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Lean Manufacturing Concepts:
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that an RFID enabled lift-truck can perform the same move operation without any human intervention. In this article we’re going put that claim to the test and see if we can actually eliminate operator scanning in lift-truck operations.
After many years of research, development, and prototypes, radio frequency identification (RFID) is finally going mobile in production on fork-lifts, clamp-trucks, and other material handling equipment (MHE). Rush Tracking Systems has combined industrial-grade RFID equipment, positioning technology, and state-of-the-art application software they created into a total solution called VisiblEdge. Given an install base of more than 50 deployed systems, Rush Tracking Systems’ clients are realizing huge benefits that will revolutionize industrial operations globally, including:
VisiblEdge is comprised of both hardware and application-specific software that is retrofitted onto an existing fleet of fork-lifts, clamp-trucks, or other MHE, as shown below.
It uses an industrial grade RFID reader designed to withstand the shock and vibration that is common in industrial operations. The reader is attached to cargo antennas, which are not only tough, but designed to read RFID tags in a 9-foot-high stack of pallets—basically what fits in the full height of a trailer. It quickly identifies a single pallet, double stacked pallets, or even nine short pallets. Depending on the composite materials of the load, the contents can also be confirmed. For example, verifying paper and cloth materials being carried is no problem but a pallet of metal items can be tricky.
A rugged rack-tag antenna is used to read RFID tags that are placed on the shelves where assets are stored. This allows the system to automatically verify the products are picked from the right shelf or slot location and record the shelf or slot location when products are placed there.
The cargo presence lift sensor triggers when the RFID reader turns on and off. It helps to eliminate reading tags on assets when the MHE drives by without carrying a load.
What ties everything together is the VisiblEdge software, which is developed by Rush Tracking Systems and runs on the vehicle mount terminal (VMT). It serves as the interface to the RFID reader and controls and coordinates all of the components. It interfaces directly to any host system manufacturing execution system (MES), warehouse management system (WMS), enterprise resource planning, or middleware system by sending clean data in the form of standard EPCglobal EPCIS messages. To these systems, it basically acts like a bar-code scanner reading serialized asset information and location data. The software on the VMT automatically cleans, filters, and buffers the RFID reads, so there are no worries about enterprise systems being overwhelmed with event data.
If the VMT is connected to enterprise systems using an 802.11-based wireless network, then it may be possible to provide near real-time feedback to the operator. For example, a $31 billion durable goods manufacturer has its warehouse in Charlotte, North Carolina, and its enterprise systems, applications, and products (SAP) running in Chicago. The two facilities are connected using the secure corporate intranet. When an operator performs a move in Charlotte, the entire verification process takes no more than a few seconds before the operator has a confirmation from SAP on their VMT screen that came back from Chicago.
This is a big change for operators, since they can now focus on driving and not scanning. It provides significant benefits and quality improvements in the process. Let’s look at a typical bar code-based asset movement operation compared to the new process.
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Typical Bar Code-Based |
VisiblEdge |
Benefits / Improvements |
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Operator receives movement instruction on VMT |
Same |
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Operator drives to pick-up location |
Same |
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Operator manually scans bar code of pick location |
Automatically scans pick location tag on floor or shelf |
Saves 2–15 seconds |
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Operator manually scans bar code of asset to be moved. Typically a product-level scan |
Automatically scans asset tag to be moved—a serialized scan |
Saves 2–15 seconds |
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Enterprise system or WMS verifies location and product to ensure proper pick |
Same |
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Operator picks up asset and begins driving to destination location. |
Same |
|
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Automatically verifies load being carried a second time without operator action. |
QA benefit without adding labor |
|
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Optional: verifies items, cases, or cartons being carried on pallet if materials permit. |
QA benefit without adding labor |
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Automatically updates current location in-transit without operator action. |
Benefit without |
|
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Optional: automatically provides optimal route-to-destination directions on VMT screen based on current location in-transit without operator action. |
Efficiency benefit without adding labor. |
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Operator arrives at destination. |
Same |
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Operator manually scans bar code of put location. |
RFID reader automatically determines location where asset is placed. |
Saves 2–15 seconds |
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Provides placement confirmation or invalid placement alert. |
Same |
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Total labor time saved: |
6 – 45 seconds |
The most obvious benefit is that the solution eliminates human intervention. An operator simply focuses on the move and they know they’ll collect accurate movement data. Not only does this improve operational efficiency, it improves safety because the operator is focused on driving, not scanning.
Beyond the obvious saving by eliminating the labor associated with scanning, there are huge consequences to quality. The data is obtained without human intervention. Most people believe that bar codes are 100-percent accurate. This is not the case. It’s not the scan that is the problem, but the inaccuracy due to simple human error (we forget to scan, we’re tired and scan the wrong box, we miss counted and scan multiple times, we get distracted, etc.). These little errors have major affects on quality and the resulting costs are not usually associated with the cost of a bar code scan. An incorrect bar code scan can result in:
It is critical to consider quality when comparing the bar code process to this process.
Click here to watch a video that demonstrates why RFID is better than bar codes for bulk storage.
There are several methods used to determine the MHE position. The method used depends on the precision required:
Option 1: Optical position systems
An optical position sensor is mounted on the top of the lift-truck and aimed at the ceiling. It captures digital images of overhead position markers (OPMs). Contemporary machine vision software decodes the image to recognize location and calculates the orientation angle and exact position of the sensor.
A wireless link (such as an 802.11 network) transmits sensor data to a controller server (shown above as an IPS engine), which collects location data from the positioning sensors on all lift-trucks. The controller stores the position data in a standard database and makes it available in real time for VisiblEdge.
The precision is based on the density of the overhead position markers. Up to one inch of accuracy can be obtained. Additionally, rotational orientation, direction of travel, and velocity is also determined.
To determine which bin or shelf location from which an asset is picked up or put away, either a height sensor or location tags are used.
Option 2: Real-time location systems
Since many operations already have 802.11-based wireless networks in place to connect VMTs to back-end systems, 802.11-based location systems are a common method of determining the position of the VMT. These solutions tend to yield approximately 15 feet of resolution depending on how many access points are installed and the density and types of materials in the facility.
To achieve finer resolution, proprietary solutions that use ultrawide band (UWB) frequencies can achieve 1 or 2 feet of resolution.
Option 3: Global positioning system (GPS)
If you have assets that are stored outside, then GPS tends to be the technology of choice so long as there is a clear line of site to the sky. Keep in mind GPS is not going to provide the resolution of optical or a well-designed UWB solution. GPS is a satellite-based navigation system made up of a network of 24 satellites. A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2-D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user’s 3-D position (latitude, longitude, and altitude). Certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers. Most GPS receivers are accurate to within 15 meters on average.
Inside, outside, or both?
If you have assets that are stored outside then you need to consider the environmental challenges as most lift-trucks are not designed to go through heavy rain or snow.
Combining methods of determining position
It’s not uncommon to use more than one method to determine position. For example, optical can be used indoors and GPS can be used outdoors. This requires some device coordination but is absolutely possible.
MHE that are on the move
There may be times when a MHE that is moving around the facility becomes disconnected from the network. This could be due to null spots in the 802.11 wireless network. Be sure to leverage message queuing to ensure events are not only received but received in the sequence they occurred.
RFID portals will be an elemental building block in most RFID strategies, but RFID-enabled lift trucks can provide better granularity within a facility. They work in those hard-to-reach locations such as rack storage, staging (i.e., assembly process), work-in-process storage, finished goods storage and staging, and holding areas.
If your operations use clamp trucks (see picture right) then vehicle mount readers are the way to go. Metal clamps reflect the radio waves emitted from RFID portal antennas and can pose a difficult challenge. Rugged antennas can actually be mounted into the metal clamps (see images below). The vehicle mount solution is also superior when stacking products that visually appear the same, but are actually slightly different, such as the rolls of paper in the picture.
Depending on the hardware required, a vehicle mount solution can be from zero to 25-percent more expensive than an installed stationary RFID portal. The variance depends on how much it costs for a portal to be installed. You may need to use an industrial enclosure, install bollards, run conduit, connect AC power, anchor and mount, etc.
If you can benefit from having better asset visibility within your facility, you should investigate the mobile solution. You may find that by outfitting half a dozen fork-lifts, you can get better visibility than you will with a dozen stationary readers.
Rush Tracking Systems has created a VisiblEdge ROI calculator which allows you to enter metrics specific to your operations to determine whether or not you can benefit from this kind of solution. You can download it here.
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Summary of the Benefits in Manufacturing and Distribution |
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The manufacturers I mentioned above are using this solution for returnable containers and racks, bulk material movement, work-in-progress management, and electronic kanban. In each operation, there is a dedicated fleet of MHE in place.
A $32 billion durable goods manufacturer went from 93-percent accuracy with manual scanning to 99.99-percent accuracy with automated scanning and has maintained that for three straight months. It has reduced labor, decreased cycle time by directing movements, eliminated errors sequencing, and greatly improved inventory and transaction accuracy.
The MHE operators love the solution because it simplifies their job and helps them reduce errors. They drive the trucks and don’t fight the system; they rely on it. Most important to them, if they make a mistake, the product isn’t left on the truck. Errors are typically caught within a couple of seconds and quickly corrected, which eases their responsibility.
Many industries are seasonal. When the influx of work arrives, companies augment their operations with temporary drivers (employees or contractors). It is nearly impossible to put in enough training, discipline, and controls to effectively bring the new people up to speed and retain the normal accuracy. Many shipping and receiving processes are handled with “institutional wisdom” or just “knowing that is how we handle things.” Temporary labor won’t have this kind of context so they make more mistakes. New hires are also an issue. When you can take the need for a human to give you the clean data out of the equation, the whole system stabilizes.
Author's note: A big thank you to the entire team at Rush Tracking Systems for helping to write this article: Chuck Thompson, Walter Tucker, Scott Andersen, George Rothwell, and Toby Rush.
Rush Tracking Systems is offering a free assessment to see how VisiblEdge can eliminate operator scanning from operations.
Louis Sirico is the founder of The RFID Network, a global community dedicated to radio frequency identification (RFID) and related technologies with a distribution of more than 100,000 professionals. He is most widely recognized as the host and producer of The RFID Network video series and has authored more than 200 published articles. Sirico has more than 25 years of experience with Fortune 1000 companies, U.S. military, and government agencies, both domestic and abroad, in architecting, building, delivering, and maintaining a wide range of global IT solutions, including logistics and RFID systems.
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