Int J Adv Manuf Technol (2001) 18:784–789
2001 Springer-Verlag London Limited
A Clamping Design Approach for Automated Fixture Design
J. Cecil
Virtual Enterprise Engineering Lab (VEEL), Industrial Engineering Department, New Mexico State University, Las Cruces, USA
In this paper, an innovative clamping design approach is
described in the context of computer-aided fixture design activi-
ties. The clamping design approach involves identification of
clamping surfaces and clamp points on a given workpiece.
This approach can be applied in conjunction with a locator
design approach to hold and support the workpiece during
machining and to position the workpiece correctly with respect
to the cutting tool. Detailed steps are given for automated
clamp design. Geometric reasoning techniques are used to
determine feasible clamp faces and positions. The required
inputs include CAD model specifications, features identified on
the finished workpiece, locator points and elements.
Keywords: Clamping; Fixture design
1. Motivation and Objectives
Fixture design is an important task, which is an integration link
between design and manufacturing activities. The automation of
fixture design activities and the development of computer-aided
fixture design (CAFD) methodologies are key objectives to be
addressed for the successful realisation of next generation
manufacturing systems. In this paper, a clamp design approach
is discussed, which facilitates automation in the context of an
integrated fixture design methodology.
Clamp design approaches have been the focus of several
research efforts. The work of Chou [1] focused on the twin
criteria of workpiece stability and total restraint requirement.
The use of artificial intelligence (AI) approaches as well as
expert system applications in fixture design has been widely
reported [2,3]. Part geometry information from a CAD model
has also been used to drive the fixture design task. Bidanda
[4] described a rule-based expert system to identify the locating
and clamping faces for rotational parts. The clamping mech-
anism is used to perform both the locating and clamping
Correspondence and offprint requests to: Dr J. Cecil, Virtual Enterprise
Engineering Lab (VEEL), Industrial Engineering Department, New
Mexico State University, Las Cruces, NM 88003, USA. E-mail:
jcecil얀nmsu.edu
functions. Other researchers (e.g. DeVor et al. [5,6]) have
analysed the cutting forces and built mechanistic models for
drilling, and other metal cutting processes. Kang et al. [2]
defined assembly constraints to model spatial relationships
between modular fixture elements. Several researchers have
employed modular fixturing principles to generate fixture
designs [2,7–11]. Other fixture design efforts have been
reported in [1,3,9,12–23]. An extensive review of fixture design
related work can be found in [21,24].
In Section 2, the various steps in the overall approach to
automate the clamping design task are outlined. Section 3
describes the determination of the clamp size to hold a work-
piece during machining and in Section 4, the automatic determi-
nation of the clamping surface or face region on a workpiece
is detailed. Section 5 discusses the determination of the clamp-
ing points on a workpiece.
2. Overall Approach to Clamp Design
In this section, the overall clamping design approach is
described. Clamping is usually carried out to hold the part in
a desired position and to resist the effects of cutting forces.
Clamping and locating problems in fixture design are highly
related. Often, the clamping and locating can be accomplished
by the same mechanism. However, failure to understand that
these two tasks are separate aspects of fixture design may lead
to infeasible fixture designs. Human process planners generally
resolve the locating problem first. The approach developed can
work in conjunction with a locator design strategy. However,
the overall locator and support design approach is beyond the
scope of this paper.
CAD models of the part design (for which the clamp design
has to be developed), the tolerance specifications, process
sequence, locator points and design, among other factors, are
the inputs to the clamp design approach. The purpose of
clamping is to hold the parts against locators and supports.
The guiding theme used is to try not to resist the cutting or
machining forces involved during a machining operation.
Rather, the clamps should be positioned such that the cutting
forces are in the direction that will assist in holding the part
securely during a specific machining operation. By directing
