Many companies that have an old Coordinate Measurement Machine (CMM) are faced with the dilemma to buy a new CMM.
Although that the above is a good decision, some companies are unaware that they can retrofit their CMM with a new CAD capable software and practically have a new CMM in most of the cases at half the price than a new one.
The CMM retrofits are viable alternative especially for the old manual CMMs. What people are unaware is that the old school of building CMMs is actually more accurate than nowadays.
Originally all Coordinate Measuring Machines were manufactured to a high very precision and were mechanically accurate. The quest for accuracy demanded the selective assembly of mating parts and the production of component parts to very high tolerances.
Highly trained and skilled craftsmen undertook the assembly of CMMs in the manufacturing plant, and technicians with similar skills were necessary to install the machine and replicate CMM accuracy at the customer's plant. It was not uncommon for manufacturers to offer 2 different grades of CMM accuracy for the same model; the higher accuracy being attained by dedicating more care and attention in the final assembly and calibration process.
In the late '80's CMM manufacturers facing severe price pressure looked to lower manufacturing costs. One solution followed was the building of CMMs from aluminium; an initiative that started a trend that has subsequently become the norm. Rather than bloated CMM companies reducing their organizations and attempting to become more efficient they concluded to engineer profit back into their products. The only issue they faced was how to make aluminium CMMs accurate. Answer: throw the large errors prevalent in an aluminium structure into the error map and force the map to make the CMM structure accurate.
Maps were designed to only meet the accuracy standard currently in vogue and assist the manufacturer in passing the "test". One by one manufacturers went to aluminium structures attracted by much reduced manufacturing costs. Manufacturers became dependant upon error correction software; their confidence in this fundamental technique increased with time and subsequently relaxed manufacturing tolerances further as they improved with experience error collection and mapping procedures. Today's aluminium CMMs are typically built by unskilled personnel and have no accuracy whatsoever until error mapped into specification.