Die Casting vs CNC, Sand Casting & Injection Molding Guide

Content

1 Die Casting vs CNC, Sand Casting and Injection Molding: The Short Answer
2 What Die Casting Is and Why It Is the Volume Benchmark
- 2.1 Die casting at a glance
3 Side-by-Side Comparison of the Four Processes
4 Die Casting vs CNC Machining
- 4.1 CNC machining wins when
- 4.2 Die casting wins when
5 Die Casting vs Sand Casting
6 Die Casting vs Injection Molding
- 6.1 Choose metal die casting for
- 6.2 Choose injection molding for
7 Typical Economical Batch Size by Process
8 Explore Our Die Casting Molds and Parts
9 How to Choose the Right Process
10 Why Most Production Parts Combine Die Casting with CNC
11 Process Selection Mistakes That Raise Cost
12 What to Include in an RFQ
13 Frequently Asked Questions
14 Get a Process Recommendation for Your Part

Die Casting vs CNC, Sand Casting and Injection Molding: The Short Answer

Choose die casting when you need thousands of identical, thin-walled metal parts at a low cost per piece. Choose CNC machining for prototypes and tight-tolerance one-offs, sand casting for very large or very small batches, and injection molding when plastic is acceptable.

3,000+Die casting: repeat metal parts

1 to 500CNC machining: prototypes and small lots

1 to 1,000Sand casting: large or low-volume parts

5,000+Injection molding: plastic parts at scale

These batch ranges are rules of thumb. The real break-even point depends on part weight, geometry, alloy and tolerance, so confirm it with a quote.

What Die Casting Is and Why It Is the Volume Benchmark

Die casting is a process that injects molten non-ferrous metal into a hardened steel mold at high pressure, then ejects a near-net-shape part within seconds. Because the mold is reused tens of thousands of times, the high tooling cost is spread across every part, and the cost per piece drops sharply as volume grows.

Ningbo Jieda Molding & Machine has built aluminum die casting molds and precision parts since 1987 in Beilun, Ningbo. Explore our die casting molds, aluminum die casting parts and zinc die casting parts.

Die casting at a glance

Injection pressure: roughly 150 to 1,200 bar
Common alloys: A380 aluminum, Zamak 3 zinc, AZ91D magnesium
Cycle time: about 20 to 90 seconds for small and medium parts
Jieda machine range: 200T to 1600T cold chamber
Quality system: IATF 16949

Side-by-Side Comparison of the Four Processes

Die casting offers the lowest metal cost per part at volume, but it demands the highest upfront tooling among the metal processes. The table below shows typical values to help you shortlist a process.

Factor	Die casting	CNC machining	Sand casting	Injection molding
Best batch size	3,000 to millions	1 to 500	1 to 1,000	5,000 to millions
Cost per part at volume	Low	High	Medium	Very low
Typical minimum wall	About 1.0 to 2.5 mm aluminum, down to 0.5 mm zinc	About 0.5 to 1.0 mm	About 3 to 6 mm	About 0.5 to 3 mm
Surface finish (Ra)	1.6 to 3.2 micrometers as cast	0.4 to 3.2 micrometers	6.3 to 25 micrometers	0.1 to 1.6 micrometers
Materials	Aluminum, zinc, magnesium, copper alloys	Nearly any metal or plastic	Iron, steel, aluminum, bronze	Thermoplastics and some thermosets
Time to first parts	About 6 to 12 weeks	Days	About 2 to 4 weeks	About 4 to 10 weeks

Die Casting vs CNC Machining

CNC wins below a few hundred parts, and die casting wins once tooling cost is spread across thousands of pieces. CNC removes material from solid billet, while die casting forms the shape in one shot.

CNC machining wins when

You need parts in days, not weeks
The design will still change after the first samples
Tolerances are tighter than as-cast limits allow
Annual volume stays under a few hundred pieces

Die casting wins when

The design is frozen and volume is repeatable
The part has ribs, bosses and thin walls in one piece
Material waste matters, since near-net-shape uses far less metal
You want a lower unit price year after year

As an illustration, a complex aluminum housing cut from billet can spend 20 to 40 minutes on a machining center and remove more than half of the starting metal. The same housing, die cast, leaves the machine in under two minutes and needs only light finishing on critical faces.

Die Casting vs Sand Casting

Sand casting wins on part size and tiny batches, while die casting wins on accuracy, surface quality and speed. Sand molds are cheap and disposable, but each mold is used once.

Size

Sand casting handles parts from grams to several tons. Die casting is limited by machine clamping force, with the largest cells in our workshop running 1600T.

Accuracy

Die casting holds roughly plus or minus 0.1 mm on small features, while sand casting typically needs several times that allowance before machining.

Speed

A die casting cycle runs in seconds to about a minute. A sand mold must be built, poured and broken out for every single part.

Tooling

Sand patterns can cost a few hundred to a few thousand dollars. A die casting mold costs many times more but lasts tens of thousands of shots.

Die Casting vs Injection Molding

Die casting and injection molding follow the same logic, a reusable steel mold filled under pressure, but die casting makes metal parts and injection molding makes plastic parts. The deciding question is whether your part needs metal properties.

Choose metal die casting for

Heat dissipation, since aluminum conducts heat hundreds of times better than common plastics
Electromagnetic shielding for electronics and communication housings
Stiffness and strength at high temperature, such as motor and gearbox housings
Pressure-tight parts like valves, pumps and pistons

Choose injection molding for

Lowest weight and lowest cost per part at very high volume
Electrical insulation and corrosion resistance
Color, texture and snap-fit features molded in directly
Non-structural covers and trim without heat load

Many products use both: a die cast aluminum frame for strength and cooling, wrapped in injection molded plastic covers.

Typical Economical Batch Size by Process

Die casting becomes the cheapest metal option once the batch passes roughly 3,000 pieces. The chart shows where each process usually makes financial sense on a logarithmic scale.

CNC machining

1 to 500

Sand casting

1 to 1,000

Die casting

3,000+

Injection molding

5,000+

11001,00010,000100,000+

Explore Our Die Casting Molds and Parts

Jieda designs the mold and manufactures the die cast part under one roof, so one team owns tooling, casting, machining and finishing. Browse a selection of our work below.

Aluminum Die Casting Molds Customized High-pressure Die Casting Mold

Zinc Die Casting Molds Customized High-precision Die Casting Mold

Lightweight Aluminum Die Casting Water Pump, Machined, Easy Installation Aluminum Die Casting Parts

Zinc Die Casting Car Luggage Rack Support Bracket Zinc Die Casting Parts

Industrial Door Operator or Forklift Gearbox Housing in Aluminum Die Casting Gearbox Housings

How to Choose the Right Process

Decide by annual volume first, then geometry, then material, because volume alone eliminates half of the options. Use the four cards as a quick filter.

Choose die casting if

You need 3,000 or more identical metal parts
Walls are thin and shapes are complex
Aluminum, zinc or magnesium meets the spec

Choose CNC if

You are still validating the design
Tolerance is tighter than as-cast limits
Volume is a few hundred pieces or fewer

Choose sand casting if

The part is very large or very heavy
You need iron or steel alloys
Batches are small and tooling budget is tight

Choose injection molding if

Plastic meets strength and heat needs
Volume reaches tens of thousands
Insulation or low weight is the priority

Why Most Production Parts Combine Die Casting with CNC

The most cost-effective route for precision metal parts is usually die casting for the shape and CNC for only the critical features. This keeps machining time short while meeting tight fits on bores, threads and sealing faces.

Mold design

CAD, CAM and CAE flow analysis predict porosity and cold shuts before steel is cut.

Die casting

Molten alloy fills the mold under pressure and the part is ejected.

Trimming

Gates, runners and flash are removed from the raw casting.

CNC finishing

Holes, threads and sealing faces are machined to final tolerance.

Surface treatment

Anodizing, powder coating or plating is applied. Read our anodizing RFQ guide.

Inspection

Dimensional checks and leak or pressure tests confirm each batch.

Process Selection Mistakes That Raise Cost

The costliest mistake is choosing a process from the prototype price instead of the lifetime volume. Avoid these five patterns.

Quoting only the first order. A CNC prototype looks cheap, but running it for 20,000 pieces multiplies machining cost every time.

Freezing the design too late. Changing a die casting mold after steel is cut is far more expensive than changing a CAD file.

Ignoring draft and wall thickness. Parts designed for machining often need draft angles and uniform walls before they can be die cast well.

Over-specifying tolerances. Tight tolerance on every dimension forces machining that only a few features need.

Choosing the wrong alloy. Zinc suits small precision parts, while aluminum suits lighter and hotter applications. Our zinc vs aluminum buyer guide explains the trade-off.

What to Include in an RFQ

A complete RFQ lets a supplier recommend the right process and quote it in one round. Send the following items together.

3D CAD file in STEP format

2D drawing with critical tolerances marked

Annual volume and batch size

Alloy or material requirement

Surface finish and treatment

Testing needs such as leak test or X-ray

Target price and delivery date

Packaging and shipping destination

Frequently Asked Questions

Is die casting cheaper than CNC machining?

Yes at volume. Die casting usually becomes cheaper once the batch reaches a few thousand pieces, while CNC is cheaper for a few hundred pieces or fewer.

Can die casting match CNC accuracy?

Not on its own. As-cast tolerances are looser than machined tolerances, so critical features are usually finished by CNC after casting.

Is a die casting stronger than a sand casting?

Die casting generally gives a finer, denser skin on thin walls, but high-pressure filling can trap gas porosity. Good mold flow design and venting reduce this risk for structural parts.

Can injection molding replace aluminum die casting?

Sometimes, for non-structural parts with low heat load. It cannot replace die casting where heat dissipation, EMI shielding or stiffness at temperature is required.

Get a Process Recommendation for Your Part

Send your drawing and annual volume, and our engineers will tell you whether die casting, CNC or a hybrid route gives the lowest total cost. Learn more about our OEM and ODM service or check the FAQ.

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