A measurement system analysis procedure is guideline to ensure that the measurement system is working within acceptable range of measurement uncertainty (M.U).
In simple language, all the important product monitoring devices are properly planed in control management. Which are helpful to establish, monitoring, and control for acceptable quality for products are studied and analyzing properly.
It is very important that, each target product monitoring devices, instruments, or equipment that are used in the manufacturing processes should be describe in the control plan. So that, measurement system analysis (MSA) procedure becomes easier to apply in the processes, as well as works within acceptable range of measurement uncertainty.
When we are going to create the measurement system analysis procedure, we have to cover some topics and important details such as inputs for the processes. The inputs of this procedure need to cover:
(1) Product Measuring devices details, and each device need to proper studied.
(2) Proper planning of the measurement system analysis.
(3) You can also include the details of new trainees and what information you will be going to study to them.
(4) The details of what and how the measurement system study and analysis are going to be conduct during the entire process.
Measurement uncertainty
To get proper results as outcomes from the procedure i.e. manufacturing processes as acceptance or rejection of measurement system needs to follows the procedure accurately. The measurement uncertainty needs to calculate for each type of product’s characteristic measuring devices. As well as each instrument, equipment or measuring devices require to identify, and also describe in the control plans.
Gauge R & R
It is obvious that, the outputs from the manufacturing processes can be possible minor variation with their require criteria. Hence, it is important for quality team to check and review these products to ensure the product as per quality requirements.
These variation in the products require to verify with special tools and measurement gauges, instrument and equipment. For variable data measurement gauges, instrument and equipment measuring repetitive data need to use as the method of calculating measurement uncertainty.
With the procedure We have to clarify that, the instrument for which Gauge R & R is to be calculate.
Describe the method of inspection
In the procedure, it is very important to describing specific method that manufacturing unit is using in the practice. However, it should be enough to comply the requirements of standards of international companies that they can accept of the materials. Herein your inspection process that you use for your products should need to describe in steps, such as:
How you managing your product inspection, method and standardization? step by steps example process we describing as under:
The first step is to collecting 10 different samples from a batch / lot from being manufacturing / production cycle.
The inspection team will be inspecting these 10 samples as per specific parameters, criteria as per standards.
The details of the inspection will be conduct in the records / documents.
As per usual inspection process, each inspector shall conduct 3 trials of inspection on the 10 sample pieces.
Later on, they will calculate average readings, range, and other parameters of trail average of each inspector.
With same process, calculation difference of inspector’s average, average range and average other parameters, and within part range of the study.
General Practice: Calculate repeatability (equipment variation), reproducibility (appraiser variation), R & R, part variation, total variation, relevant percentages & ‘NDC’ (No. of distinct categories)
Specify Acceptance Criteria
You have to define the Gauge R & R %, which may help you to use as basis for accepting the gauge as below:
- R & R Below 10 % = Measurement system is acceptable.
- R & R 10 % to 20 % = Measurement system may be acceptable based upon importance of application, cost of gauge, cost of repair etc.
- R & R over 30 % = Measurement system needs improvement.
Remember that, for a good measurement system analysis NDC (Number of Distinct Categories) shall be minimum 5.
To improve measurement system, it is much important that, actions identified needs to implement, and each effect require to verify with standards.
It is important to include in the procedure, in case whenever any new type of measurement system is going to introduce the Gauge R & R studies shall be conducts. Second thing, it is important to Improvements in current measurement system due to results of Gauge R & R studies.
Measurement uncertainty
Usually in the manufacturing units, the measurement uncertainty of all attribute gauges is calculate using some short methods such as:
First of all, quality inspector will select the gauge to be study. From the different production lines and times, they will collect atleast 10 samples. Quality team may be select two inspectors doing this stage inspection activity regularly.
The inspectors to take two trials on each sample & record the results. Later on, they will calculate values as per their needs and criteria, herein will suppose consider they may calculate ‘Kappa’ value.
If ‘Kappa’ value is more than 0.6 the gauge can accept.
Otherwise, the gauge shall be improved /reconditioned, if not possible it should be scrapped & replaced by new gauge.
Gauge acceptance study as above shall be conducted minimum for 1 gauge of each type for every year.
BIAS Study
Whenever you are going to draft the Measurement system Analysis procedure, you have to also need to include the BIAS and its requirements for the quality. Herein sample steps that may help you to increase the procedure more accurate.
For BIAS study of measuring device which are used for repetitive measurement of variable data can calculate with following steps:
- Select a known measured.
- Take min. 20 repetitive readings of same measured, every time adjusting the equipment to zero setting.
- Calculate bias as difference between average value of measurement and known measurand.
- Linearity and Uniformity studies shall be conducted for measurement systems used to measure different spans of measurement.
- Select different measurands over span of measurement of system.
- Take minimum 10 readings of each reference.
- Calculate Bias and Repeatability for each set of observations.
- Linearity is indicated by change in bias over span of measurement. Uniformity is indicated by change in repeatability over span of measurement.
Include monitoring
Process efficiency / effectiveness monitoring is one of the important parts of the process. Hence it should be included in the procedure.
At the end of the procedure, we have to describe how to interpreted of MSA study and its results. Usually, the control plans requirements are one of the prime sources that we can match and understand the process results.
The suitability while device is in use indicates effectiveness of the process. Hence, in monitoring process we have to consider it.