1. ISO/TC184/SC1/WG7 Status Report Regarding the Standardisation of a New NC Programming Data Interface
Laboratory for Machine Tools and Production Engineering Aachen University of Technnology
08 October 1999

2. Outline Aims and strategy of ISO 14649
Overview of the current status in ISO/TC184/SC1/WG7
Integration with ISO 10303
Open issues

3. NC programming using ISO 6983
machine-specific part program with axis data generated by a postprocessor %
N05 G54
N10 G00 Z10.000
N15 G91 G0 Z200
N20 T5 D1 WW
N30 G90 M5
N35 G00 X Y
N40 G00 Z5.000
N45 M08
N50 S
N55 M03
N60 F
N65 G00 X Y
N70 G00 Z5.000
N75 G00 X Y
N80 G01 Z-0.500
...
vendor-specific extensions of the original standard
only primitive motion and switch commands
no standardised data format for spline processing and sophisticated NC technology

4. Aim of ISO 14649
Re-establish an accepted standard for the transmission of NC data to the shop floor!
Provide motion control data based on splines for sophisticated, high-speed NC cutting operations
Avoid intermediate data formats (CLDATA)
Provide all necessary data for easy modification of NC data at the machine controller
Task-oriented data structure
Enable feedback of modified NC data from the shop floor to higher-level departments
Minimize the need for data conversion by using standards for geometric representation

5. Use cases for ISO 14649
Note: ISO is a data interface (CAM to NC), not a user interface!
The NC’s HMI may present the data to the operator in any desired form.

6. The workingstep concept
Geometric and technological information will be linked, not mixed
Each workingstep can be parameterised after instantiation, e. g. regarding tool, feed etc.
Tool movements are combined into groups with clearly identifiable semantics
Intelligent NC controllers can autonomously calculate tool movements for standard features

7. EXPRESS-G schema (simplified excerpt)
workpiece
workplan
geometry
S[0:?]
L[0:?]
machining_feature
machining_workingstep
geometry 1
L[0:?]
pocket
plane
hole
region
machining_operation 1
L[0:?]
plane_milling
side_milling
drilling
tool
technology
geometry
toolpath 1
strategy
cutter_contact_trajectory
cutter_location_trajectory
parameterised_path

8. Current status: Modeling
Final deliberations of WG Sept 1999:
ISO Part 1: Introduction
ISO Part 11: Process model for milling
ISO Part 11/1: Tool model (will be obsolete after the arrival of ISO 13399)
Parts 1, 11 and 11/1 will be put forward as DIS after the finalization of editorial work
Part 11 defines 160 entities and 15 types (plus references from ISO 10303)
Part 51 of ISO shall later present the mapping of Part 11 into the AIM
Further process models for other technologies need to be developed

9. Current status: Selection of a physical file format
Aim: To exchange NC programs at physical file level with high efficiency
Coding of the EXPRESS data structure based upon ISO Part 21
Problem: How to define the logics and sequence of operations for complex NC programs
a programming language seems to be needed
US proposal: SDAI-Java
Sequence coded in Java
main() {
wpl.exec()
... }
#21 = WORKPLAN(...);
#22 = WORKINGSTEP(...);
...
Technological and geometric model coded in ISO

10. Integration with ISO 10303: Geometry and topology
The search for an existing geometric model lead to ISO 10303
Comprehensive geometric library in Part 42
Strategic advantage of using a future-oriented universal standard
However: ISO has been aiming for a stand-alone standard, not a STEP application protocol
A mapping of the required technological and machining data into STEP seemed not feasible
Scope and size of STEP collides with the needed real-time behaviour for reading NC programs
Transmit only process-relevant data
Support file-based data transfer

11. Integration with ISO 10303: Intended data flow
Process
Planning
NC Code
Generation
(CAM)
Inspection Code
Product
Design
(CAD)
Milling
Turning
Grinding
Inspection
Features
ISO 14649
Part 11, 21
Part 12, 22
Part 1X, 2X
Part XX, XX
STEP AP 213
(stock, tools, fixtures)
STEP
AP 224
(process sheet)
All
Manufacturing
Execution
STEP Part 4X Integrated
Resources, via SDAI

12. Open issues Is there an alternative solution for sequencing?
Could the sequence even for non-linear cases (branches, loops, ...) be coded in STEP Part 21? Advantage: Only one physical file needed.
How close should the integration with STEP be?
Is the request for a mapping into the Integrated Resources feasible and sensible?
Is STEP prepared to integrate such process-specific, low-level, machine-oriented data?
Does the mapping yield to the requirement of extremely compact and easy-to-process files at the shop-floor level?