Metrology Fixture Design Best Practice Overview

June 9, 2022

Metrology Fixture Design Best Practice Overview

June 9, 2022

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The performance of metrology fixtures can have a major impact on the efficiency and productivity of your quality control processes. In industries like medical device manufacturing, this reality is amplified by compliance and safety requirements, as well as the tight tolerances that often apply. Therefore, it’s essential to follow metrology fixture design best practices.

The Primary Objective of Metrology Fixture Design

In some respects, metrology fixtures have a straightforward function. They need to hold a part securely in place so inspection processes can be completed accurately. This simplified description applies to all methods of inspection, including CMM, flexible gaging, and vision machine inspection.

Of course, the reality in real-world production environments is not as straightforward as this simplified description sounds. Achieving repeatability and accuracy are the main challenges.

As a result, the objective of the metrology fixture design process is to optimize the positioning and securing of parts in the fixture while minimizing the need for operator intervention. This, in turn, mitigates operator variance as much as possible.

The Repeatability Priority

Consistency is essential in metrology, particularly in sectors like medical devices where inspection processes influence the performance of high-volume production lines.

To achieve consistency, metrology fixtures need to be designed to ensure maximum repeatability. Modern inspection machines provide technical solutions to the issue of repeatability by adjusting for small positioning and alignment errors. However, these technologies can only correct so much.

Larger problems with positioning the part will have a significantly negative impact on the inspection process, including rejecting parts unnecessarily.

If an operator has to work out how to position the part, the risk of error increases. Therefore, fixtures must be designed to make the positioning of parts intuitive and simple.

Automation solutions also enhance inspection repeatability. This includes both automating the process of putting the part on the fixture, as well as auto-rotating the part during inspection. Both levels of automation enable the inspection process to take place with minimal, if any, operator intervention, eliminating the risk of human error.

Reproducibility and Why It’s Important

Modular fixtures are often the most practical and cost-effective solution for your quality control requirements. However, with modular fixtures, the question of reproducibility becomes important in the fixture design process.

In other words, ensuring fixture components can be accurately and easily positioned on the base plate to measure different parts. Making the fixture setup process as accurate and easy as possible reduces downtime and removes operator variance, improving the efficiency of your inspection and quality control processes.

The most effective method of achieving this objective when designing metrology fixtures is to label holes for fixture components in an alphanumeric grid on the base plate.

The process for setting up the fixture for a specific part can then be documented in the quality standards documentation using the alphanumeric grid references, ensuring accurate reproducibility.

Maximum Measurements, Minimum Steps

Metrology fixture design engineers will aim to design fixtures to achieve the maximum number of measurements in the minimum number of steps. The ideal scenario is to enable all necessary measurements in a single setup.

Multi-Station Fixturing

Measuring a single part is not always the most efficient use of an inspection machine. This especially applies when measuring small parts such as those that are common in the medical device industry.

What you often end up with is a large inspection machine measuring a small part with lots of wasted inspection space. Addressing this issue to improve the efficiency of the overall inspection process is another consideration that is often important in the metrology fixture design process.

Multi-station fixtures are the solution. With multi-station fixtures, multiple parts can be added to the fixture where they can be inspected simultaneously, improving operator and inspection machine productivity.

Tried and Tested Metrology Fixture Design Process

Metrology fixture design is a process that, when followed, optimizes timescales, maximizes the quality of the finalized fixture, and ensures maximum benefit for your quality control processes. At Verus Metrology, we use a robust design process that is tried and tested. It has seven main steps:

  • Initial concept development
  • Internal review with our metrology engineers to refine the concept
  • Design qualification with the customer
  • Approval stage 1
  • Final design of the fixture including the creation of production drawings
  • Second design qualification with the customer
  • Release for manufacture

Finally, the Importance of an End-to-End Service

Offering an end-to-end metrology fixture service is also beneficial to the design process. An end-to-end service includes metrology fixture design, manufacturing, programming, and validation. After all, the design of a metrology fixture is only one part of getting to the stage where you can accurately and repeatably inspect manufactured components and parts in your lab.

At Verus Metrology, for example, our end-to-end service ensures maximum efficiency, quality, and returns on investment. It also ensures we maximize the benefits of the best practices that apply in metrology fixture design.

Introduction 

As 2024 unfolds, the field of metrology is witnessing transformative changes. At Verus Metrology, we recognize the importance of keeping pace with technological advancements and new trends in the science of measurement. In this rapidly evolving landscape, innovations in metrology are not just about achieving precision; they are about meeting the evolving challenges of industries like medical devices, where accuracy is critical for ensuring safety and quality. This article explores the emerging trends and technological breakthroughs shaping metrology’s future. 

As 2024 unfolds, the field of metrology is witnessing transformative changes. At Verus Metrology, we recognize the importance of keeping pace with technological advancements and new trends in the science of measurement. In this rapidly evolving landscape, innovations in metrology are not just about achieving precision; they are about meeting the evolving challenges of industries like medical devices, where accuracy is critical for ensuring safety and quality. This article explores the emerging trends and technological breakthroughs shaping metrology’s future. 

Metrology Fixture Types – What’s Available, and Which is Best?

9 February 2023

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Fixture type and use cases

Metrology fixturing technologies continue to develop at a rapid pace, offering manufacturers in the medical device industry new and innovative solutions. Those solutions don’t just meet inspection and quality process requirements, but they also deliver efficiency savings and productivity gains. How do you know what metrology fixture types are available and which is best for your application? In this blog, we’ll outline the main options, their underlying technologies, and the use cases they are best suited for. 

However, it is also important to point out that the fixture types described in this blog represent broad categories. Within those categories, there is an infinite number of ways that a fixturing solution can be developed to meet your specific needs, reduce risk, and take advantage of opportunity

While there are metrology fixture types that we can explore, every fixture solution that we develop here at Verus Metrology is completely unique. In other words, fully customised for the product or component being measured, as well as the inspection machine, quality department workflows, production processes, and any other influencing factor. 

Metrology Fixture Types 

There are six main metrology fixture types: 

  • Auto rotational 
  • Manual rotator 
  • Multi-station
  • Proof of Principle (POP) 
  • Vision system 
  • Docking station 

 

Auto-Rotational Fixtures

Isometric view of an auto rotational metrology checking fixture, the automatic part of the fixture is the turning of the rail by a motor. The fixture has white plastic components held in place using brown clips

 

At a fundamental level, the job of a metrology fixture is to hold a product or component securely in place so it can be effectively inspected and measured. However, there are situations where the inspection process requires the part to be presented at different orientations to enable all the relevant measurements to be taken. This requirement for measurement in multiple orientations is increasing as medical device products become more complex and intricate. 

Auto-rotational fixtures enable the inspection of products and components in multiple orientations with minimal operator intervention. An auto-rotational fixture can be a single-station set-up, but they more commonly come in multi-station designs to minimise the time it takes to achieve your required sample rate. 

The most important feature of an auto-rotational fixture is that you can measure multiple components in multiple orientations in a single setup. 

Manual Rotator Fixtures

Manual Rotator Metrology Fixtures by Verus Metrology

Manual rotator fixtures offer similar benefits to auto-rotational fixtures. The obvious main difference is that operators manually rotate components once they are loaded into the fixture. 

Manual rotator fixtures can be multi-station. They are also designed so that all measurements in all orientations can be taken in one set-up. So, while the operator will need to manually control the rotation mechanism, there is no requirement to touch or adjust the components as the fixture holds them securely in place during rotation. 

The benefits of manual rotator fixtures include: 

  • Significantly reduced operator intervention 
  • Improved measurement accuracy 
  • Elimination of errors 
  • Faster and more efficient metrology processes 

Furthermore, we can design your manual rotator fixture so it can be loaded with components away from your CMM. This improves CMM availability as the machine doesn’t have to sit idle while components are being loaded onto the fixture. 

Multi-Station Fixtures 

multi station rotator

According to FDA regulations and ISO 13485, it is essential that you can statistically justify sampling rates in your quality procedures using a risk-based approach. The operational part of this requirement isn’t covered in the guidelines, but it is an important business consideration. How do you efficiently, accurately, and cost-effectively inspect the number of products or components that are required to hit your sampling rate target? 

Multi-station fixtures are a common solution. We can design multi-station fixtures in any configuration. This could be a large cavity multi-station fixture, a fixture to inspect very small and complex medical devices, or solutions for products or components of any size, geometry, or characteristic. 

The benefits of multi-station fixtures include: 

  • Operator intervention is greatly reduced 
  • Fixtures only need to be loaded once before full inspection routines can take place on multiple products at the same time 
  • Reduce human error 
  • Speed up inspection processes while achieving your sampling rate target 
  • Reducing the cost of inspections 

 

Proof of Principle Multi-station Prototype Fixtures 

proof of principle

 

In many product development and process change situations, it is beneficial to have a POP fixture that can be used for verification and validation purposes. The approach we typically take at Verus Metrology is to design a multi-station fixture to deliver on your requirements. 

However, before this multi-station fixture design goes into manufacturing, we design and produce a single-station POP prototype fixture. This POP prototype can be manufactured quickly in our advanced manufacturing facility. We’ll then put it through a gage R&R study to give you confidence in its repeatability and reproducibility, before sending it to you for evaluation and testing. 

POP prototype fixtures offer a range of benefits: 

  • Facilitates design for inspection during the product development process 
  • Minimises delays in process verification 
  • Enhances and speeds up the design transfer process 
  • Reduces time to market in line with regulatory requirements 

 

Vision System Solutions

We also design and manufacture fixturing solutions for vision systems in addition to the fixtures we design for use on CMMs. Fixturing solutions that are optimised for vision systems have a number of specific and differentiating features, including ensuring there is a clean and clear view of the part. 

Vision system solutions can also allow for backlighting where necessary. Furthermore, a single set-up is all that is required for the full inspection routine to take place, with parts securely held with as little force as possible. 

 

Docking Systems 

Docking System Verus Metrolody

Docking systems enhance the efficiency of quality departments that use multiple fixtures and/or have high sampling rates. Docking systems are securely fixed to CMMs to make it quick and easy for technicians to load fixtures that are fully set up with components ready for inspection. Once the inspection routine for a fixture is complete, it can be quickly and easily removed from the docking system ready for the next fixture to be loaded. 

With a custom-designed docking system, you can have confidence that each changeover results in precisely secured fixtures for repeatable and reproduceable inspections. 

Choosing the Right Fixture for Your Requirements

There are many factors to consider when choosing the best type of metrology fixture for your requirements. Your budget is an important consideration, as are your ROI goals, quality processes, quality resources, and future requirements. 

The best approach is to speak to a fixture design expert to explore the options and get an understanding of what is possible. Contact us today to find out more. 

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About Verus Metrology Partners

Verus is committed to the enhancement of our client’s metrology laboratories, machine efficiencies, and inspection processes. Since our beginning, our expert metrology engineering team has partnered with some of the world’s largest MedTech multinationals.

 

We specialize in high quantity, difficult to measure, yet critically important, medical device parts. As well as working in the MedTech, Pharmaceutical and Personal Care industry, we also work with metrology departments in the FMCG and Aerospace industry.