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Buyer: Purchasing Steel castings

To get the best value from a steel casting requires a cooperative effort by both the buyer and the seller from the early stages of the design through the manufacturing process. Good planning ahead of time will pay dividends for both you and your supplier.

Purchasing Policy

The responsibility for buying steel castings lies primarily with the purchasing department. However, contributions toward the evaluation, selection, and monitoring of vendors are being made more frequently by various departments. These may include product design, manufacturing, quality control, inspection, and general management. This trend towards broad input clearly indicates the need for a defined purchasing policy that defines the responsibilities of the people involved and the extent of their authority. The objectives of the steel casting buyer still remain:

  • acceptable costs,
  • quality,
  • reliability,
  • and delivery,

These goals can be readily attained when all parts of an effective purchasing program are put into action.

Each steel casting is specifically designed and manufactured to perform a given function under predetermined operating conditions. Due to the varied requirements of each user, the steel casting industry has staffed itself with qualified personnel to provide the user with expertise in the selection of the specifications, casting design, foundry techniques, and finishing processes.

Quotation Procedure

The purpose of requesting a quotation for a steel casting is basically to determine the lowest purchased casting cost. The buyer then must weigh all of the provisions of the quotation including exceptions taken to drawings, specifications, and processing requirements, as well as vendor experience, tooling requirements, tolerances, finish allowances, and delivery. Such factors as reduced machine work, better tolerances, and reliability are particularly important to determine the lowest end cost of the casting.

To avoid misunderstandings, reduce costs, and expedite the processing of quotations the following information should be included in a request for a quotation:

Material and inspection requirements.

ASTM or other nationally recognized specifications should be used whenever possible to identify the material and inspection requirements. See Specifications in Steel Castings

Acceptable casting weight.

Actual weight information is preferred. Estimates should be provided in the absence of actual weight information.

Drawing.

Machine drawings are preferred over casting drawings. Target points should be included in the drawing. Drawings are required regardless of the existence of patterns.

Pattern.

If patterns and core boxes are available, the request for a quotation should indicate the type and condition of the equipment.

Delivery.

Present and anticipated need should be included in quotation requests together with required delivery schedules.

Beyond these basics, there are levels of buyer requirements that could include vendor liabilities, which affect the casting cost drastically. These could include receiving inspection acceptance and back charge policy, casting return policy, expediting procedures, and sophisticated controls not normally associated with the standard inquiry. A complete understanding of these areas is best developed by an open relationship between the buyer and the foundry representative, and the professional attitudes and experiences that both can provide during the quotation evaluation phase.

Selection of Casting Supplier

Every service a steel casting buyer may need is available in the steel foundry marketplace. The question then becomes "where and who?" The Steel Founders' Society of America publishes a directory of its members and a detailed listing of all steel foundries in the United States, Canada, and Mexico providing the buyer with pertinent information relative to plant personnel, capacities, special services, types of steel produced, and relative size of castings. With the Directory as a starting point, an initial list of potentially acceptable suppliers can be established. The refinement of this list may require collaboration between the buyer's engineering, manufacturing, and quality control departments depending upon the scope of the company's purchasing policy.

The listing of SFSA member companies from Directory of SFSA Member Steel Foundries is available on line.

Specifications

Industry approved specifications as discussed in Specifying Steel Castings, provide the casting buyer with the tools necessary to establish criteria for almost any casting application. These specifications do not preclude special requirements that the buyer's technical staff members may require. Variations from standard specifications can result in misunderstandings, higher costs and disqualification of potential vendors. If exception is taken to a provision in the main body of a specification requirement (as opposed to taking exception to a supplemental requirement of a specification), the resulting casting cannot be held to compliance with that specification.

Patterns

Pattern equipment design and the resultant costs can constitute a major source of misunderstanding between buyer and vendor. The need to construct new pattern equipment when existing equipment is available, a requirement for a full split core box in place of a half core box, pattern material, and mounted or loose patterns are but a few of the many areas of discussion that effect the cost of the equipment. Invariably, the lowest casting cost and highest casting quality evolve from the more sophisticated pattern equipment, which generates the highest pattern cost.

Order Placement

Order placement is the most important phase in the buyer-seller relationship, not only because it is the first pure contractual agreement between buyer and seller, but also because it requires acknowledgment of schedules and specific commitments.

For purchase commitments to be fulfilled according to schedule, all relative information previously developed in the preliminary phases must be detailed in the purchase contract. The basic elements of the contract that should be clearly defined are:

  • Purchase order number and date
  • Pattern number and /or part number
  • Pattern and machine drawing numbers with current revision notation
  • Quantity required
  • Material specification
  • Casting price
  • Delivery requirements
  • Shipping instructions

If sample casting are required, the following additional requirements should be provided:

  • Number of samples required
  • Non-destructive examination requirements
  • Dimensional examination requirements, if any
  • In-process inspection, if required
  • Final machining approval, if required
  • Special tests, if required

If patterns are to be constructed by the supplier, the following additional information should be provided:

  • Pattern price
  • Description of pattern to be supplied
  • Pattern delivery

If the patterns are to be supplied by the buyer, the following additional information should be provided:

  • Pattern mounting and rigging price
  • Description of pattern services
  • Pattern accuracy liability
  • Pattern delivery

If the castings are to be supplied to special process specifications, any of the following additional requirements can be requested:

  • Chemistry certification
  • Mechanical test certification
  • Brinell hardness ranges and test location
  • Impact test, type and results required
  • Ultrasonic examination including coverage requirements, specification and quality levels
  • Magnetic particle or dye penetrate testing, include coverage requirements, specification, and quality level
  • Radiographic examination including coverage requirements, approved shooting sketch, specification, and quality level(s)
  • Special surface requirements
  • Special packaging
  • Preferences regarding the method of shipping.

It is extremely important that initial casting orders be complete and accurate and that verbal orders be avoided due to their propensity for generating errors through omission.