Making MES more efficient

Not every company with a manufacturing execution system (MES) can cite specifics of how MES has helped them, but that’s not the case at Troy Design & Manufacturing Co. (TDM). The company—whose operations include a facility in Chicago that modifies Ford motor vehicles for police use—counts 7 seconds as the building block for time savings from data capture into its MES solution.

That 7 seconds of savings comes from using radio frequency identification (RFID) technology to track each vehicle as it progresses through the plant, as opposed to hand-scanning bar codes to track work in process. With four production lines and 10 work centers per line outfitted with RFID data capture, that means there are 40 locations in the process where information is automatically gathered without human intervention, says Lee Murray, director of technology for TDM.

By affixing an RFID tag to each vehicle as it enters the facility, the RFID technology acts as a trigger to the MES, telling it which specific vehicle entered a particular work center, and recording exactly when it entered the location. “We wanted to remove as much non-value-added work from our production process as possible, and let’s face it, anytime anyone has to hand scan something, that is not directly contributing positive value to the end product,” says Murray.

MES solutions have been around for decades, spanning functionality such as work-in-progress tracking, electronic work instructions, quality management functions, and production performance metrics. Not all MES solutions are alike, but work-in-progress tracking is considered a core MES function and is an advancement over the days of paper-based methods of shop floor control.

Bar code data collection is commonly used to support MES deployments, but in recent years, some plants have chosen to affix RFID to vehicles, major assemblies or totes to track work in progress in a hands off way. When data captured by RFID is fed into an MES and pushed out to a Web dashboard, the MES deployment takes on an Internet of Things (IoT)-like aspect because a near real-time insight into work in progress can be gleaned from a browser. In fact, at TDM, a browser-based dashboard into production status is displayed on several oversized flat screens on the plant floor, and managers also can access it with their devices.

Hands off data capture
TDM is a Detroit-based Ford metal stamping subsidiary that had expanded into the vehicle conversion business with its Chicago modification center for police vehicles. Located about a mile from Ford’s Chicago assembly plant, the facility modifies Ford’s Explorer SUV model and Taurus sedans for police use. The center adds options such as ballistic door panels, storage consoles and flashing safety lights to the vehicles.

The center has four production lines with 10 work centers per line, modifying in total about 150 vehicles per day. To support the plant’s production management needs, TDM realized that paper-based methods of work-in-progress tracking and reliance on paper-based work instructions would be too inefficient, so the company deployed a work-in-progress tracking focused MES (Lowry Solutions).

While TDM could have opted to feed the system with data captured from bar code scans, the decision was made to go with RFID because of the way it automatically captures data about when each vehicle enters and exits a workstation. Additionally, says Murray, because the RFID tag holds the unique vehicle identification number (VIN), it also prompts the MES to display what needs to be done with that vehicle at each work center, calling up the appropriate work instructions on a touchscreen computer. With some procedures, the MES prompts the operator to record data using the touchscreen, or to swipe his or her employee badge to the associate who installed a safety critical part.

Most of the RFID readers at the TDM facility are outfitted with four antennae (Motorola Solutions, recently acquired by Zebra Technologies), with one antennae capturing data for one workstation. There are a couple of places where the columns in the building only make it possible for one reader to cover two locations, but for the most part, one reader tracks four locations.

Mark Wheeler, director of industry solutions for North America with Motorola Solutions, says RFID is a good fit with MES because it’s an accurate, efficient way to capture data that is essential to MES’s core tracking function. “With RFID, you have automatic, near real-time visibility into when work or inventory enters and exits a particular location,” says Wheeler.

While some factories in apparel, footwear and vehicle assembly use RFID tags on end products to enable tracking, in many other cases, says Wheeler, it’s a container like a cart, tote or pallet that is tagged, acting as a proxy for whatever materials are being moved on it. “We often see a reuseable asset being tagged and tracked passively by the RFID infrastructure,” Wheeler says. “You can tag that asset once and track it for life.”

One benefit of pairing RFID with MES is time savings. TDM calculates that automated work-in-progress time stamping saves 7 seconds per read versus an operator-driven bar code scan. “That might not seem like an enormous amount of time, but when you start adding up the 40 different work centers we have on the production lines, and the quantity of vehicles we are producing, it becomes a significant time savings over the course of a day or a week,” says Murray.

The RFID data capture also means operators don’t have to remember to scan a vehicle as soon as it enters a workstation. Operators still have to interact with the MES and its work instructions, but the data collection related to work-in-progress tracking is taken out of their hands.

“We know that as soon as a vehicle gets moved into a station, the time and date stamp for cycle time is automatically captured,” says Murray. “Overall with this solution, we wanted to make it as easy as possible for operators to focus on adding value to each vehicle. They should be focused on outfitting the vehicle in a high quality manner to the specs that are in the system, rather than performing bar code scans, or digging through pieces of paper,” says Murray.

Process history benefits
Another benefit of detailed data on the manufacturing process is the ability to quickly see what was done to a vehicle, as well as to see where it is located in the process. These benefits stem from both effective data capture and a software system such as MES that can display status and metrics.

At TDM, the work-in-progress tracking function in the plant floor system feeds a Web dashboard application that gives personnel on the plant floor as well as authorized users logging in from a browser a view of the current state of vehicles in process, where they are located, and what’s being done to them. Through the dashboard, everyone can see if the pace of work is on track. The system also links to a Ford database, so TDM is able report vehicle receipt, production progress and shipping updates back to Ford in a timely manner.

According to Murray, the plant floor dashboard isn’t a true real-time system—there is a 15-second lag time between actual RFID time stamps and status update on the Web user interface—but that’s effective enough for work-in-progress tracking.

The combination of the automated RFID reads at each location and further inputs into the MES also create a detailed process history of what was done to each vehicle. There is some semi-automated data collection involved in using the plant floor system, says Murray. For example, serial number information on ballistic door panels is scanned into the system.

Certain pieces of safety equipment that are installed as options call for the operator to perform a badge swipe to record who installed the equipment. Or, an operation may require that some assembly procedures be confirmed, such as torqueing a bolt to a specific setting.

The end result for TDM is an online repository of information on how each vehicle was built. “I can go look up a VIN from the middle of last summer and can quickly tell you when it came in the plant and was commissioned, what line it went down, and what it was outfitted with,” says Murray. “By looking at the system, I can also tell you if it was required for the part, which operator installed an item.”

The combination of RFID and MES results in accurate data for cycle time analysis because there is no human error involved. “It’s not that we don’t trust our operators to carry out data collection steps, but there’s no need to bother them with it when you can automate the time stamping and take out effort and risk in managing throughput,” says Murray.

The system also fits in with TDM’s methods for plant and quality management, which include lean manufacturing and Six Sigma analysis. Specifically, says Murray, using MES and RFID fits in with the lean philosophy of eliminating waste.

“We’re trying to eradicate waste, which can come in the form of operators having to perform excess bar code scans, or the handling of a lot of paper,” says Murray. “I think most plant managers would agree, they want their people turning wrenches or otherwise directly adding value, rather than clicking buttons on a scan device, or shuffling through paper.” 

Companies mentioned in this article
Lowry Solutions, lowrysolutions.com
Motorola Solutions, recently acquired by Zebra Technologies, motorolasolutions.com