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Recent manufacturing trends are turning the phrase, “the bigger the better,” on its ear. Micromachining takes advantage of the high precision, speed, and repeatability of CNC machining to create intricate components smaller than the human eye can appreciate. Precision on such a small part needs a different set of quality control measures. Micromachining can refer to incorporating small design features on standard part sizes or separate micro parts. Consider the tiny screws used on eyeglass frames as an example in this category.
How Small is Micro?
International Tolerance guidelines classify a CNC machine based on these 4 grades:
Class 1: ±0.2″ or ± 5.08 mm.
Class 2: ±0.01″ or 0.254 mm.
Class 3: ±0.005″ or 0.127 mm.
Class 4: ±0.0005″ or 0.0127 mm.
These classify most CNC machining applications and set an industry standard around the world. An acceptable accuracy for most mills and lathes is around 0.1 mm, or Class 3. When dealing with minute parts, those tolerances must be even tighter. With the cutter smaller than 1/8″, or about 3mm, the tolerances are typically accurate to 0.0001” or less. Some may be surprised to know that tools as large as 0.100″, or 2.54 mm diameter can be considered micromachining.
Approach to Raw Materials
The properties of the material must be taken into consideration to determine the best approach to any machining task. Working in micro-movements the natural heat, friction, and other factors involved in CNC machining become paramount.
A range of polymers and metals can be fabricated with micromachining. Their physical and chemical characteristics dictate which process is best. Various equipment, such as laser and ion beam cutting can provide precision cuts on brittle materials with low conductivity, like titanium and some plastics. Conductive materials, like steel and stainless, can utilize ECM (electromechanical) cutting to achieve similar results or CNC machining.
Diamond-tip cutting tools used on CNC machines for micromachining are highly effective due to their ability to dissipate heat. Diamonds do have a chemical reaction with some metals including Iron, Cobalt, Nickel, and Chromium.
Cutting Approaches
The use of 5- or 6-axis machines is needed to facilitate effective material removal from all angles and without the need to reset the part. Shallow cuts and exacting calibration work with precise workholding to process parts. Sensors, guides, and cameras all work to create what the human eye can’t see. It isn’t about the physical tools so much as it is the correct approach with workholding, the right tool, and automated quality control.
Feeds and speeds can’t be calculated as they would for a normal application on a CNC machine. Specific software uses algorithms as the cutter diameter drops to compensate for micromachining calculations. Due to the small size of the cutting tool, the chip load can be larger or smaller than the tool itself and must be addressed when setting the tool path to appropriate negative or positive tolerances. The miniature size of the cutting tool makes them extremely susceptible to breakage. And shorter tools must be utilized due to the increased stress load of 2-20 times more than conventional machining. Careful attention must also be placed on chip clearing due to the compact environment for the cutting operation. This miniature world places a lot of strain on the cutting tool and breakage rates can be high when first learning the process.
Applications
As we see the world shrink around us, the applications for micro components become greater. The reduction in the size of phones and laptops creates a perfect industry for the growth of micromachined electronic parts. Applications also include:
The concept of micromachining is more about the technology than the size. The advent of new technologies and better CNC machines allow the production of repeatable, precise parts of any size. Machines can be multi-purpose, capable of producing standard-sized components as well as micromachining. Just as quality control may need to be provided through cameras or robotics for larger parts, the same approach with micromachining creates the flawless, tiny parts we see in a variety of uses.
When designing parts for CNC machining, many engineers focus solely on functionality while overlooking how design choices impact manufacturability and cost. At Rapid Enterprises,
CNC Machining has been stated to be one of the most versatile methods of production, but converting it into a cost-effective one requires something more than mere machinery that is optimized. One factor that goes unnoticed most of the time is the material selected.
A decade ago, manufacturers faced potential threats like rising wages in low-cost regions, fragmented customer demand, and a scarcity of skilled talent. The Great Recession of 2008–2009