Tool Making - Precision means...

                                 It’s important not to limit the definition of precision to one in particular, but instead expand the definition to three unique precision types: micro precision, ultra precision and nano precision. Some companies go beyond the word precision and define themselves as military precision, medical precision or commonly Swiss precision. So the question is: What defines precision today?

Defining Precision

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.

Understanding Microns

                                                 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.

Moving Beyond the Pack

                                      Embracing technology is necessary for survival in Indian 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.

                                             Manufacturers that use such advanced equipment are capable of meeting the higher demands of new product designs, tighter tolerance requires and lower labor cost through a decrease in part handling by increasing surface finish quality. By investing in the latest technology, manufacturers can truly identify themselves as a best in class micro, ultra or nano precision manufacturer, and therefore move beyond the pack.

Behind the Technology

                          Nano technology within a milling machine can bring a lot of skepticism. Holding ±1 micron or ±1000 nanometers while obtaining surface finishes of Ra 0.05um, should certainly be questioned. Anyone with any experience in holding tight tolerances should have some doubts about these capabilities, but rest assured the technology is available and results are astounding.

Similar to high-speed machining, nano precision machining or NPM requires a complete circle of technologies that complement each other. NPM shouldn’t be considered machining at slow feeds and speeds in order achieve closer tolerances but rather the opposite.

Using HSM practices is actually one of the center points of NPM where as HSM doesn’t guarantee precision. The primary focus in achieving nano precision tolerances on your parts is centered on the machine tool itself. On the other, your CAD/CAM system must be able to handle the increased tolerance output requirements and this would include surface tolerances.

Another important aspect is the ability to control heat within the entire machine tool. A polymer-base machine tool is the start of precision, but to achieve even better results every aspect of the machine tool needs to be completely temperature controlled. 

Quality Assurance Infrastructure

NPM doesn’t stop at the machine tool. Having the technology and the quality assurance infrastructure to check such precise parts is quite important. Coordinate measurement systems and 3-D vision inspection systems have been able to stay ahead of the advances in precision machine tool technology. Some of today’s finest CMMs have the ability of measuring uncertainties of 250 nano meters at a resolution of 7.5 nano meters. Additional, 2-D vision systems now have the ability to measure depths. Equipped with a combination-touch probe, laser and white light sensors, vision systems have taken vision inspection into a 3-D world. White light sensor technology for probing has reached into the submicron level by splitting pixels into thirds.

To ensure your nano parts are indeed nano precise, understanding your quality assurance infrastructure is just as important as your nano precision machining infrastructure. If the two technologies work together, re-defining your precision will move you toward the ability to reclaim your position as a real precision manufacturer producing near perfect parts.