Page 251 - Mechatronic Components Roadmap to Design

230 Mechatronic Components

Case 2: How to choose the right material for a lightweight
throwable robot

Military applications of mobile robotics are gaining more popularity and the
design of robots with more payload capacity is very important in the battle-
field. The weight of the robot can be divided into two parts: the weight of
the machine and the payload capacity. When a mobile robot is being designed
if the weight of the machine can be kept lower, the payload capacity can
be higher.
In ordertobeabletomakethe robotlightweight, different types of mate-
rials should be studied (Chapter 5). Considering that the robot will be working
in the field, the material should be corrosion resistant. Considering the
density and strength of the material, aluminum and titanium are good choices.
When the 7000 series Aluminum is examined, the designer can see that
strength to weight ratio is very high and this material is very good for light-
weight design.

Case 3: Manufacturing process selection
Unfortunately, so many engineers think that designing a machine is drawing. In
reality, the manufacturing of the part is also very important and it is easy to
design a part that is difficult and expensive to manufacture. The technical draw-
ing programs are very advanced. In Chapter 8, the drawing programs are sum-
marized. The two-dimensional (2D) softwares have been replaced by 3D ones
over the years but the 2D softwares are still very good for layout designs and are
used by civil and industrial engineers. For manufacturing purposes, 3D pro-
grams are more useful in that these designs can be used by CNC machines.
The designer can generate the necessary g-codes to manufacture the part; how-
ever, during this process manufacturing methods, cutting tools, and the material
properties should be considered.
For example, if the part is cubical rather than cylindrical, it is mostly man-
ufactured by a milling operation. If the number of parts is high enough, a cost
analysis should be done, and the parts can be manufactured by molding. If the
strength and fatigue resistance of a part are important, forging will be a better
choice than casting, but it will be a more expensive procedure. The manufactur-
ing process depends on the part shape, material of the part, and cost analysis.
The assembly of the device is the next step after manufacturing and the parts
should be designed for ease of assembly as well.
In order to design a device for ease of assembly, the number of parts should
be minimized, parts should be self-locating and fastening, and top-down assem-
bly process should be used. Using standard parts with modular and symmetrical
design also helps.