An Error Proofing Challenge


How would you error proof this material handling / logistics situation? I have a few ideas, but thought this would make for interesting discussion. I won't set up a “spend no money” rule, but cheaper and simpler ideas are always best.Here's a pallet of material at a hospital (click on the photo for a larger view). There's a pink sign that says, “Carrier, DO NOT Double Stack or Break Shrink Wrap.”

Barking orders at people is a very weak form of “Error Proofing” (it isn't really error proofing at all). What if they don't see the pink sign? What if they don't respect it? Would you ever know? Can you explain “why” if you have to use a sign?

If you absolutely needed to ensure that the pallet wasn't double stacked, can you think of a way of error proofing that? Click “comments” to submit your idea. No prize, other than bragging rights amongst your Lean peers.

On a very coincidental note, at the airport buying water today, I overheard the employees talking about a pallet of bottled water that got crushed because it was doublestacked and shouldn't have been. Maybe there's a market for something here.

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Mark Graban
Mark Graban is an internationally-recognized consultant, author, and professional speaker, and podcaster with experience in healthcare, manufacturing, and startups. Mark's new book is The Mistakes That Make Us: Cultivating a Culture of Learning and Innovation. He is also the author of Measures of Success: React Less, Lead Better, Improve More, the Shingo Award-winning books Lean Hospitals and Healthcare Kaizen, and the anthology Practicing Lean. Mark is also a Senior Advisor to the technology company KaiNexus.


  1. Easy: put a single box on the top of the stack instead of filling the whole layer! Makes shipping slightly less efficient, but barely… and not when netted against shrinkage.

    Actually I’m a little surprised it wasn’t as my previous employer, name prominently displayed on the pallet of boxes in your photo, started doing that right before I left 7 or 8 years ago.


  2. A single box on top won’t stop a Teamster – it just makes an irresistable target! You would need to pyramid pack the pallet (unfortunately), and have the top box higher than the half-way point of a standard trailer box height so a 2nd pallet couldn’t be stacked on top.

    Or, take away fork lifts and only allow pallet jacks in the shipping area. You put a “through the wall” shuttle line so that pallets of only X by X size fit through the hole in the wall from production and are picked up by a pallet jack on the shipping dock.

    Truckers are loathe to load their own trailers so they won’t unload your pallet just to restack – it takes time, and they’re on a federally mandated maximum driving hours time clock. If you’re in a union shop they’re not allowed to load the truck anyway.

  3. To prevent the breakage of shrinkwrap, how about asking what the shrinkwrap is for? Is it to keep a bunch of little boxes together on one pallet? That is what it looks like, but I also see bands of tape criss crossing.

    Why the heck is there such a huge pallet of stuff anyway? Shouldn’t these boxes be shipped directly to the station that needs them? This looks like a batch process that needs 5 whys.

  4. I like the pyramid design, but anything that lowers the amount stackable or shippable (is that even a word?) would not be an easy sell. Someone could design some sort of “pallet top” that would be placed on the top of the stack. This pallet top would be a wedge design that would make it impossible to stack ontop of. Could be made out of wood like a normal pallet so it would be cheap and of course reusable! We’ll be rich!

  5. What about a crate? If you put all the stuff in a crate, then you can stack them and neither shrinkwrap nor the pink sign matter anymore.

  6. Lots of great ideas! This was something that just caught my eye and got me curious… I’m not trying to outsource my own work in a subtle way.

    I was thinking something like a wedge, as Tom was saying. I like the idea of just trying to stack the boxes differently, but that imposes a different cost. Would the shipper charge more for not having a cubed pallet?

    Very observant about the material quantities and the overwrap issues. I don’t know what the material was or what department it was going to. it’s hard to gauge on size alone, it could be some sort of large supply, you never know. Well, maybe Kevin knows.

  7. The shrink wrap is for safety reasons: while in-transit, the cartons remain together. This is critically important especially if the pallet would need to go to a mezzanine location bin.

    Here’s an idea: This pallet containing 4×4 cartons looks like it is at a staging area, which is not unusual (yes, even Toyota has staging areas — I know, I worked at the Hebron, Kentucky plant). At Toyota, we placed the location of where the pallet would need to go on top of the 4×4 pallet. This location marker was colored, large, and looked like an orange cone. The location would be something like (isle:bin).

  8. I would use No-Stack Cones!!! The solution has already been invented. Was that the kind of wedge you were thinking about?

    For internal use though I would use 12″ orange sport cones. Like the kind you used in gym class. They’re totally reusable and you can get a stack of the really cheap kind for like a dollar or two each cone.
    Though in the spirit of not spending money i would had to mention jumbo red plastic disposable party cups upside down or paper water cooler cones. If you have any of those paper cocktail umbrellas in your breakroom you could tape one to each of the top corners of the shipment. What teamster would touch anything with a girly-drink umbrella on top??

    okay back to the nostack cones

  9. First, there is no problem statement. You just saw something you thought was a problem. Is there damage? How much? What is the cost of the loss? How many times does the customer get hosed? Ever try to work a freight claim? Talk about WASTE! What are those costs?
    Your directive not to spend is nice, but, it may suboptimize a solution…or worse…drive WASTE into the system. Figure out your current cost structure and design a suitable, all affective solution.
    Some more thoughts,
    Does the note mean don’t put me on top of anything or don’t put anything on top of me?
    A pallet moving through the transportation system that is not stackable is a form of variation. I say consider making the pallet stackable, making this pallet like all the others and an increased chance of success. Of course, the cost of doing that has to be weighed, that’s why we need the cost structure for current state.

  10. To the last anonymous, that’s a great point. To me, the pink sign is an indicator that there had been a problem (or someone was proactively anticipating a problem). The pink sheet is ambiguous, you’re right. It doesn’t explain “why”, it’s just barking an order. It could be more specific “Do not double stack, product could be crushed or damaged.”

    Great thoughts there. Thanks for the reminder that, if we were really working on this, to define the problem correctly. I was leaping to solutions, wasn’t I?

    I like your reminder to minimize total system cost. Spending a little money might be acceptable to minimize total shipping waste (It wasn’t a “directive” to spend no money, just a goal).

  11. It would require plastic pallets with plastic “top caps” that allow stacking (if the boxes are sturdy enough, I assume), right?

    Maybe the distributor could transition to plastic re-usable containers that just cycle back and forth, eliminating the cardboard waste? With plastic containers, that would be more easily stackable, right?

    Because the pink sign doesn’t say “why”, is it that the boxes aren’t strong enough to prevent crushing? Just the vendor’s desire to not have stacked pallets topple over?

  12. Seems like the “pyramid pack” approach is a simple, no-cost, no-extra-effort (I assume…and yes I have packed a few pallets in my day) error proofing solution. I agree that it’s hard to plan for the disgruntled Teamster. I suppose if they really want to damage the goods, they’ll find a way. However, with today’s electronic tracking tools and cameras everywhere, that might come back to haunt them.

    Another waste issue that didn’t come up…what happens to all that packaging material? Looks like ~60 cardboard boxes, probably 100 feet of shrinkwrap, some banding, and a pallet that all need to be disposed of. Plus someone needs to break down all those boxes, and move all the refuse. Hopefully the cardboard is recycled (with lots of energy input). The pallet probably gets moved to a big pile of pallets that the Hospital doesn’t need and gives away (maybe it heats someone’s house, which is OK I guess).

    When I visited Toyota Georgetown, they mentioned they are working to eliminate 100% of the packaging material waste at the plant. No boxes or pallets. And I saw very little cardboard, and little shrink wrap in the plant. They have figured out how to containerize almost 100% of the car parts they use.

    When I worked at a drug store as a kid, I recall that all our goods came in those grey totes, having been sorted and picked at a regional warehouse. While I sure there is plenty of waste at the warehouse, we didn’t need to throw away much at the store, and stocking the shelves was much easier (the truck was loaded somewhat in order of the shelf locations in the store, so little transport waste for us).

    This all points to a greater need for supplier partnership. Toyota makes containerization work because they work with their suppliers on waste reduction. Perhaps the hospital could work with their volume suppliers to make a better material transport system, maybe with shipping containers that are double-stackable and easy to handle. The return logistics probably look pretty expensive, but looking at the whole system (packaging cost, unpacking labor, material handling of the waste, etc), it might be reasonable. However, that kind of analysis is unlikely to happen if the supplier and customer have the usual “yearly cost down” squeeze, and constant threats of loosing the business.

    The waste is everywhere!!!

  13. Mark,

    On the subject of containerizing goods, you might consider blogging about a recent WSJ article about Walgreen’s commitment to hiring disabled workers at a regional warehouse. The article explains how they were able to error proof the workstations and improve their training to the point that they could hire folks with significant disabilities that would otherwise be thought to be unemployable.

    It’s a story about applying lean concepts to help solve a big societal problem, and make a profit at the same time. Kinda made my heart go pitter-patter, and opened my eyes to the possibilities for lean to help save the world. Makes me want to quit making junk people don’t need, and instead apply my skills on something that solves a real problem.

    The article is called “Erasing ‘Un’ from ‘Unemployable'”, Thursday Aug 2 WSJ Marketplace section. The photos show some of their workstation, which look very well done (highly visual, seemingly ergonomic).

  14. How about placing bubble wrap on top of the palette? The sound of placing another on top should be just enough to prevent it from happening again.

    As far as breaking the shrink wrap, that sound like a problem with the supply distribution system.

  15. What is the occurance percentage that Hospira or the hospital or the distributor of the IV products have with getting damaged or crushed?

    If this is for a hospital’s operation I think you are wasting your time on this equation. This will be broken down and sent to their storeroom or pharmacy (if refrig. needed).

  16. Bob, it could be a waste of time. This isn’t something I am actively working on, it was just a question (and an attempt to illustrate how signs aren’t effective error proofing).

    If it’s a waste of time, then why the pink sheet with the warning?

  17. I am still curious though, was this through a distributor or the manufacturer. Hospira has direct and through distributors.

  18. Yes, that article on WSJ was great. Glad to know there’s a place for me to work.

    I like these puzzles that you put up. Keep them coming.

  19. First Anon is back…
    Mike, with your permission.
    Colleagues…Lean is about Value Streams thinking not individual problem solves or solvers. We need to assess the value stream before we design solutions…even error proofing. Why? Because when you change anything, you change everything.
    This is an interesting topic, so why not work it together. Let’s SEE the current state through a series of entries here and then decide an appropriate Waste reducing solution.
    I will start by listing some assumptions.
    This shipping qty is on takt for current customer/supplier relations.
    Flow is regular and repeating to a well defined but growing North American market.
    Total packaging costs are 1.0% of the piece cost.
    Damage/shrinkage is currently @ 2% of piece cost.
    Customer satisfaction is 90%. Dissatisfaction with handling the damage and getting credited for it and getting replaced/reimbursed accounts for all 10% dissatisfaction.
    The label was introduced 1 yr ago when damage was @ 3% of piece cost and cust sat was @ 85%.
    The customer is looking at other suppliers due to the damage trouble.
    The label means don’t put anything on top of me.
    The material flows through break/bulk (cross docking) freight system.
    Now, let’s discover. What else do we need to know about this scenario?

  20. I would go back to the point a couple of people have made here. If your pallet is at risk from the transport method, either change your transport method (direct courier, v.expensive), change the packaging so that others can’t stack on top (may have your shipment rejected by courier), or change your packaging so that it CAN be double stacked and handled by anyone.

  21. If there are a fixed set of individuals disregarding the instruction not to double-stack, send out an occasional “training” pallet configured to spectacularly self-destruct if double stacked, preferably in a manner which requires calling for assistance to clean up.

  22. interesting discussion.

    Some issues may be resolved by changing the scheduling. Simply delaying the loading order for this product type might (i say might) avoid double stacking.

    I am a fan of showing up errors at the point they occur, so anything that does that is going to get my vote. I have seen bags of coloured dust taped to racking uprights in high risk areas. You try denying it was you when your forklift is covered in dust. It also has a hassle factor sufficient to make peopel more careful when you are not there.

    I wonder whetehr a simple extension of this would solve the issue.

  23. yeah you are right. but increasing the vigilence without direct management input certainly helps.

    I am with some logistics industry professionals tomorrow and thought i might set them the task. Will update you with ther responses.

    Recoding in the load planning so it is loaded last rather than first when possible will most likey sort out the majority of issues.


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