When designers and manufacturing companies specify surface finishes more often than not we’re talking in micrometres (µm), but what exactly is a µm?
1 µm is 0.001mm or one thousandth of one millimetre. In other words it is a very fine measurement and as such it can be hard to comprehend. So the best way to understand it for many of us is to compare it to everyday things we’d know, such as a cigarette paper, human hair, paperclip wire or needle.
This image from our partners Haas illustrates how these items measure up and what a µm equates to in comparison. For more details on their range of machining centres please visit their website at: http://www.haas-schleifmaschinen.de/en/
In comparison to microinches (written as µin or µ”) 1 µm = approximately 40 µ”. 1 µ” being equal to one millionth of an inch (0.000001”). (So a 15µm surface finish = 600µ” and a 320µ” surface finish = 8µm as examples of conversions).
While today’s foundry operations are mostly automated, surface treatment frequently still involves a lot of manual labour resulting in one of the most costly operations within a foundry. Automated systems tailor-made to the unique requirements of desanding, deburring, cosmetic finishing and overall surface finishing of raw castings not only significantly reduce costs but also increases process safety.
Regardless of how a component is cast, tasks such as desanding, deburring, and surface cleaning are often still carried out manually. Not only are they extremely time consuming and highly labour intensive but the quality of manual blasting strongly depends on the skills of the person who is blasting, resulting in a process that is neither consistent or documentable. High quality shot blast results are however a crucial aspect for any foundry product as well as being an important competitive factor.
People associate shot peeningwith automotive and aerospace components. However, did you know it’s used in the medical implant and component industry. Bone screws, dental implants, and hip and knee replacement components are just a few of the medical implants that are shot peened.
Please note these tables highlight the actual requirement and are only a guide.
It is always advisable that your supply exceeds this as there could be other uses and discrepancies, and therefore exceeding the required power, free air delivered (FAD) and volume of air is necessary.
Post written by Haydn Kitchen
Shot Blasting Technical Manager
Ksi means kilopound per square unit and is derived from psi(lbs/square inch). Kilo, which is often used in the metric system basically means a thousand (1000). It comes from the Greek word for 1000. Therefore, a kilopound is 1000 pounds.
A Megapascal (or MPa) is a variation on a pascal. Mega in this case means 1,000,000 and again it means “great”. As you may guess, when using MPa you are usually working with something heavy or with a high pressure!
Both ksi (kilopound per square inch) and megapascal (MPa) are units of pressure measurement – the former is an Imperial unit of measurement and the latter a metric unit.
Ksi values are commonly converted to MPa, as the metric system is the more widely used system of measurement.
Shot peening is a cold work process used to enhance the life of metal components, to prevent fatigue, stress corrosion failures and prolong the product life for the component part.
Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localised structural damage that occurs when a material is subjected to a cyclic loading.
Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold point microscopic cracks will begin to form at the stress concentration points, such as the surface, sharp points in the deviation in shape and the internal grain structure. Eventually a crack will reach a critical size, the crack will elongate suddenly, and the component will break.
Shotblasting of steel plate, profiles, construction, and fabrications is a process to clean, descale, provide a specified surface profile and edge break as a surface preparation. The process detail is subject to the hardness and start condition of the steel and it is vital to know these factors prior to shotblasting and before application of a coating or paint to maximise the adherence potential and corrosion control.
This is a document made up of five parts on “How Do You Make Your Coatings Stick Better?”