Developments in die-cast zinc alloys permit casting of the finest wall thicknesses. Aesthetics, feel, shape, and weight – everything must be right for this dental camera with a surface-treated die-cast zinc housing.
COURTESY OF Initiative Zink, Germany

Die-cast zinc can support a range of precision instruments used for internal medicine, ensuring that doctors can concentrate entirely on their patients. Designer materials characterized by high mechanical strength, toughness, and rigidity, die-cast zinc alloys provide high performance, long service lives, and a good cost-benefit ratio.

Mechanical properties and many possible surface treatments make zinc alloys an effective construction material in terms of time and cost. Whether switches, handles, moldings, panels, or elements with a technical function – zinc can be cast with near-net accuracy in almost any desired shape and offers precise surface structures and properties that can be integrated during casting. Die-cast zinc also offers excellent prerequisites for surface treatments, such as galvanic coatings.1, 2, 4

In terms of accuracy, zinc alloys are almost unbeatable for casting even complex filigree components without machining. For small parts, a reproducible dimensional tolerance3 of less than 0.03mm can be maintained – an order of magnitude achieved with modern machines and computer-controlled casting simulations. There are few processes that produce parts this reliably and accurately, often making mechanical machining unnecessary.

Central carrier unit for attachment of optical, electrical, and mechanical components for imaging plate technology used in dental medicine.
Courtesy of Initiative Zink, Germany

Medical technology requirements

In addition to precision, die-cast zinc can address hygiene regulations for components that come into contact with humans and their surroundings (not located within a machine). Such components must withstand the regular use of detergents and disinfectants without impairing functionality or appearance.

The wide range of surfaces that can be achieved with die-cast zinc means that a suitable solution can always be found, even in demanding environments. Whenever die-cast zinc parts are used in an aggressive environment or are intended to meet aesthetic requirements, a wide range and quality of conversion layers, organic coatings, or electroplating (nickel or satinizing and bright chrome-plating) can be used.

High-quality casting is a basic prerequisite for achieving excellent surfaces. Economical mass processes such as barrel finishing can be used for further decorating the surfaces of zinc parts in their as-cast condition. Smooth surfaces can be achieved with buffing or chemical polishing before surface treatment. The high fluidity of zinc alloys allows target areas or complete castings to be given defined surface textures in the as-cast state. In addition, writing or logos can be directly molded onto parts.

Frame part and lid for carrier and transmission of functions of a slit lamp used by ophthalmologists.
Courtesy of Initiative Zink, Germany

Handheld devices, such as dental cameras that doctors move inside patients’ mouths or optical devices to measure the human eye, must be well balanced, comfortably used, and reliable.

Zinc’s high density and capability of casting extremely thin walls offer designers a high level of freedom, permitting them to influence weight, balance, quality, and inertia. Cool touch (the typically cold feel of metals) and other sensual impressions are factors appreciated by many users of die-cast zinc. Die-cast zinc parts can also be provided with a warm feel.

Protection against radiation is an important property whenever it’s present. This may involve protecting humans against radiation, such as X-rays, and it’s often necessary to prevent the functionality of a sensitive device from being influenced by the electrical or electromagnetic radiation of other devices. Zinc’s screening properties represent a desirable additional benefit for such sensitive situations. Some medical products are manufactured in high unit numbers, such as hospital beds and bedside cabinets. In such cases, the cost-benefit ratio is decisively important.

Reliable functionality, economic efficiency, and increasingly aesthetics – properties offered by the structural material zinc – are becoming more and more important in hospital technology .
Fotolia © upixa

Future developments6,7

New alloys: Flow-filling and mold-filling capacities have been optimized by adapting alloy compositions using grain-refining elements, among other methods, so that maximum quality can be achieved – particularly with very thin-walled components (down to 0.3mm thickness) or high surface demands. Optimized alloys for thin-walled castings and intelligent designs permit weight savings up to 30%1, 2, 4

New casting techniques:Developments in casting technology and surface treatment include:

  • Sprue-free, low-sprue techniques increase the resource- and energy-efficiency of the process5
  • Zinc foam casting can reduce required material by more than 50%, leading to workpieces with internal, desirable pores and an exterior with a closed surface that can be polished and electroplated.

Initiative Zink
www.initiative-zink.de

International Zinc Association
http://diecasting.zinc.org

About the author: Sabina Grund is project manager at Initiative Zink and can be reached at informationen@initiative-zink.de.

1 Frank Goodwin and Didier Rollez: ‘Zinc alloys’, Ullmann’s Encyclopedia of Industrial Chemistry, 7th edition, Wiley-VCH 2013. 2 Sabina Grund and Hans-Helmut Jeschke: ‘Zink und seine Legierungen’, Handbuch Konstruktionswerkstoffe, 2nd Edition, Hanser Verlag 2013, Pages 505 - 515. 3 ‘Druckguss aus NE-Metallen’, Technical guidelines. Publisher: Verband Deutscher Druckgießereien (VDD) and German Foundry Association (BDG), edited 2016 version. 4 Sabina Grund: ‘Normgerechte Legierungen als Basis für qualitativ hochwertigen Zinkdruckguss’, Giesserei Praxis, Issue 4/2014 . 5 Sabina Grund: ‘Ressourceneffiziente Gießtechniken beim Zinkdruckgießen’, Giesserei, Issue 9/2016, Pages 36 - 38. 6 Homepage Initiative Zink: http://www.initiative-zink.de/basiswissen/das-metall-zink/zinkdruckguss/. 7 Homepage of the International Zinc Association: http://diecasting.zinc.org/