Lean manufacturing in metal fabrication: How are your parts presented?

Figure 1
Presenting parts so that welders do not have to work in awkward positions and giving them room to move about a cell and move parts help to sustain productivity in a job shop.

Piece parts, components, and work-in-process (WIP) are the lifeblood of a manufacturing plant. Without these, we would have no finished goods to sell. And without finished goods, we have no revenue!

We often focus on managing finished goods or warehoused items. (Are procured items in stock? Will finished products be ready for the delivery truck?) As important as these are, I want to shed light on material that does not get the same level of attention: WIP, and more specifically, how WIP is presented to assemblers, welders, press brake operators, and those at other work centers.

Paying greater attention to WIP at this stage of production can have big implications for overall operational performance. The way parts are presented will affect employees’ productivity, product quality, and part flow velocity—that is, how quickly jobs progress through the plant.

Presentation Problems

At its worst, part presentation can be a very loose process. Everybody does it their own way. The material handler wants to drop the material and run. The operator or assembler wants the material close and accessible. The quality control person wants the material stacked in such a way so that he can easily pull out a sample. The supervisor just wants the material completed and moved to the next station. Does this sound familiar?

Let’s imagine a high-mix, low-volume custom fabrication job shop that specializes in complex parts. Consider how flat plasma-cut parts are presented to the fabrication department, where forming, drilling, and welding occur. The finished product has pieces cut from five different thicknesses and grades of steel.

The plasma table and the downstream fabrication operations are separated by some distance. Some parts just cut by the plasma go several hundred feet to a different part of the plant; others go several miles to another facility the fabricator owns across town. Either way, there is a physical break in the process.

The plasma cuts all the parts needed of a given thickness and grade at one time. Operators place cut parts on skids for further processing, including grinding, slag removal, and inspection. The plasma then cuts the next thickness and grade, and the entire process repeats until all five material thicknesses are cut.

To prepare the pieces for the next stage of production, workers must combine all the cut parts onto as few skids as possible so they can move the WIP in as few trips as possible. Remember, the fabrication department (again, where drilling, forming, and welding take place) is far away from the burn table. To reduce the number of skids, material handlers need to mix different gauges and grades together. Workers then transport the skids to fabrication.

Stacking parts on skids becomes a free-for-all with no organization, and the parts show up in fabrication in one big lumpy, mixed collection. So what is the first thing that needs to be done before any value-added work can begin? You got it: People must sort and present the parts to machine operators and welders.

Sure, this parts handling arrangement makes things easy for material handlers, who don’t have to think about where to stack parts, and for the truck drivers, who can move jobs downstream in just a few trips. But their process is disconnected from the fabrication department. Put another way, it is optimized functionally (the function in this case being transportation) but suboptimized for the whole operation, because of the amount of non-value-added sorting and handling in the fabrication department. This takes skilled people away from value-added operations. There is lots of room for improvement here.

Now consider another example about part presentation in a welding cell. Parts need to go from the incoming skid to the weld tacking and assembly fixture, then on to final welding and an outgoing skid.

Although the parts and assembly are lightweight, they are long, awkward, and manually lifted. The welder bends down to take parts off the incoming skid and reaches up and over the fixture to position the pieces for welding. The higher up and farther out he reaches, the greater the strain on his body. Such strain means that the welder has a greater chance of not only mislocating parts in his weld fixtures, but also incurring some significant muscle injuries.

A steady stream of these products flow through the weld cell all day long, and such poor parts presentation can affect the welder’s output dramatically, both in terms of quality and quantity. Productivity becomes an issue because when the welder isn’t laying a weld bead, he is not adding value.

The presentation and handling of materials may have a dramatic impact on the welder’s output. A lost unit of production here, a defective unit there, and time spent stepping away from the weld station result in lost capacity. For a constrained operation, this is a big deal!

Internal Customer Needs and Ergonomics

These two hypothetical situations show what can happen when parts presentation and handling aren’t a focus for improvement. Most likely, other measures and results (did the finished product ship on time?) overshadowed the details of parts presentation and handling.

So how could these situations be improved? First, consider the needs of the internal customer and internal supplier. What can the internal suppliers (those sending parts downstream) do in their processes that will make the jobs of internal customers (those receiving parts) easier, safer, and more productive?

Also pay attention to ergonomics (see Figure 1). People should not have to bend or contort them00selves excessively to handle incoming or outgoing work. Dedicate and mark spaces for incoming and outgoing products at the workcell. Position skids, tubs, or other conveyance devices so that the operator does not have to climb over, go around, or otherwise reach, stretch, bend, or contort. Also pay attention to the height of fixtures and work surfaces. Consider adjustable-height fixtures and tables so that operators, welders, and assemblers can work in comfort.

Minimize the number of times operators need to flip or otherwise reorient parts, especially when fabricating large or heavy workpieces. Consider the entire sequence of the operation. Could a process step be eliminated? Fewer flips mean fewer opportunities for errors and accidents.

Also, use lifting devices to minimize worker strain, especially when dealing with large, heavy, or awkward parts. Be creative with the variety of options commercially available, or perhaps build a device that is custom-fit to the operation and product. If you see employees lifting items using poor ergonomic practices, then a jib crane, hoist, or an alternative lifting mechanism may be well worth the investment.

A Better Approach

What would that weld cell look like with better part presentation? For starters, you would see the intersection of 5S, visual control, and flow … all ingredients in the lean body of knowledge.

Open space allows the welder to navigate safely within the cell. Material handlers place incoming work in designated locations. Welders and material handlers move parts from step to step without stress or strain. The weld tables and fixtures position parts so that the welder does not have unnecessary movement and can easily access all areas that need welding.

In turn, the supervisor can be confident that the work is being done safely and effectively. The welder is less fatigued, and there is a steady rhythm through the workcell. When parts go missing or containers are full, it is obvious. In short, the weld cell is much more effective than before.

How about the part flow between plasma cutting and the fabrication department? If people considered the internal customer, the flow would look a lot different. Material handlers in the cutting department would group parts on the skids by job and assembly. Sure, drivers may need to make a few extra trips delivering all the skids, but people in the fabrication department would no longer spend valuable time hunting for the parts they need.

Small Details, Big Impact

Parts presentation is not a panacea or silver bullet, but it is an area ripe for improvement. These small improvements at a detailed level can lead to a more productive and safer workplace.

My challenge to you is this: Go to gemba. Observe some workstations and see how work arrives and departs from the area. Put yourself in the shoes of the person doing the work. Is there room for improvement to make it a win for the employee, the company, and the customer?

Jeff Sipes is principal of Back2Basics LLC, 317-439-7960, www.back2basics-lean.com. If you have improvement ideas you’d like to read about, contact him at jwsipes@back2basics-lean.com or Senior Editor Tim Heston at timh@thefabricator.com.