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Attendees <br>
Martin Hardwick, STEP Tools, USA <br>
Mikael Hedlind, KTH, Sweden <br>
Andreas Archenti, KTH, Sweden<br>
Ronnie Fesperman, NIST, USA<span style="color: rgb(31, 73, 125);"></span><br>
Fred Proctor, NIST, USA <br>
Bengt Olsson, Sandvik, Sweden <br>
Erik Jacobson, GE Energy, USA<b><br>
</b>Vincent Marchini, Ameritech, USA<br>
David Odendahl, Boeing, USA<br>
Leon Xu, Boeing, USA <br>
Michael Mariani, IQL, USA<br>
Buzz Callaghan, IQL, USA<br>
Larry Maggiano, Mitutoyo, USA<br>
Bob Erickson, Pratt & Whitney, USA<br>
<br>
Apologies for Absence<br>
Sid Venkatesh, Boeing, USA<br>
David Loffredo, STEP Tools, USA <br>
<br>
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. <br>
<br>
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. <br>
<br>
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.<br>
<br>
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.<br>
<br>
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:<br>
<br>
1. Restriction of the facets to triangles<br>
2. Links from the facets back to the STEP faces that were used to
create those facets<br>
3. More compact and efficient data structures for accessing the
facets.<br>
<br>
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.<br>
<br>
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.<br>
<br>
<a class="moz-txt-link-freetext" href="ftp://ftp.steptools.com/private/Undecided/2011-06-03_Machine_Tool_Accuracy_Modeling.ppt">ftp://ftp.steptools.com/private/Undecided/2011-06-03_Machine_Tool_Accuracy_Modeling.ppt</a><br>
<br>
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. <br>
<a class="moz-txt-link-freetext" href="ftp://ftp.steptools.com/private/Undecided/stepmanuf_telecon_20110603.wmv">ftp://ftp.steptools.com/private/Undecided/stepmanuf_telecon_20110603.wmv</a><br>
<br>
Action Items<br>
1. David Odendahl to investigate the possibility of implementing a
STEP-NC demonstration for tape laying.<br>
2. Fred Proctor to investigate if we can get access to NIST
developed additive manufacturing programs for the CDS part.<br>
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