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Category Archives: Die Casting Process

Design for Manufacturing – Die Casting

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design-for-manufacturing-die-casting-partimage1There are several processes which can be used to efficiently manufacture parts.  When a project engineer has a solid idea of how the parts all come together to make the end product, it is time to consider which manufacturing process will be the optimal solution for the individual components.  Die casting is one of many processes that should be considered.

Is Die Casting Right for My Part?

To learn more about if die casting is the appropriate process for your project, DOWNLOAD TO VIEW THIS WEBINAR.  You can also contact the CWM Engineering Team for any questions you may have at sales@cwmtl.com or 630-595-4424.

Application Review

When considering DFM for a die casting, even the smallest details may affect cost and performance.  It is imperative for the die cast engineering team to understand the application of the end product and what the part function will be.  The following factors are considered in the initial review:

  • Mating Part review – what does this connect with? Is it an assembly?
  • Environment – what are the features and functions of the part?
  • Product testing – Are there any additional tests the part needs to undergo? What other tests will the product need to undergo that pertain to the die casting?
  • Are there any cosmetic or finish requirements? (Click Surface Finishes for Die Castings or Guide to Surface Finishing for more information on finishes)

Preliminary DFM meetings It is important to remember that working with the die caster and providing as much as detail as possible in preliminary meetings will determine whether or not die casting is the correct process for the application.  Selecting a die cast supplier with in-house capabilities for post-casting operations (i.e. filing, deburring, CNC, machining, coating, assembly, etc.) will make the process much easier and keep the project running as smoothly as possible.   It is vital to find a die caster that is transparent in all their communications and non-biased.   Reputable die casters would never recommend the die casting process; a specific alloy; or a design that is not going to be an effective solution.

Web-based meetings or face-to-face meetings can be either on-site at a die caster or arranging a die caster to visit a desired location.  A visit to the die caster will open the opportunity for both the die casting team and the in-house team to develop a partnership, review best practices, and get an idea of what technology they currently use and what their plans are for the future.

Hosting an in-house company seminar (where the die caster visits) will allow the program to be tailored to the needs of a company and allow the die caster to review numerous in-house samples.

Whichever option is selected – it gives each team the ability to capitalize on strengths and get a feel for the feasibility of a project when considering die casting.

4 Major Factors in Part Design to Consider for Die Casting

In the preliminary stages of moving from concept to ready-to-tool design, a product engineer engages in exploring manufacturing solutions would be best for the part.

In order to get an idea of what to consider in DFM for die casting, here are 4 factors that are important to consider:A die cast part and wall thicknesses.

  • Uniform Wall Thickness

Uniform wall thickness aids filling, improves quality, and lowers cost.  Heavy mass areas should be avoided.  Ribs should be utilized where increased strength or stiffness is needed.

  • Design/Cost Trade-Offs

“As-cast” parts provide a consistent geometry, but sometimes machining is needed (to hold tighter tolerances).   Similarly, more complex tooling can be used instead of machining, but in addition to increasing tooling costs, it may result in stepped parting lines and higher costs to remove flash.  There is also the possibility to having several mating parts consolidated into a single casting resulting in substantial piece cost savings.  Cosmetic or performance requirements, are cost drivers and can involve added polishing, coating, or corrosion protection strategies.   These are just a few of the cost tradeoffs to be considered.mold flow analysis of a die casting helps teams determine where design changes can (or can't) be made.

  • Mold Flow Analysis

Running a mold flow analysis can give engineers on both sides a look at optimizing for part geometry and filling.  It solves several of the major issues upfront so a re-design can be worked in prior to creating the tool and going into production.  This ultimately will translate into both time and cost savings.

  • Drawing Development

It is generally suggested that notes from a previous process are to be excluded from updated drawings.  The notes should be specific to what is required in the die casting process.

additional details on the CAD drawings will determine if the part is suitable for a die casting.Datum schemes and tolerances are very important and can influence whether the part can be made as-cast, or if it will require machining?    Notes can help guide interpretation of the drawing, but it is best to work with a die caster who can help to align the notes to the manufacturing process best suited to your application.   The use of industry standard terms and specification guidelines is strongly recommended.

A good die caster will know whether the part can be made with the die casting process.   A great die caster will have enough know-how to direct an individual towards another process if die casting is not a good fit, or help you to optimize the design if die casting is a good fit.   Contact our team today for more information on how die casting can benefit your project.  E-mail sales@cwmtl.com or call 630-595-4424.

Die Casting 101: Hot Chamber vs. Cold Chamber

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hot chamber and cold chamber die cast parts groupHigh pressure die casting (HPDC) is a process where molten metal is injected under very high pressure into premium steel molds (dies) in order to manufacture high precision die cast products.  The die is designed to cast engineered shapes and complex features with great accuracy and consistent replication.

There are two types of HPDC which Chicago White Metal provides: hot chamber die casting and cold chamber die casting.  Although there are several similarities between the two types, they exist separately for different purposes.

Hot Chamber Die Casting

This is the hot chamber die casting process when the plunger is in the "up" position. Hot chamber die casting is a type of die casting that uses alloys with low melting temperatures (i.e. Zinc, some Magnesium alloys).  Using alloys with high melting temperatures would result in
damage to the gooseneck, nozzle and other components.

In a hot chamber die casting machine, the fixed die half is called a cover die, which is mounted to a stationary platen (large plate to which each die half is mounted) and aligns with the nozzle of the gooseneck.  The movable die half is the ejector die and is mounted to a movable platen, which slides along tie bars.

This is an illustration of the hot chamber process when the plunger is in the down position. The metal is contained in an open holding pot, which is placed in the furnace and melted to the needed temperature.  When the plunger is in the “up” position, the molten metal flows into the shot chamber.  As the plunger moves down, it forces the molten metal through a gooseneck and into the die at injection pressures ranging from 1,000 – 5,000 psi.

The machine pushes the moving platen towards the cover die and holds it closed with great pressure until the molten metal is injected.  The plunger remains in the “down” position to hold the pressure while the casting “cools off.”  After solidification, the plunger is retracted and the cast part is either ejected, manually removed from the machine or pushed off the cover die.  This ejection system, which includes an ejector die and ejector pins, allows the casting to be pushed out while releasing the die halves.

Watch an animation of a hot chamber die casting machine by clicking the following image:
Hot Chamber Die Casting Process Illustrated in a Video

Cold Chamber Die Casting

This is an illustration of the cold chamber process. The ladle is pouring the molten metal alloy into the shot chamber. Cold chamber die casting is a type of die casting that is used for alloys with high melting temperatures (i.e. Aluminum and some Magnesium alloys).

As a contrast from hot chamber die casting (pumping molten metal into the machine), molten metal is ladled from the furnace into the shot chamber through a pouring hole.  While the general function of the cold chamber machine is similar to hot chamber, cold chamber works with a horizontal orientation and does not have a gooseneck.  The ram is pushing the molten metal from the shot chamber into the die cavity to create the die cast part. Instead, the plunger forces metal through the shot chamber into the die at pressures ranging from 2,000 and 20,000 psi.  The plunger holds the pressure and retracts after solidification.  The clamping unit and mounting of dies is set up the same as hot chamber, however the cover die for a cold chamber machine does not have a gooseneck or nozzle, and therefore aligns directly from the shot chamber.

Watch an animation of a cold chamber die casting machine by clicking the following image:
Cold Chamber Die Casting Video

If you would like to discuss how CWM can help you with your die casting project, please call 630-595-4424 or contact us at sales@cwmtl.com with your inquiries.

Tactics for Optimal Product Design for Die Casting

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Developing an optimum product design for die casting is similar, in most respects, for any material/process combination. In capitalizing on today’s advanced die casting processes, however, specific attributes of die casting alloys and the die casting process offer opportunities for distinct product advantages and cost reductions that require somewhat different tactics. These should be applied when a totally new product is being developed, and are critical when an existing product made from another material or process is being redesigned for die casting.

An engineer going over a CAD design for custom die casting designWhen a custom die casting design (or any design) is started from a clean sheet of paper, the designer must disassociate the design constraints from the materials and processes traditionally employed. This is the path to the optimum cost-effective results. Three principles are helpful:

• Think function, before traditional form.
• Performance must be sufficient, not equal.
• Match material properties to performance specifications.

Function Before Traditional Form
In many cases form does not reflect function, but is instead determined by the traditional material and process employed. Therefore, it is essential to think of the function(s) that the component is to perform, and disregard the traditional or previous process form. For example:

• A powdered metal part may have relatively thick walls in structural areas, with throughholes to remove excess material. A die casting typically achieves maximum structural properties by utilizing thin walls with corrugated sections or rib reinforcements.

• An injection molded plastic component may be attached with through bolts and nuts, which are required because the viscoelastic (relaxation) behavior of the plastic makes it necessary to apply only compression loads. Or it may utilize metal inserts. A die casting with superior creep and relaxation properties can employ tapped threads to an advantage.

• A billet machined part may have block like features to obtain functions, for example: square pockets, sharp edges, flat and cylindrical surfaces. The same part designed as a custom die casting may obtain function with smooth filleted pockets, generously radiused edges and contoured and shaped surfaces.

The function before traditional form principle can often be applied to die castings made a few years ago. In many cases, wall thicknesses have been dictated by the limitations of then existing casting technology, so that the die casting component was over designed in terms of functional and structural criteria. Yesterday’s die castings can often be redesigned and produced by today’s advanced, custom die casting technology with thinner walls, reduced draft, and closer tolerances that more nearly reflect the functional criteria.

It is important to note that the definition of form in “function before traditional form” is the traditional shape that is required by specific manufacturing processes. This is not to be confused with a purposely designed form or shape that may provide value or function to the product design. The die casting process easily produces complex design shapes that may be difficult, costly or impossible to produce with other manufacturing processes.
Zinc Magnesium Aluminum Die Casting Optimization

To read more, Chicago White Metal Casting published a technical paper titled, “Developing an Optimum Product Design, Capitalizing on Die Casting.”  The paper reviews two additional designing principles mentioned in this post: 1) Performance must be sufficient, not equal and 2) Match material properties to performance specifications.  The technical paper is available as a free download in our Die Casting Design Center (DC2) to any subscriber.  Subscribe now and download the technical paper.

Contact CWM today to discuss your custom die casting project!