The production of a high quantity of parts requires a lot of attention to detail and maintaining a good quality of production. Quality and precision are the most important factors of such a process. As society and industries evolve, the requirements and expectations of the final quality of
produced parts grow.
Said values are important not only from the client's point of view – the precision of the production also has a strong psychological impact: well-manufactured parts work better in bigger mechanisms, provide longevity and deliver a flawless performance for years.
Still: the technical aspects of production are the most important part of that puzzle. A deeper look into it allows us to see the bigger picture of overall metal parts manufacturing. The quality of the final product is an effect of good coordination and precision of the whole process – from the part project and selection of materials to final machining and bettering the surface.
RADMOT - a manufacturer of metal parts
Modern quality management – developed by statistician William Edwards Deming, inspired by the post-WWII Japanese economy – led to the definition of methods and tools that helped to increase production standards.
Examples of the most developed systems of quality management are visible in the automotive industry. Automotive Industry Action Group (AIAG) defined so-called "reference manuals” – based on the IATF standards.
Said documents contain a list of requirements that allow a manufacturing company to organize its production and decrease the possibility of inconsistencies.
These rules are condensed as:
- Plan the quality – to understand the actions inside a team and/or company and to implement a new project (APQP)
- Analyze risks – to presume all of the process elements that can cause problems and inconsistencies (PMEA)
- Be sure you can control the whole process – to be sure the chosen control / measure tools and the operators can define an objective result of actions (MSA)
- Control the inconsistencies – to react in time for changes in process by monitoring the key characteristics of manufacturing or the whole process (SPC)
- Prove you understand the whole process and work – to prepare complete documentation of the production process as a proof of execution order (PPAP).
On the one hand: these rules are the foundation of a production of parts process – focused on details and quality. On the other – how do these rules apply in reality?
Who should plan the quality of metal parts production (APQP)?
First of all: the quality of the parts is strongly related to the given specification, requirements of a client, and the goal of the whole process is his satisfaction. High quality of a final product can lead to an increase in ordered amount, tightening business relationships, and building a strong brand as a professional parts manufacturer.
On that note: who is responsible for understanding the customer and answering (well) his needs?
Metal parts production above all requires a person responsible for the quality or project manager – a leader focused on delivering tasks that lead to completing the whole production process. Said person is responsible for building client requirements awareness in the team. APQP process always begins with the forming of an interdisciplinary team – the working group – in which each of the members:
- knows his/hers duties,
- is responsible for project execution and delivery.
In other words: the APQPprocess is a key element of manufacturing strategy.
Quality design in CNC machining requires:
- selection of the right technology (milling, laser cutting, turning, etc.),
- selection of appropriate machines and tools,
- risk management,
- designing the whole measurement process (with the tools calibration),
- selection of an optimal material,
- and finally: manufacturing on time.
Effect of Uncertainty on Objectives (FMEA)
The next step of the process is risk management. The international norm (ISO 31000) defines risks as an effect of uncertainty on objectives. Metal parts production and realization of orders is nothing less than answering the client's requirements. These are the foundation of selected the APQP stage goals.
Although these goals are strong and in most situations clear, the uncertainty remains the biggest challenge. Many problems can lead to under-delivery – machine malfunction, flaws in used material, unexpected tools wear, human error, problems with tools calibration, etc. The list is getting longer with an increase in the required precision of the manufacturing process.
FEMA (Failure mode and effects analysis) is a useful risk management methodology that supports the whole manufacturing process. Helps to analyze types of problems and possible consequences of their occurrence during production. Said method supports failure prediction and helps to proactively prevent it.
The additional advantage of said methodology is the increase of the whole process awareness – helps to gather information about the planned work. Such attention to detail is very important in machining plants – overall process control helps to increase productivity and decrease possible problems with malfunctions by prediction.
Complete measuring results (MSA)
The proper quality analysis is hard to perform without well-calibrated controlling and measuring systems. These tools are important due to their impact on overall quality control, but also from the perspective of measuring standardization.
One of the requirements of the IATF systems is measuring system analysis. To maintain control it is required to perform a statistical study to analyze changes in results during a control, the measurement precision, and the testing gear system (IATF 16949:2016). The tool for that purpose remains a Measurement System Analysis.
In other words – if we have a competent and well-qualified controller and controlling equipment – but still need to be sure of the measurements, the MSA analysis delivers control over the controller.
Statistical Process Control (SPC)
Another element that supports the whole manufacturing process for decades is Statistical Process Control. To be blunt: it is impossible to produce metal parts in high quantities with zero differences. Each system – manufacturing included – has its unique set of variabilities that are a part of the process.
On the other hand – there are no natural variables that can impact the whole process and in effect: cause problems in the manufacturing process. These "unnatural” problems and challenges are usually responsible for less than optimal / expected quality.
Statistical Process Control utilizes statistical techniques to reduce said "unnatural” causes of variability. For example, a production of a 30 mm bearing on the new CNC lathe with new blades can deliver stability and precision of the whole process although negligible differences (micron-ish).
But – if the cutting blade will be damaged (eg. chipped) – the unnatural / special cause occurs and the manufacturing team needs to remove the cause of the problem. SPC methodology helps to point out a problem by analyzing the results and addressing the cause.
Production Part Approval Process (PPAP)
PPAP is often misunderstood – many people think the goal of that process is to send a document related to the production to the client. In reality – the said process is a final acceptance of the production of a whole batch of parts or serial production and seals the agreement.
Said document should contain proof of understanding of the whole process and the client requirements in the form of delivering documentation and samples (that depend on the type of PPAP).
That process proves the manufacturer understands and can produce parts according to specifications and the client's requirements. The PPAP is a wider look at the whole manufacturing process.
Continuous Improvement of the systems
It is worth mentioning the implementation of said quality improvement rules is continuous. The metal parts production requires said iteration development and continuous seek of improvement. That includes an application of automatization, Poka-Yoke implementations, or the improvement of standards.
These core tools are the foundation of hundreds of thousands of metal parts that were manufactured without flaw and as an example of a perfect understanding of client requirements.
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