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    Measurement

    Metrology, skills to deliver

    • By MTDCNC
    • September 17, 2020
    • 9 minute read

    This is the third and final instalment of a three-part article that started back in May to discuss metrology skills. We have looked at how measurement is your business intelligence agency, giving you data on your process and quality to make crucial production decisions. But what if your measurement is feeding you bad data, a ‘fifth columnist’ disrupting and destabilising you. Ian Wilcox reports.

    In the previous two articles, I put forward what I believe are three key considerations to control your measurement, enabling cost-effective measurement and giving confidence in your data. By looking at how you manage these considerations and if needed, improve them, you will have started your journey in managing metrology effectively within a business and getting it working for you. This will help you to improve productivity and quality.

    Each element is important, but like a three-legged stool, if one leg fails, it will bring the other two down, no matter how strong they are.   

    1. Performance/Capability

    Metrology offers various methods to check your current measurement capability, giving you data to either provide confidence in your measurement results or at least warn that improvement is required. One such method is Gauge Repeatability and Reliability (GR&R). This common tool is one of many available within Measurement Systems Analysis (MSA).

    2. Process/Precision

    Understand your measurement processes and what may cause variation within them. Treat them as you would any process within your business andlook to control and improve them. Implement internal common practice and procedures to mitigate any unacceptable levels of variation. Without full automation, not everything can be a fixed, codified procedure. The balance is between people skills and procedures, and is often a fine one. Even automation does not eradicate skill, it just pushes it to the planning stage. 

    3. Calibration/Accuracy

    No company is an island. You will either be a supplier or rely on a supply chain beneath you, most likely you will have both. To connect yourself to the required standardised world of defined measurement units and traceable measurement, we use calibration and its traceability chain to certify your measuring equipment, providing the link to internationally defined units such as the Metre.

    Metrology Skills

    Skills in metrology are numerous, how effectively they are deployed is often inextricably impacted, by the level of awareness within a business regarding the opportunities that good metrology can realise. Is measurement a necessary but unproductive sideshow to production; there to tick a customer box? Or do you wish to use the data that measurement gives you to drive competitive productivity and quality. We all know what we know, without an external stimulus and new knowledge, how can we ever grow and enhance capability. Any drive for improvement will face competitive reality, usually meaning that budgetary constraints also apply. Whatever you do, it must pay for itself – generally over ever shorter periods.

    With metrology skill, we can split this into the functional application of measurement (by a measurer) and the application of supporting metrology (by a metrologist). A measurer can be anyone who collects production-related measurements within the business, and a metrologist being a person who supports measurement planning, correct application and problem solves measurement processes.

    A critical foundation skill required by both is understanding the causes of variation in any measurement process. The causes differ for each measurement process which creates its unique blend of causes, creating an effect that needs to be recognised, understood, and managed as generic groups or singular cases. I have discussed this more in part 1 of the article published in May.

    Metrology like a lot of industrial processes is not an on/off switch. It is complex layers of cause and effect that you progress through. Often for every question investigated and resolved, the next layer of optional questions is exposed. However, the rewards are that as each layer is peeled away, it leads to a better understanding and therefore unlocks the next level of productivity and new opportunities for further continuous improvement. Competitiveness in production comes from removing waste and increasing productivity.

    Knowing what skills you need is a challenge. When embarking on metrology improvement; materials, measurement environment, and the technologies utilised differ from company to company, making for varied demands for required skills. Basic engineering skills topped up with relevant metrology skills will give you the right individuals to deliver effective measurement.

    Some skills such as reading technical drawings and its GD&T are fundamental to all those in dimensional measurement. As is understanding how your actions when measuring can impact the result. But the issues around large part measurement requires a different mix of skills when compared to small parts, each having their unique issues blended with the common ones.

    The two extremes of approach to Metrology upskilling are to work with an advisor or external expert to develop a metrology upskilling programme, quickly uplifting an organisations skill. Alternately, you can start by developing a single or group of champions within an organisation. A champion can act as the tip of the spear, proving benefit, helping to mentor others and guiding a targeted follow-up skills programme. This may be slower but can be more flexible.

    An example of the type of skill/knowledge required

    In part 1 of this article, I illustrated how temperature will impact measurement results. An increase in temperature will cause most materials to expand. The expansion would be in all directions and proportionate to its length, width, depth etc. So, what about a metal washer, does the inner diameter get smaller or bigger as the metal washer expands? The answer later.

    Expansion is not an instant change. The thickness of material would mean any temperature changes would ripple through the part from the exterior, working in towards the core. Features of the part such as holes, slots and ribs all alter the rate of change as they thin or thicken sections of the part. They all create variation, as the product soaks up the temperature change. During that soak time, the temperature may change again, causing ripples to overlap ripples.

    What is the source of the temperature change and how is it transferred? Human contact (body heat), factory heating blowers or radiators, seasons of the year, external roller shutter doors opening/closing and air movement are just some of the many sources and mixes. Do not forget uncertainty? Just how accurately are you measuring the temperature in the first place to calculate material change and therefore estimate effect? It would be wonderful to comprehend it all, but realistically just knowing it exists and being able to estimate it against your tolerance is a great start.

    We have discussed the part, but remember that it is only an element of the whole process. Clamping devices if measuring on a system, and the measuring device itself can all move with temperature change, but by how much? Knowing how you can estimate the impact, from prior experience, generic testing or from engineering science is a useful skill, even if only to rule it out as a concern. Knowing what amounts to enough variation to cause concern and threaten your measurement processes capability is a core skill of the Metrologist.

    How much of those skills and other measurement skills does a machine tool operator need to know to measure samples as part of process control? In my last article, I mentioned the balance in processes between creative freedom and fixed procedures. With no guidance or procedural constraint, you would argue that the operator needs to know it all, as they make all the process decisions. But if the measurement process has been planned with procedures specifying the measurement tool, basic method, cleanliness, temperature boundaries etc – then the operator needs fewer skills. If that process is automated, then of course repeatability is vastly improved. However, someone still needs to issue a procedure via a software interface to mitigate non-human variation, including what temperature band is acceptable.

    Every measurement process is unique. Even the same process carried out seconds after the first can create meaningful variation, that is why we test. In one measurement process what may be a large cause of variation could be an insignificant cause in another. For example, changes in ambient light will not affect contact CNC CMM’s but can adversely affect a vision CMM’s capability in returning a consistent result. If you measure metals, humidity has no immediate effect on the measurement, but Nylon can expand and contract with changes in humidity as a percentage of its weight.

    When I talk to engineers, I tell them it is surprising how much you already know about physics. You may not understand it fully, know how to quantify and evaluate its impact, but you see it every day. Proper training and education should link knowledge to skills and mix it with your own current experience.

    Now, what about that washer. Firstly, think as a solid block of metal 100mm by 100mm by 2mm, expansion occurs in all directions, and so that block would expand in length, width and depth proportionately. If you drill a hole in that block, the metal that surrounds the hole will still expand. Therefore the hole would be stretched out with its surrounding metal and get bigger. How much it expands depends on the diameter of the hole, as it will expand at the same material expansion rate, per degree, per metre as the block. The hole, however, is smaller so will expand proportionately less.

    If the washer is made of steel, and I state that the expansion co-efficient is 0.011mm per degree per metre. The whole washer at 100mm diameter if heated by 5 degrees, would expand by 0.0055mm. The hole in the middle is not steel, but it is surrounded by steel. The 50mm between the two inner blue lines represents the hole and at half the outer diameter would expand half the amount of the outside diameter, 0.00275mm.

    So, the outside diameter of 100mm would expand by 0.0055mm but the inner hole would only expand by 0.00275mm

    For more information and formal descriptions, you can explore: The Vocabulary of Measurement https://jcgm.bipm.org/vim/en/index.html

    Calibration and Traceability https://www.npl.co.uk/calibration

    Metrology https://en.wikipedia.org/wiki/Metrology

    And don’t stop there, Metrology like Lean has a core, but it is also formed from many opinions and applied approaches, keep exploring, keep learning. 

    https://cdn.mtdcnc.global/cnc/wp-content/uploads/2020/09/17140547/54-56-GOM_ATOS-Q_2-640x360.jpg

    Metrology, skills to deliver

    This is the third and final instalment of a three-part article that started back in May to discuss metrology skills. We have looked at how measurement is your business intelligence agency, giving you data on your process and quality to make crucial production decisions. But what if your measurement is feeding you bad data, a ‘fifth columnist’ disrupting and destabilising you. Ian Wilcox reports.

    In the previous two articles, I put forward what I believe are three key considerations to control your measurement, enabling cost-effective measurement and giving confidence in your data. By looking at how you manage these considerations and if needed, improve them, you will have started your journey in managing metrology effectively within a business and getting it working for you. This will help you to improve productivity and quality.

    Each element is important, but like a three-legged stool, if one leg fails, it will bring the other two down, no matter how strong they are.   

    1. Performance/Capability

    Metrology offers various methods to check your current measurement capability, giving you data to either provide confidence in your measurement results or at least warn that improvement is required. One such method is Gauge Repeatability and Reliability (GR&R). This common tool is one of many available within Measurement Systems Analysis (MSA).

    2. Process/Precision

    Understand your measurement processes and what may cause variation within them. Treat them as you would any process within your business andlook to control and improve them. Implement internal common practice and procedures to mitigate any unacceptable levels of variation. Without full automation, not everything can be a fixed, codified procedure. The balance is between people skills and procedures, and is often a fine one. Even automation does not eradicate skill, it just pushes it to the planning stage. 

    3. Calibration/Accuracy

    No company is an island. You will either be a supplier or rely on a supply chain beneath you, most likely you will have both. To connect yourself to the required standardised world of defined measurement units and traceable measurement, we use calibration and its traceability chain to certify your measuring equipment, providing the link to internationally defined units such as the Metre.

    Metrology Skills

    Skills in metrology are numerous, how effectively they are deployed is often inextricably impacted, by the level of awareness within a business regarding the opportunities that good metrology can realise. Is measurement a necessary but unproductive sideshow to production; there to tick a customer box? Or do you wish to use the data that measurement gives you to drive competitive productivity and quality. We all know what we know, without an external stimulus and new knowledge, how can we ever grow and enhance capability. Any drive for improvement will face competitive reality, usually meaning that budgetary constraints also apply. Whatever you do, it must pay for itself – generally over ever shorter periods.

    With metrology skill, we can split this into the functional application of measurement (by a measurer) and the application of supporting metrology (by a metrologist). A measurer can be anyone who collects production-related measurements within the business, and a metrologist being a person who supports measurement planning, correct application and problem solves measurement processes.

    A critical foundation skill required by both is understanding the causes of variation in any measurement process. The causes differ for each measurement process which creates its unique blend of causes, creating an effect that needs to be recognised, understood, and managed as generic groups or singular cases. I have discussed this more in part 1 of the article published in May.

    Metrology like a lot of industrial processes is not an on/off switch. It is complex layers of cause and effect that you progress through. Often for every question investigated and resolved, the next layer of optional questions is exposed. However, the rewards are that as each layer is peeled away, it leads to a better understanding and therefore unlocks the next level of productivity and new opportunities for further continuous improvement. Competitiveness in production comes from removing waste and increasing productivity.

    Knowing what skills you need is a challenge. When embarking on metrology improvement; materials, measurement environment, and the technologies utilised differ from company to company, making for varied demands for required skills. Basic engineering skills topped up with relevant metrology skills will give you the right individuals to deliver effective measurement.

    Some skills such as reading technical drawings and its GD&T are fundamental to all those in dimensional measurement. As is understanding how your actions when measuring can impact the result. But the issues around large part measurement requires a different mix of skills when compared to small parts, each having their unique issues blended with the common ones.

    The two extremes of approach to Metrology upskilling are to work with an advisor or external expert to develop a metrology upskilling programme, quickly uplifting an organisations skill. Alternately, you can start by developing a single or group of champions within an organisation. A champion can act as the tip of the spear, proving benefit, helping to mentor others and guiding a targeted follow-up skills programme. This may be slower but can be more flexible.

    An example of the type of skill/knowledge required

    In part 1 of this article, I illustrated how temperature will impact measurement results. An increase in temperature will cause most materials to expand. The expansion would be in all directions and proportionate to its length, width, depth etc. So, what about a metal washer, does the inner diameter get smaller or bigger as the metal washer expands? The answer later.

    Expansion is not an instant change. The thickness of material would mean any temperature changes would ripple through the part from the exterior, working in towards the core. Features of the part such as holes, slots and ribs all alter the rate of change as they thin or thicken sections of the part. They all create variation, as the product soaks up the temperature change. During that soak time, the temperature may change again, causing ripples to overlap ripples.

    What is the source of the temperature change and how is it transferred? Human contact (body heat), factory heating blowers or radiators, seasons of the year, external roller shutter doors opening/closing and air movement are just some of the many sources and mixes. Do not forget uncertainty? Just how accurately are you measuring the temperature in the first place to calculate material change and therefore estimate effect? It would be wonderful to comprehend it all, but realistically just knowing it exists and being able to estimate it against your tolerance is a great start.

    We have discussed the part, but remember that it is only an element of the whole process. Clamping devices if measuring on a system, and the measuring device itself can all move with temperature change, but by how much? Knowing how you can estimate the impact, from prior experience, generic testing or from engineering science is a useful skill, even if only to rule it out as a concern. Knowing what amounts to enough variation to cause concern and threaten your measurement processes capability is a core skill of the Metrologist.

    How much of those skills and other measurement skills does a machine tool operator need to know to measure samples as part of process control? In my last article, I mentioned the balance in processes between creative freedom and fixed procedures. With no guidance or procedural constraint, you would argue that the operator needs to know it all, as they make all the process decisions. But if the measurement process has been planned with procedures specifying the measurement tool, basic method, cleanliness, temperature boundaries etc – then the operator needs fewer skills. If that process is automated, then of course repeatability is vastly improved. However, someone still needs to issue a procedure via a software interface to mitigate non-human variation, including what temperature band is acceptable.

    Every measurement process is unique. Even the same process carried out seconds after the first can create meaningful variation, that is why we test. In one measurement process what may be a large cause of variation could be an insignificant cause in another. For example, changes in ambient light will not affect contact CNC CMM’s but can adversely affect a vision CMM’s capability in returning a consistent result. If you measure metals, humidity has no immediate effect on the measurement, but Nylon can expand and contract with changes in humidity as a percentage of its weight.

    When I talk to engineers, I tell them it is surprising how much you already know about physics. You may not understand it fully, know how to quantify and evaluate its impact, but you see it every day. Proper training and education should link knowledge to skills and mix it with your own current experience.

    Now, what about that washer. Firstly, think as a solid block of metal 100mm by 100mm by 2mm, expansion occurs in all directions, and so that block would expand in length, width and depth proportionately. If you drill a hole in that block, the metal that surrounds the hole will still expand. Therefore the hole would be stretched out with its surrounding metal and get bigger. How much it expands depends on the diameter of the hole, as it will expand at the same material expansion rate, per degree, per metre as the block. The hole, however, is smaller so will expand proportionately less.

    If the washer is made of steel, and I state that the expansion co-efficient is 0.011mm per degree per metre. The whole washer at 100mm diameter if heated by 5 degrees, would expand by 0.0055mm. The hole in the middle is not steel, but it is surrounded by steel. The 50mm between the two inner blue lines represents the hole and at half the outer diameter would expand half the amount of the outside diameter, 0.00275mm.

    So, the outside diameter of 100mm would expand by 0.0055mm but the inner hole would only expand by 0.00275mm

    For more information and formal descriptions, you can explore: The Vocabulary of Measurement https://jcgm.bipm.org/vim/en/index.html

    Calibration and Traceability https://www.npl.co.uk/calibration

    Metrology https://en.wikipedia.org/wiki/Metrology

    And don’t stop there, Metrology like Lean has a core, but it is also formed from many opinions and applied approaches, keep exploring, keep learning.