[step-manufacturing] Minutes of December 16th conference call and demonstration

[Martin Hardwick]

Attendees
Martin Hardwick, STEP Tools, USA
David Loffredo, STEP Tools, USA
Vincent Marchini, Ameritech, USA
Mikael Hedlind, KTH, Sweden
Yujiang Li, KTH, Sweden
Andreas Bergstrand, Volvo, Sweden
Bengt Olsson, Sandvik, Sweden
Fred Proctor, NIST, USA
Ronnie Fesperman, NIST, USA
Alain Brail, Airbus (retired), France
Sid Venkatesh, Boeing, USA
Bob Erickson, Pratt & Whitney, USA

Apologies for absence
David Odendahl, Boeing, USA
Arnaud KREMER,  Ecole Nationale Supérieure d'Arts et Métiers, France

A four stage demonstration of kinematics data exchange was given by 
Volvo, KTH and STEP Tools.

1. The initial data was defined in Catia with kinematic descriptions for 
the X, Y and Z axes and exported as a STEP AP-242 file
2. The AP-242 file was read into NX and kinematic descriptions were 
added for the A and C rotation axes. The modified data was saved as a 
new STEP AP-242 file.
3. The modified data was read back into Catia and the validity of the 
axis descriptions was verified by simulating some movements.
4. The modified data was read into ST-Machine and used to machine the 
Impeller.

The scenario is illustrated in the following document

ftp://ftp.steptools.com/private/CAM_exchange/KTH_Volvo_STEP_Tools_AP242_kinematic_data_exchange_2011-12-16.pdf

Here is the modified AP-242 STEP file sent from KTH to Volvo and STEP Tools

ftp://ftp.steptools.com/private/CAM_exchange/Hermle_AP242_kth.stp

The Catia to NX data exchange featured the import and export of the 
kinematic links with limits defined for the movement ranges. Sufficient 
information was exchanged to allow the machine tool definition to be 
moved manually in both systems, first with just the X, Y and Z movements 
defined, and then with the A and C rotations added.

The STEP Tools component of the demonstration featured the automated 
assembly of the workpiece and cutting tools onto the machine. In order 
to do this intelligent features were added to the model in NX. These 
features defined the assembly points for the workpiece and cutting 
tools. On seeing this we immediately wanted to define other features for 
the placement of the machine feet on the floor, the operation of the 
tool changer, the operation of the machine doors and so on.

The concept seems so powerful that we should think carefully about how 
to define application specific features for the long term. In general we 
need to enable their definition in CAD systems, and their operation in 
shop floor applications. One method might be to define PLIB catalogs of 
the properties explaining what is allowed and what is required in each 
feature for each type of application. For example, a PLIB catalog of the 
properties that can be defined for milling tools, a similar but 
different one for turning tools, and so on for all of the other types of 
machines that might be included on a shop floor.

We also discussed the implications of the demonstration for machine tool 
accuracy modeling. STEP has rich methods for defining tolerances that 
are now being extensively exercised by the DoD as part if its migration 
to Model Based Definition in MIL STANDARD 3100. These tolerances may be 
applicable to machine tools as well, so that, for example, a constraint 
may be placed on the flatness of the machine bed. Other tolerances may 
be placed directly on the kinematics so that the range of movements 
allowed during the machining can be constrained and predicted. This is 
all closely related to the ASME B59.5 standard for machine tool 
accuracy, but with the addition of kinematics to AP-242 we may be able 
to define these properties generically and graphically in CAD systems.

The team agreed that these issues are best contemplated during the 
consumption of Christmas cake so further discussion was postponed until 
the next meeting on Wednesday January 4th. A full recording of this 
meeting is at the following URL and includes screen shots of the three 
systems exchanging the machine tool data.

ftp://ftp.steptools.com/private/Undecided/stepmanuf_telecon_20111216.wmv

Wishing everybody a merry Christmas and a happy new year.

Martin Hardwick
Team Leader ISO STEP-Manufacturing