[step-manufacturing] Minutes of Conference Call on Friday June 3

[Martin Hardwick]

Attendees
Martin Hardwick, STEP Tools, USA
Mikael Hedlind, KTH, Sweden
Andreas Archenti, KTH, Sweden
Ronnie Fesperman, NIST, USA
Fred Proctor, NIST, USA
Bengt Olsson, Sandvik, Sweden
Erik Jacobson, GE Energy, USA*
*Vincent Marchini, Ameritech, USA
David Odendahl, Boeing, USA
Leon Xu, Boeing, USA
Michael Mariani, IQL, USA
Buzz Callaghan, IQL, USA
Larry Maggiano, Mitutoyo, USA
Bob Erickson, Pratt & Whitney, USA

Apologies for Absence
Sid Venkatesh, Boeing, USA
David Loffredo, STEP Tools, USA

We discussed additive manufacturing. The additive machines can be 
divided two types: six axis tape laying machines with the extra axis 
being used to define a direction for the tape head; and two axis 
material deposition machines with indexing on the third (Z) axis.

CAM programming for tape laying machines can be very complex and 
sophisticated because the material must lay flat with no "crinkles" on 
the part. Most tape laying machines have their own CAM system and 
post-processor but new systems are beginning to emerge that will take 
tool paths programmed on other systems. One of the challenges of tape 
laying is how to lay a lot of tape quickly to create large structures 
for applications such as airframes.

Two axis "printing" machines for material deposition are more common. 
Today these machines are usually programmed by slicing STL files 
(facets) but they can also be controlled by programming tool paths for 
the deposition head. The programming of these machines becomes 
"interesting" when there are complex internal structures, when there are 
tight tolerances, and when the printing must take place on a larger 
structure.

We discussed the role of STEP-Manufacturing in additive machining.  
Other committees in ISO are developing standards for additive machines 
including a new Technical Committee TC 261, and SC1 of TC 184. Our role 
with respect to other standards is to integrate their models into the 
STEP-NC when appropriate. The purpose of the integration is to make it 
possible for end users to build complete and unambiguous models of 
manufacturing data with all the necessary information assembled into a 
single coherent context. We integrated the SC1 machining models with the 
SC4  feature, GD&T and PMI models to create STEP-NC AP-238 Edition 1. 
For Edition 2 we are experimenting with integrating the AP-214 
kinematics model, the ISO 13399 cutting tool model, and the ASME B59 
machine tool accuracy model into the same framework. As our experiments 
with Additive manufacturing continue we may wish to do the same with one 
or more of the new Additive manufacturing models.

We reviewed the results of the recent SC4 meeting Portland. A new 
standard for STEP facets has been proposed by Dassault Systemes in 
France. Conformance Class 5 of STEP already models facets  but the new 
standard adds the following value:

1. Restriction of the facets to triangles
2. Links from the facets back to the STEP faces that were used to create 
those facets
3. More compact and efficient data structures for accessing the facets.

STEP-Manufacturing is very interested in the new standard because we can 
use it to share in-process models for machining simulations with 
inspection and vision systems.

A presentation on measuring and estimating machine tool accuracy was 
given by Ronnie Fesperman of NIST. In the NIST method a series of 
matrices are constructed to measure the exact behavior of each axis and 
the dependencies between those axes. With this data the as-defined 
location of a tool path can be converted into an as-estimated actual 
location. NIST has built a Matlab application to perform this 
conversion. We can use it to implement a STEP-NC simulator that predicts 
if the tolerances of a workpiece will be met when a machining program is 
run on a machine.

ftp://ftp.steptools.com/private/Undecided/2011-06-03_Machine_Tool_Accuracy_Modeling.ppt

A recording of the call is on the ftp site at the address below. The 
next call will be at the usual times on Friday June 17.
ftp://ftp.steptools.com/private/Undecided/stepmanuf_telecon_20110603.wmv

Action Items
1. David Odendahl to investigate the possibility of implementing a 
STEP-NC demonstration for tape laying.
2. Fred Proctor to investigate if we can get access to NIST developed 
additive manufacturing programs for the CDS part.
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