Page 188 - Modular design for machine tools

148 Modular Design Guide and Machine Tools Description

the NC lathe by choosing both the inclination angle of guideways rang-
ing from horizontal, through slant, to vertical types and the relative loca-
tion of the guideway to the spindlestock as the solution entities. In
addition, he considered the following objective-oriented attributes [12].
1. Swarf dropping ability
2. Approachability to work
3. Approachability to tool head
4. Loading and unloading capability by crane
5. Possibility to allocate many tool heads
6. Possibility to cover machining space with safety panel
7. Observation of machining space
8. Influence of self-weight of work to machining accuracy

4.1.4 Estimation of assembly accuracy
in design stage
As an extensive application of the functional description, the assembly
accuracy of the machine tool can be evaluated, at an early design stage,
in full consideration of the position errors of the structural body com-
ponents located within an FOF. In fact, the assembly accuracy results
in the relative variation within the coordinates of the machining point [13].
In this case, the layout pattern of structural body components, i.e.,
roughly the kinds and types of the machine, affects also the assembly
accuracy of the machine tool, because of changing susceptibility of the
error in each structural body component to the machining accuracy.
Assuming the jth structural body component within a machine to be
in connection with the other at a point O j , which is taken as the origin
of coordinates, the errors of its position can be characterized by the
T
vector { j } { jX , jY , jZ , jX , jY , jZ } , where ji and ji (i X, Y, Z)
are linear deviations of the point O j , and rotation of the structural body
component about the axes passing through this point.
In short, the vector {
} of deviation components at the machining
j
point caused by { } can be written as
j
} [T ]{ } (4-1)
{
j j j
where [T ] is the transfer matrix.
j
In due course, Moriwaki and his colleagues applied their description
method to the kinematics error analysis and structure generation. In
short, the total relative kinematics error at the machining point can be
computed as the sum of transfer errors at each traveling and rotational
movement concerned with form generation by the matrix operation [14].