The Engineered Product Division of ETCO Inc., Warwick, RI, installed a production monitoring system primarily for inventory accuracy. The system soon evolved to include statistical process control (SPC). Now, this metal-stamping company is a nearly paperless manufacturing environment.
View of ETCO's shop floor
Seven years ago when Dennis Herdegen joined ETCO as operations manager he had the concept of a paperless shop floor with a real-time quality system. His tasks also included increasing the company's productivity, reducing its capital expenses and enhancing its profitability. Using a shop-floor data collection system he was able to reduce the number of presses from 21 to 10, while increasing overall production.
"The production monitoring system adds to our company's ability to reduce damage and downtime, and to increase productivity and quality," says Herdegen, now vice president of manufacturing. "It reports finished goods more accurately. We can schedule jobs more accurately. We can predict more accurately when a tool might fail. Now I'm working on the real reasons for quality defects, rather than the perceived reasons."
ETCO will stamp any proprietary design as well as many catalog items used in electrical applications. The plant has 10 presses (ranging from 22 to 60 tons) and five operators. Press speeds vary from 600 to 1800 spm. The average stamping run is about 500,000 pieces.
The company carries about 100 million parts in inventory. Of that, about 35 million parts are true inventory, the rest is work in process (WIP). Ultimately, WIP is build-to-order, rather than to stock, but the plant tries to schedule jobs to increase its efficiencies with overruns.
About six years ago, ETCO found it "had a built-in system that was about 20 percent accurate in reporting finished goods," explains Herdegen. "Our homegrown inventory system running on an IBM AS/400 reports finished goods in inventory, and then back-flushes the raw material. We have to report every hit to keep raw-material inventory accurate, but that does not necessarily mean all of our parts are good. We needed a system that could differentiate setup from production hits, as well as good parts from bad."
Also, the company had no handle on its true efficiencies; those were more like best guesses of uptime and downtime. In addition, it needed to track "multiple-out tools" - tools that could produce more than one part per machine cycle. "Sometimes an operator would write down a one-out tool when it was a four-out tool," explains Herdegen, "so there would be four times the amount of finished goods in inventory than we thought. We were out of control, and being a short run stamper, this spelled disaster."
Herdegen read about, then bought and installed, a production monitoring system from Production Process, Londonderry, NH. The key to this system is its ability to collect and associate time-stamped process parameters and statistical information with the data files for a finished product. Data is displayed in real time. "Just collecting product compliance data does not do you much good unless you can tie it to some effect in the process, which is SPC," explains Herdegen.
CAD drawing of ETCO's information system.
In operation, ETCO's production scheduling office releases a job to the pressroom, and the monitoring system automatically loads all the critical data into the machine monitors at the presses. This information, visible on the machine monitor's display, includes the name of the part, the part code, the work order and the quantity on the reel. Simultaneously, the system releases part dimensional information to gage stations on the shop floor. The gage stations, networked PCs, are interfaced to electronic measurement devices - calipers, micrometers, force testers and optical comparators. It is here, next to the stamping presses, that the operators measure parts for SPC purposes.
The process is user friendly. The gage stations display the jobs that are running, parts in production and details of quality plans for each part. The operator needs only select the press that made the parts and the rest is driven by the computer. A database contains all the pertinent quality plans and dimensions relative to each part - number of samples, number of dimensions, nominals, tolerances and measurement instructions. The measurement stations accept electronic gages directly and support manual data input where necessary. The system eliminates the need for the operators to write anything. They simply measure and push a button on the caliper. If the measurement is out of control, the system will automatically say so. The operators are performing statistical analysis as they enter data.
The operator is informed in real time if a measurement is out of specification and given a chance to measure again. At the end of each sample session the gage station displays a complete statistical recap. A key element is the ability to attach an assignable cause to each sample session. If necessary, this provides a history of unusual events to analyze quality and process problems.
Also, at the end of each session the operator may display an X-bar and R chart for each characteristic in the quality plan. This provides valuable quality feedback to the operator on the shop floor while the job is still running. Now it is possible to prevent process problems before they occur, or at least minimize their effect.
The gage stations have eliminated a large amount of paper. The system also eliminates all the quality plan paperwork. Instead of writing, measuring, keeping documents on file and maintaining revision levels, the electronic database collects all the quality information about a job, its production and its inspection.
Electronic setup and process sheets tell the setup personnel, press operators and quality control department how to run a job: packaging required, what coils to use and special instructions. With the push of a button the operators can view these documents at the gage stations. The latest revision is instantly available. Herdegen reports, "Since we have so many different part codes, we could not take the time to update all our paper sheets. If we were changing from one lubricant to another across the board, there would be more than 3000 paper documents to correct. With the system we can change one code and every setup and process sheet is updated."
MDT monitor interfaced with a Bruderer
press.
At ETCO the operators measure parts at predetermined intervals. The system provides a signal based on the last check. At the conclusion of each sampling session readings are stored for SPC purposes and the session is recorded in a date- and time-stamped log. This log provides a complete record of shop floor SPC activities.
The data collected from the gage stations serves many purposes. ETCO can run hard copy inspection reports for any job that they have or are running. The system provides an archive capability that makes it possible to access quality information from as far back as is necessary. Using Custom/QC, from Stochos, Schenectady, NY, ETCO performs SPC analysis functions. These activities are common to most metal stamping plants, but ETCO has implemented real time SPC.
Once a sampling session ends at one of the gage stations data is transmitted to a computer running SPC-Direct, a real time SPC package from Stochos. SPC-Direct performs control testing on all the measured characteristics using the last session and 99 prior sessions. Capability calculations are displayed in real time. According to Herdegen, "The system displays job status using color codes. Jobs that are running at standard are in green. If a job is in the green and its Cpk is greater than 1.33, then I don't have worry about it." All users have access to control alarms and capability numbers through the system.
ETCO has implemented a proactive tool and press maintenance system. The Production Process system tracks actual run time and machine strokes on each tool and each press. When predefined maintenance limits are reached, the system provides alerts so that maintenance action can be taken. By combining production and SPC data, the production department can monitor the effect of tool wear on parts, before a failure occurs.
Color monitors around the plant display the status of the presses: green identifies presses running at the standard rate, yellow identifies presses running below standard, red identifies stopped presses.
Inputs to the machine monitors vary. One is cycle counts directly from the press. A second input is from a die-fault sensor inside the tool on the press. When the sensor picks up misfeeds, tool jams and other in-process faults, it automatically triggers the machine monitor to shut down the press. A fiber optic sensor on the inbound side of the press is a third input. This sensor monitors the welds on raw material coiled on spools; noting the change in a coil helps track potential SPC variations.
ETCO manufactures small electrical connectors that are usually packed on reels and then boxed. The Production Process system tracks each batch or reel of parts providing outputs that are used to generate a bar-coded label for each reel of parts. Each is date- and time-stamped with its job sequence number, the exact number of parts on the reel, as well as the metal vendor's lot number for the raw material. A database of each reel is maintained. Sampling and production are tied together by the system, because the reel sequence number is entered by the operator at the end of each measurement session.
X-bar and R chart
The company's overall quality level has been improved by the automatic bar-code system. Herdegen reports that two years ago there were 11 shipments where the wrong parts were sent to a customer. Last year there were no such wrong shipments.
The system generates shift and daily production reports. Information includes part code and description; work order number; tool number and job strokes; standard and actual press rates; downtime; setup, unscheduled and slow time; order quantity, quantity of good and setup parts, and quantity to go; material used and hours left to finish a work order. Other reports include production efficiencies, machine utilization and reasons for downtime by number of occurrences and total time.
Files are uploaded to the AS/400 at the end of each shift. There, the inventory system looks for the part codes and quantities produced of good and setup parts. It combines these numbers and reports the total to the raw-materials module. The module back-flushes its inventory records based on pounds per thousand parts, and drops the setup-part counts to generate an accurate count of finished goods inventory. Herdegen notes, "by directly uploading production data from the machine monitors to the AS/400, we've eliminated all the counting, manual keypunching, and paperwork shuffling to get production reported to the AS/400. We can now work on those machines that show high levels of downtime."
Dennis Herdegen believes, "That someday all metal stampers will have to implement the same kind of system or they will be unable to compete with the companies that have." MF