Which Type of Metal Casting Is Right For You?

Written by nicolas.poulain | Aug 9, 2022 2:00:00 PM

Choosing the right type of metal casting for your product design can be challenging with the numerous metal casting processes. This is a decision best made during the early stage of product design. Design is typically 5% or less of the product cost, affecting 70-80% of the final product cost. Therefore, it is advisable to form a cross-functional team when moving forward with the optimal metal casting process decision.

Design Variables to Consider

The designed product is a great starting point for determining the desired result. There are a lot of variables to consider; for example, what is the desired product quality? What are the concerns regarding surface finish, dimensional tolerance, porosity, texture, etc.? What about the component geometry?

Minimum sectional thickness and core size should be considered as they are critical to the selected molding process. It is also essential to consider the production parameters, including sample production quantity, development, tooling costs, equipment costs, lead-time, heat treatment, machining, quality control procedures, and measurement equipment. Can the process be fully automated?

Types of Metal Casting: A Guide

Below is a casting guide to provide an overview of the different casting processes, including the advantages and disadvantages:

METAL CASTING GUIDE
Casting Process	Advantages	Disadvantages
Continuous Casting
This process feeds molten metal into a mold. Water cooling partially cures the part. Semi-solid metal is then sent through a guide that stretches the material to the desired thickness. Metal continues to cool and solidify. The product is then sent through straighteners and cut to length.	Little/no material waste	Set-up costs
	Dimensional consistency	Mold costs
	The product can withstand pressure applications	Simple shapes only
	The product can withstand pressure applications	Large footprint
Shell-Mold Casting
Like sand casting, shell-mold casting is an expendable mold casting process that uses resin-covered sand to form the mold. Shell molding uses sand mixed with a bonding resin to cover a heated pattern and form a mold. Sand is packed over the form to create a cavity used as a casting mold. Ferrous materials can be cast along with softer materials like aluminum alloys and brass.	Dimensional accuracy	High equipment costs
	High volume manufacturing	Phenolic resin is expensive
	Complex geometries	Shrinkage and porosity
	Smooth surface finish	Gating system part of the pattern
	Low tooling costs	Gating system part of the pattern
	No moisture, few gases	Additional machining required
	A variety of alloys used	Poor material strength
	Not labor-intensive
	Complex geometries

METAL CASTING GUIDE
Casting Process	Advantages	Disadvantages
Pressure Die Casting
Molten metal is forced under pressure into a permanent mold. Once the metal cools, the mold separates, and the part is removed. Aluminum and aluminum-zinc alloys are commonly used materials.	Dimensionally accurate part	Equipment and tooling are expensive
	Good surface finish	Equipment and tooling are expensive
	Recycle scrap metal	Ferrous metals are more difficult to cast
	High Strength	Must trim parts
	High volume manufacturing	Limited die life
	Not labor-intensive	Long set-up times
	Product detail
Permanent Mold (Gravity) Die Casting
Molten metal is poured from a ladle or vessel into a permanent mold. Once the metal cools, the mold separates, and the part is removed. The molten material is gravity fed and adjusted by tilting the die. This process can use iron, but yellow brasses are not advised.	Smooth surface finish	Slow casting rate
	Dimensional accuracy	Rough surface finish
	Stronger than sand casting	Minimum 4mm wall thickness
	Can cast thinner walls	Simple design
	Can cast inserts into part	Tooling is more expensive than sand casting
		Tooling is more expensive than sand casting
Semi-Permanent Mold Casting
Like permanent mold casting, the cores used in the casting process may be expendable sand cores. More complex core shapes are possible. Molten metal is poured from a ladle or vessel into a permanent mold. Once the metal cools, the mold separates, and the part is removed. The molten material is gravity fed and adjusted by tilting the die. This process uses zinc, aluminum, magnesium, tin, or copper.	Produce more complex core geometries	Slow casting rate
	Produce more complex core geometries	Rough surface finish
	Smooth surface finish	Simple design
	Dimensional accuracy	Tooling is more expensive than sand casting
	Stronger than sand casting	Tooling is more expensive than sand casting
	Can cast thinner walls
Slush Casting
Slush casting is excellent for hollow products (lamps, statues, toys, etc..) Molten metal is poured into the metal mold, and it is allowed to cool for a short time such that only the outer surface metal gets solidified. The excess molten metal is then poured out of the hollow shell. The hollow casting is obtained when the halves of the mold are separated.	Less expensive	Strength difficult to control
	Can produce hollow casting light in weight	Poor internal geometry control
	Can produce hollow casting light in weight	Poor internal geometry control
	Simple, low-cost die	Low melting temperature metals
	Good surface finish	Low melting temperature metals
	Accurate outer geometry	Requires mechanical turning mechanism
	Ideal for hollow products	Requires mechanical turning mechanism

METAL CASTING GUIDE
Casting Process	Advantages	Disadvantages
Squeeze Casting
A combination of gravity and pressure casting. Metal is poured into the preheated mold, and a ram applies pressure from the top to force the metal into the product shape. Sand cores are often used. The process can use a wide variety of alloy choices.	Good microstructure	Limited to smaller size parts
	Low porosity	Long cycle time
	Equipment is less expensive	Smaller production runs
	Good strength and ductility	Limited geometry
Centrifugal Casting
This process uses a water-cooled mold rotated using rollers on its central axis at high speed while liquid metal is poured into the mold. Centrifugal force pulls the liquid metal along the mold’s surface in an even layer. The process is ideal for pipe and tubing. Materials often used include zinc, aluminum, magnesium, tin, or copper.	Product forms almost any wall thickness	Inaccurate casting ID
	Product forms almost any wall thickness	Not suited for all alloys
	No parting lines
	High output, low defect
	Higher mechanical strength
	Best for pipes and tubes
Sand Casting
Compacted sand is mixed with a bonding agent and packed around a form part. A flask holds the sand in place. The pattern is removed, and hot metal is poured into the sand mold. Once cool, the sand is removed from the cast product. There are variations to this process depending upon the automation involved. Suitable for casting ferrous materials.	Inexpensive	Rough surface finish
	Versatile	4mm minimum wall thickness
	Low tooling cost	Slow casting rate
	Up to 70% of sand reclaimed	Additional machining required
	Commonly used method
	No product size limitation
*Investment Casting (lost wax casting***)
Best for detailed, dimensionally accurate pieces with minimal machining required. Injection mold forms wax patterns that are ceramic coated. A heated mold melts the wax, and molten metal is injected into the ceramic mold. Ceramic mold, gates, and riser are not needed in the process.	Versatile	Costly set-up
	Relatively low-cost	Pattern preparation is time-consuming.
	No parting lines	Pattern preparation is time-consuming.
	Machining rarely required	Not suited for high-volume manufacturing
	Smooth surfaces	Not suited for high-volume manufacturing
	Complex geometries
Lost Foam Casting
Similar to investment casting but uses polystyrene foam instead of wax. Best for detailed, dimensionally accurate pieces with minimal machining required. Injection mold forms wax patterns that are ceramic coated. Heated mold melts the wax and molten metal into the ceramic mold. Ceramic mold, gates, and riser are not needed in the process.	Versatile	Low volume
	Dimensionally accurate	Preparation is time-consuming.
	No parting lines	Patterns easily damaged
	Machining rarely required
	Smooth surfaces
	Complex geometries

Processes Without the Guesswork

Once the best metal casting processes are established, several other steps are needed to ensure the product is brought online without delays, defects, or tooling problems. This is where strong consideration of high-performance simulation software is essential to a smooth start-up. These products allow virtual engineering across various forming processes, including liquid materials, metallic solids, and polymers.

The addition of casting simulation software takes the guesswork out of the design and avoids the problematic relationship between process parameters and casting properties before the first part is in production. This allows the company to expedite the time to market, productivity, and utilization and reduce scrap to minimum levels.

Learn More

The first step to consider is the benchmark software by Transvalor Americas. We carry 3-D simulation software for different types of metal casting processes, including the industry's best technical support and problem-solving built into the casting software. Contact Transvalor USA to learn how casting simulation software guarantees a faster, smoother time-to-market.

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