Fabrication

Fabrication is the act of taking raw stock material and turning it into a part for use in an assembly process. There are many different types of fabrication processes. The most common are

1. Cutting
2. Folding
3. Machining
4. Punching
5. Shearing
6. Stamping
7. Welding
8. Additive Manufacturing

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Let’s look at the types of fabrication processes in greater detail here:

1. Cutting. There are many ways to cut nowadays. The old standby is the saw. Others now include plasma torches, water jets, and lasers. There is a wide range of complexity and price, with some machines costing in the millions.
2. Some parts need to be bent. The most common method is a press brake. It has a set of dies that pinches the metal to form a crease. This operation can only be performed in very specific cases due to the range of movement of the part during the bending process and the possible shape of the dies. Designing for Lean manufacturing, though, can help prevent complex shapes that slow down production. Sometimes using two different types of fabrication processes or two different pieces fastened together work better than one complicated piece.
3. This is the process of removing metal from a piece of material. It might be done on a lathe, where the material rotates against a cutting tool, or in some other cutting machine where a rotating tool is moved in a variety of ways against a stationary piece. Drills fall into this latter category. The range of motion of the cutting head is defined by the number of axes (i.e. a 3-axis machine).
4. Punching is the act of a punch and a die forming a scissor effect on a piece of metal to make a hole in it. Obviously, the punch and die must be the same shape and size of the desired hole. In some cases, the main piece of material is kept, as in when holes are added for fasteners. In other cases, the piece that is removed is the desired product-this is called “blanking”.
5. Shearing is the process of making a long cut on a piece of metal. It is, in effect, just like the action of one of those paper cutters with the long chop-handle. This is done on sheet metal.
6. Stamping is very similar to punching, except the material is not cut. The die is shaped to make a raised portion of material rather than penetrating.
7. Welding is the act of joining two pieces of metal together. A variety of types of welding exist for use in different applications and for the range of metals used in manufacturing.
8. Additive Manufacturing. This is a relatively new technology. In effect, a machine layers material to form a part. It functions similarly to a three-dimensional printer that produces components in plastic (or other similar materials) but can be done at much larger scale and with more varied materials than typical printers. They can even be big enough to produce entire houses. The geometry of the component produced can be limited due to the effect of gravity on the fluid materials before they become rigid.

There are many other types of fabrication processes that are less common than the ones in the list above. There are also constantly new types of fabrication methods being developed (such as additive manufacturing listed above).

Fabrication processes are particularly well matched to Lean. The motion of operators, their interaction with machines, and the need to manage inventory are all right in Lean’s power alley.

Fabrication processes are especially compatible with implementing jidoka (autonomation) and hanedashi devices (autoejectors). Both of those devices are prerequisites of the chaku-chaku line (load-load).

But there is one area where Lean can struggle. Some extremely large machines are well matched to the products they are making. But far too many big machines with too long of a changeover time drive up inventory and promote overproduction. It is best to “right-size” machines and put them into work cells if possible. That helps create flow.

The biggest impediment to making flow in a fabrication shop is the preponderance of large, multi-function machines that take a long time to change between parts. This drives up the lot size, creating inventory. It also means that a machine may be used to produce many different components for several product lines. Deciding where to put it is a challenge. If you include it in flow of one line, even the biggest line, it would be a problem for all the other lines.

The task in this case is first and foremost to reduce the changeover time so that the machine does not run large lots. At that point, you can keep reducing the amount of inventory that the machine creates. The second task is to get away from buying large, expensive machines when smaller, dedicated ones will suffice. In many cases, a small machine can be automated with jidoka and hanedashi to make their efficiency rival that of large CNC machines.

One challenge with linking fabrication and assembly processes tends to be the painting process. In many cases, parts leave the fabrication shop to go out for painting or go right to an in-house paint center. In either case, the flow is disrupted, and the delays cause more inventory. Again, use the CI tools at your disposal to minimize this impact—reduce cure time, reduce the changeover, make smaller batches, go to smaller, dedicated paint booths. Do what you can to keep coming closer to flow.

Continuous Improvement in Fabrication

Fabrication processes are generally target-rich environments for continuous improvement. There are great chances for visual management and 5S to make processes run more smoothly. There are immense opportunities to reduce setup time to help lower lot sizes. Kanban helps with knowing what to make—especially on the extremely large machines. Right-sizing machines can help make flow better—smaller machines fit in smaller spaces that can be set up as dedicated lines for higher volume products.

Fabrication processes tend to have another great opportunity in continuous improvement—the working environment. “Fab” processes tend to be hot and grimy. Small metal shavings are everywhere, as are coolants and lubricants. Parts are often heavy. Smoke and debris are in the air.

To top it off, safety concerns abound. Machines are unforgiving. They are designed to work with metal—hands and other body parts don’t even slow them down.

Machines are extremely loud. Unless you have experienced it, is it hard to imagine…

Extended Content for this Section is available at academy.Velaction.com

Take a close look at your fabrication processes and identify all the issues that pose safety risks or that are generally frustrating to your team. Rank order the problems. (Note: The safety issues should be at the top of the list.)

Begin applying your Lean toolkit to removing these issues. It might sound a bit like a haphazard approach, but the goal is one that aligns with the big picture. You are attempting to build support for the problem-solving processes that continuous improvement demands. Once team members see that there is some benefit to them, they will be more willing to take on the bigger projects that improve flow.

Those types of changes—running smaller lots and arranging by product line rather than function—generate much more resistance. Having a solid track record of success makes people more accepting of change.