Getting Inspection Right the First Time
How to decide whether to contract measurement services when 100% inspection is required.
Deciding whether to perform inspections in-house or to hire contract service providers is not solely a question of upfront investment versus long-term need. For some suppliers, a third-party contract service can also provide assurance that parts have been inspected and approved by an unbiased party.
In cases when a manufacturer has a 100% inspection requirement, contractors can also provide next-level tools that are not commonly found on an everyday shop floor or lab—even part makers with robust inspection departments and a variety of CMMs and other tools may not have their own computed tomography scanner at the ready.
Metrologists often use the term “100% inspection” in two different ways. One definition is that every part coming off the production line is checked. Another common meaning for the term is that 100% of a part’s technical specifications need to be checked. Quality spoke with Frank Valdez, sales manager for Zeiss Metrology Services, to focus on the latter definition—how manufacturers can decide whether to contract out their metrology services when 100% of the specifications on the technical drawing need to be verified.
Quality: When is it most common for manufacturers to contract 100% inspection requirements?
Frank Valdez: You’ll see it a lot in aerospace and medical, where they call it a first article inspection. Essentially, what they’re doing is proving out their process and making sure they made everything exactly right. They’ll make their first piece or the first few pieces, and for those pieces they’ll check every single dimension, every single specification on the drawing to make sure it was made correctly.
QM: What are the main benefits of hiring contracted service?
FV: Equipment and also expertise, because sometimes you run into some companies that have inspectors, but they’re maybe less experienced. They’re not engineers and they haven’t been properly trained on reading GD&T, or Geometric Dimensioning and Tolerancing. You need to be able to interpret those details correctly to do the right analysis. So, yeah, it’s equipment but it’s also staff experience and staff certifications.
QM: What are the benefits to keeping it in-house?
FV: The benefits to keeping it in-house are your costs are immediately going to be lower because you’re not paying a service firm to do it. Also, maybe speed, it really depends on the company. Sometimes we’re faster than if they do it in-house. But that should be a key benefit.
QM: What trends do you see in who is choosing to hire contract measurement services?
FV: I see clients experiencing a lot of growth, where they can’t handle what’s going on in their inspection department right now. So they have to outsource it.
QM: What is the most common tool used in 100% inspection jobs?
FV: The most common one I would still say is a CMM. But we are seeing a shift towards CT in the plastics industry.
QM: Why CT?
FV: It’s because CT is a high-accuracy system that captures all surface and internal data, which allows you to capture all necessary features very quickly. Part qualifications that could have taken a week to do can now be done in a day or two.
Also, you get more data because a CT scan is essentially a 3D rendering of the actual part, versus in all those other tools, you’re taking points on the part or you take a picture of it with a vision system. CT captures the entire part geometry, including internal geometries, and allows for an easy-to-understand visual representation of the part quality.
QM: What are some reasons someone might choose optical inspection tools for this?
FV: Flat components are a perfect example of an application fit for optical inspection. If it’s something you can’t touch, something you shouldn’t come into contact with, and if they just want images of certain areas of the component, then optical inspection would be the correct tool for the job.
QM: What are reasons for choosing non-contact options?
FV: If a component is flexible or will be compromised if touched, then that would be a good reason for selecting non-contact inspection.
QM: What are some other benefits of contracting measurement inspections?
FV: You have an objective party doing it. Sometimes what we've seen is that when people do it in-house they’ll just try to get everything to pass. So, with contracting, you really have an objective party with a lot of capabilities machine-wise. And that’s what they do; they’re experts at doing those types of inspections.
Contract inspection services firms are able to give different insights, maybe something the manufacturer didn’t catch or something they didn’t think of. We work with these companies as a direct extension of their quality department. Sometimes they come to us as a referee. “Our vendor said this, our inspector said that. What’s the right measurement?”
QM: What’s the turnaround time for a job
FV: It does depend on the job, but usually we stick to 3-5 days standard lead time. And then there’s also expedite options. So if you need it next day, if it’s possible to do it next day, customers can pay for that.
QM: Do you have a sense whether the industry is trending towards or away from contract services?
FV: Yeah, we see more and more manufacturing companies reaping the benefits of outsourcing complex first article inspections to service firms who specialize in this type of work, they just pay experts to do it faster and more reliably.
QM: Do you have tips for someone who is considering their options?
FV: When you’re choosing a contract house, you need to thoroughly make sure what kind of equipment they have. A lot of people will just send [the part] out because they found somebody on google, but they should be checking what equipment they have available, and who trained their staff, or what kind of training their staff underwent to learn how to operate that machinery.
And also, what is their understanding of the different industries? How much have they done inspection in automotive, in medical and in aerospace? Staff expertise is really key. Also, look for somebody reliable that’s going to be able to deliver the data when they said they would. If they quote you 3-5 days, it better be done in 3-5 days.
This interview was edited for clarity and length.