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Category Archives: Miniature Zinc Die Casting

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.

Many Places for Mini: Miniature Zinc Die Castings

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A group of miniature zinc die casting components shown are projects that CWM has worked on over the years.

Miniature zinc die casting is a precision die casting process which addresses the need for smaller component production.  The process is similar to conventional hot chamber die casting, but has the ability to produce castings with faster cycle times, tighter tolerances, and minimal value-added operations.  It can also be an economical replacement for other processes such as screw machine or stamping.

These miniature parts can be cast with great precision in comparison to larger die castings.  

This electronic whiteboard part is a miniature zinc die casting from CWM.  This image compares the size of the part with a quarter.

Thin walls, minimal flash, and ability to produce complex geometries are among the benefits of choosing miniature die casting for smaller parts.  Miniature die casting can be used in many different industries such as: medical, military/government, electronics, computers & peripherals, lawn & garden, alternative energy, telecommunications, global positioning services (GPS), lighting, consumer products, automotive, and many others. n also be an economical replacement for other processes such as screw machine or stamping.

 

A miniature zinc die cast part for a handheld bar code scanner is compared against a quarter.

Using four-slide machines and single cavity tools, cycle times are significantly faster than conventional die casting, yet still offer great accuracy and repeatability.  With a single cavity tool, tolerances of +/- .001 of an inch are possible on select features. This becomes a crucial advantage as die cast parts get smaller, as costly secondary machining can be avoided.  If larger volumes are required, it is not uncommon to utilize multiple cavity tooling.

For more information on miniature zinc die casting, visit our Mini Zinc Die Casting Page or e-mail us at sales@cwmtl.com.

NEW and FREE Download:  A Quick Overview of 10 Different Miniature Zinc Die Castings!

OEMTechBrief47-10-Mini-Zinc-Die-Casting-Case-StudiesFor more information on Miniature Zinc Die Casting, check out the rest of this article today by downloading our newest document!  This article gives a brief overview on 10 CWM Case Studies, specific to Miniature Zinc Die Casting.  Register and download today!

Register for or log into your account at dc2.cwmdiecast.com.  This resource for design assistance is at NO COST TO YOU and is entirely FREE to use.  Download PDF documents, past webinar presentations, and other resources that will prove useful in the die cast engineering process.

For additional resources online to assist with the engineering design of your die castings, you may also access our FREE Die Casting Design Center (DC2) for webinars, case studies, and other documents pertaining to all things die casting.