production will stop whenever cuts are about to be made that do not meets design requirements.

Resources: Step Tools, Inc. http://www.steptools.com/library/stepnc/

Working Steps & AdvanctagesWorking StepsSTEP-NC changes the way that manufacturing is done by defining data as "working steps": a library of specific operations that might be performed on a CNC machine tool. In other words, it breaks down every machining operation into the steps required to perform the operation. In the past, CNC machine tools had to be programmed using G and M codes (from ISO 6983), which were instructions that only told the machine what moves to make, without any semantic content that referred to the part being processed. STEP-NC will make G and M codes obsolete.

AdvantagesWith the concept of "working steps" in place, the manufacturing process becomes streamlined. Now, a machine tool can receive a file with STEP-NC data, "know" what it means, and proceed milling the piece without any more instructions. There will be no more programming the machine tool for each individual piece. Moreover, the benefit of the standard goes further. With a set of standard "working steps" in place, all manufacturers will be able to share information reliably and instantaneously. A STEP-NC converted CAD file that is completed on the east coast can be sent over the internet to a machine shop on the west coast and they can immediately start milling the part.

Resources: Step Tools, Inc. http://www.steptools.com/library/stepnc/

ApplicationsStep NC will enable:-• Smart Process Control

• Smart Process Monitoring• Smart Manufacturing

The current programming standard : G-code

CAM Post-processor

M216 G0 Z25 G0 X50 Y60 G1 X95 M02

G-Code

• Based on principles of the 60’s

• Ambiguous semantics in some cases

• Vendor-specific extensions

• Difficulty of changes on the machine tool

• Impossible Feed back

• Use of post-processors

As many configurations as CAM softwares / machine tools

• more than 4500 today

Step_NC: a new approach

Benefits of Step_NC A new vision of the numerical chain

Total integration of CAD-CAM-CNC

No information lost

Implementation of a single file

Bidirectional data flow

Design Production Planning Production

CAD

Simulation

Step_NC

CNC

CAM

Step_NC: a new approach

• No more post-processors, no G & M codes• Machine-unspecific program

Comparison G code – Step_NC

CAD/CAM

Post-Processeur

CAO/FAO

Shoop floor

Design NC planning

Step_NC

bidirectional data flow

Curent Standard : G codes Step_NC StandardDescription of

entitiesToolpaths description

Step_NC: a new approach

CNC in Step_NC numerical chain

Axis command

Part machining

Operations schedulingToolpaths generation

Machine tools characteristics

Data process estimationEntity

geametryMachining parameters

ToolsWorplan Etc.

Read of Step_CN file

Step_NC

Simulation

CAM

CAD

CNC

Step_NC: a new approach

Structure of a Step_NC file

…

Step_NC: a new approach

Korean prototype of Step_NC numerical chain

11

PosSFP :

Feature recognition

Choice of machining strategies attributes

Step_NC file generation

Machining entities

Step_NC: a new approach

Study situation in Step_NC developmentInterpreted Step_NC programming

Step_NC Interpreter

G-code CNC

G-code File

Interpretation Read File

Axis command

Operations schedulingToolpaths generation Post processing

Part machining

Step_NCfile

Integrated Step_NC programming

CNC

Interpretation Axis command Part machining

Machine tool characteristics

Résultats de mesure ou autres données pièce

Operations schedulingToolpaths generation

Step_NCfile

Advanced Step_NC programming

CNC

Interpretation

Process data estimation

Axis command Part machiningOperations schedulingToolpaths generationStep_NC

file

Machine tool characteristics

First step :

Goal :

Interpreted programming

Evolution with :

Integrated programming

Advanced programming

Step_NC: a new approach

First step : Contribution to standard development

Enrichment of strategies proposed in Step_NC :

Unidirectional

Contour-bidirectional

Center millingContour

spiralContour parallelBidirectional

Bidirectional-contour Explicit

All others strategies

Pattern strategies : GUIDE CURVE + PATTERN

Exemples of strategies built on pattern curves :Trochoïdal

milling :

Plunge

milling :

Pattern strategies : a new method to build toolpaths

Validation of this proposition of integration

14

CAD part

Machining

PosSFPReading

toolsToolpath

generation Adaptation

Step 1 :Implementation of trochoidal milling in : - Step_NC Standard - PosSFP

Step 2 :Building of reading tools and toolpaths generators

Step 3 :Machining test parts

Step_NC

Strategy parameters Toolpaths

Step_NC File

Integration of pattern strategies in Step_NC

Conclusion & More Benefits of Step NC

• Creation of an interpreted Step NC numerical chain

• First Step through advanced programming

• possibility to work with Step NC on conventional means

• Interest of pattern strategies

• Generation simplicity

• Few attributes needed to generate a complete toolpath

• Easy portability

• Compatibility with Step NC standard and high level programming

• Enrichment of Step NC possibilities

Pattern strategies

Step NC

Conclusion

- G-code programming is no more the solution

- Bidirectional data flow

- 1 single file (no lost of data, no redundancy, etc.)

- Less correction time

- Step_NC file portability

- Total integration of CNC – feed-back to design and NC planning

- Capitalization of shop floor feedbacks and experiences

- New possibilities for toolpath generation and machining strategies

- Ability of real-time adaptation and optimization of toolpaths and machining parameters

Advanced Step NC