Frequently Asked Questions
FAQ Category: Purchasing
Is the best time to review a design with a die caster in the preliminary product planning stage or after detailed part prints have been prepared?
Unless the product engineer understands all of the fundamental requirements for a design intended for die casting production, he or she is best advised to consult a die caster at the product concept stage, before important product features and specifications have been locked in. This is, of course, true with any manufacturing process. After heavy OEM investment in design development and CAD refinement, combined with time constraints, there is a tendency to avoid design alterations and press the manufacturing process to produce what can often only be done with difficulty and substantial additional expense.
What purchasing guidelines should be followed in obtaining an accurate die casting quotation?
It is a good practice to review your precise dimensioning and tolerancing requirements against the NADCA industry specification standards for manufacturability. A CWM Sales/Engineering Representative can provide you with a copy or your company can purchase this 211-page NADCA Product Standards Manual from CWM at a special discount (see description and discount order form ). The manual contains a "Part Production" Checklist and "Part Finishing" Checklist, which cover virtually all of the factors which impact on piece-part costs. A "New Die Casting Die" checklist is also included in the manual.You will need to estimate the projected weight of your part (volume in cubic inches times the density [pounds per cubic inch] of the selected alloy). Alloy density data is part of the NADCA manual's Alloy Section. You should provide both anticipated annual requirements and periodic release quantities to aid in optimizing the specific tooling configuration. For accurate cost estimation, a 3D part model in addition to 2D prints is required. In addition, a prototype, or sample should be forwarded, if they exist. Request specific descriptions of the tooling to be designed, the production operations planned, and the current price per pound of the alloy being quoted. With a die caster unknown to you, a plant visit should always be included. A preliminary discussion of your project, and an inspection of CWM's facilities, can be arranged with your CWM Sales/Engineering Representative or by calling the CWM Sales Dept. at 630-595-4424.
Who has ownership of the tooling produced for die casting production?
The purchaser of the die castings retains ownership of the die casting die, even though the die remains with the die caster. By industry practice the design and construction of the die casting die is generally performed by the die caster to its own specifications. The practice is based on the extensive experience and expertise required to design the die and the features of the die that need to precisely match the die casting machine selected by the die caster. Options and details of die ownership are outlined in the NADCA Product Standards Manual which is available from CWM. E-mail firstname.lastname@example.org or call 630-595-4424 for more information.
Is it possible to purchase parts made from an existing die?
Since die casting dies held by custom die casters are the property of the OEM customer who authorized and paid for them, they can be used by authority of that owner and for that owner's purposes only. Companies wishing to purchase existing die cast parts are advised to contact the marketer of the products which include those die castings.
Who has responsibility for die maintenance, repair and replacement: the die caster or the OEM customer?
The responsibility and criteria for maintaining tooling, on the one hand, and replacing the tooling, on the other, should be understood in the contract between the customer and the die caster. The most common practice is for the die caster to provide minor maintenance, and the purchaser to provide major repair and replacement. Minor maintenance is generally described as "run-to-run" maintenance of a serviceable die to maintain die casting production. Major maintenance would cover the replacement or rebuilding of an entire die cavity, die section, or complex core slide that makes up a significant percentage of the casting detail, or the major resurfacing of a die. Die maintenance responsibilities are outlined in greater detail in the NADCA Product Standards Manual which is available from CWM. E-mail email@example.com or call 630-595-4424 for more information.
Should you expect a transferred die casting die, constructed and run by one die caster, to be put into production easily at another die caster?
Dies can be successfully transferred from one die casting plant to another with certain qualifications. A different die casting machine may require modifications to the die's ejection system, its molten metal entry components, and the die's gate and runner system. A receiving die caster will inspect the die to estimate adaptation expenses before incurring such pre-production costs. A special "Inherited Die" Checklist is provided in the NADCA Product Standards Manual which is available from CWM. E-mail firstname.lastname@example.org or call 630-595-4424 for more information.
What can be done to help assure longer life for a die casting die?
Die life is a function of many factors. Among them are part design, part configuration in the die, part quality expectations, type of tool steel used for the die, the heat treatment of the die and the type of alloy being die cast. An understanding of expected die life should be discussed in the initial phases of a project. Progressive die casters can provide tool steel specifications and heat treat specifications that have been developed through extensive NADCA research programs. The specifications include recommendations for stress relief during machining, the removal of the “white layer” after EDM operations and a number of other considerations, including special surface treatments.
What are the pros and cons of purchasing a die directly from an independent tool builder?
When tooling is procured through a reputable die caster, tooling costs may be somewhat higher than if a purchaser dealt directly with the tool builder. The die caster will be closely involved in evaluations and decisions that will translate the product design into the optimum die casting die for successful production. The increased costs almost always represent a bargain in terms of overall costs during the life of the die. An inexperienced purchaser who purchases tooling purely on a cost basis will nearly always find that the costs over the life of a die will be significantly higher because of a lower-quality tool, although this will not be immediately apparent when the tool starts running. It cannot be emphasized too strongly that good quality tooling, which will cost more in the beginning, will pay for itself many times over in the life of a typical die casting die.
What procedures are followed if a product design change occurs before production but after the die casting dies have been made?
If any changes are required by the purchaser to finished die casting dies, or other production tooling, which deviate from the original print provided for the dies and tooling at the time of quotation, the die caster reserves the right to requote the cost, quality, expected die life, and delivery of the tooling. Any changes to the order must be agreed to by the die caster, in writing. Some changes after die completion can be made relatively economically; others may be costly or virtually impossible to make without remaking the entire die cavity. In the case of cancelled orders, the die caster will usually require some payment. Such payment is necessary to compensate the die caster for costs of work in process to the date of cancellation and commitments made by the die caster for purchases relating to the original order.
Why do dies remain with the die caster after completion of the production run?
Even when a future production run has not been decided on, it is customary for the die caster to retain control and possession of die casting dies and production tooling. Since the full cost of engineering, designing, obtaining, and maintaining the die casting dies and production tooling is not fully reflected in the charges to the purchaser for these items, an additional charge may be necessary for these unreimbursed costs if the die casting dies and production tooling are removed from the die caster’s plant. It is also customary, in the case of die casting dies and production tooling which have not been used for three consecutive years for production of die castings, for the purchaser to be notified that this time period has occurred and that unless notification and arrangements for shipment to the purchaser are made in a reasonable time, the die caster will be allowed to scrap the inactive dies and tooling.
What are the responsibilities regarding “first piece” samples of die castings when received by the purchaser?
After the first die cast samples are received from a die casting die, the die caster or purchaser will usually be required to measure the samples and verify that they meet specifications. Modifications from the original print which have no effect on part function or appearance can be discussed at this time to ensure that high production rates can be maintained and premature die maintenance avoided. Procedures for handling changes in the print specifications for the die casting should be agreed upon. Any costs and delivery delay incurred by such changes should be quoted by the die caster immediately after they are received. Authorization for the changes should be given by the purchaser in writing on each change order.
When is a savings on metal, that might be possible with lower quality alloy, justified?
Quality metal is the foundation for good castings. Even a chemical analysis does not fully define all the metal quality specifications that are necessary for good die casting. Low-cost, low-quality metal cannot be expected to meet all die casting requirements. For example, when aluminum or magnesium alloy does not meet established criteria, machining may be more difficult or surface corrosion accelerated. When zinc alloy does not meet established criteria, mechanical properties important in field use will be progressively and seriously reduced in use with time.
How will a die caster be determining the price for metal that will be used in a die casting?
Metal pricing for die castings is based on the die caster’s prevailing cost for the alloy specified on the day the estimate is prepared. In some instances, the die caster’s quotation may make reference to various published alloy prices or other indicators. Metal price is commonly established from quotations from an approved metal supplier, or based on known industry indicators such as the daily American Metal Market, the London Metal Exchange or the Aluminum Association. If the purchaser elects to use an industry indicator, he or she may forfeit the advantage of spot metal buys at lower than market price. The cost for the die casting alloy is subject to fluctuations beyond the control of either the purchaser or the die caster, and the actual price charged for the die casting will reflect the changes required to adjust for all metal market variations. Similar adjustments may be made on each release and/or reorder.
Does Just-In-Time delivery have any impact on tooling costs?
Yes. If just-in-time (JIT) delivery is to be the mode of operation, it should be considered in the initial stages of quoting. JIT may require rapid die change and other systems that will work more efficiently only on certain types of tooling. For example, building the die to quick-change specifications may require a different die size and configuration than the normal practice. Although the initial tooling price will change, the advantages gained from rapid die change may be the governing factor. It is essential that these factors be considered in the design phase of the project, since product design sets the die design and construction parameters. JIT can raise some questions about reliability of delivery. If the purpose of JIT is to reduce inventory, it is frequently desirable to anticipate emergencies and provide for backup tooling, a small amount of emergency inventory or some other way of addressing the catastrophic failure that can occur in any volume production process based on sophisticated tooling.
How can questions regarding dimensional accuracy be avoided?
Die castings may not be rejected if they vary from finished sizes or dimensions within limits agreed upon. Where a very close tolerance or particular dimensional accuracy is specified, the permissible variations shall be agreed upon before die design is begun. In the absence of applicable standards, tolerances will be subject to the commercial variations generally prevailing in the industry.
What is the warranty covering custom die castings?
Die casters, like other responsible manufacturers, stand behind their product. However, it should be understood that the die caster in assuming this proper responsibility focuses its engineering efforts upon the die cast manufacturing feasibility of the component, rather than the component’s product function, which is the responsibility of the purchaser. In general, die casters agree, at their option, to correct, replace or issue credit for, defective die castings, subject to specific limitations and exceptions such as: No warranty attaches to a die casting which has been altered, machined or finished after delivery by the die caster; No claim for defective die castings will be recognized unless made in writing within the time after delivery specified by the die caster; Losses, damages or expenses arising from the use of a die casting, or labor costs or other charges incurred outside of the die caster’s plant, or transportation costs, as well as losses due to other causes, are not acceptable bases for claims against die casters under the warranty provisions.
What is the product liability of the die caster regarding a die cast part that fails in field use?
Die casters cannot be expected to have technical knowledge relating to the end product of the many industries they service. While they may freely offer design services to make a product less costly to manufacture, at no time does this imply a knowledge of the strengths, stresses or other forces that may be induced in the product’s end use. This must be exclusively the liability of the buyer and design suggestions are offered by die casters with this understanding. The die casting industry has always maintained the position that a die caster is not liable for the failure of a die casting in a buyer’s product, if the part furnished to the buyer meets the prescribed specification. Die casters accept the responsibility of manufacturing a part to the buyer’s specifications within the agreed acceptance level. It is anticipated that the buyer will indemnify and defend the die caster from any damages or claims arising from the use of die castings or other goods produced to the buyer’s specifications. (Further details on the limitations of die caster product liability appear in the Product Liability section of the Buyers Guide publication from the North American Die Casting Assn., titled “NADCA Commercial Practices for Die Casting Buyers.” This valuable 16-page resource is available as a downloadable PDF in the CWM Resource Center.)