Page 61 - Robotics Designing the Mechanisms for Automated Machinery

50 Concepts and Layouts

However, this conceptual solution does not permit rotation of the spindle, it being too
cumbersome to rotate a coil of, say, one meter diameter. We have to invert the process.
The solution is to rotate the cutters, drills, etc., around the rod, which is kept immo-
bile in the chuck.

Exercises

Explain the concept underlying the following automatized manufacturing
processes:

1. Sewing machine.
2. Meat-chopping machine.
3. Automatic record-player.
4. Slot-machines of different kinds.
5. Automatic labeller (for bottles, say).
6. Machine for filling matchboxes.
7. Machine for wrapping 10 boxes of matches in a parcel.
8. Machine for producing nuts of, say, 5-mm thread diameter.
9. Machine for assembling a ball bearing.
10. Machine for sorting the balls of a ball bearing into, say, 5 groups correspond-
ing to their size tolerances.

2.3 How to Determine the Productivity
of a Manufacturing Process

We have thus determined the concept underlying our process, and the next step is
to estimate the main parameters characterizing the productivity or efficiency of our
concept. The way to do this is to construct the so-called sequence or timing diagram.
The first example considered in Section 2.1 will illustrate the procedure. The diagram
is given in Figure 2.14. Here each horizontal line corresponds to a specific mechanism.
The first line describes the behavior of the wire-feeding mechanism, the second line
that of the wire-cutting mechanism, and the third that of the mechanism for horizontal
bending of the link. It is convenient to consider this bending as a two-stage procedure.
The first stage (3a) is creation of the horseshoe-like shape, which involves only a right-
ward movement of the tools 5 (this procedure is called swaging). The fourth line cor-
responds to the action of the vertical bending mechanism, and the fifth to the support
4, which must be countersunk at a certain moment to make way for some other tool.
The sixth line describes the action of the mechanism 9 whereby the link is pushed
towards the opening (where it falls to the lower level and causes the assembly of the
links into a chain), and the seventh line corresponds to the last operation, closing the
links. The vertical axis of this diagram usually represents some kinematic value: speed,
displacement or (less frequently) acceleration. The scale of these values can be differ-
ent for each mechanism. The horizontal axis represents the angular values yf (because
of the periodical nature of the process) or time t, which is related to the angles \i/ through
the velocity CD of the distribution shaft as follows: