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Improving efficiencies in plasma cutting to avoid the cost of rework

Have you ever taken the time to really understand the true cost of rework? One or two parts falling to the bottom of the cutting table every shift or being damaged by the cutting arc before they can be retrieved may not seem like much, but it can add up. So, what is the real cost impact of these lost parts to a business? Unfortunately, the true cost may be shocking.

The shock factor really comes to light when you realize that it’s not just the additional machine time or material costs to consider. There are, in fact, many hidden costs involved and, in turn, many operating areas to scrutinize. A good place to start is to understand how parts get lost or damaged in the first place.

When parts fall below a cutting bed, the cost to fish out those parts or recut them can quickly add up.

For those running a CNC plasma cutting machine, parts can fall through the slats of the cutting table, and depending on the table design, they may be difficult to retrieve. In some cases, the fallen parts are simply abandoned because of the time it takes to fish them out. In other situations, such as a plasma cutter that features a water table filled with 12 in. of black water, retrieving fallen parts can be downright dirty work.

If the parts can be retrieved, oftentimes spatter has adhered to them and although they can potentially be salvaged, it requires secondary work, such as chipping and grinding. More often than not, however, the part must be recut.

Cumulative costs

When you consider all of the hidden costs to recut or rework a part, the practice might need to be reassessed. For example, if your plan is to retrieve parts that have fallen through the table slats, are you committed to additional labor time and lost efficiencies? Are you willing to designate an employee to stand guard as the plasma machine is cutting each plate to be able to quickly retrieve the fallen part?

Additionally, the spatter may need to be cleaned off once the part is retrieved. Sometimes, the part may be deemed as non-usable based upon the severity of the damage. If and when it is, just think of the labor costs and inefficiency you just sank into that part.

The TracKlean self-cleaning table, which features a slag bin and detachable plow, reduces the costs associated with lost parts and recutting those parts.

Too often, manufacturers only evaluate the material costs and machine time that’s required to recut or rework a part. But machine time and material costs are only a small part of the total cost of rework. If your material costs 60 cents per pound and the part that needs to be recut is 20 lbs., that only totals $12 – a fraction of the total cost to recut the piece.

So where and how does real substantial rework cost add up? Primarily, in labor inefficiency. Therefore, a good exercise is to evaluate the “touch points” of employee labor that are needed to recut a part.

For example, if the production staff must inform a supervisor that a part needs to be recut, that’s lost efficiency. If the engineering team needs to reschedule the part and identify the correct material to cut, that’s lost efficiency. If the programmer needs to add the part to a future nest to be cut, that’s lost efficiency.

And then there are the other parts associated with the one that has to be recut. Those parts may have to wait for the missing part to join them in the manufacturing process, which could delay further processing, and that’s lost efficiency, too. And, in extreme instances, there may be a delayed product shipment because of the missing part, which is totally unacceptable lost efficiency and, worse, could lead to an unhappy customer experience.

Other considerations might include moving fixtures, juggling manufacturing processing time and coordinating the parts to be painted with the right color batch. If those scenarios sound familiar, just imagine how all of those past inefficiencies have affected your shop and its profitability – just from the simple act of recutting one part.

The focus, therefore, is on reducing recuts or rework to increase efficiencies and, in turn, profitability. With the growing concern of labor shortages, companies absolutely must identify their labor inefficiencies and integrate solutions to solve them.

Table solutions

Regardless of the amount of recuts or rework, a process can’t be properly managed without analyzing it. Some companies might be nervous that they aren’t establishing the right metrics to track rework, but, truly, there is no “right” and “wrong” method. Just start and be consistent.

By establishing some type of measurement within your business, you can define the baseline and starting point. If changes are made, you can determine whether or not the change had a positive or negative impact. You cannot do this if you don’t have a baseline with which to compare your progress.

No matter the manufacturer, the goal is to produce the quantity of parts that are needed – no more and no less. A missing part, therefore, must be quickly produced to reduce the labor inefficiency and potential loss of production or, worse yet, missed shipment dates.

To get ahead of the situation and significantly reduce rework, one solution can be found in self-cleaning cutting tables now available on the market. Such tables include a servo-driven car and slag trays that are synchronized with the gantry motion of the bridge. This design allows fallen parts to be retrieved within seconds of falling into the slag trays. And, for parts that fall outside of the moving slag trays, they are protected, as they are never subjected to the potential damage of the cutting arc. Self-cleaning tables also include a plow that pushes the fallen parts to the front of the table for easy retrieval in less than 60 sec.

In fact, a Park Industries’ CNC cutting machine programmer who schedules the work on one of the company’s Kano plasma cutting machines with a TracKlean self-cleaning table, laid out the amount of parts that needed to be re-nested and recut each week due to parts being lost in the cutting table or damaged by the cutting arc before they could be retrieved.

“We average 1,000 parts per week and only have to rework a couple each week,” he says. “It’s a direct result of the self-cleaning table. Years back, when we had our old water table, I recall cleaning out the tank and finding lots of parts that had all been lost in the sludge.”

Whether the goal is to reduce bottlenecks and increase efficiency or simply to steer clear of fishing parts out of a reservoir full of sludge, equipment manufacturers are focused on providing a variety of solutions. As a business owner, however, it’s important to remember that new equipment can’t do it all. It’s critically important to evaluate your rework and understand the true cost and impact it’s having on your bottom line.

Park Industries Inc.