[step-manufacturing] Minutes of fifth conference call

[Martin Hardwick]

Attendees
---------------
Matthew Lloyd, CCAT
Martin Hardwick, STEP Tools, Inc.
Mikael Hedlind, KTH
Magnus Lundgren, KTH
Bengt Olsson, Sandvik
Fred Proctor, NIST
Ian Stroud, EPFL
Sid Venkatesh, Boeing
David Odendahl, Boeing
Larry Maggiano, Mitutoyo
John Horst, NIST
Bruce Wiener, Geometric Technologies, Inc

Apologies for absence
--------------------------------
Gary Hargreaves, Mastercam
Xun Xu, University of Auckland/TU Aachen
Aydin Nassehi, University of Bath
Stephen Newman, University of Bath
Alain Brail, AlBavis
Bob Erickson, Pratt and Whitney


We discussed how to place a STEP-NC program into a machine tool model 
for simulation. Machine tools have a gauge line on the spindle that 
defines the origin of the tool length. They have an origin that 
usually corresponds to an XY in the middle of the machine bed and a Z 
that is the same as the gauge point. Older machine tools have a home 
position that is at the extreme range of the X, Y and Z axis but this 
is less common on more modern machine tools that can determine their 
position on start up using internal gauges.

The geometry assembly for the KTH model has it origin at the machine 
tool origin. For other machine tools we may need to define the 
relationship between the assembly geometry origin and the machine origin.

The tool length is defined by the overall assembly length attribute 
in a STEP-NC file and by the functional length attribute in an ISO 
13399 file. These lengths define the distance from the gauge line to 
the functional cutting point. The physical tool can be longer. In an 
ISO 13399 file the physical length is defined by the protruding 
length attribute. In an AP-238 file it is defined by the shape of the 
cutting tool geometry.

The machine tool simulation software currently has the ability to 
define the geometry of the machine from an AP-203 assembly and to 
define which components of that machine are attached to each axis of 
the machine. For the next stage we will define an interface that can 
be used to place the STEP-NC part onto the machine tool.  We will 
then be able to simulate machining for the four categories of machine 
tools currently supported in the library - Gantry, Fixed Spindle, AB 
table tilt and BC table tilt.

CCAT has given us a model of the DMU e70 used to machine the impeller 
in the last demonstration.

The University of Bath has given us the latest version of the EXPRESS 
schema for the STEP-NC machine tool model.

The STEP Tools translator for Mastercam has been updated so that it 
can translate the program nesting hierarchy in a Mastercam file into 
nested workplans in a STEP-NC file.

We discussed two issues related to the translation of the Mastercam 
signature part to STEP-NC. The first arose because this file contains 
arc's in the YZ and ZX planes. If Mastercam can define arc's in these 
planes then there was a concern as to whether or not helix's might 
also be defined in these planes. The current STEP-NC definition given 
in the Technical Corrigendum (TC) for a helix using via points 
requires the axis of the underlying circle to be defined from the 
tool axis. This dependency can be removed if we require an additional 
via point to be defined for each helix (the start point and two via 
points will then define the plane and the end point will define the 
depth). We decided NOT to change the TC at this time but to retain 
the alternate definition in case it is needed in the future.

The second issue arose because Mastercam can define multiple machine 
tool groups. Each group defines a different machine tool. Therefore, 
when a program is translated to STEP-NC we may need to create 
multiple STEP-NC programs one for each machine plus a Master program 
that shows the relationship between the sub-programs. In AP-203 e2, 
an assembly component can be defined by an external file. In AP-238 
we may want to allow a machining operation to be defined by an 
external file so that one AP-238 program can define a machining 
operation for another AP-238 program. STEP Tools will continue to 
investigate this possibility.

The current plan for the next physical meeting is to spend one day at 
Boeing (May 14) for machining demonstrations, one day at Mitutoyo 
(May 15) for measurement demonstrations, two days at SC4 for 
technical discussion (May 18 & 19) and half a day at SC4 (May 20) for 
the implementor's forum. The URL for the SC4 meeting is:

http://www.eccma.org/2009isosc4%20conf/iso-sc42009.html

Bengt Olsson has sent APT and IGES data to STEP Tools for the Tebis 
"mushroom" part.

The next conference call will be held after the Christmas break on 
Wednesday January 7th at the usual times.

Action items
------------------
1.   STEP Tools to extend the machine tool simulation software to 
include the placement of a STEP-NC part onto the machine
2.   Fred Proctor to contact Keith Freimuth to see if we can get 
access to his library of machine tool models