April 28, 2014
How do you error-proof a hardware insertion operation? One half involves the hardware insertion process itself, including proper training, but the other half entails inventory management: making sure operators have easy access to the right hardware at the right time.
Missing or incorrect hardware got under Ed Kittelson’s skin. Nothing was worse than answering a call from an annoyed customer about a batch of parts with incorrect or missing hardware. So the president of Micron Metalworks, a Ham Lake, Minn., custom fabricator, and his management team decided to do something about it.
They labeled and organized the fastener inventory. They bagged fasteners to ensure every part in a batch had all the fasteners it needed. If there were fasteners left in a bag, there was a problem.
The later an error occurs in a job, the more expensive that error is, especially when a problem part ships to the customer without being caught. “There’s nothing more a customer hates than a hardware problem,” Kittelson said.
The price of fasteners belies their importance. Even minor hardware errors can be expensive, both for the custom fabricator and its customer. On critical parts, errors can even be life-threatening. “Using the wrong fastener could create a failure with whatever product it’s fastened to,” said Winona, Minn.-based Jeremy Johnson, director of sales, Fastenal Managed Inventory (FMI), at Fastenal. “This is a serious topic. Spending a little time on the right thing can be meaningful in the long term.”
All sources agree that errorproofing hardware insertion of course involves operator training: what hardware goes with which part or which material grade, how much force it requires, and why. But so much in the hardware insertion arena involves everything that happens before the actual act of inserting hardware into a workpiece: organization; labeling; and tight control over inventory, particularly in the highly variable environment of the sheet metal job shop.
To that end, here are three questions shop managers can ask to make life easier for the hardware operator. Each essentially takes one step back in the chain of events that leads to a fastener being pressed into a sheet metal part.
“An organized, well-lit, well-labeled stocking area with signage is the first step to ensure the right parts are easily found,” said Johnson, who emphasized the value of color-coding: labeling and color-coding certain fastener types to corresponding products or product families, for instance. And then there are the basic visual management tools, like putting part photos or drawings on the bins themselves.
Sources also recommended kitting in boxes or bags. Lean manufacturing discourages processing large batches just to save on setup; flooding the floor with work-in-process makes part flow that much more difficult to control. The same thinking applies to fastener inventory.
In a white paper, Neal Lober, director of sales and marketing at Allied Fasteners, Los Angeles, described a typical case study. A bin of fasteners had a safety stock of 500 parts, stored and replenished in bags of 250—quite a lot, but typical for inexpensive purchased items (what the Institute for Supply Management calls “Class C”). “Because of the small price and high importance of C items,” Lober wrote, “most manufacturers carry excessively high levels of C inventory.”
After all, running out of fasteners can halt an operation, so when it doubt, pad the stock, right? Of course, just as in WIP between workstations, a large amount of hardware inventory can make a process more difficult to control. Hardware can go missing, get lost, or mixed in with other hardware. An operator may open a large bag, and fasteners would spill into crevices.
To streamline matters, the company in Lober’s case study organized hardware into 30-piece “per-assembly” bags.
Like splitting an order up into smaller batch sizes, such bagging effectively decreased the batch size of fasteners and allowed for more precise inventory control. Like at Micron Metalworks, when operators emptied a bag, they knew they had installed all the necessary hardware for the job at hand.
Bin arrangements can make a difference as well, as described by another Allied Fastener white paper, this one authored by Greg Liepman, executive vice president. As with a lot of elements of 5S, the idea is to make the system obvious for everyone, no matter how much experience they have or how much training they receive. Someone may be having a bad day and absentmindedly pull hardware from the wrong bin.
Part replenishment systems often entail two bins, one primary and one secondary. Depleting the primary one triggers a replenishment order, and the secondary bin moves over to the primary bin location.
But say an untrained worker grabs a handful of hardware from the secondary bin, uses a certain amount, then throws back the remainder in the primary bin. As Lober wrote, this can easily happen, and it sometimes takes more than clear labeling to fix it.
A shop may have primary and secondary bins that are side-by-side or even in a rotating arrangement, in which a two-sided rack has primary bins on one side (usually the side closest to the workcells), with secondary bins on the other. The problem in both cases is that workers (and anyone, really) can access the secondary bin somewhat easily. If an operator is having a bad day, he may unknowingly reach into the adjacent bin. In a rotating two-sided-rack arrangement, a new employee who may have forgotten recent training may mistakenly take hardware from the wrong side of the rack.
If a primary bin has parts, why does anyone—outside the people replenishing stock—need easy access to the secondary bin? This is why Lober recommends a back-to-back arrangement. “In a back-to-back system, the racks themselves are deeper, and the secondary bin is physically placed behind the primary bin. When the primary bin is exhausted, it is turned over as a replenishment signal, and the secondary bin slides forward to become the new primary bin.”
This is classic kanban. Two full bins represent the maximum stock, only one full bin represents the minimum, timed as such so that replenishment occurs before the shop reaches its safety stock level, the emergency savings account of sorts that’s there just in case replenishment problems should arise.
But how much “just in case” inventory does a hardware insertion operation really need, and for which fasteners? This can be a challenge to pinpoint, especially for high-product-mix, low-volume operations with a wide variety of parts, part geometries, and associated hardware. This is where the next question comes into play.
In a vendor-managed inventory, or VMI, arrangement, the vendor actively manages a fabricator’s inventory, replenishing when needed. In traditional arrangements, the vendor sends a representative to the facility to check bin inventory levels and replenish them as needed. But according to sources, in recent years this process has become far more immediate and responsive, thanks in large part to technology.
Consider an operator who depletes a bin of hardware. He may scan an empty bin with a bar code scanner, signaling that it’s time to replenish. That information is transmitted immediately to inventory management software, which keeps a comprehensive history of usage, which in turn helps plan for future needs.
“Technology has been a huge driver here,” Johnson said. “It’s now so much easier to identify which parts need to be managed, and at what stocking levels. The technology is actually very straightforward, but it can really make a difference, both for the supplier and fabricator. If I walk into a facility and see someone hand-writing parts down [to replenish fastener stock], that’s a red flag. There’s potential for error.”
The technology need not be sophisticated or expensive, either—even at some of the largest contract fabricators. Fastenal actively manages the hardware inventory of Mayville Engineering Co. (MEC), a $312 million contract manufacturer based in Mayville, Wis. For some of its hardware, MEC has simple webcams aimed at certain inventory bins. Fastenal representatives need not visit the facility to check inventory levels. Instead, when they see that the hardware reaches a certain level on the webcam, they send in a replenishment order.
“It’s an intelligent bin, so to speak,” said Bob Kamphuis, CEO at MEC. “Previously they had to send someone to take inventory. Now they can get a sense [of inventory] without sending a person in to do it.”
According to the Institute for Supply Management, manufacturers spend more money on expensive purchases, what it calls “Class A and B” items, but spend far more time ordering and managing Class C items, which of course includes fasteners. As Lober put it in his white paper, “A well-run VMI program addresses this imbalance by automating much of the ordering process for Class C items.”
As Johnson explained, part of what makes a VMI good is setting goals at the outset: inventory reduction, material costs, the labor involved with stock replenishment, country of origin requirements, and so on. Establishing these goals from the get-go, he said, will determine the direction the program takes.
Next up is a review of the current state of things, focusing especially on a comparison between what parts are in stock versus what parts are moving on the shop floor. “If there are old parts not moving,” Johnson said, “they may need to be thrown away or sit in a staging area for a specific amount of time before disposal.”
This review also covers the current organization strategy (as described in question No. 1): labeling, color-coding, bin arrangement, worker access to inventory, and so on. These small changes can make all the difference in the world. As Kittelson said, “It really comes down to the little things.”
Next comes determining the parts to be managed: Which represents the most used parts, those that take up the most time in purchasing? How much does the demand vary over a period of time? Are there unexpected spikes? Johnson added that if a fabricator doesn’t have this data, the vendor may be able to draw information from similar operations as a starting point. All this helps determine inventory minimums, maximums, and safety stock levels. Over time the VMI program can use historical data to identify usage patterns so as to better manage the inventory.
Still, the reality on a job shop floor can be extremely complicated. A new part print may call for plating or other engineering changes, which of course affect the fasteners used in hardware insertion. A fabricator may need to manage numerous fasteners, and that variety adds complexity, which in turn can create unpredictability. Here, the third question comes into the picture.
Although not an option for every situation, some fabricators get involved during the early stage of product design. Better communication among the fabricator, the fabricator’s customer, and fastener vendor can (theoretically, at least) minimize surprises that can change hardware insertion.
Is there a reason nonstandard fasteners are used for a certain product? Could a clinching or an alternative hardware-free joining method work instead? Does the operator need to maneuver the part as many times as he does to insert all the hardware? These questions and others like it could lead to time-saving results.
And when a new job does come up with unusual hardware requirements, some fabricators will communicate with their fastener vendor on the front end. “Some are sending our folks locally a print to review,” Johnson said, “to make sure we can find a conforming product to meet the deadline.”
It’s easy to order a lot of fasteners, of course. It makes sense to pad a stock of inexpensive items, especially if the cost of running short is really high.
ut hoarding parts can lead to disorganization, which in turn can lead to the wrong or missed fastener going into a subassembly. As sources explained, regardless of how cheap or expensive something is, there are costs and risks of having too much.
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