Computer Technology in
Metal Construction Manufacturing

The metal construction industry is a fast growing, highly competitive field. A manufacturer needs to consider the latest computer technology as a practical means of improving both the quality of the end product and efficiency of the operation.

This paper will consider the unique aspects of metal construction. It will outline some practical objectives of an upgrade project. Applicable computer technology will be explained and the impact of this technology on the manufacturing process will be discussed.

Metal Construction Manufacturing

The metal construction industry is defined as manufacturers of metal components used in the construction of residential and commercial buildings. These products include roofing, siding, decking, framing, and structural components. The manufacturing of most of these products has the following common characteristics:

• Most parts are made to order instead of made for stock.
• Material costs are high.
• Highly skilled labor is required.
• Most parts are fabricated in a single operation then packed for immediate shipment.
• A high price is paid for any mistakes made.
• Last minute changes are common.

Most of the products previously mentioned are manufactured on roll forming machines. For simplicity, this paper will be limited to this type of machine. The principles covered are generally applicable to other types of manufacturing processes.

Objectives

The objectives of any upgrade of the manufacturing process should be to improve the quality of the finished product and to reduce the cost of the process. Computer technology can achieve both objectives.

Improved Quality

The most obvious way to improve the quality of goods produced is to add safeguards to insure that the correct product is shipped to the customer. Most manufacturers have experienced the wrong length, the wrong quantity, the wrong gauge, or the wrong color being shipped to a customer. These are caused by human errors and can be reduced by minimizing the number of data entry points in the manufacturing process. An alert human can enter data with better than 99.9% accuracy. However, that 0.1% error rate can have very expensive consequences. Short shipping only one building panel can cause expensive delays at the job site, possible back charges and a great deal of expense in shipping and handling that one piece.

There are ways to verify the material used against the material specified on the order. A link between the machine and an inventory control system can insure the proper material is being used.

Most manufacturers depend on the diligence of the machine operator to detect flaws in the material or roll formed shape. There is emerging technology that will automatically detect flaws and take corrective action.

Product quality can also be enhanced by adding identification to each part produced. This identification can be done to insure proper routing or can be an aid at the job site. Such identification can enhance the value of the product and may command a higher price.

Improved Efficiency

Metal construction manufacturers look at the total number of man-hours needed to produce 1000 lineal feet of product as a figure of merit in gauging the efficiency of a plant. This parameter not only measures the efficiency of the machine operator but all other plant personnel. Computer technology can increase the running time of a machine which will increase the footage produced per hour. It can also automate some record keeping that may be presently entered manually. This would not only benefit machine efficiency but would also reduce clerical labor if this data needs to be entered in the office computer system.

Applying Computer Technology

Figure 1 shows a simplified diagram of a roll forming operation. Coils are received and placed in inventory. Coils are selected from inventory and loaded on the roll former. The material is roll formed and cut into specific lengths to fill orders. The cut sheets are crated and loaded on a truck. In this simple process, the roll form machine operator is a key figure, often involved in all steps. By concentrating on this employee’s job functions, benefits of computer technology can be significant.

There are many ways roll forming companies handle the flow of data in their process. Most companies encountered have computers for accounting purposes but do not tie the computers to the manufacturing process. In this situation, a typical flow of data is as follows:

1. Order is taken by a sales person
2. Cut list is keyed into office computer by a clerk
3. Computer prints out a work order describing quantities, lengths, profile, and material
4. Machine operator keys in quantities and lengths into the roll former length controller
5. Machine operator manually labels the finished product
6. Machine operator fills out an operator’s log indicating the order run, inventory coil used, and amount of material used
7. Office clerk updates inventory and generates invoices based on operator’s log

In this process there are five steps that involve manual data entry. This means five opportunities to make mistakes in five time consuming tasks. The objective of computer technology is to reduce these manual data entry steps to only the initial entry of the order.

Direct Numeric Control (DNC)

In order to eliminate the many data entry steps, a method to get data to and from the roll forming machines must be established. With present technology, the most efficient method of communications is Direct Numeric Control or DNC. With DNC, a communication network is established between the office computer and a computer located at each machine. The roll form machine’s length controller is a computer in most cases and can serve a dual role as machine controller and interface to the office computer.

A diagram of a DNC system is shown in Figure 2. In this configuration, an intermediate PC has been added to standardize the system. There are a wide variety of mainframes in use and establishing a universal computer interface to the machine controllers would be impossible. However, most mainframe systems have established networking tools for connection to a standard PC. This PC can also serve as a work station for a scheduler or production supervisor.

The DNC system performs the following tasks:

1. Download cut lists to the machines
2. Verify material used on the order
3. Upload data on the time and material required to complete an order
4. Monitor the present status of each machine from the supervisor’s office

Download Orders

With DNC, the cutting list for an order is loaded into the machine controller automatically. There is no opportunity to enter the wrong quantity or length.

Since the operator does not have to key in the cutting list, the machine has less down time. Many manufacturers are surprised to find out just how inefficient their roll form machines are. A typical building panel line may only run two hours in an eight hour shift due to frequent coil changes, low quantity cutting lists, and packaging delays. It has been reported that downloading of orders can add one additional hour of actual running time to the machine. This is, in effect, a 50% increase in production.

Verify Material Used

Each order should specify a material to be used. Normally, a standard code number is established that identifies the type, gauge, width, color, and finish. This will be referred to as the Material Identifier (MID).

A plant may have several coils that fit this material code. Each coil needs a unique identifying number for inventory control. This number may come from the supplier or may be created when the coil is received. This number is referred to as the Coil Identifier (CID).

Normal practice is for the order to specify a MID, not a specific CID. This gives the operator the flexibility to select the most convenient coil to meet the order requirement. Otherwise, if the CID were specified, that particular coil may be on the bottom of a stack or may be damaged.

By letting the operator choose the coil, it becomes necessary to enter the CID each time the coil is loaded. This number along with the order number and MID can be sent to the office computer for verification. If the CID is not valid or the MID of the coil does not match the MID of the order, a warning can be sent to the operator.

Upload Production Data

The length controller on the roll forming machine precisely measures all material passing by the length transducer. As a computer, the length controller should be capable of keeping accurate time records. With these two features, an accurate record of time and material usage can be maintained.

The data collected by the length controller can be uploaded to the office computer. This data should include the following information in order to give a comprehensive picture of the activity at the machine:

1. Quantity and length of good parts produced
2. Length of any scrap encountered
3. Date and time of production start
4. Date and time of production stop

With this data, the office computer can do the following tasks:

1. Mark items complete and automatically generate customer invoices
2. Reduce footage remaining of inventory coils based on usage
3. Compile scrap reports
4. Analyze running time versus down time

In addition, a permanent record of all of the machine’s activities is obtained in a computer data file for any future reference. If a customer should complain of a short shipment, this data can be printed out to either substantiate or counter the claim.

Production Monitoring

In the configuration shown above, each roll forming machine is connected to the office PC via the LAN. This gives the opportunity to monitor the status of each machine from a central location. Such items as the current order, current material, line speed, and total footage for the shift can easily be displayed for each machine. A supervisor can track orders and detect production delays before they cause serious problems.

Identification Systems

In many cases, machine operators must manually identify roll formed parts as they are being produced. They either mark each piece or fill out a shipping ticket for each bundle of goods produced. New computer technology makes available several devices which can automate this process.

Bundle Ticket Printers

If a bundle of parts must be identified as to its contents, the options are to manually write the ticket, use tickets printed on an office computer, or print the ticket at the machine as the bundle is being produced. Writing the tickets by hand is time consuming and can create problems of legibility.

Using preprinted tickets solves these problems but it reduces the flexibility at the time of production. Preprinted tickets means the contents of each bundle is predetermined. Often, breaking an order up into reasonably sized bundles requires human intervention from an experienced operator. Also, several bundle tickets would be present at any given time at the machine. This increases the possibility of losing a ticket or putting the wrong ticket on a bundle.

Printing the bundle tickets on demand at the machine solves these problems. The operator can set contents of a bundle and print a ticket reflecting his decision. Since only one ticket should be present at the machine, the possibility of a mix up is eliminated.

The downside of printing bundle tickets at the machine is the expense of adding multiple printers. Also, machine running time may be diminished if frequent changes of printer stock are required.

Ink Jet Printing

In some cases, it is necessary or desirable to mark each piece produced. Ink jet printers are ideal for such applications if the printing requirements are limited to less than 50 alphanumeric characters.

Ink Jet printers have a series of nozzles which spray a fast drying ink directly on the part as it is being produced by the roll former. The pulsation of the nozzles is timed to the movement of the material, forming coarse block letters.

There are two types of ink jet printing systems, drop-on-demand and recirculating ink systems. In the drop-on-demand system, the ink is stationary at the nozzles, waiting for a command to spray. This system produces large characters ranging from about ½ to 2 inches in height and are seen most commonly on many shipping cartons. In the recirculating ink systems, the ink is constantly moving from the reservoir past the spray nozzles and back to the reservoir. When printing is required, the stream of ink droplets is diverted onto the metal. This system produces small characters ranging from about 1/8 to ¼ inch in height and are most commonly seen on the bottoms of can goods.

The advantages of the drop-on-demand system of ink jet printing is the lower initial cost and large characters readable from a distance. The disadvantages of this system are higher maintenance and higher usage of ink. If the machine should sit idle for any length of time, the nozzles may have to be cleaned.

The advantages of the recirculating ink system is the lower maintenance and lower ink usage. Since the ink is constantly moving, there is little chance for the ink to dry out and clog the system. The disadvantages of this system are a much higher equipment cost and the small size of the print.

In the metal construction industry, the need for large, readable characters in the field dictates the use of the drop-on-demand system. Users must live with the cleaning demands of the spray nozzles for the application to be successful.

Label Applicators

Equipment is available to apply adhesive backed labels to each part as it is produced in the roll former. Such labels are necessary if bar codes such as UPC retail codes are required. In most cases, these labels are preprinted on large spools and applied at the machine. Each time the product changes, the spool of labels must be changed. It is possible to print the labels at the machine. This is required for any low volume applications where label requirements change frequently. Printing time will vary with the amount of information to be printed but an average rate is about one label per second.

Bar Code Scanning

Bar code scanners are commonplace in the retail industry. They are beginning to be seen in the metal construction industry as well. Any instance requiring fast, accurate input of predetermined data is ideal for bar code scanners. The most common usage is the reading of bar codes on coil tags since most suppliers now print bar codes on their tags. Bar codes are also being used input complex instructions to the controller while the operator is away from the control console. For example, if the controller has a function to make an extra piece if a defect is observed, a bar code for this instruction can be printed on a sheet located where the operator normally stands to stack finished parts. When a defect is seen, the operator scans the code for this defect without returning to the console.

One thing to consider when choosing a bar code system is the location of the scanner. Most scanners have a limited length cable and a longer cable may be difficult to maintain and may be a safety hazard. The operator may need to scan bar codes at the uncoiler, operator’s console, and at the stacking station. This may cover a span of over 100 feet. A solution to this problem is a wireless scanner which uses a radio frequency transmitter. Scanners are available that cover a 75 foot radius and do not require an FCC license to operate. Operators carry them in a holster or attach them to a vest with Velcro.

When selecting a bar code scanner, be sure to specify one with a rugged case. Most scanners specify a maximum drop distance on a concrete floor without damage.

Automatic Inspection Systems

As technology improves the roll forming industry, new challenges must be faced. As production rates increase, new machinery for handling the finished product will be required in order to take full advantage of the gains in speed. The ultimate solution is a fully automated bundling system. However, such equipment will remove the only quality control mechanism on the machine, the watchful eye of the operator.

In the next few years, emerging technology will be available for automatically inspecting roll formed products. These systems will check for length, profile, twist and camber. In the case of painted material, optical sensors should be able to detect paint flaws and take corrective action. Demand for such equipment will hasten its development.

Conclusions

Computer technology is available to greatly improve the quality and efficiency of the metal construction industry. The key to success is the fast, accurate flow of data from customer to shop floor and back to the customer. Controlling the flow of information is what computers do best.

A common problem in automating a manufacturing process is the conversion from human data to computer data. With a human system, an order can be written with a color specified as HARVEST GOLD or HARVEST GLD or HARV GLD and most humans will know it as harvest gold. However, a computer would see these as three different colors.

The key to successful computerization is flexibility. An attitude of "this is the way we’ve always done it" may negate most of the anticipated gain. A manufacturer must understand the capabilities and limitations of computers and be willing to adapt.

On the other hand, the computer personnel must understand the most important aspect of the metal construction industry, the need for rapid change. The computer system must be flexible and not get in the way of a manufacturing process. It may be necessary to take a coil of material immediately off one truck, run it through the roll former, and load the finished goods on a truck at the shipping dock without entering anything in the computer system. The manufacturer must be able to make the product first and handle the data later.