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Attendees
<br>
Martin Hardwick, STEP Tools, USA
<br>
Mikael Hedlind, KTH, Sweden
<br>
David Loffredo, STEP Tools, USA
<br>
David Odendahl, Boeing, USA
<br>
Fred Proctor, NIST, USA
<br>
Sid Venkatesh, Boeing, USA
<br>
Bengt Olsson, Sandvik, Sweden
<br>
Fiona Zhao, NIST, USA/New Zealand
<br>
Bob Erickson, Pratt & Whitney, USA
<br>
Leon Xu, Boeing, USA
<br>
Erik Jacobson, GE Energy, USA<b><br>
</b>Ronnie Fesperman, NIST, USA<span style="color: rgb(31, 73,
125);"></span><br>
Aydin Nassehi, University of Bath, UK<br>
Buzz Callaghan, IQL, USA<br>
Andreas Archenti, KTH, Sweden<br>
<br>
We continued our discussion on how to measure and predict machine
tool accuracy. Many factors impact machine tool accuracy including
the servo motors, the machine geometry, the bending force, and
thermal conditions. KTH, NIST and IQL (US Army) have on-going
projects that are investigating how to measure and predict machine
tool accuracy. So far the results are highly encouraging. Making the
initial measurements is time consuming, but once the measurements
are made they are reliable and consistent, and their continued
validity can be verified using a Ballbar test. <br>
<br>
The results of the measurement tests can be represented as stacked
Homogeneous Transformation Matrices' (HTM's) for the machine tool
axes. There are emerging ASME standards for these results- B5.59-1
and B5.59-2. <br>
<br>
We discussed how to apply machine tool accuracy to STEP-NC. There
will be many applications. Two key ones are:<br>
<br>
1. Predicting if a machine can produce a part that will meet its
tolerances.<br>
2. Correcting a program by modifying its nominal tool paths for the
accuracy of the machine.<br>
<br>
The STEP-NC program describes how the part is to be machined and
what tolerances are required for the final part and also for
intermediate parts as well. The machine tool model defines the
kinematics of the machine and with the HTM information added
predicts the as-executed tool paths. We can define the machine tool
models in CAD systems as AP-214 or AP-203 data. Using the Siemens NX
export extension developed by KTH, or by hand-editing, we can add
the machine tool kinematics to the STEP AP-214 file. The next step
is to add the HTM accuracy data to the kinematic data to produce an
AP-214 file that can be used to predict machining accuracy.<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 April 22.
<br>
<a class="moz-txt-link-freetext"
href="ftp://www.steptools.com/private/Renton/stepmanuf_telecon_20100929.wmv">ftp://www.steptools.com/private/Undecided/stepmanuf_telecon_20110408.wmv</a><br>
<br>
Action Items
<br>
1. STEP AP-214 to be shared with ASME B5.59 experts.
<br>
2. ASME B5.
59 to be shared with STEP experts.<br>
<br>
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