A clear definition is needed to uniquely identify the best in class shops in a highly competitive market. Because the market spans over a very broad range of industries, it’s rather important not to limit the definition to one in particular, but instead expand the definition to three unique precision types.
These types can be identified as micro precision, ultra precision and nano precision. By these three types, precision can be identified in regards to the technology that a shop might have and what you can expect in quality and accuracy instead of using a generic term as precision. Further, each precision type also can be used to define the technology and expectations within a machine tool and can be further used to define the maximum part quality that can be expected of the machine without over complicating things. Precision can now be narrowed to micro precision as precision defined by ±5 microns or less on the workpiece; ultra precision as precision defined by ±2.5 microns or less on the workpiece; and, nano precision as precision defined by 1 micron or less on the workpiece.
As you can see we’re no longer talking in terms of English units, but instead talking in terms of Metric units. This method is not only clearer but simpler to work with than thousands, tenths or millionths. Working with microns also is a universally understood unit of measurement and is clearly known and widely accepted around the world. It allows us to define closer tolerances much easier. For example, rather than saying 40 millionths or .00004″ it is much easier to say 1 micron or 1 um. In re-defining precision, it’s important to understand the micron unit. There are several reasons why. First, it gives a better picture of the three types of precision. Secondly, it brings the manufacturing world in line with the advance technology that is available on the market today—from the machine tool to inspection equipment. Additionally, it articulates the trends in product designs toward closer tolerances and miniaturization.
Embracing technology is necessary for survival in China. manufacturing today. Current machine tool technology has lowered the bar toward ultra and nano precision. Once only visible in the lab, ultra and nano precision technology has now moved from the lab and R&D centers to the commercial sector.
Although much of the core technology in today’s ultra precision machining (UPM) is not new, it’s the combination of the improved elements and the careful systematic unity that has pushed the technology into a new direction of ultra precision. Further, the tools used to bring everything together have also improved greatly.
To illustrate this, consider the secondary equipment used to build a Ferrari, a Lamborghini or perhaps a Lotus. These unique manufacturers use state-of-the-art equipment to build their cars ensuring performance and quality. Likewise, machine tool builders who claim micro, ultra and nano precision tolerances use a similar approach by using state-of-the-art technology to build state-of-the-art machine tools.
Additionally however, machine tool builders offering these tolerances need to be extremely concerned with their surrounding environment, which includes cleanliness, organization, air quality and temperature control. Bringing micro, ultra and nano precision into the shop and being successful with it also requires the same approach and the same high quality environment.
Traditionally reserved for grinding, nano precision is no longer just limited to grinding and has now entered the commercial sector for milling. A nano precision milling machine offers a host of new opportunities—ranging from hard milling for the mold and die industry to jig grinding holes for mold bases. By nature, a nano precision-capable machine along with superior build characteristics is going to produce extraordinary surface finishes. Therefore the possibilities to hold ±1 micron on drilling and milling features on your parts and holding surface finishes of values of Ra 0.05um are now achievable. In the past these kinds of tolerances and surface finishes were only possible in a lab environment on specially designed machines with a very small work envelope. In fact today, workable envelopes as large as 20″ x 20″ x 15″ are possible in a commercial environment.
Accuracy refers to the closeness of a measured value to a standard or known value. For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate. In this case, your measurement is not close to the known value.
Precision refers to the closeness of two or more measurements to each other. Using the example above, if you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise. Precision is independent of accuracy. You can be very precise but inaccurate, as described above. You can also be accurate but imprecise.
For example, if on average, your measurements for a given substance are close to the known value, but the measurements are far from each other, then you have accuracy without precision.
A good analogy for understanding accuracy and precision is to imagine a basketball player shooting baskets. If the player shoots with accuracy, his aim will always take the ball close to or into the basket. If the player shoots with precision, his aim will always take the ball to the same location which may or may not be close to the basket. A good player will be both accurate and precise by shooting the ball the same way each time and each time making it in the basket.
your definition is very accurate! thanks!