It's about time you told us..
What is it?
It's called a Layout Machine.
First introduced by the Portage Machine Company, a manufacturer of boring mills, in 1958. Since then, the incredibly simple and kinematically correct triangular column design of the Portage Layout Machine has been copied by every manufacturer of layout and co-ordinate measuring machines of this type.
The Portage machine, also licensed and built by Sheffield and later Bendix is now supported by employees of the machine shop that built the original machines in 1958.
R.W.D Enterprises bought the rights to the design from Bendix in 1983 when Portage Machine closed and is now the soul supporting company for machines of this type. The machines they manufacture, calibrate and install are unchanged from the original Portage machine except for the possible application of digital readouts to customer specifications.
What Was it Built For?
The Layout Machine was designed for one application: Preparing large castings and forgings for machining by layout. Proper casting layout is important because these parts are not always identical before machining. Cores especially have a tendency to move during the pour.
The purpose of casting layout is to determine if all the critical features, especially cored bores, will clean up during machining. Each critical feature on a casting will be roughed in with a layout machine using a table of dimensions or a "setting stick". Every single part in the Doxford photos that has layout paint on it would have been touched and influenced by a Portage machine only a few years after the photos were taken.
The Portage machine saved a significant amount of time over using a surface gauge as shown in the Doxford photos because it negated the need to flip the casting three times to reference the datum plane, or use large squares, as a surface gauge is only capable of locating height from the surface plate. By using special Portage Layout Plates, which have grooves every 5 inches in both X and Y, accurate measurements can be made in all three axes and lines scribed in X, Y, and Z with special spring-loaded scribing attachments. Bores could be laid out with a circle-scribing attachment, negating the need to locate and block the center of the bore with a piece of wood before scribing the bore with a divider as shown in the Doxford photos.
Layout plates are generally recessed into the floor at many companies as they will be in my shop. The common plate size is 5' by 5' by 4,800lbs per plate. Each plate is individually leveled in the floor pit and bolted to it's neighbor before grouting in. Thus, plate size is governed entirely by how many plates you bolt together.
Examples of installed plates and machines:
What Else Can it Be Used for?
Layout machines were quickly adopted for use outside of heavy machining. Made in various standard sizes from 2' tall to over 10' tall, automotive stylists and clay modelers quickly adopted them for locating critical features in clay models and preserving symmetry. The Portage machine has become a critical tool in the design of automobiles since their adoption. Both "bibles" of automotive and industrial modeling have entire sections on the application of the Portage Machine. The Portage machine is preferred over all others for it's smooth, well-balanced feel and ease of use.
Ford Motor Company adapted a Portage #72 for digitizing clay models in 1965. GM and Chrysler quickly made their own versions of this machine. By the early 1970's Chrysler had a fully CNC controlled Portage machine with automatic scanning and a non-contact probe. In the process, they inadvertently created one of, if not the first computerized Coordinate Measuring Machines.
Portage was working on a new machine however, called the Portage Inspection machine. Guided by laser interferometers and electronic differential levels on a hand-fitted cast iron and granite base, it was the first high-accuracy CMM. High-accuracy CMM's are now an integral part of manufacturing and inspection the world over, but it all started with a low accuracy problem: Avoiding scrap castings due to boring holes in the wrong location.
