Frequently Asked Questions

FAQ Category: Production

What are the most important considerations for minimizing porosity in a die cast part?

Vacuum-assisted production can greatly reduce gas entrapment in a casting and thus improve its integrity. Vacuum systems, however, should be considered an important supplement, not a substitute for a product design which addresses minimizing the creation of porosity and sound die cavity, runner, gating and overflow design. Depending on the part configuration and porosity specifications, good part and die design can often provide all the casting integrity required for trouble-free machining without the use of vacuum. In addition, use of the latest furnace technology and sound molten metal handling procedures can help to minimize porosity.

Can conventional die castings be produced to 100% pressure tightness?

With special attention to controlling porosity in the design of the part, in die design, and in production processing, most die castings can be cast pressure tight, particularly if this requirement is not essential throughout the casting's entire cross section. The die caster should always be informed of pressure tightness requirements before any die design takes place. Where a part design with heavy sections, for example, will not allow modification and 100% pressure tightness is required, impregnation techniques can be used with conventional die castings. Impregnation processing forces organic material into the surface pores of the casting, effectively sealing the parts. Pressure tightness is discussed in more detail in the NADCA Product Standards Manual which is available from CWM. E-mail or call 630-595-4424 for more information.

Are cast-in-place inserts, positioned during part production, a routine die casting operation?

Virtually all custom die casters have the capability of accommodating inserts during casting, but many have operational policies that exclude them for personnel safety reasons. While such inserts can offer performance that exceeds that of the die casting alloy itself, their use will always reduce cycle times and increase costs. This must be weighed against post-production alternatives. CWM does not offer the production of die cast parts using cast-in-place inserts.

What types of part inserts can be used as an alternative to cast-in-place inserts?

Steel, brass and bronze inserts are routinely inserted into die cast parts as a post-casting operations. The shape, galvanic and stress considerations of inserts should always be discussed with the die caster before specifications are finalized. Note that post-casting inserts, and particularly cast-in-place inserts, should be distinguished from alternative die cavity insert modules. Such modules can be substituted in the die cavity to produce an entire run of castings with special, alternate features.

What are the most important considerations in assuring the cosmetic surface of a die casting?

The part design itself must be configured so that die casting production will be capable of maintaining the proper metal flow to assure surface quality. The quality of the surface preparation of the die casting die will also be a key factor in the surface quality of the casting produced. Extra time and costs will be involved in the required die preparation, and such dies will require added surface maintenance during their expected life. The results are part surface finishes that cannot be duplicated by any other high-volume production process. Attention must also be given to the proper placement of the parting line, in-gates, overflow gates, and the ejector pins that must be used to eject the casting, so that the important cosmetic surfaces are not affected. CWM is especially experienced in the production of as-cast, highly-cosmetic surface finishes on die cast components. An 8-page Guide to Surface Finishing for die castings is available in the CWM Resource Center.

What are the most important considerations in assuring problem-free post-casting machining (secondary machining) of a die cast part?

Any and all post-casting machining that will be required for a die cast part, to achieve specifications not feasible as-cast, must be made clear to the die caster well before the die design stage, and preferably during early product planning. When post-casting machining is to be performed, the die caster must plan for a die design that assures the proper casting density in the areas where machining will take place. Changes in machining locations after die construction can make certain machining operations impossible, based on the fact that the optimum mechanical properties and density of a die casting cross-section are rarely constant. Recommended machining stock allowances for the guidance of product designer are outlines in the Coordinate Dimensioning section of the NADCA Product Standards Manual which is available from CWM. E-mail or call 630-595-4424 for more information.

What does custom die caster membership in NADCA and the DDC indicate?

Affiliation with the North American Die Casting Association (NADCA) , the world's largest die casting industry organization, means that a custom die caster has available the latest training tools for the continuing technical education of its operating personnel; is gaining early access to industry R&D and technological evaluations of new developments, such as significantly extending die life; is aided in transferring the latest die casting production technology to the plant floor; is supporting the development of the latest design specifications for die casting part design; and is enhancing its management skills to maintain a strong organization for OEM service into the future. CWM was a charter corporate member of NADCA's predecessor organization, the American Die Casting Institute, and as a corporate member of NADCA its personnel today hold board and several committee positions. The Diecasting Development Council (DDC) was formed by NADCA to bring a range of valuable die casting design and production information to OEM product designers, engineers and purchasing specifiers. NADCA subsequently took over and expanded this effort into an aggressive program of development, publication and distribution of die casting design, engineering and specification information for all OEM personnel engaged in product design, development and purchasing. This OEM program includes a design website, die casting design seminars, application white papers, manuals, videos and CD-ROMs. NADCA OEM reference manuals and CDs are available from CWM at a special OEM discounts. E-mail or call 630-595-4424 for more information.

What does custom die caster membership in the IMA mean?

CWM has been a member of the International Magnesium Association (IMA) since the onset of its volume Mg die casting production. A pioneer in the hot-chamber magnesium die casting process in North America, CWM operates three of among the world's largest hot-chamber mag die casting machines in one of the largest Mg custom die casting departments in North America. IMA support, program participation and interaction with its worldwide membership of Mg alloy producers, machinery builders, and die casters has enabled CWM to remain on the forefront of die cast part design and production in the die casting industry's most rapidly growing alloy category. CWM's CEO was elected president of the IMA for an unprecedented three terms, and CWM's executive vice president, CFO, has served as its treasurer.

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