Page 54 - Kaleidoscope Academic Conference Proceedings 2020

J-Link enables the interaction between a Creo model and Since the terminology for each vendor-specific software
JSDAI. J-Link provides documentation, guidelines, and already exists and is being used, this needs to be considered
program examples to support developers and users of Creo. during the model conversion. It could also be argued that the
Since the interface and programming environment are terminology should be standardized but it will be a long way
vendor-specific, developers of STEP generators will need to to go not only for the development of the standard, but also
have knowledge and programming skills for multiple tools. for all vendors to comply with the standard. Note that also
How the machine model is defined in a CAx specific the complexity of the conversion will increase with the
software will impact how the data that represents the feature, number of axes, e.g., a five-axis machine is more complex
part, and object of the machine can be manipulated. than a three-axis machine.

5.2 Challenges with the converting of machine There are also remaining challenges for the definition of
models and kinematics information kinematics in AP 242. It was first introduced in 2014 but is
still not widely used or implemented in industry. Is AP 242
In this study, a couple of constraints (kinematic a perfect solution for representing all machine models? In
properties/pairs) have been converted to the STEP format. other words, are the definitions in AP 242 complete for all
However, automatically identifying and converting all the needs of the kinematics definitions? This needs to be
constraints of the machine model is still challenging. More further investigated.
effort is needed to ensure the correct usage of the EXPRESS
schema when generating the STEP representations The current situation is that kinematics information is
automatically, i.e., the machine model data exported from managed manually in some companies by using a text-based
the CAD software is converted correctly to the STEP format. description or a spreadsheet-like tool. Manual steps
This involve the STEP generator including the integration of involving humans always has the risk of creating errors.
J-Link and JSDAI applications for exporting the complete Most other smaller companies are not even capable of
machine model on a neutral format. This leads to an dealing with kinematics settings at all because of the lack of
important topic, the verification and validation (V&V) of the knowledge and access to the information. This may cause
converted machine model. Is there anything missing during production delay, product quality issues, more vendor
the model conversion? Does the newly generated STEP dependency, and cost increase.
machine model exactly represent the original vendor-
specific machine model? Although V&V has not been a 5.3 Challenges with commercial software and data
focus of this study, techniques for V&V of the machine reuse for end users
models have been investigated.
Even though STEP is now an integrated interface in most
Kinematics information is crucial for the behavior of a CAD software, there is still an unwillingness from the CAx
machining system and the accuracy of the kinematics model developers for further implementation of STEP
determines the precision of the overall machining. representations of kinematics modeling. This is because of
Kinematics modeling is one of the most common sources of the complexity of the implementation, but also because the
errors for a machine model. Therefore, when remodeling of vendors and solution providers would like to take advantage
kinematics information of a machine tool, it is important to of the situation with customer retentions and lock-in effects
ensure the kinematics information is converted completely [7]. Most CAx software developers provide vendor-specific
and correctly between various systems and formats using the solutions so that customers need to depend on their software.
STEP generators. In order to do that, a fundamental This situation causes information silos and makes it difficult
requirement is that the coordinate systems in ISO 10303-105 for interoperability. It also causes more issues for model and
(STEP part21 file) and in the CAD software need to be the data reuse for manufacturers because of the diverse
same. In ISO 10303-105, a link frame is used to define the landscape of software and systems they use. It used to be the
local coordinate system of a kinematic pair and all relevant same situations for post-processing and Geometric
geometric definitions are defined relative to this link frame. Dimensioning and Tolerancing (GD&T), which have
On the other hand, commercial CAD software has its own currently been implemented using a standard format by most
way of defining coordinate systems. Many of them use a CAx vendors. So, we hope kinematics modeling is the next
world coordinate system (or a global coordinate system). So one that people will turn to standardized solutions since there
before converting the machine model to the STEP format, is a clear need for it from the manufacturing community that
the coordinate system needs to be converted; this includes could motivate the CAx software to provide a standardized
the location and orientation information of each pair, in Creo, solution in the same way as it is for GD&T now.
and it is for each constraint. The terminology usage in
different CAD environments for the same concept also 6. CONCLUSIONS AND FUTURE WORK
causes a lot of confusion which was encountered in the case
presented here; what is referred to as a part in one software The case study presented in this paper demonstrates the
may be called a feature in another software. What is called feasibility of generating a complete STEP model that
constraints in Creo will be called pair or link in STEP. This includes both geometric and kinematics information of a
poses implications for the extraction of kinematics data and machine model. This is done by developing a STEP
needs to be adjusted for each vendor-specific CAD software. generator to extract geometric and kinematics data and

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