Editorial

Editorial

If, like me, you have previously considered cams to be rather old-fashioned and perhaps a bit boring then I hope this issue will help redress the balance and show just how useful they can be. Until relatively recently only mechanical cams were available; however, the advent of electronic cams which almost (but not quite) mimic their older cousins has opened the doors to allow cams to be used in a wide range of flexible assembly systems.

Watching a US History Channel video about robots sent to me by Joanne Pransky, our US Associate Editor, I was fascinated (in the short gaps between advertisements) to see the history of automatons outlined. I was particularly impressed by a mechanical doll created in the late 1700s by the Swiss engineer Henri Maillardet. His "writer" was able to write three poems (of about eight lines each) and draw four pictures. Three cam followers gave three axes of movement ­ left/right, in/out and pen raise and lower. From the video I would estimate that the writer had a resolution of about 256in. x and y directions which means that each "location" could be represented by two eight-bit numbers in today's terminology. These pictures were highly detailed and I would guess that each picture required the equivalent of about 2,000 pen locations to be stored. This all adds up to approximately 28Kb storage capacity which is about ten times that of the first electronic controlled industrial robots. The level of skill demonstrated in its fabrication is impressive by any standards but considering that it was made more than 200 years ago I find it rather humbling as well.

In this issue we major in describing developments and applications for electronic or "smart" cam systems. However, I share Joseph Farkas's (see "Cam technology for assembly automation") enthusiasm for mechanical cams and would not like anyone to consider them old-fashioned or below consideration. One advantage that I see for mechanical cams over their electronic "equivalents" is that they are made of solid materials and literally hundreds of cams can be firmly locked together in perfect synchronisation by a single shaft. Electronic cams can only aim for perfect and instantaneous synchronisation ­ they will never achieve it.

To state the opposite, the engineer with a smile on his face while watching his 100 mechanical cam assembly machine will soon have that smile removed if he is asked to set up the machine for a different assembly sequence and given anything less than a month to do it in. His electronic colleague, however, can perform the reprogramming in the space of a few minutes.

Both approaches have their advantages and disadvantages, and both are worthy of consideration and should be kept in every engineer's tool bag of available resources.

Clive Loughlin