Casting products,Casting manufacturers, Casting suppliers, Casting exporters, China factories

 

The purpose of requesting a quotation for a steel casting is basically to determine the lowest purchased casting cost. The customer then must weigh all of the provisions of the quotation including exceptions taken to drawings, specifications, and processing requirements, as well as supplier foundry experience, tooling requirements, tolerances, finish allowances, and delivery. Such factors as reduced machine work, better tolerances,Precision Casting Products improved delivery schedules 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, all or some of the following information should be included in a request for a quotation:

 

Design - What is the part? See DESIGN below.

Quantity - What is the anticipated or required volume, both present and future?

Material and inspection requirements; what should the part be made of, and how should the part be tested before delivery? ASTM or other nationally recognized specifications should be used whenever possible to identify the material and inspection requirements. See MATERIAL SPECIFICATIONS and SOUNDNESS below.

Actual or estimated casting weight. Actual weight information is preferred. Estimates can be provided by the supplier foundry in the absence of actual weight information, but this may require offering prices that are subject to changes based on the actual weight of the casting(s) in question at the time of production.

Drawing. Machine drawings are preferred over casting drawings. Drawings or sketches are mandatory if samples or patterns are not available. Drawing should include dimensional tolerances, indications of critical areas and surfaces to be machined. See MACHINING below.

Pattern. If patterns and core boxes are available, the request for a quotation should indicate the type, condition and set up of the equipment. See PATTERNS Metal Castings below.

Production/delivery schedules required. Present and anticipated need should be included in quotation requests.

Beyond these basics, there are levels of customer requirements that could include supplier foundry liabilities, which affect the casting cost drastically. These could include receiving inspection acceptance and back charge policy, investment castings 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 customer and the supplier foundry representative, and the professional attitudes and experiences that both can provide during the quotation evaluation phase.

 

Design

 

To achieve the most efficient production and the highest quality product, the part should be designed to take advantage of the flexibility of the casting process. The supplier foundry must have either the designer's drawings or pattern equipment and know the length Marine castings of the run (number of parts to be made).

 

Castings are generally furnished with un-machined as-cast surfaces, unless otherwise specified. To take advantage of the casting process, the supplier foundry should also know which surfaces are to be machined and where datum points are located. The acceptable dimensional tolerances must be indicated when a drawing is provided. Tolerances are normally decided by agreement between the supplier foundry and customer. Close cooperation between the customer's design engineers and the supplier foundry is essential to optimize the casting design.

 

Material Specifications

 

Industry standard specifications Automotive investment Castings provide the casting customer with the tools necessary to establish criteria for almost any casting application. These specifications do not preclude special requirements that the customer's technical staff members may require. Variations from standard specifications can result in misunderstandings, higher costs and disqualification of potential supplier foundries. 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.

 

Mechanical properties may be verified by the use of test bars cast either separately or attached to the castings. The mechanical properties obtained represent the quality of the steel, but do not necessarily represent the properties of the Aluminum casting themselves, which are affected by solidification conditions and rate of cooling during heat treatment, which in turn are influenced by casting thickness, size and shape. In particular, the harden ability of some grades may restrict the maximum size at which the required mechanical properties are obtainable. Short of destructive testing of an actual casting sample, the use of a test bar is the best measure of the steel quality.

 

Soundness

 

Soundness of metal components refers to the level of freedom from impurities and/or discontinuities such as sand inclusions, slag inclusions, macro porosity, and shrinkage.

 

Steel castings begin to solidify at the mold wall, forming a continuously thickening envelope as heat is dissipated through the mold-metal interface. The volumetric contraction that occurs within a solidifying cast member must be compensated by liquid feed metal from an adjoining heavier section, or from a riser which serves as a feed metal reservoir and which is placed adjacent to, or on top of, the heavier section. The lack of sufficient feed metal to compensate for volumetric contraction at the time of solidification is the cause of shrinkage cavities. They are found in sections which, owing to design, must be fed through thinner sections. The thinner sections solidify too quickly to permit liquid feed metal to pass from the riser to the thicker sections.

 

Testing ensures that the material meets the requirements of the specification; consequently, testing may be mandatory. More frequent testing or other tests may be imposed, by use of supplementary requirements of material specifications or general requirement specifications. In addition to specifying test methods, Sand castings acceptance criteria must be agreed upon between the purchaser and the foundry. The more testing and tighter the acceptance criteria the more expensive the product will be - without necessarily increasing quality or serviceability. Hence, the extent of testing and acceptance criteria should be based on the design and service requirements.

 

It is impossible to produce a defect free casting, only castings with defects of varying degrees of acceptability. The acceptance and/or rejection of such castings can only be determined by examination and analysis of parts (in accordance with internationally recognized standards such as ASTM) based on customers' formal engineering requirements. A defect in one application may not be a defect in another application and it is impossible to make a casting without some kind of flaw. The size of flaw(s) can vary significantly, and what is acceptable and what is defined as a REJECTABLE defect depends on agreement between the supplier foundry and the client prior to production. Large cavities often exist in thick-section castings and can be perfectly acceptable depending on the application and the location within the casting. On the other hand, some applications are very critical and tiny flaws (or even micro-porosity - as defined by a specific NDT process and acceptance/rejection level) may be considered as defects that may be detrimental to the intended use of the product.

 

Acceptance  and rejection criteria for castings production must be determined at the time of quotation and certainly at the time of order, as such criteria affect the price of castings, as well as the production procedures and processes used to produce the castings. 木雕 , castings