Even before the age of metal, cams were made from such materials as wood,
bone or perhaps even rock. The 'standard' type of machinery cams we manufacture are made of a
special hardenable cast iron suitable for most service requirements. Typically,
the shape or 'profile' is produced
by cutting a 'blank' of cast iron or other material with a 'milling machine'
that moves the material through a rotating hard steel cutting tool called an
'end mill'. Unique numerical information is generated by a computer to describe
a given profile. The information
is fed to the milling machine. The
picture below is that of a cam being profiled in one of our CNC milling machines.
We find that servos are indeed the right choice for applications that, for example, require tracking or adjusting to a variable parameter or need to adapt to a variety of product sizes easily and quickly, ("Intelligient Manufacturing"). Over the years of producing long-run production machinery, we have not encountered many applications with such requirements.
In comparison with pneumatics - there is little to compare. The pneumatic machine approach is often a good choice for short run equipment that need to be designed and built quickly and we have built many such machines. However, keep in mind that the speed of a pneumatic machine is impeded by the need of a controller to verify the completion or 'safe point' of a given stroke before a potentially interfering stroke may be initiated. Cam stroke position is known and repeatable for any point in time. It therefore offers an advantage to design two or more actions with potentially interfering paths to occur at the same time with the confidence that they will always just miss each other. (barring catastrophic failure which could, of course, occur to any system). In contrast, pneumatic motion is not as certain being subject to pressure fluctuation, valve speed, lubrication condition, wear condition, logic controller throughput, etc. Pneumatic machines will also require more maintenance effort than cam driven machinery for many of these same reasons.
Lately, some air cylinder manufacturers have begun to offer digital positional control. Such are basically electro-pneumatic servos that may offer an advantage for a limited number of special situations.
** A single axis servo control, amplifier and motor PLUS the typical costs of procurement engineering time, programming, wiring, mechanical installation and debug.