What are test fixtures and why are they useful in product development? 

When in the product development cycle should you consider using test fixtures? 

We sat down with Nathan, a test fixture engineer at Blur, to understand when test fixtures are needed and why they’re valuable. 

Julia

Thanks for joining us today, Nathan. Can you describe what you do here at Blur? 

Nathan

I am our test engineer here at Blur. So I design and develop test fixtures, manufacturing fixtures, assembly fixtures, things like that. I’m also involved with the design verification and validation to make sure that our products are functional and safe before we send them to clinical or to the open market or wherever they may go. And that about sums it up in a nutshell. 

Julia

How long have you been in this field of test fixtures and creating test fixtures, and how did you determine that that’s what you wanted to do as a career? 

Nathan

So, In 2009, when I was 15, I got a job at a third party test lab in Pennsylvania, where I used to live. I started there sort of washing windows, scrubbing carpets, and not so fun things like that. But I was still in high school, so it was okay. They were a very large aerospace test facility, and their market was that they were third party, so they don’t have any weight in whether the results pass or fail which is always what you need at the end of the day to get a system passed for use by the FAA or different things like that. So I’d worked there for a while, I knew the background of where I worked. 

And when I went to college, I got a degree in mechanical engineering. When I got out of college, I was offered a position as a project manager at that business and that would have been in 2016. So I started there and I worked in non-metallics, so composites, plastics, things like that. 

And that’s where I really got into this because, at the time when I got into it, the use of composites and plastics for structural components in the aerospace industry was still fairly new. So it was a new department that we had opened up at the place that I worked and everything there was, at that time, a lot of stuff that they hadn’t done before. So that’s where a lot of the designing new tests and new fixtures and things like that came in because they had 40 or 50 years experience testing metals, but it’s a totally different animal once you get into, in particular, the composites, the carbon fibers, those are very complex tests. So that’s where I got started on it. I did that for five or six years before I came here and now I’ve sort of been doing a similar thing since I got to Blur. 

Britt

Yeah, that’s great. I’ve worked a lot with Nathan, specifically in the manufacturing area with fixtures and yeah, he can come up with pretty much anything. So I’ve definitely had a lot of great experiences with Nathan. 

For our listeners out there though, it would be good to kind of hear your process a little bit. First thing, how do you know when a fixture is needed? Like how does our client know they should be actually reaching out to you for a fixture? 

Nathan

That can vary. Sometimes we are told by the operators who are working with a specific device, to either assemble it or test it, “Hey, this is fairly complicated, it’s labor intensive, it’s not really working out well for us.” So really it’s whenever you make an observation that something could be improved by, you know, minor automation or less human involvement. Whenever you notice things like that, that’s really a good time to consider that it might be a good idea to make a test fixture and assembly fixture, depending on where you’re at in the project. 

Unfortunately, there’s not a direct answer for that. There’s no right answer. It’s really whenever someone observes that something could be improved, that’s the appropriate time to consider investing the time in making something like that. 

It depends on how complex the system that the fixture that you’re considering making is also. If it’s minor, like an alignment jig or a holding jig or something like that, we can come up with something like that typically within a day. It’s not very labor intensive, it doesn’t cost a lot to do something like that. But, if we’re getting more into an automation type thing, that can obviously take a little more time and it’s a little bit bigger of an investment. 

So it’s all about weighing the investment that you’re putting in now to develop some sort of fixture versus, you know, what it would take for someone just to do it. If it’s a, if it’s a small builder, if it’s a minor thing versus a large complex system that is going to take more time and money to come up with. 

Britt

And what’s your process for coming up with a fixture? Are you typically just thinking of it from the user’s perspective and then working through how to make it easier or like what are your steps? Do you draw it out first or do you just start pulling materials and start playing around with things? 

Nathan

The first step for me is I like to see what the problem is. So if we’re working on something in manufacturing and we’re having trouble with assembly, we’re having trouble holding it apart or whatever, I like to watch the process to visually see, okay, this is what they’re trying to do and this is potentially how we could improve it. 

Outside of that, it’s nice here because we have all the materials and resources to rapidly prototype a lot of things. So it’s easy to come up with a simple design to sketch it out, to get it drawn up in a 3D modeling system like SOLIDWORKS. From there we can cut some simple parts out of plastic on the laser and assemble a simple mock jig that way, or we can 3D print something if we think that’s more appropriate. 

Really it’s looking at the process, trying to see what the problem is, coming up with a quick solution to it, and prototyping it to get it in the hands of the people who are using it to make sure that that they see this as a benefit that it’s actually working how they think it will. And from there, after we have that initial prototype, it can be improved to something more robust and more permanent. The first step in the process is to come up with a simple design just to make sure that we’re headed in the right direction and then we can, I don’t want to say complicate it, but we can make it better from there. 

Britt

That makes sense. And it sounds like for the most part, a lot of your fixtures are related to making things more automated or easier for the user. Do you also see a lot of need for fixtures when it comes to electrical testing or in process testing to prevent end of line failures? Where do you see the most fixtures coming out of? 

Nathan

A lot of fixtures that we’re making, at least since I’ve been here related to testing, are life-cycle type things. For most of our design verification campaigns, there’s portions where you want to cycle certain components of the device for the expected life. So, we may unplug and plug something in up to thousands of times to make sure that it’s going to survive what we expect it to see when it’s in service. And obviously, it’s easy to have someone sit there and unplug and plug in a cable 10,000 times, but for things like that, there comes a point where it’s no longer cost effective to pay someone hourly to do that as opposed to investing the time upfront to come up with an automated system for it. 

We have numerous fixtures here that run on linear actuators, things like that, to make repetitive motion automated so that we don’t have to have someone sitting there doing it. And it’s twofold because it saves time, because these are kind of set and forget type things where you set it up, you tell it to go and you check on it when the test is done, once the fixture’s been validated and all that, but it also gets you a more repetitive process where you sort of taking the human error out of the test that you’re doing because you know that it’s doing exactly what it was designed to do every time without fail. So you’re eliminating a variable essentially, depending on what kind of test you’re doing. 

Britt

Yeah, and you’re saving somebody a lot of time from having to do that a thousand times. 

Nathan

A lot of times that somebody is me. So it’s nice. That’s why I save myself some time there. 

Britt

What’s your, a fixture that you’re most proud of? 

Nathan

One of the ones that I did earlier in my time here, it’s basically a cyclic fatigue fixture that takes a round medical device and curls it into a G shape and then extends it back to a straight line. It cycles it that way, you know, a couple thousand times. And then that fixture is also able to take the sensor in a straight line and twist it so it’s like a torsional type test. That one was one of the more complicated ones that I worked on here. So once we got it together, it worked out pretty good. I’m fairly happy with that one. 

Another one that we get a lot more use out of is another cyclic fatigue type fixture that applies a shear stress to a bond line of one of our devices to simulate the stresses that it might see in use. That one involved some usability type testing where we had people wear the device and said, okay, do jumping jacks, do pushups, sit up, stand down and tried to evaluate what kind of stress was actually on that bond line when we were using it. And then taking that and sort of getting a fixture to emulate the stresses that the device sees during actual wear. So that one, the mechanical side of that one isn’t as complicated, but the setup, it’s definitely a lot easier to tie it into the real world use of the device. So that’s another one that I’m fairly happy with. 

Britt

That’s great. 

Julia

Wow, those are cool. 

Britt

Yeah, very cool. I guess my last question I have is just what would you recommend for our clients in that test world or fixture world for them to start thinking of sooner rather than later in their process?

Nathan

I think the earlier that we get started on these, they’re almost like side projects compared to the big scheme of the devices we’re making, but the earlier we can recognize that we need them and we can get started on the development of them, that gives us more time to do some iterations and get a better functioning system. As opposed to, you know, sort of getting it at the last minute and saying, “We need this now, this has to go out, we have to do something quick,” which we’re more than capable of doing, but the more time you have, the cleaner the systems can be, the better they can work. 

I think one of the challenges is that a lot of times with assembly fixtures, we don’t realize we need them until we’re in the assembly process. And there’s two sides of that: On the R&D side, the assembly is typically a little simpler because we’re doing small volumes, but once it gets to the manufacturing side and we’re in more of a production volume, we start to recognize that this could be made, this could be improved, we can make this a little easier. So if we can get it earlier on, it gives us more time to develop it. And on the testing side, it’s the same sort of deal where a lot of times we’re getting into design verification and it’s sort of a rush and we realize that we need this. And again, we’re always capable of getting a quick solution like that, but the more time we have, the better of a system we can come up with. 

Britt

Yeah, that’s great. I really appreciate you being here. 

I think that we can gain a lot from your knowledge. I’ve definitely had to pull Nathan several times to help with assembly for sure in the manufacturing process. The one great thing is having him on site and being able to, as he said, rapidly create a prototype for us to try out and then get into manufacturing quickly and without any downtime. 

I’m glad you’re here today to help educate our clients.