[step-manufacturing] Minutes of sixth conference call

[Martin Hardwick]

Attendees
---------------
Matthew Lloyd, CCAT
Martin Hardwick, STEP Tools, Inc.
Mikael Hedlind, KTH
Magnus Lundgren, KTH
Bengt Olsson, Sandvik
Ian Stroud, EPFL
David Odendahl, Boeing
Larry Maggiano, Mitutoyo
John Horst, NIST
John Callen, Autodesk
Bob Erickson, Pratt and Whitney
Alain Brail, AlBavis


Apologies for absence
--------------------------------
Gary Hargreaves, Mastercam
Sid Venkatesh, Boeing
Xun Xu, University of Auckland
Fred Proctor, NIST

A machining simulation for the Impeller on the KTH machine tool was shown.

The next machine tool to be simulated will be the DMG DMU e70 machine 
used at the CCAT meeting. This machine has a B axis that is not 
orthogonal to the X, Y or Z axes so simulating this machine will make 
the simulator more flexible. Currently the simulator is limited to 
five types of machines - gantry, fixed spindle, AB Table tilt, AC 
table tilt and BC table tilt. The University of Bath machine tool 
model does not have these restrictions.

In the current simulator, the cutting tool is not placed correctly in 
the spindle because the AP-238 geometry for a tool is measured from 
the tip instead of the gauge line as recommended by ISO 13399. We 
will change the AP-238 recommendation to conform to the ISO 13399 
definition. Therefore in the future tool geometries should be 
generated so that the tool axis is the Z axis with z = 0  at the 
gauge line and with the tip having a positive Z value.

The cutting tool geometry can be used to define the ideal overall 
assembly length for a tool when the cut point is at the tip of the 
tool. If the cut point is not at the tip of the tool then the overall 
assembly length parameter must be used. This value is sometimes given 
in the Load Tool command in APT files.

ISO 13399 can communicate both the ideal (as defined) overall 
assembly length of the tool, and the actual overall assembly length 
of a tool instance as measured at the tool assembly station. 
Therefore, it is the best communication method to use for last minute 
changes to the tooling.

Various strategies for simulating the tool change behavior were 
discussed. It was agreed that it is more important to simulate the 
behavior of the tool as it returns to the home position than to 
simulate the actions of the tool changer because, in general, more 
problems occur for the former than the latter. CNC machines use PLC 
ladder logic to describe these behaviors. We will try to define them 
using an extension to the XML language of the Machine.xml file.

A tool reference direction attribute is required to describe the X 
axis orientation of tools that are not rotating. The example shown 
was of a tow head for a composite tape laying machine. We were warned 
that many more attributes will probably be required to describe the 
behavior of tape laying machines, but there was agreement that a tool 
reference direction attribute should be added to the standard with a 
definition similar to that of the tool axis attribute. We may be able 
to test the new attribute by using it to control the orientation of 
the insert of lathe cutting tools on mill-turn machines.

The demonstration goals for the Boeing/Mitutoyo/SC4 meeting were 
discussed. Alain Brail suggested we demonstrate a two-stage scenario 
in which a prime-contractor captures all of the machining 
requirements and develops a process that demonstrates that the part 
can be machined. This machining process will then be shared with the 
"sub-contractors" as an AP-238 file. They will then make whatever 
changes are necessary in order to machine the part on their machines 
(fixtures, cutting tools, cutting tool paths) while continuing to 
meet all of the constraints.

David Odendahl suggested that we demonstrate the scenario with a 
simplified version of the Mastercam part that contains less ribs and 
can be machined more quickly. The part has the advantage of being a 
mold and we will be able to verify that each site has produced the 
same result by mating their male and female halves.

Martin Hardwick suggested we capture the machining constraints using 
an AP-203 e2/AP-214 e3 file. The CATIA e2/e3 translator allows 
tolerance constraints to be documented in the traditional way using 
text data and leader lines. We will convert these tolerance 
constraints into semantic constraints in the STEP-NC explorer so that 
they can be used for automated measurement.

The next conference call will be held on Wednesday January 21st at 
the usual times.

Action items
------------------
1.   STEP Tools to extend the machine tool simulator to include the 
behavior of the tool changer.
2.   STEP Tools to prepare a simulation of the DMG DMU 70 used by 
CCAT at the October 2008 meeting.
3.   David Odendahl to prepare AP-238 data for the simplified Mastercam part.
4.   David Odendahl to prepare AP-203 e2 data for the tolerance 
constraints on the simplified Mastercam part.
5.   David Loffredo to add an optional its_tool_direction attribute 
to the definition of Trajectory objects in the AP-238 Technical Corrigendum.
6.   David Loffredo to add language describing how to define cutting 
tool geometry to the AP-238 Technical Corrigendum.