General Cam Information
Many of the machines that we design and build employ cams as the means to achieve a controlled motion. Cam actuation, though truly an ancient technology, has endured and remains a reliable and cost effective means for actuation in present day high speed automatic machinery. The principle has remained the same; place something against a rotated irregular shape to thus create a controlled repetitive motion. Today, in addition to machinery, cams are used in such ubiquitous places as car engines, toys, lamp switches,pens, etc.

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. Continued...

Comparison of Cam, Servo and Pneumatic Actuation Systems

As opposed to electric servo control systems that are programmable via software, cams are 'Solid Steel Logic'. For a set of specifically desired repeated motions, cams easily out-perform servos in terms of cost, following error, acceleration-deceleration control and smoothness of operation with large loads. Cams also can withstand harsh environments of high temperature, moisture, (stainless steel cams), and electrical noise which must always be considered with a servo system. For long-run production machinery, we have found that a $1500 cam-lever system is a logical choice over a **$6000+ digital servo for a given repeated motion requirement.

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.

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Last modified - January 19, 1997