This is the white paper version of a presentation on how common warehouse system design errors and remedies.

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Q: Why accuracy? Isn’t velocity more important?
A: Accuracy should come before efficiency, especially in applications
requiring track and trace compliance like HACCP and S-OX. Without
accuracy, any time saved rushing will be lost several times over as a result
of errors.
Start with two accounting reasons
- Fixing errors consumes resources
- Lowering stock levels frees up capital
Follow with two of the many of customer service reasons
- If you can’t find it, you can’t sell/use it
- If you have it but don’t know it, you might as well throw it away
© Copyright Greg Dow, 2016

2. Some mistakes happen because the jobs requirements are complicated
- Unit of Measure Conversion
- Kits versus Components
- Trace Violations
- LIFO vs FIFO
Some mistakes happen because the tasks are just plain boring
- Mis-counting items
- Missing an entire line item
- Transpositions & typos
But according to Deming, almost everything is the responsibility of management,
even warehouse errors. It’s management’s job to fix the systems and train the
people.
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3. People come first! The use of bar codes does not eliminate the need to read the
item markings. Customers and consumers may not have scanning equipment, and
your own material handling staff need to find the correct items before scanning
them.
By legibility, I don’t just mean font size. It is helpful to have some logical pattern to
item codes and location coordinates. Use optical cues in long codes like
punctuation, font changes, underlines and boxes for the benefit of the reader.
Display any aliases such as the supplier part number or customer part number.
Populate any alias fields in the system and program the transactions to accept the
aliases in lieu of the native codes.
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4. Errors increase with task difficulty. So if data entry is made more difficult by
technology, data entry errors will increase too.
For example, did anyone ever like typing alpha messages when they only had a
numeric keypad? Thirteen year old girls who do nothing except text might disagree,
but they are in the minority. Here are a few pointers for key entry
- Upper case only and have software convert all lower case characters to upper
case
- Minimize alpha
- Eliminate punctuation or use data masking to automate this
Now try to get a straight scan beam across the entire barcode at the same time.
These barcodes would scan a lot faster with two label design improvements
- Increase the aspect ratio (height to width)
- Add more white space left and right. These are called quiet zones. One quarter
inch at each end is recommended.
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5. Most of us can read line one of the above eye chart from a long distance. Only
Bugs Bunny can read line 11 from across the room. I couldn’t read line 11 if it was
right under my nose.
Barcode and RFID readers have well documented scanning ranges. These ranges
vary with the size of the barcode or RFID tag antennae. Test your intended readers
with your intended media before you buy.
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6. Industry standards exist for a reason. They are created by subject matter experts to
ensure that their specific industry supply chain is best served by common product
and shipment markings. Standards exist not only for the markings, but also for the
EDI data formats. Compliance is typically demanded by consumers of their
suppliers, who, in turn, demand compliance of their suppliers. Thus, these
standards propagate up and down the supply chain.
If you industry has them, then use them.
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7. If your industry doesn’t have any compliance standards, create your own and
request compliance from your suppliers. This way, all items that you receive will
have legible and relevant markings.
Base your compliance standard on the closest thing from a similar industry. That
way, many of your suppliers may already be compliant with your request, reducing
their resistance.
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8. In this case, and manufacturer in the aerospace and defence industry created their
own standard based on the standards used in the electronics industry.
A single scan of this 2D barcode would parse the messaged into six items and
populate the appropriate fields on the mobile terminal receiving window.
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9. In order to reduce resistance from their suppliers, they created and distributed an
MS Excel spreadsheet that would concatenate the appropriate data and create a 2D
barcode image that could be copied for pasting into packing slips and item shipping
labels. This made things more accurate and efficient for both the manufacturing
company and their suppliers.
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10. Data entry doesn’t end with just the items. Just about any piece of data can be
replaced with a barcode or RFID tag.
Locations marking is important because if the barcode is scanned when items are
put away, the system knows exactly where they are, eliminating most of the
difficulties finding things.
Also, make sure that the coordinate numbering scheme can be properly sorted as a
text file. Make each segment fixed length and pad the leading edge of numeric
sections with zeros.
A common numbering convention is ZABC – Zone, Aisle, Bay, Level. In the top left
image, the rack is the 123rd bay in zone A, aisle B. Slot A is the floor below the first
beam. Slots B, C, D and E are on the 1st, 2nd, 3rd and 4th beams of the bay.
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11. A proper location master file should have more than just a list of LocationIDs. Each
location should have properties for zone, temperature, dimensions, elevation,
required equipment, ABC classification, pick sort order, hold status, and any security
flags that exist in the central business engine.
Why?
- Because ice cream MUST be stored in the freezer
- Because a lift truck won’t fit in the shelving aisles
- Because a pallet wont fit in a small parts bin
- Because a picker on foot can’t reach the top level of racking
- And many more reasons specific to your operations
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12. When the new distribution centre in Vaughan Ontario was built, there was a mix of
lift truck storage and rack storage. The scanners intended for use on the clamp
trucks were specified for long distance scanning of large mill rolls and ceiling
mounted location barcode signs. However, in the racking area, transactions were
made both “man-up” using stairs, and “man-down” using lift trucks.
A special sheet label set was designed, printed on retro-reflective sheet stock, with
colour coded borders. The bottom half of the label set was applied to the lowest
beam and had a barcode for each level of racking. This label would be scanned by
man-down operators. The three labels with individual borders were applied to the
3rd, 4th and 5th beams and could be scanned man-up from the ladders.
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13. The size of a storage location should proportional to the size of the storage
containers.
Having a small number of large locations seems easy, from sitting at a desk.
Putting things away is easy. The problem is finding them again. A stock locator
should be able to direct a material handler to within arms reach of the desired item
minimal change of selecting the wrong item from the right location.
So what is the right size? Well that depends. For small parts, the location may be
the bin or drawer section, for automobiles, it might be the parking space. The
answer is really “whatever reduces errors in your situation”.
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14. In fixed stock location systems, places are reserved for specific items. When an
item is out of stock, the location is left empty. This waste of space is called
“honeycombing”. In a random stock location, those empty spaces are taken by
other materials as they need to be stored.
This only effects accuracy in situations where similar items are stored in close
proximity. It is very easy to mis-pick an item with similar appearance from an
adjacent location. But if adjacent items are obviously different, operators are less
likely to mis-pick.
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15. Here is a good place to repeat W. Edwards Deming’s quote:
“Most troubles and most possibilities for improvement add up to proportions
something like this:
94% belong to the system (the responsibility of management)
6% are attributable to special causes”
It is critical that the system match the process. For example, in processes where
multiple items or LPs are transacted together, the mobile application must allow
items to be transacted in exactly that way. If users must work around the system,
they will make more mistakes.
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16. Consider License Plates for unit loads. LPs are like the license plate on a car. It is
unique, but has no information about the vehicle. A data look-up must be performed
to find make, model, year, colour, owner, etc.
Without an LP, the pictured load would have to be moved using three transactions,
one for each item/lot. Once the effort has been made to build a load, a single scan
move of an LP, let’s the software handle the details of moving all of the contents.
If you move loads of mixed items, lots, or traces, license plates may reduce
transactions, and thus errors. Also, LPs can carry attributes for track and trace that
can be assigned on a desktop control centre and enforce on mobile terminals.
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Enforce business rules when and where the work gets done in real-time. To do this,
the computing devices used on the shop floor need to be connected to the central
business engine so that all transactions are processed centrally and validated
against the live database. Typically this involve equipping the workforce with mobile
computers connected to the wireless LAN and running an application to perform
every warehouse transaction against the central business engine.
Q: What’s so good about real-time?
A: All data is instantaneously shared with the central system. With central
data being immediately available and accurate, mobile transactions can be
validated field by field to inhibit errors from being entered into the system.
The need to rekey data is eliminated and there are far fewer errors to back
out of the system.

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Barcodes are as simple as black and white, but you have to aim a beam across the
barcode it to scan it. Typically, you only get one read per pass of the scan beam.
The error rate is 1 in 3 million characters, or five nines accuracy, so the minimal cost
of equipment and labels is far offset by the virtual elimination of key entry errors.

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RFID sends tag data to readers by RF signal
Eyes free, means that you don’t need to see the tag to scan it
Hands free means that there are automated “portal” readers available. You don’t
need to aim a beam or press a trigger.
Readers can decode large numbers of tags at the same time.
Each tag is inherently serialized.
Yes, RFID readers ad tags cost a lot more than other data collection technologies,
but in some cases, it is the only solution to high speed high volume scanning of
randomly oriented items.
Also, RFID systems are tricky to install and tune. The materials being tracked and
the environment can have sources of RF interference that inhibit operation. For
example, RF energy is absorbed by water, but reflects off of metal.

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Voice Directed Logistics is eyes and hands free.
Eyes free improves accuracy by not having to look away from your work at paper or
a screen
Hands free improves accuracy and efficiency by eliminated non-value add handling
of paper or IT devices.
Beyond that, he accuracy depends on how the application is engineered. System
checks are usually build in to the processes to confirm locations, items and
quantities.
Conversions from speech to text and text to speech are typically performed in the
mobile device carried by each user. This means that all network traffic is in text only
– low bandwidth and high speed.

21. This last case study is about a regional grocery chain. They had two full distribution
centres, and were planning to double the number of stores and build a new DC
within 5 years. They already had a WMS (Warehouse Management) system so
most material transactions were already paperless. While already reasonably
accurate, they needed to greatly increase productivity without sacrificing accuracy.
They decided on the use of voice directed picking for their high touch case pick
operations, while leaving full pallet transactions to conventional barcode technology
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22. Within an order, there are hundreds of lines.
Within a line, there may be any number of items. Some quantities exceed that of a
full pallet. Orders are split so that full pallets could be selected from bulk racks
using lift trucks.
The remainder of the order would be for full cases, and would be split again
between dry goods and catch weight freezer items.
Dry goods are picked using walkies and a voice only picking interface.
Catch weight items are picked in the freezer using walkies and colt temperature
rated voice terminals with ring mounted barcode scanners.
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23. In the voice picking process, voice prompts are made into the pickers’ headsets.
Their replies into the microphones are converted to text and transmitted as data. All
text/speech conversions are made on the mobile terminals to reduce the load on the
wireless network.
Pickers are directed to the next location in pick route order, where they confirm their
location by reading back a random check digit. Only one SKU is in each location,
so no item checks are required – The confirmed location is sufficient to confirm the
product.
They system prompts the picker with the desired quantity and subtracts each reply
that is made. Pickers are instructed to say what they pick in each lift, and the
system tells them how many more to select until they are done.
The pickers hands and eyes are available for work at all times, leading to a 15%
productivity improvement over barcode based picking.
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24. The catch weight process differs from the normal case picking process by making
use of the industry standard labeling. Reading and typing of speaking both the case
weights and case serial numbers is a large source of error and delay. By scanning
the barcodes that already exist on the cases and parsing out the data, the accuracy
and efficiency can be maintained.
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25. Barcode and RFID readers have well documented scanning ranges. These ranges
vary with the size of the barcode or RFID tag antennae. Test your intended readers
with your intended media before you buy.
You can download and use this document to help you organize your reader and
media purchases. All that I ask is that you don’t alter or remove my copyright and
contact messages.
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