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Materials Science in Additive Manufacturing Base shape generation for HAM

is still focusing on the macro- and microplanning tasks as volume, called base, base plate or substrate, attracted the
introduced above, but there are not so many systematic attention of a group of researchers. Eldakroury et al.
[41]
researches on CAPP for HAM in the past. HAM has been attempted to use primary shapes, cylinder, and cuboid
proposed and investigated for more than two decades. to approach the initial CAD model’s subvolume through
Karunakaran et al. [27,28] have conducted intensive research a set of simple sequential rules to help process planners
on the HAM process development, through which the identifying optimal candidate substrate. However, they did
concept of HAM processing chain has been implicitly not analyze the solution space of the substrate, nor applied
mentioned, but the idea of adopting CAPP for HAM and any optimization tools to enable automatic searching. The
the main challenges of adopting CAPP in HAM have results presented in the paper may not be comprehensive,
never been formally discussed in their works. Later, after covering only the local optimal candidate substrates. In
a research on HAM process development, Liou et al., for addition, the word, “substrate,” may cause confusion to
the first time, proposed an integrated process planning for the NAM processing module’s planning. More recently,
[42]
their developed multi-axis HAM process [23,29,30] . Kerbrat Chen and Frank proposed a method to optimize the
et al. also conducted manufacturability analysis related stock size for component families or groups and use the
[31]
to CAPP for HAM according to the two-level CAPP stock as the processing starting point for the following
concept definition proposed in Zhang and Bernard . HAM processing. In their method, manufacturing begins
[15]
Subsequently, Newman et al. [32,33] proposed systematic with a base plate, where a set of subtractive steps will first
CAPP solutions for HAM process at a relative generic create a portion of the design geometry. Next, the additive
level. More recently, in face of the development of and manufacturing process will be planned to create geometry
increasing application demand for HAM processes, the on the machined base plate in two opposite directions,
research on CAPP for HAM is booming. A couple of to minimize support structure, and build height. Finally,
researchers investigated how to connect AM with NAM a secondary machining process is planned to produce
process with automatic CAPP solutions [34,35] . These works finished surfaces on the additively manufactured near
mainly focused on how to decompose a CAD model into net shape geometry. However, there is no work about
two processing sets of subvolumes, called features, for AM how to identify an optimal stock for a given CAD model
[43]
and NAM processing modules. They discussed more about in their paper. On the other hand, Reichler et al. did a
the decomposition strategy, feature assignment scheme, similar work, but they tried to extract a subvolume from
and the processing sequence determination. There are also the initial CAD model as starting base for incremental
some researchers focusing solely on toolpath generation manufacturing, where AM is applied to add customized
with consideration of AM or NAM constraints, for example, features for variant part. However, they did not explain
collisions, to obtain an automatic full HAM processing how to obtain an optimal base volume automatically for
chain [36,37] . These studies focus more on the micro planning the start point.
stage, where processing model transformation is the As reviewed above, research addressing the question
priority. Recently, a CAPP platform at a generic level about HAM processing starts from zero or existing
that enables a more general planning for HAM has been volume is scarce. If the process starts from an existing
proposed . However, they are still situated in the micro volume, how to identify an optimal starting volume is a
[38]
processing chain level even though they added monitoring fundamental question to be solved. This study is aimed
unit in their CAPP loop. In a very interesting work, Liu at filling this knowledge gap. We started from an existing
et al. discussed a very microplanning task for iterative volume and proposed a generic solution to automatically
[39]
HAM, where the switch moments between the two generate an optimal starting volume, called base shape,
processing modules need to be analyzed and optimized for HAM processing. The proposed method is expected to
according to processing constraints, time and cost. Except meet the needs of different multi-axis HAM processes by
for full CAPP solution development for HAM, some adapting related processing constraints as the boundary
critical planning tasks in the macro or microstages also conditions of optimization. The following section gives a
attracted research attention since they are important for detailed explanation about our method. A CAD model of
the processing chain. How to plan for HAM starting from a relatively complex tree structure is adopted to illustrate
an existing part has also been extensively discussed [32,33] , each key step in the calculation procedure.
with a particular focus on how to reuse existing parts/
legacy products to save cost for HAM process. Researchers 3. Proposed method
applied HAM for remanufacturing existing physical HAM processes combine the advantages of
components in adherence to this logic [6,40] . Gradually, the additive processing and subtractive processing or other
benefits of starting the HAM processing from an existing traditional processing such as casting and stamping.

Volume 2 Issue 4 (2023) 3 https://doi.org/10.36922/msam.2103