Tools, Fixtures and Jigs – What?

[Post by Chuck Krugh, May 21, 2024]

I know it’s been a while since I wrote a blog, but I needed a little break from all the writing. I also was having a hard time coming up with new topics to discuss. After all, I wrote a lot of them – and I never even thought I could write as many as I did.

As it turns out, I have a few more topics that I would like to cover.

One of the topics I’ve been pressing our operations team on is to use more tools, fixtures and jigs in our build process. When I talk to our high-seniority mechanics, they tell me how we used to have lots of tools, fixtures and jigs before we started the DDG 1000 class. Unfortunately, we apparently got rid of those tools when we thought we weren’t going to build the DDG 51 class again. That’s been unfortunate for us, but completely understandable.

The other unfortunate factor in our reduced use of tools, fixtures and jigs is the loss of our senior mechanics over the past five years. They had that tooling knowledge, and when they retired, that knowledge left with them. They had learned how to build efficiently over time with the experiences they gained. Their valuable, detailed knowledge of the build process and knowledge of the tooling they used – which may not have been written into the build plans – went with them.

Fast forward to today: our workforce has less experience (fewer years in the job) and fewer repetitions (i.e., has only built a few ships). This isn’t bad; it takes time to build a portfolio of work and gain experience to have intimate knowledge of the build process. This is just a fact of our business. Adding an additional layer of complexity, the introduction of the Flight III ships changes the build yet again.

One of the ways to decrease our build hours and cycles is to use tools, fixtures and jigs. For ease of writing and reading, I will call these three items just “tooling” – the array of tools, fixtures and jigs used to make a part within a certain tolerance in a manufacturing process. Tooling is the general category that contains tools, fixtures and jigs.

Tools are exactly what you would imagine – hammers, drills and other hand tools. This category can also include specialized tools used for specific tasks and activities. Specialized tools can also include Go/No-Go tools.

Go/No-Go tools are generally inspection-related tools used for checking and verifying that the outcome of the build station meets the engineering requirements for the part. Say a part needs a 12-degree angle between one part and another; a mechanic may choose to use a simple piece of metal cut at a 12-degree angle to check the work he or she did and verify that it is built to the engineering. This Go/No-Go tool is not a build tool because it takes too much time to use, doesn’t hold any of the parts in position and usually requires an extra hand when building.

I know personally from my past that using tools, attempting to hold a part that’s being worked on and trying to conduct an operation on said part, you can exceed the number of hands you have available to do the work.  A simple holding fixture that holds the part at 12-degrees is far easier to use, reduces the time the mechanic needs and produces a better product. After using the fixture, the mechanic can use the Go/No-Go tool to verify that the part meets the 12-degree engineering requirement.

Fixtures are those tools that generally hold a part or assembly in a specific place to ensure that the part shape, dimension or location stays where it’s supposed to be per engineering. Products are oriented in a specific position as it relates to the engineering and held so they cannot move before the next operation. By holding the product in place so it cannot move, you are sure that the product produced is the same every time and meets the engineering requirement. Fixtures come in all shapes and sizes, ranging from immense fixtures that may take up a manufacturing bay to small ones that go on the benchtop. It’s easiest to think of fixtures as holding tools.

Jigs are generally used to hold one piece or even several pieces of material in position in order to cut, drill or fasten the parts together. They can be stationary tools used in one build station, or they can be attached to the part or assembly for use across several build positions. Like other tooling, they make the job of performing work easier, repeatable and more standardized.

As I walk the deckplates, I do see mechanics using Go/No-Go tools, but some of them are using them as part of the build process rather than as I described above. While I’m definitely happy they have the Go/No-Go tool, the build sequence is harder than it needs to be because they aren’t using a fixture to hold and secure their work. This is one of the opportunities that I see where we can improve: making some of our work safer and easier for our mechanics.

Developing simple tooling is often done at the point of execution by the mechanic. In my tool box at home, I have many examples of tools and small fixtures that I built while working on aircraft. These include simple things like hold-downs for drilling, special bucking bars for riveting or modified tools to reach into specific areas on the aircraft.

We have almost endless opportunities to build simple tools or fixtures to help us build a part or unit the same each time or to position parts in the ship properly the first time and consistently every time.

More complex tooling for large products relies on a manufacturing engineer (ME) to work closely with the operations and planning team so they can understand the build strategy/plan, the engineering constraints and the dimensions that must be constrained during the build. Because of their potential size, weight and reusability, engineers are tasked with designing them. The ME will incorporate the holding locations, attachment points, tooling points and the operation of the fixture into the design, and then will follow the use of the tooling to ensure that it achieves the desired result.

This is a short description of what happens in the tooling design process, but it gives you an introduction to the concept.

This is an area that we will start to really focus on since we have more DDG 51s to build.

See you on the deckplates!

Safely Execute High-Quality Work

President, General Dynamics Bath Iron Works

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