[step-manufacturing] Minutes of March 28 conference call

[Martin Hardwick]

Attendees
--------------
Martin Hardwick, STEP Tools, USA
David Loffredo, STEP Tools, USA
Mikael Hedlind, KTH, Sweden
Bengt Olsson, Sandvik, Sweden
Leon Xu, Boeing, USA
Fred Proctor, NIST, USA
Ronnie Fesperman, NIST, USA
Bob Erickson, Pratt & Whitney, USA
Alain Brail, Airbus (retired), France

Apologies for Absence
-------------------------------
David Odendahl, Boeing, USA
Ian Stroud, EPFL, Switzerland

1. Programming Issues and  Interest in Modelica for modeling the 
function in "form, fit and function".

New research programs are making extensive use of STEP assemblies with 
externalized files. In this representation the STEP data for an assembly 
is essentially a directory with each file representing one component and 
a master file describing how to assemble those components into an 
assembly. This has the advantage of allowing components to be replaced 
without having to read and write the data for all the assembly into a 
specialist CAD tool.

In STEP Manufacturing we experimented with using STRL's (STEP Resource 
Locators) to distribute STEP-NC data between multiple files but this 
method does not allow the data to be managed and manipulated outside the 
context of a STEP-NC aware tool. Therefore, STEP Tools suggests that the 
STRL method should be replaced with an external reference mechanism 
similar to the one being used for assemblies.

In outline the new mechanism would allow for external executables where 
the details of the executable would be stored as another STEP-NC project 
stored in an external file and the current file would only store a stub 
for the excecutable. We would then establish naming conventions to allow 
the required executable to be found in the external file. With the 
proper conventions we should be able to make modular STEP-NC programs 
that can be composed out of other STEP-NC programs reusing executables 
for shared operations as appropriate.

The conventions used for modular STEP assemblies are described in the 
CAX-IF document. In the short term STEP Tools will experiment with using 
these conventions to externalize the product models for the as-is and 
to-be shapes in a manufacturing process.

ftp://ftp.steptools.com/private/CAM_exchange/rec_prac_ext_ref_v21.pdf

2. CAM to CAM Data Exchange

We talked briefly about the letter encouraging vendors to participate in 
the anticipated CAM data exchange project. Boeing and Airbus are sending 
drafts of this letter through their management chains. We discussed the 
possibility of getting letters sent from Pratt and Whitney and 
Caterpillar. Bob Ericksson will look into this for P&W and Fred Proctor 
will try the idea out with his contacts at Caterpillar.

ftp://ftp.steptools.com/private/CAM_exchange/CAM_exchange_plan.gif

We reviewed the slides sent by Xun Xu of the University of Auckland in 
New Zealand and found them most encouraging because they mean another 
party has been able to read STEP-NC data into a CAM system.

ftp://ftp.steptools.com/private/CAM_exchange/NZ_STEPNC_import_for_Creo.pptx

3. June Demonstration

ftp://ftp.steptools.com/private/Stockholm2/STEP_manufacturing_demo_scenario_14_June_2012.pdf 


A gear part is being considered for the June demonstration. The scope of 
how much of the part will be machined is being determined. The part has 
a large outer diameter which will be the focus of our accuracy predictions.

ftp://ftp.steptools.com/private/Stockholm2/crown_wheel_raw_final.pdf

KTH hopes to have STEP data for the part ready for the next conference 
call on Wednesday (one week earlier than normal). In April KTH will 
measure the positional performance of a 3 axis Mazak machine and capture 
the data as AP-242 data that will then be translated to ASME B5.59 for 
testing with the NIST path evaluation tool. Stiffness tests will then be 
made using a loaded double ball bar and these tests will be used to 
compute tool deflection data. In some cases the tool deflection error 
may cancel out the positional error and in other cases it may amplify 
that error. For the demonstration we will assume that the two errors are 
additive and use the combined error to determine if the part outer 
diameter will be in or out of tolerance by comparing the nominal and 
predicted paths in ST-Machine

The next telecon will be held on Wednesday April 4th - one week EARLIER 
than normal to get us back on schedule and avoid some conflicts with 
April 11th.. A recording of this meeting is at the following ftp site

ftp://ftp.steptools.com/private/Stockholm2/stepmanuf_telecon_20120328.wmv

Martin Hardwick
Team Leader STEP-Manufacturing