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Rolvsøy Metallindustri

Thinner walls, sharper detail, longer die life — and almost no Norwegian suppliers.

Zinc die casting

Pressure die casting in zinc alloy for components where detail reproduction, dimensional accuracy or mass is critical. Four of the eight parts we show are cast in zinc.

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Pressure die casting · zinc

Zinc die casting in Norway

Zinc die casting in Norway starts from a low melting point: zinc melts at around 385 °C. Everything good about the process follows from that single figure — thinner walls, sharper detail, better dimensional accuracy, and dies that last many times longer than in aluminium.

Send a drawing Zinc or aluminium?

The process

What zinc die casting is

Molten zinc alloy is forced under high pressure into a steel die. The cavity fills in a fraction of a second, the metal solidifies against the cooled steel, and the die opens. Ejector pins push the part out, runner and overflows are broken off, and the next shot begins. A cycle is measured in seconds.

The method is the same as pressure die casting in aluminium. The difference lies in the metal, and that difference is bigger than most people assume.

Zinc melts at around 385 °C against aluminium's 660 °C, and aluminium is cast at 680–700 °C. Nearly 300 degrees less metal temperature means dramatically less thermal shock every time the steel die meets the melt. That is why zinc dies survive far more shots, and it is also why zinc reproduces detail better: the melt is fluid and fills tight features before it freezes.

Material choice

Zinc or aluminium?

This is the question we get most often, and there is no single answer. There are six properties that decide it.

See the alloy table
Zinc or aluminium?
Kriterium Zinc (Zamak type) Aluminium (AlSi type) What it means for your part
Density 6.6 g/cm³ 2.7 g/cm³ The same geometry weighs 2.4 times more in zinc. If the part is carried, held or accelerated, zinc loses. If it has to damp vibration or feel solid in the hand, zinc wins.
Melting point approx. 385 °C 660 °C Less thermal shock in the die. Zinc dies last many times longer than aluminium dies — and you are the one who owns the tool.
Wall thickness Thinner Thicker A fluid melt fills thin sections. Zinc can therefore claw back much of the weight penalty — a zinc part does not need as much section for the same stiffness in an enclosure.
Detail reproduction Very good Good Sharp edges, fine ribs, text and logos straight from the die. Cast-in threads are feasible in zinc where they are not in aluminium.
Heat treatment No Yes — but only gravity cast If the part needs maximum strength through heat treatment, gravity cast aluminium is the answer, not zinc.
Anodising No Yes Zinc can be painted, powder coated and plated, but not anodised. If the drawing calls for an anodised surface, the material choice is already made.

The short version: choose aluminium when weight is a cost, when the part will be anodised, or when it must be heat treated for strength. Choose zinc when the detail is fine, the walls have to be thin, the dimensions have to hold — or when mass is genuinely an advantage. Density and melting point are standard material data; see the alloy table for tensile strength, yield and elongation per alloy.

Suitability

When zinc is right — and when it is not

Choose zinc when

  • Mass is a function. A heavy housing damps unwanted vibration. That is why the loudspeaker housing in our portfolio is cast in zinc — the weight is chosen, not tolerated.
  • The detail is fine and plentiful. Thin ribs, sharp edges, text cast directly into the part.
  • Dimensions must hold across the whole series, without sorting and without rework.
  • The wall has to be thin, but the part still has to be stiff.
  • Volume is high and die life dominates the total economics.
  • The part will be tapped. Zinc machines easily, and we tap it here.

Choose something else when

  • Weight is a cost. If the part is carried, hand-held or accelerated, 6.6 g/cm³ hits hard. Then aluminium is right.
  • The part carries sustained load at elevated temperature. Zinc creeps under sustained load when it gets warm.
  • The drawing calls for an anodised surface. Zinc cannot be anodised.
  • The part must be heat treated to reach its strength requirement. Then gravity cast aluminium is the route.
  • The series is a few hundred parts a year. Then the tool does not pay for itself, whichever metal you pick.
  • The part is large and heavy. The density of zinc means the weight limit is reached on a physically smaller part than in aluminium.

Example

The loudspeaker housing: where weight is the point

A loudspeaker housing has two jobs. It has to hold the components in place, and it must not start singing itself.

A light housing vibrates with the cone and colours the sound. A heavy housing stays put.

Here zinc is not a compromise you accept because aluminium got too expensive. It is the right material, chosen because 6.6 g/cm³ does a job that 2.7 cannot. At the same time a housing needs thin, even walls, sealing faces that seal and a good surface — three things zinc die casting does better than aluminium.

That is how we approach material selection: what does the part have to do, and which metal does that job best. Not which metal is lightest, or which one happens to be in stock.

See the product examples

Datablad

Specifications — zinc die casting

We publish what we can document. The rest reads “Available on request” until it has been verified. Call, and you get the figure straight away.

Machine park

Processes in house
Pressure die casting (aluminium and zinc), gravity die casting, CNC turning, CNC milling, boring, heat treatment, blasting
Processes we do not have
Sand casting, toolmaking, anodising, powder coating
CAM software
Autodesk Fusion 360
Number of die casting machines
Available on request
Clamping force
Available on request
Hot or cold chamber
Available on request
Maximum shot weight
Available on request
Platen size and maximum die height
Available on request
Gravity casting stations
Available on request
Maximum mould size, gravity
Available on request
Melting furnaces and melting capacity
Available on request
CNC lathes
Available on request
Maximum turning diameter and length
Available on request
CNC mills
Available on request
Milling work envelope
Available on request
Boring machine
Available on request
Heat treatment furnace
Available on request
Blasting equipment
Available on request
Automation
Available on request
Machining operations
CNC turning, CNC milling, boring, tapping, sawing, grinding
Machining experience
More than 30 years år
Number of axes, milling
Available on request
Heat treatment applies to
Gravity die cast aluminium parts
Heat treatment — effect
Higher tensile strength and higher ultimate strength
Tempers we run
Available on request
Blasting
In house
Anodising
Via subcontractor — aluminium only, zinc cannot be anodised
Powder coating
Via subcontractor
Finishing subcontractors
Available on request
Die ownership
The customer owns the tool. We procure it, specify it for our machines and maintain it.
Typical tooling cost
Available on request
Die life, aluminium
Available on request
Die life, zinc
Available on request
Storage and insurance of customer-owned dies
Available on request
Shift pattern
Available on request

Alloys

Metals
Aluminium and zinc
Feedstock form
Ingot from established suppliers
Aluminium supplier
Metallco, Toten, Norway — secondary aluminium realloyed against international standards
Aluminium melting point
660 °C °C
Aluminium casting temperature
680–700 °C °C
Alloy selection
Made together with the customer, as part of the design review
Aluminium alloys, pressure die casting
Available on request
Aluminium alloys, gravity
Available on request
Zinc alloys
Available on request
Customer-specified alloy
Available on request
Material certificate
Available on request
Melt and batch traceability
Available on request
Recycled content
Available on request

Part sizes

Part weight
From a few grams to several kilos Estimat
Maximum part envelope
Available on request
Maximum projected area
Available on request
Minimum wall thickness, aluminium
Available on request
Minimum wall thickness, zinc
Available on request
Minimum wall thickness, gravity
Available on request
Minimum draft angle
Available on request
Minimum cored hole
Available on request
Insert casting
Available on request
Multi-cavity tooling
Available on request

See also the alloy table, the machine list and the tolerance page for the complete data.

Further down the chain

What happens to the part afterwards

A zinc part is rarely finished when it leaves the casting machine. These operations are in the same building.

CNC machining

Tapping, hole positions and seating faces. Zinc machines easily and cleanly.

Surface finishing

Blasting here, paint and plating at a subcontractor. Zinc cannot be anodised.

Tooling

The zinc die is yours, and it is the longest-lasting tool we run.

Questions and answers

Zinc die casting — common questions

Zamak-type zinc die casting alloys have tensile strength in the same range as die cast aluminium, and better elongation — they are tougher. What they take less well is sustained load at elevated temperature. See the alloy table for figures per alloy.

External threads can be cast in zinc where the parting line allows it. Internal threads we normally tap afterwards — that gives better thread quality and a more reliable result. We do it in the same building, so the part is not shipped out for it.

Available on request. Zinc runs thinner than aluminium, but we will not publish a figure before it has been verified against our own machine and our own tooling.

Very few. Norwegian foundries work mainly in aluminium, and the largest run sand and gravity casting. Zinc die casting as a stated capability is almost absent in Norway — most buyers source it from Sweden, Germany or Asia.

Should your part be in zinc?

Send a drawing or a STEP file. We will tell you which metal fits — including when the answer is aluminium.

Send an enquiry

Henger sammen med

Aluminium die casting

Thin walls, complex geometry and seconds per shot — in recycled aluminium.

Gravity die casting

Lower tooling cost, smaller series — and the only route to heat treated strength.

Heat treatment

Where the strength comes from — when casting alone is not enough.

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