Permanent Mold vs. Die Casting – Comparing Technology, Costs and Quality

Permanent mold casting and high-pressure die casting are two methods of casting aluminum in durable metal molds. They differ in how the mold is filled: in permanent mold casting the metal flows in by gravity, while in high-pressure die casting it is injected at high speed and held under high pressure. This determines tooling cost, the economical batch size, wall thickness, accuracy, and whether the casting can be heat treated or welded. We compare both technologies and advise how to choose the right one for a given part.

In brief

• Permanent mold: lower tooling cost, castings with good leak tightness and mechanical properties, T6 heat treatment possible; economical from short runs to large series.
• High-pressure die casting: more expensive tooling, but a shorter cycle, thinner walls and tighter tolerances (typically DCTG 5–7); cost-effective for large series.
• High-pressure die castings usually contain more gas porosity, so as standard they are not solution treated and aged, nor welded.
• As-cast surface roughness: permanent mold approx. Ra 4–6 µm, high-pressure die casting approx. Ra 0.8–1.6 µm.
• Our foundry uses both technologies: permanent mold castings from 0.1 to 50 kg and high-pressure die castings in series of up to 100,000 pcs per year.

What are the main differences between permanent mold and high-pressure die cast aluminum castings?

Both methods use reusable metal molds, but they operate under very different conditions. We have summarized the key differences in the table.

Feature	Permanent mold casting	Die casting
Mold filling	gravity – metal is poured into the mold	piston injection (metal in the gate reaches several dozen m/s) and holding pressure of several hundred bar
Mold	cast iron or steel mold; metal or sand cores	hot-work tool steel die with temperature control channels; metal cores and slides
Mold cost	medium	highest
Economical batch size	from short runs to medium and large series	large series – thousands to tens of thousands of pieces per year
Cycle time	typically from about one minute to several minutes	typically from a dozen or so seconds to 1–2 minutes
Wall thickness (approximate)	from approx. 3–4 mm	from approx. 1–1.5 mm
Tolerances per ISO 8062-3	DCTG 6–8	DCTG 5–7
Surface Roughness of the As-Cast Part	Ra approx. 4–6 µm	Ra approx. 0.8–1.6 µm
Gas porosity	low with proper process control	higher – air from the cavity can be trapped in the casting
T6 heat treatment, welding	possible (e.g. EN AC-42000)	not as standard – risk of blistering
Alloys at our foundry	including EN AC-42000 (AlSi7Mg), EN AC-51300 (AlMg5)	EN AC-46200, EN AC-46500, EN AC-47100

Values are indicative and depend on the size and shape of the casting. Tolerances and surface roughness are given according to ISO 8062-3 and the handbook "Odlewnictwo" (M. Perzyk et al., WNT); for more on DCTG classes, see our article on casting tolerances according to ISO 8062-3.

Basic technological differences in the production of aluminum castings

In permanent mold casting, molten alloy is poured into a preheated mold made of cast iron or steel and coated on the inside with a protective coating. The metal fills the cavity under its own weight, calmly and relatively slowly, and solidification can be directed by the gating system and risers. Cavities and holes are formed with metal or sand cores, which makes it possible to produce complex internal shapes.

Aluminum high-pressure die casting uses cold-chamber machines: a shot of metal goes into the shot chamber, and a plunger forces it into a steel die in a fraction of a second and holds the pressure until solidification. These conditions allow thin walls and fine details to be cast, but they require a massive die with temperature-control channels, slides and ejector pins – and it is the die that determines the cost of starting production.

Production costs in permanent mold and high-pressure die casting aluminum foundries

The price of a casting has two components: the one-time cost of tooling (permanent mold or die) and the cost of each part – metal, energy, machine time, finishing and inspection. A permanent mold is considerably cheaper than a die, so for short and medium runs it usually gives a lower total cost. A die costs more, but the short cycle and reduced machining lower the per-part cost – for large runs, it comes out ahead.

The point at which high-pressure die casting becomes cost-effective depends on part size, the number of cavities in the die, machining requirements and annual demand. That is why it is worth comparing quotes for both options. What makes up the price and how to compare quotes is explained in the article how much an aluminum casting costs.

Quality and applications of different types of aluminum castings

Permanent mold castings have a dense, fine-grained structure and low porosity, so they perform well in parts that are mechanically loaded, pressure-tight and intended for heat treatment – in housings, casings, brackets and valve and fitting components. The PN-EN 1706 standard specifies higher minimum mechanical properties for permanent mold castings than for sand castings of the same alloy.

Die castings are chosen for thin-walled housings, covers, heat sinks and parts with complex geometry that need to be lightweight, accurate and repeatable – often with no machining or with machining of functional surfaces only. The limitation is gas porosity: with deep machining, pores can be exposed, and solution heat treatment or welding risk blistering on the surface.

Why choose an aluminum foundry in Greater Poland?

Proximity to the foundry matters mainly for new projects. It is then easier to review the drawing on site and quickly agree on any changes to the mold or die. Shorter transport also means a lower risk of damage and simpler logistics for orders collected in several deliveries.

Our foundry is located in Janikowo near Poznań, about 9 km from the center of Poznań. Visits and pickup of castings are possible by prior appointment, and we deliver castings throughout Poland and abroad – delivery terms (the Incoterms rule) are specified in the quote.

Permanent mold, sand and die casting under one roof

We cast aluminum alloys only – in permanent molds, in sand molds and by high-pressure die casting. This means the same part can be quoted in several processes, and you can choose the one that best suits the run size and requirements. Patterns, core boxes and permanent molds are made in our own pattern shop (for some projects we work with trusted partners), while dies are designed in CAD/CAM with melt flow simulation and made from tool steel in our own tooling department. You will find the full range of services in the production offer.

Machining and finishing without additional suppliers

We machine castings in-house – on 3- and 5-axis CNC machining centers and automatic lathes – and on request we also grind, polish and powder coat them in RAL colors. We operate under ISO 9001:2015 and ISO 14001:2015 systems, certified by TÜV Rheinland Polska.

How to choose the right aluminum foundry for your project?

Before you compare prices, check whether the foundry suits your part. These questions can help:

• Technology – does the foundry have a process suited to your run size and requirements (permanent mold, sand casting, die casting), or only one?
• Weight and size range – does your casting fall within its capabilities? At our foundry: permanent mold from 0.1 to 50 kg, sand casting from 1 to 100 kg in flasks up to 1000 mm.
• Alloys – does it cast the grade specified on the drawing according to PN-EN 1706?
• Tolerances and acceptance – does it declare realistic classes according to ISO 8062-3 and clearly define acceptance conditions?
• Machining and finishing – will it deliver a finished part, or only a raw casting?
• Quality systems – ISO 9001 certification and, if it matters to you, ISO 14001 as well.

A complete inquiry shortens quoting and makes it easier to compare offers – you will find the list of required data in the guide how to prepare a request for quotation for a foundry.

Key aspects of working with an aluminum die casting foundry

High-pressure die casting is usually a multi-year project: the die runs for tens of thousands of cycles, and the order is delivered in batches. At the start, it is worth agreeing on:

• part design for the die – draft angles, radii, wall thicknesses, ejector pin locations and the position of the parting plane are set before the die is designed; later changes are costly,
• volume forecast – annual demand and batch size determine the number of cavities in the mold and the unit price,
• quality requirements – tolerance class, as-cast and machined surfaces, permissible porosity and leak tightness; specify them on the drawing and in the acceptance conditions,
• machining and finishing – who machines the castings, which machining allowances and datums apply, and whether painting is required,
• keeping the mold – regular maintenance and refurbishment extend its service life and protect the dimensions of the castings,
• delivery – batch size, packaging, schedule and Incoterms rule.

We design high-pressure die casting molds in CAD/CAM with melt flow simulation and build them in our own tool shop, then cast on an automated line with control of temperature, pressure and cycle time. Alloys, series range and how we work together are described on the page of our aluminum die casting foundry.

Frequently asked questions

We will compare both technologies for your part

Send a 3D model and a drawing with the planned annual quantity – we will prepare a quote. See also our aluminum permanent mold casting i high-pressure die casting. Request a quote.