Maintaining production tooling in cost-effective style: with the majority of pattern shops still relying on manual modeling methods, a multi-step process can help an operation achieve optimal pattern use and improve production.

Optimizing a casting project from design to machining is something all metalcasters stive to achieve. Although facilities may not experience the same dilemma when it comes to maintaining their production tooling, they each still have to face the issue of how long they can use a tool before it expires. By identifying improvement areas within the industry, metalcasters and, in this case, sand casters, must evaluate how much effort is spent on planning and maintaining their production tooling. From the utilization of advanced product quality planning and feasibility studies to the design of tooling and determination of storage, all elements compiled together in a strategic decision can result in a cost effective reduction of waste.

Plants that have adequate resources, such as modeling programs, gating software and numerous technical advisors, probably address these areas regularly. Whether a software package or CAD/CAM, computers have been addressed as the sole tool used in aiding pattern and tooling layouts, and designs usually are based on newer technology. However, an estimated 80% of metalcasting facilities still rely on brain power and previous history when it comes to tooling.

Even though this doesn't pose a problem to most metalcasters, many of today's facilities have yet to adapt to those technologies, especially in an environment where finances are stringently watched and funds are not available for technological improvement beyond production controls. To compete in a technologically driven market, facilities should practice production methods for a financially safe operation.

This article addresses a four step process to optimize cost-effective tooling maintenance to help metalcasters improve their production and bottom line.

Motivation for a Method

Automotive metalcasters are familiar with the standards posed by most TS and QS requirements. For example, ISO/TS 16949:2002 mandates top management to designate personnel with responsibility and authority to ensure customer requirements are addressed. This includes selection of special characteristics, setting quality objectives and related training, corrective and preventative actions and product design and development. It also makes mandatory requirements for manufacturing design that cannot be excluded from the quality system.

QS-9000:1998 requires a company to utilize appropriate mistake-proofing methodologies during the planning of processes, facilities, equipment and tooling. It also demands feasibility reviews of proposed products before contracting.

Even with these requirements, however, companies still might not take into account how to achieve them at an optimal level.

When addressing production tooling, the successful back-flow method (Fig.1) helps achieve customer focus while ridding the production line of any miscues. By paying close attention to each step in the back-flow process and having complete participation from those involved in the project, a company can plan and maintain tooling in a manner that not only achieves customer satisfaction, but saves many dollars in investments.

[FIGURE 1 OMITTED]

Each of the four steps of the back-flow method involves several departments of a facility and the departmental personnel. These individuals can add technical knowledge that impacts production tooling and the associated costs.

The four steps the method addresses in regards to patterns are: design and layout, building, usage and maintenance.

Pattern Design & Layout

Many factions of the industry need to be present during the pattern design and layout stage. Representatives from production, metallurgy, quality and sales will all have input in the pattern design. While maximum space needs to be utilized on the pattern, layouts also need to allow for maximum yield and fillet spacing.

If there are various types of molding machines to choose from, then production requirements also should be addressed with a focus on adaptability. A job that has a potential of 2,000 pieces/yr., and a 6-on pattern could be ideal for a squeezer machine; how ever, if the pattern design were large enough to mount on a automatic machine, it would alleviate production crams on the squeezer. Plus, if production requirements were to increase to 5,000 pieces/yr., and the pattern was designed to fit the automatic machine, the facility wouldn't be over-burdened and cost efficiencies for man hours could be saved.

This also is critical when looking at pattern wear and breakdown. As the pattern starts wearing on an automatic system, its life could possibly be extended by switching to a squeezer machine without having to redesign the pattern.

Pattern Build

Because of design and financial reasons, metalcasting facilities must pay special attention to the building stage of their production tooling. For starters, a toolmaker that has experience in the "old school" of patternmaking could work best. They are capable of finding issues in jobs that others may overlook, such as identifying areas that may not pour correctly, casting design flaws and layout issues based on pattern design.

Although some newer-generation toolmakers lean on computer models for cutting masters and coreboxes, those electronic models may not be capable of providing the same production knowledge.

Manual inspection is beneficial while monitoring pattern fillets and shrinkage rates during the building of production tooling. A lapse in proper fillet or the shrinkage rate will automatically lead to production and quality issues. Typical shrinkage rates for gray iron is 1/8 per foot, ductile iron is 1/16 per foot, and aluminum match plates should be 5/32 per foot.

Pattern drafts also are critical, because if a "backdraft" is built into the pattern, the shop will spend tremendous hours cleaning it up just to make production. Typical draft for aluminum plates should be 2 degrees. Fillets for larger jobs should be no larger than 0.25 in. with smaller jobs ranging from 0.187 0.125 in.

The type of shop also must be considered during building of production tooling. For example, an aluminum green sand facility that runs a particular molding machine might achieve only 5,000-10,000 "shots" against a pattern before expecting pattern wear, whereas a gray and ductile iron green sand facility using the same machine monitors patterns after 50,000 "shots."

This aluminum facility has to determine how the casting will be laid out. Further, if casting surface is directly in the path of the blow chamber, toolmakers should see a significantly higher wear in patterns. Thus, a nickel/chrome wear coating is used to extend pattern life by two to three times. The main reason behind this is the use of olivine sand in the green sand mixture, while ferrous facilities utilize silica sand.

Pattern Usage

Molding operators are key in maintaining production tooling. They have the hands-on knowledge of the pattern condition, along with the responsibility to communicate tooling issues to the pattern, quality and production departments.

Establishment of key communication channels from the mold line to these departments is essential in tooling maintenance. The sooner an issue arises with a pattern, the less severe it will be to production count and easier and less expensive to fix. It's advisable to create pattern work orders, or similar documentation routes, to provide a history of tooling repairs and review them annually to search for molding trends that may cause damage. Further, communication of these orders back to the layout department can assist similar products or pattern designs in the future.

Molders also should be educated on handling and storing production tooling. While every molder seems to agree that a rawhide hammer or parting spray is essential to produce quality molds, they never seem to figure out that consequences evolve based on their conveniences.

Pattern Maintenance

Companies must establish proactive procedures for pattern set up and storage sites. Pattern shop employees must be able to view patterns before issuing them out for production and before placing them into storage facilities.

Guide pins, risers and fillets are just a few areas that need to be reviewed to determine if repairs are needed. In permanent mold shops, even ejector pins should be monitored Casting impressions should be diligently looked over after every run. Loose impression can cause molding issues, while dings, scrapes and broken impressions can lead to faulty castings, resulting in missed delivery dates or customer rejections.

Also, when not in use, patterns must be stored in an organized manner. Assigned storage areas are beneficial as they help provide a robust method of pattern storage and prevent loss of pattern equipment.

Use Advanced Product Quality Planning

Process control plans help establish defined measures to identify specific areas within processes and products that need to be monitored, as well as how to monitor and what to look for. Table 1 depicts how basic information can determine the level of quality and costs associated to production tooling. Information on the control plan is simple, yet establishes set intervals and criteria for all workers of a project to address.

This particular control plan also references feasibility studies. These studies should be performed before accepting a project to see if the facility has the capabilities to meet the production demands. A review of these studies will alleviate future production headaches, especially if they're completed properly and cover all aspects addressed on the feasibility forms with precise information. Like the backflow method, these studies work with production tooling.

Tooling with Success

While there are more areas where tooling maintenance can be addressed, especially with details including production and after-life issues, at company's role to be proactive during the planning and maintenance of production tooling is a vital part of an operation. Although the back-flow method is apt for tooling, it is helpful for almost all aspects of the metalcasting industry. Many simple steps are involved, but the key to success is the use of cross-functional teams, education to all departments involved on how their inputs are critical to saving costs and retaining the knowledge for future projects.

This article was adapted from a paper (04-036) presented at the 2004 Metalcasting Congress.

Table 1. An Example of a Process Control Plan for Production Tooling

                  Process Name/
Part/Process        Operation           Machine Device, Jig,
   Number          Description          Tools for Manufacture      No.

                pattern design &      layout sheet, blueprints
                     layout
                  pattern build                  CNC
                   pattern use       squeezer, machplate molding
               pattern maintenance   storage sites, pattern shop

   Process Name/
     Operation          Characteristics
    Description             Product                   Process

 pattern design &         dimensional        production yield, machine
      layout               chemistry                capability
   pattern build      dimensional core fit    casting, parting, core
                                                      layout
    pattern use              visual             mold hardness sand
                                                    capability
pattern maintenance   dimensional physical
                              wear

                                       Methods

                                                               Sam-
                                                               ple

   Process Name/       Product/Process        Evaluation/
     Operation          Specification/        Measurement
    Description           Tolerance            Technique       Size

 pattern design &     space requirements   feasibility study
      layout
   pattern build      product tolerance        shrinkage
    pattern use          sand checks,      set-up techniques   1-5
                       operator checks          Hartley
pattern maintenance   defined parameters   proactive storage   100
                           methods         and setup methods

                                  Methods

                        Sample

   Process Name/
     Operation
    Description        Frequency      Control Method     Reaction Plan

 pattern design &         100%       cross-functional
      layout                               team
   pattern build        initial        master layout
    pattern use        initial 20    work instructions    production
                         mins.                              stopped
pattern maintenance   before/after   work instructions   pattern work
                       production                           orders
                          runs

For More Information

"Maximize Furnace Efficiency to Temper Aluminum Melt Costs," G. Tackes, MODERN CASTING, January 2002, p. 35-37.

About the Author

Nick Fox is a casting coordinator at Galesburg Castings Inc., Galesburg, III.