Manufacturability analysis to combine additive
and subtractive processes
Olivier Kerbrat, Pascal Mognol and Jean-Yves Hascoet
IRCCyN, MO2P, Nantes, France
Abstract
Purpose – The purpose of this paper is to propose a methodology to estimate manufacturing complexity for both machining and layered
manufacturing. The goal is to take into account manufacturing constraints at design stage in order to realize tools (dies and molds) by a combination of
a subtractive process (high-speed machining) and an additive process (selective laser sintering).
Design/methodology/approach – Manufacturability indexes are defined and calculated from the tool computer-aided design (CAD) model,
according to geometric, material and specification information. The indexes are divided into two categories: global and local. For local indexes, a
decomposition of the tool CAD model is used, based on an octree decomposition algorithm and a map of manufacturing complexity is obtained.
Findings – The manufacturability indexes values provide a well-detailed view of which areas of the tool may advantageously be machined or
manufactured by an additive process.
Originality/value – Nowadays, layered manufacturing processes are coming to maturity, but there is still no way to compare these new processes
with traditional ones (like machining) at the early design stage. In this paper, a new methodology is proposed to combine additive and subtractive
processes, for tooling design and manufacturing. A manufacturability analysis is based on an octree decomposition, with calculation of manufacturing
complexity indexes from the tool CAD model.
Keywords Operations and production management complexity theory, Production equipment, Production processes
Paper type Research paper
1. Context of the study: hybrid modular tooling
In order to improve competitiveness in modern mass
production industry, products have to be designed and
manufactured with the following two goals that are often in
opposition:
1 decreasing time and cost; and
2 improving quality and flexibility.
These objectives imply two design and manufacturing
constraints: a rapid manufacturing and a high level of
reactivity when design evolutions are required. The current
field of tooling (dies and molds) does not break these
constraints and one answer to the problem is to design and
manufacture hybrid modular tools, with modular and hybrid
points of views:
1 Modular point of view. Instead of a single-piece tool, it is
seen as a 3D puzzle with modules realized separately and
further assembled. The two advantages are: each module
may be produced simultaneously and few modules may be
changed without changing the whole tool. With this point
of view, several alternatives of the same product may
advantageously be manufactured with the same mold,
changing one module to provide new part functions.
2 Hybrid point of view. Each module of the tool is
manufactured by the best process, in term of time, cost
and/or quality. Presently, focus is put on comparison
between a subtractive process (high-speed machining
(HSM)) and an additive process (selective laser sintering).
Another research topic investigates the combination of
these two manufacturing processes.
To illustrate the advantages of using hybrid modular tooling,
Figure 1 shows an industrial example, developed at IRCCyN
(Mognol et al., 2007). It is a part from automotive industry,
manufactured by injection molding (Figure 1). In this part, the
positions of the circled shapes have diversifying alternatives,
there are a marking that changes with the model and an
evolutionary feature for the seal positioning (Figure 1(b)). The
part with its evolutionary areas may be produced with just one
mold creating modules for each changing area of the piece. So
modules are designed (Figure 1(c)) and realized with the best
process (Figure 1(d)), and changed when the product model is
modified.
2. Manufacturability analysis issue for hybrid
modular tooling
The two points of views, hybrid and modular, have allowed
creating rapid tools and rapid prototypes with the multi
components prototype concept (Rivette et al., 2007). This
concept aims to decompose a mechanical prototype part on
an assembly of several components. There are two main
reasons for the multi-components decomposition to:
1 include the evolutionary requirement of the prototype
regarding to the tests that are performed on it; and
The current issue and full text archive of this journal is available at
www.emeraldinsight.com/1355-2546.htm
Rapid Prototyping Journal
16/1 (2010) 63 –72
q Emerald Group Publishing Limited [ISSN 1355-2546]
[DOI 10.1108/13552541011011721]
Received: 24 October 2008
Revised: 9 April 2009
Accepted: 12 May 2009
63