[step-manufacturing] Minutes of January 25 conference call

[Martin Hardwick]

Attendees
--------------
Martin Hardwick, STEP Tools, USA
David Loffredo, STEP Tools, USA
Vincent Marchini, Ameritech, USA
Mikael Hedlind, KTH, Sweden
Magnus Lundgren, KTH, Sweden
Alain Brail, AIrbus (retired), France
David Odendahl, Boeing, USA
Fred Proctor, NIST, USA
Bengt Olsson, Sandvik, Sweden
Ian Stroud, EPFL, Switzerland
Arnaud KREMER,  Ecole Nationale Supérieure d'Arts et Métiers, France
Buzz Callaghan (and team), Independent Quality Labs, USA

Apologies for Absence
-----------------------------
Sid Venkatesh, Boeing USA
Tom Scotton, CCAT, USA
Aydin Nassehi, University of Bath, UK

1. Planning for the ISO STEP Meeting, June 10 to 15 in Stockholm

ftp://ftp.steptools.com/private/CAM_exchange/TC184_SC4_Stockholm_Juni_2012_(T24_presentation_2011-11-18).pdf 


A team of KTH students are looking at the XML of the WebGL 
demonstrations and have some confidence that they will be able to use it 
as the input for the Holographics Visualization demonstration.

STEP Tools gave a brief WebGL demonstration of the impeller being 
machined on the Hermle machine.

We discussed the accuracy demonstration. We would like to show how to 
use AP-242 and AP-238 to determine if a part will be machined within its 
defined tolerance. We propose to do this by calculating the forces on 
the cutting tool to determine if the deflection is sufficient to take 
the surface being machined out of tolerance.

1. We can use the cross section data in AP-238 to determine the forces 
on the cutting tool.
2. We can use the accuracy data that we are going to add to each joint 
in the AP-242 kinematics model to determine the unloaded programmed 
position of the tool.
3. We can use the stiffness data that we are going to add to each joint 
in the AP-242 kinematics model to determine the programmed position of 
the tool under load.
4. We can determine a machining error by comparing the deflected 
position of the tool to the nominal position of the surface.
5. We can compare the error to the semantic tolerance defined for the 
surface on the workpiece and decide if the error is within the tolerance 
(most likely a profile tolerance) defined for the surface.

We put the data required for #1 into the AP-238 data for the Impeller 
and Boxy when we gave demonstrations of feed-speed optimization at CCAT, 
NIST and Boeing. For the new demonstrations we will need new algorithms 
to calculate the forces on the different machine joints from this cross 
section data, the feeds and speeds of the machining program and any 
necessary cutting efficiency data from the cutting tool.

We need to add models for the accuracy and stiffness errors to the 
AP-242 kinematics model and to then populate the machine tool models 
with this information. We are using ASME B5.59 Part 2 as our guide for 
creating this information and we have some test data sets from NIST to 
guide us when populating the data sets.

We need to add software to one of the systems (ST-Machine Desktop or 
ST-Machine Webtop) to calculate displacements using all the forces and 
accumulate an error by multiplying out the relevant Homogeneous 
Transformation Matrices.

We need to add presentation and semantic tolerances to the workpiece 
being tested. The presentation tolerances can be created using one of 
the CAD systems that support AP-203 Edition 2 or AP-242 (NX, Catia, 
Pro/E etc). We can create the semantic tolerances using ST-Machine or 
the KTH extension to NX. The algorithms will use the semantic tolerances 
because they are attached to the surfaces using direct links contained 
in the data model.

The next meeting will be held at the regular times on Wednesday February 
7th. A full recording of this meeting is at the following URL.

ftp://ftp.steptools.com/private/Undecided/stepmanuf_telecon_20120125.wmv

Action Items
----------------
1. KTH to develop information models for the accuracy and stiffness of 
the machine joints.
2. STEP Tools to publish new web demos showing Boxy and the Impeller 
running on the machine tool models.

Martin Hardwick
Team Leader ISO STEP-Manufacturing