Lost Foam Casting Foundry

SIPX provides superior quality lost foam casting parts and components for a wide range of industries including automotive, food dairy, machinery, medical, plumbing, watering, mining, petrochemical, electrical, energy, aerospace, submarine and others.

Most casting methods require reusable patterns that must be withdrawn from the mold prior to casting, the removal of the pattern from the mold must be taken into consideration when planning the pattern layout. Contrarily, using foam patterns that remain in the mold during casting and are evaporated helps reduce some of these limitations.

What is Lost Foam Casting

Lost-foam casting (LFC) is a casting method used to create solid metal parts from molten metal, which is similar to investment casting. When a part is created through casting, a mold is used to produce the desired shape. In lost-foam casting, the mold is made from polystyrene foam, which is lost during the casting process as the liquid metal melts it and replaces its shape, hence the name “lost-foam.” Although lost-foam casting is often used to make machine parts, decorative and other objects can be produced using the same method. The tools used by casters range from homemade devices to industrial-grade equipment.

The foam maiking process uses beads of polystyrene that are heated inside an aluminum die to expand and fill the die. A completed polystyrene foam mold is then covered with a ceramic refractory coating to create a barrier between the foam and the sand in which the foam mold sits. The small amount of waste gas created can escape into the sand.

Why Choose SIPX

With over 10 years of experience, Sipx is well versed in this field. Yes, you are dealing with masters. You can trust us with your needs and expectations.

You will save 20-30% of the cost because of our excellent production capacity. Furthermore, we only insist on making high-quality casting products.

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Aluminum is often used in lost-foam casting, especially by hobbyists, but it is possible to use any metal as long as it is hot enough to evaporate the foam mold. The castings can be produced from a fraction of a pound up to thousands of pounds. Slightly more advanced techniques are used for very large castings.

Generally, all ferrous and non-ferrous materials can be successfully cast using the Lost Foam process. Because the foam pattern and gating system must be decomposed to produce a casting, metal pouring temperatures above 1000°F are usually required. Lower temperature metals can be poured, but part size is limited. In addition, very low carbon ferrous castings will require special processing.

How Are Lost Foam Castings Made?

1. Patern Molding

A foam pattern is made using expanded polystyrene. This can be formed by closed-die moulding, machining or assembly from multiple parts. Risers and gates are included at this stage.

2. Cluster Assembly

Multiple finished patterns (including gating system) are glued together to form a cluster.

3. Coating

The cluster is coated with a permeable refractory slurry, usually by dipping. Once dry, the refractory coating forms a hard shell around the foam pattern.

4. Compacted In Sand

The cluster is then placed in a foundry flask or box and surrounded by loose, un-bonded sand which is then vibrated to aid compaction.

5. Melting And Casting

Molten metal is then poured into the mould. The foam pattern instantly vaporises and metal fills the cavity left within the refractory shell.

6. Shakeout And Finish

Once the casting solidifies, the sand and shell are broken away. The remaining operations such as, shakeout, cut-off, grinding, heat treat, etc. are straightforward and similar to other casting processes.

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Advantages of Lost Foam Casting

Requires no draft to aid removal from the mould.
Has no parting lines and no flash is formed providing a better, more consistent surface finish without the need for further machining.
Unbonded sand is used which is simpler and cheaper than greensand or resin bonded sand.
Fewer steps are involved than with investment casting so costs are lower.
Natural directional solidification takes place, so casting is more predictable with fewer defects.
Foam patterns are easy to manipulate, carve, glue and handle.
Multiple parts can be consolidated in a single complex casting, reducing the need for post casting assembly.

Materials Available

Aluminium Alloys.
Carbon Steel: Low carbon, medium carbon and high carbon steel from AISI 1020 to AISI 1060.
Cast Steel Alloys: ZG20SiMn, ZG30SiMn, ZG30CrMo, ZG35CrMo, ZG35SiMn, ZG35CrMnSi, ZG40Mn, ZG40Cr, ZG42Cr, ZG42CrMo…etc on request.
Stainless Steel: AISI 304, AISI 304L, AISI 316, AISI 316L and other stainless steel grade.
Brass & Copper.
Other Materials and Standards on request.

The Ultimate FAQ Guide – Lost Foam Casting

What type of surface finish can be achieved?

Because a permeable refractory coating is applied around the smooth foam pattern, the resultant finish is excellent. Each casting facility is different, but generally Lost Foam castings have a surface finish within the 60-250 RMS range. If surface finish, due to cosmetic requirements, is a critical issue then surfaces can be targeted to maintain an exceptionally smooth finish.

What tolerances can be expected?

Typically, a linear tolerance of +/-.005 inches/inch is standard for the Lost Foam process. This tolerance will vary depending on part size, complexity and geometry. Subsequent straightening or coining procedures will often enable even tighter tolerances to be held on critical dimensions. A targeted effort between the foam pattern producer, the casting producer and the casting user will often result in a Lost Foam casting that substantially reduces or completely eliminates previous machining requirements.

What is the cost of using the Lost Foam process?

Lost Foam castings are generally more expensive than forged parts, or parts made by other casting processes. The value inherent in the Lost Foam process versus other processes is seen in tighter tolerances, weight reduction and as-cast features which all results in less machining and cleanup time. Many castings that require milling, turning, drilling and grinding can be made in the Lost Foam process with only .020” – .030” of machine stock. It is imperative that the features to be cast are discussed by all parties to determine the net finished product cost.

What quantities need to be made to make the Lost Foam process practical?

The answer, simply, is not as many as you would think. Tooling amortization is a key factor in this determination. Potential overall savings for your application will aid in your decision. Generally, 500-1000 pieces per year is the minimum production run to be economical. Prototyping runs, however, may be as few as 3-5 pieces for Fabricated Foam patterns or 20-100 pieces for Quick-Cut CNC machined aluminum tooling.

What type of tooling is required and at what cost?

Typically, tooling is composed of a split-cavity machined aluminum die that is the negative mold from which the foam pattern is produced. The tooling is highly specialized and must be constructed by experienced tooling manufacturers familiar with the requirements of the foam molders and foundries. Most tooling for Lost Foam patterns will compare favorably with permanent and die cast tooling. Prototype and simple tools may be in the $3000-5000 range while high-end tooling for complex or very large parts can be in the several hundred thousand dollar range. As a result of the materials used and the process stresses, Lost Foam tools can be expected to have 3 to 4 times the cycle life of permanent mold or die casting tools.

What lead times can be expected when ordering a Lost Foam casting?

As with all processes, lead times vary greatly depending on part complexity. Generally, 8 to 16 weeks is typical for completed tooling and first castings produced. After casting approval, 6 to 12 weeks is typical for production run startup. Rapid prototyping methods can produce castings in as little as 2 to 3 weeks.

The information provided in this feature article is of a general nature and is intended to provide initial guidelines for process consideration. As with all processes, each project will face advantages and disadvantages during design and production. If you have more specific questions for a project that you are considering, please contact us using the Request More Information form on our website. We will be happy to discuss your project with you.

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