What’s a Water Spider?

Most of us are familiar with material handlers.  They drive lift trucks, push carts or carry plastic tubs of materials to their point of use.  In Lean, however, we try to eliminate this non-value adding job by placing materials close enough to the operator that the operator can easily retrieve them.  

There are times, however, when material replenishment requires someone other than the operator.  For these tasks, we turn to a water spider.

FUNCTION:  The function of the water spider is to replenish the materials used at each station so that the production personnel can focus on the process of adding value.  Once every Takt Time* the water spider walks the entire length of the assembly line and places the exact materials required to make one product at each station.  The water spider then returns to replenish and starts all over.  Water spiders are typically only used when Takt Time is three minutes or greater.

So, when might you use a water spider?  Usually three things govern their use.  They are:  exact part, exact place, exact count.  

EXACT PART:  When the product varies and different parts are required each time it is assembled, the water spider is used to place the exact parts required for the next assembly at each station.  The change in part(s) often signals the assembler what product they are to build next.

EXACT PLACE:  Placement of parts can be critical.  When an operator knows that a part is always in the same place, they don’t have to take their eyes off their work to grasp the next part.  This allows them to devote their full attention to their work.

EXACT COUNT:  Count can be used as a quality check.  When the operator knows that the water spider has placed the exact number of parts in the exact place, it allows them to perform an ongoing quality check.  If they run out of parts early, it means they’ve assembled a part in the wrong place.  If there are parts left over, the assembler stops the line, because the product is not fully assembled.

WHO:  One might think that a water spider is an entry level job, but it is not.  The water spider is usually the most experienced assembler on the line.  They understand the product being built, how to perform every step in the production process, how it is tested and what quality checks are performed on it.  Should anyone need to step away from the line, the water spider can backfill any position. 

* When part count is not critical and parts don’t vary from product to product, the water spider might place enough parts at each station to make multiple products.  When this occurs, the water spider walks the entire line in multiples of Takt Time; e.g. if Takt Time is 300 seconds, the water spider might walk the line every 1,800 seconds (30 minutes) and place six new parts at each station.  The water spider may also be used to move finished goods at the end of the line before returning to replenish.

Total Productive Maintenance (TPM)

Lean concepts like Standard Work and Just In Time are predicated on dependability: dependability of materials, dependability of workers, and dependability of equipment.  It’s this latter subject that I want to address in this post.

A standard maintenance program uses maintenance personnel to perform routine functions like oiling and lubricating equipment.  When a machine fails, the maintenance department repairs it; yet, rarely brings it back to it’s original specs.

In a preventive maintenance program, machines are maintained prior to failure.  These programs are often like the 15,000 mile checkup on a car.  The mechanic performs all the routine functions specified by the checkup and then runs a diagnostic to give the owner advance warning about potential problems.

How does productive maintenance differ from these?  First, the goal of a productive maintenance program goes beyond merely keeping machines running.  In a TPM Kaizen event, machines are cleaned, restored to their original specifications and then minor changes made to improve both the functionality and longevity of the machine. 

In addition, the Kaizen event establishes areas that need to be attended to at least once a day.  These points are marked on the machine and on an operator’s dashboard (usually a laminated card with photos of the machine and the numbered locations of all inspection points matching those on the machine).  It then becomes the operator’s (not the maintenance department’s) responsibility to check these points, and perform any minor maintenance indicated, at least once a shift.

This means the operator oils and lubricates, looks for leaks, reads all gage values and calls maintenance immediately when anything is not what it should be.  The operator also keeps the machine wiped down and dusted as a way of ensuring that it's constantly being inspected for leaks, broken hoses, broken gages, broken sight glasses, etc.  In short, the operator is the first line of defense in maintenance of the machine.

A quick story:  A colleague of mine was touring a plant in Asia and found a bumper sticker on the side of a machine that had a red heart in it.  Since it was in Koren, he asked his guide what the sticker meant.  He was told that it translated “I love my machine.”

Seeing the quizzical look on my colleague’s face, the guide went on.  “This man’s livelihood is derived from that machine.  Not only his, but also his family’s and extended family’s; sometimes even others in his community."

When workers are able to make that connection between their equipment and their livelihood, it changes their perspective about preventive maintenance.  This relationship frequently leads Lean organizations to assign responsibility for each piece of equipment to a single operator.

Often as part of the TPM Kaizen event, the “capability” of a machine is determined.  The machine’s capability is a measure of it’s ability to reach and hold tolerances.  These capabilities are then used in the designing of new products and in choosing to which machine to assign new designs.

Now, the maintenance department is not off the hook.  First, it works with operations to monitor drift of the machine’s capability.  When the machine cannot hold tolerances, it is shut down or at least slated for PM.  Notice: the machine is still making good parts.  It's shut down because it can't hold tolerances.

Beyond that, the maintenance department establishes a program to perform critical maintenance functions for which the machine needs to be shut down; e.g. replacing hoses or gears.  These preventive maintenance events are placed on the operations and maintenance calendars.  Every effort is made to maintain the machines on those dates, but some organizations allow operations to shift the date, one time, to the right or left on the calendar.  TPM is taken so seriously that there is no additional shift allowed.

In summation, TPM is a critical part of Lean.  As I said at the beginning, an organization cannot really establish standard work, or meet Takt Time, until they have established a TPM program on their equipment.

From the Middle Outward

In the past I’ve written that, to be sustainable, a Lean transformation needs to start at the top and flow downward. I won’t retract that statement, but I’m learning a different model ... firsthand.

Okay, I’ll admit that the jury is still out, but I will grudgingly admit that it just may be possible for a transformation to start somewhere other than the very top and still succeed.

Here’s what I’m learning…

I was hired into a position and title that were buried well below the top of the organization. The manager who hired me would have preferred to have done my job herself, but knew that, to be successful, the new Lean practitioner would need support and a degree of cover. She’s provided all that and then some.

As I espouse, I began with an overview of the business – did I say that it was in a completely different industry than I’d ever worked in before? I looked at the major muscle movements using a flow chart. “Why didn’t you use a Value Stream Map?” you ask. The answer is that this value stream isn’t A value stream. It’s dozens. They all start and end in the same place, but what a knot in between.

Also, as I espouse, I started at the end of the value streams and began working backwards. I conducted one Kaizen event, then another, then a third and fourth. I’m preparing for #5 as I write this.

So far, I’ve had the teams concentrate exclusively on Standard Work and they have achieved some noteworthy results: reduced interdisciplinary handoffs by 50%, reduced processing time of core activities by 60% and developed a communication tool that keeps all practitioners, as well as the customer, appraised of progress.

Monetarily, when these are rolled out across the value streams, these improvements are expected to save in the hundreds of thousands of dollars.

I’ve tried to gain audiences with whomever I could to showcase what the teams have done and, one by one, the C-Suite has started to take notice. Let me say, results alone didn’t do it. It took the constant lobbying of my boss and her boss to get us to this point. Without them, I'd have surely failed, no matter how successful the Kaizens.

So, here’s what I’m prepared to admit: With the proper support, it may be possible to start a transformation below the C-Suite and succeed. We haven’t succeed yet and won’t until the C-Suite owns the transformation, but there is a glimmer of hope that it just might happen; a glimmer that wasn’t there a year ago.

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