The Advantages & Disadvantages Of Using Investment ...

When it comes to manufacturing, every component needs to meet its exact specifications to create a final product. There are various processes available to make necessary parts unique to a product, but investment casting is one technique that stands above others in many ways.

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Investment casting is an old way to form metal using minimal machinery and energy. It is best for creating intricate parts, and it is still beneficial in today&#;s industrial environment.

This blog will explain why this old-world metal forming technique stands the test of time and how various industries use it today.

What Is Investment Casting?

The metal forming process known as investment casting dates back almost 5,000 years. Other names for this technique include lost-wax casting and precision casting. Manufacturers use this technique to accurately cast metals with a high heat tolerance using a plaster, plastic, or ceramic mold and a wax pattern that melts away.

Investment casting is ideal for creating precise components with unique shapes that require tighter tolerances and better surface finishing.

A Glance into the Investment Casting Process

The pattern and mold creation process sets investment casting apart from other metal fabrication methods like die and sand casting.

Here is a breakdown of the process:

1. A design engine first makes a wax pattern using a metal injection die. The pattern will have all the details for a section or portion of the finished component but with slightly larger dimensions to account for thermal contraction.
2. Next, the engineer creates the runner and gating system by connecting multiple patterns to form the final component. Molten metal will flow through the runner system as it fills cavities in the mold, creating a well-balanced casting. Gates are the openings between the runner and the cavity that feeds molten metal into the space.
3. Once the entire pattern is complete, it is dipped into a ceramic slurry and covered with sand stucco. The design engineer repeats the dipping process until the shell achieves the appropriate thickness. At this point, the dried shell&#;s durability is strong enough to withstand the heat from the molten metal. Also, it will retain its shape during the last step.
4. The wax melts away under high temperatures, and trace amounts soak into the plaster or ceramic mold. The void left by the melted wax pattern will be filled with an alloy to create a precise metal casting.

How Is Investment Casting Used Today?

This casting process is excellent for creating products and prototypes. It has widespread applications across various industries, primarily the automotive and industrial industries.

So, what is the best metal for casting? Well, how different industries use the castings today depend on the metals they need, but refractory metals with high melting points work best.

Aluminum Alloy

Design engineers use this material the most in investment castings. A blend of aluminum, silicon, and magnesium is strong enough to create premium automotive components, but casters also use the alloy for electronics and industrial equipment.

Steel

Steel is known for its durability, which is why this variety of metal is a popular choice for various components. Casters use this material to craft everything from auto parts to golf club heads. For a full review of the benefits of stainless steel investment casting, read another article we published here.

Titanium Alloy

Metalworkers turn to titanium alloy when making castings that need to be strong enough not to fracture when it has a crack. For example, golf clubs and marine components are a common choice for titanium castings.

Advantages of Investment Casting

This method is ideal for crafting small, complex geometric shapes that have intricate features with one mold.

Investment casting is highly versatile. Because you can combine multiple wax patterns to create one unique mold, you can configure parts you could not make with a machine or tools, making it a worthwhile alternative to weldments.

Dimensional precision and smooth finishes are other benefits of this casting method. The casters form the ceramic shell around even patterns, leaving behind no parting line because only one mold makes the casting, not two. The result is a smooth finish averaging around a 125 micro finish, but post-process smoothing can achieve a more refined finish, if necessary.

Other advantages of investment casting include:

• Reusable Materials: Design engineers can reuse the melted wax for another pattern. They can also reuse the mold, thanks to its strength.
• Tight Tolerances: Investment casting can have a tolerance of .003&#;, which is tighter than most casting processes such as die casting.
• Design Capabilities: With investment casting, design engineers can incorporate identifying markers to the casting, such as numbers, logos, and product IDs.

Disadvantages of Investment Casting

Despite the beneficial nature of lost-wax casting, it does have its drawbacks. The most significant disadvantage is the size limitation. Because so few design engineers can produce large parts using this technique, it may not be the best option for a client who needs to fabricate a bulky component.

This process is best for casting small intricate components. Parts exceeding 75 pounds are better suited for other casting methods.

Investment casting shells also have limitations on their size and depth. They cannot be smaller than 1.6mm or deeper than 1.5 times the diameter. If your casting design requires cores and cannot fit these requirements, you may need to seek another process.

This technique is more complicated than other casting processes, and it requires a substantial amount of preparation and specialized equipment. As a result, the upfront cost of investment casting can be more expensive than sand casting or die casting, but the production cost per unit decreases with larger orders.

Start An Investment Casting Project Today With TFG USA

Investment casting may have roots dating back 5,000 years, but it still has beneficial applications in modern society. Throughout the world, industries rely on precision casting to produce intricate components with smooth finishing, unique geometric shapes, and tight tolerances, including the industrial,, automotive, firearm, food processing equipment, and agricultural equipment manufacturing industries.

The Federal Group USA offers superb investment casting services.

We use specialized shell making and wax processing equipment to fabricate patterns and cast quality components quickly.  If you would like to learn more about our investment casting services and receive a free quote on your upcoming project, contact our team today.

Stainless steel has its characteristics of rust resistance, corrosion resistance and shining appearance, therefore, it is always preferred as the forming material of various metal products. Stainless steel casting, as its name implies, is the casting process of stainless steel alloys. Investment casting or lost wax casting, is the most precise casting method to manufacture stainless steel products, especially those irregular or complex structures, so stainless steel investment casting is almost equal to stainless steel precision casting. The whole casting stainless steel process contains several steps: mold making, wax model making, tree assembly, dipping and dewaxing, pouring, etc.

Stainless Steel Casting - Wax Patterns

Want more information on high quality stainless steel lost wax casting company? Feel free to contact us.

Stainless Steel Casting - Shell Building

Stainless Steel Casting - Pouring & Cooling

CFS Stainless Steel Foundry, located in Ningbo, China, has started its business of stainless steel investment casting since 30 years ago. In recent years, we continuously improve our production and management experience, and have become one of the largest stainless steel casting manufacturers and exporters in China. Currently, we can supply our customers all types of stainless steel castings with OEM services. To serve our customers better, value added services including heat treatment, post machining, surface finish are all available. We aim to supply our customers best quality, while competitive prices.

Common Cast Stainless Steel Grades

Grades Features Applications 304 Austenitic stainless steel with Ni content more than 8%, food grade alloy, can be used to cast stainless steel components for both household and commercial applications. It is the most widely used stainless steel casting material.304 stainless steel castings can be used in environments where the air is less corrosive. Medical, food industry, chemical industry, mechanical equipment, pipe industry, automotive industry, etc. 316 Also austenitic stainless steel with Ni content more than 10%. For its higher Ni content, 316 stainlesss steel castings has better corrosion resistance than 304 stainless steel castings. Such stainless steel castings better suit for the marine environment with relatively harsh air conditions or chemical materials need to be contacted. Fire fighting, auto parts, marine hardwares, chemical, pipeline, construction, decoration, food industry, etc. 304L / 316L The mechanical properties are close to those of 304 and 316 materials. L represents lower carbon content, which makes the material more ductile, has good welding performance, and has more reliable corrosion resistance. The price is higher than that of materials of the same grade. Food, chemical, medical, plumbing, etc. 410 & 416 Series 400 belongs to martensitic stainless steel, which is characterized by high strength, good processing performance and high heat treatment hardness, and does not contain Ni, so the corrosion resistance is weak. Auto parts, tools, knives, etc. 17-4 PH 17-4 belongs to martensitic stainless steel with a Ni content of 3%-5% and good corrosion resistance. It has the highest strength in the stainless steel series and is usually used for products and components that are not prone to deformation. Military, medical, mechanical components, machine tools, turbine blades, etc. Duplex stainless steel is a composite stainless steel consisting of 22% chromium, 2.5% molybdenum and 4.5% nickel-nitrogen.It has high strength, good impact toughness and good overall and local resistance to stress corrosion. Sporting, pump & valve industry, etc.

 

Chemical Compositions Grades Elements C Si Mn S P Cr Ni Mo 304 &#;0.08 &#;1.00 &#;2.00 &#;0.03 &#;0.045 18 ~ 20 8 ~ 11 &#; 304L &#;0.03 &#;1.00 &#;2.00 &#;0.03 &#;0.035 18 ~ 20 8 ~ 12 &#; 316 &#;0.08 &#;1.00 &#;2.00 &#;0.03 &#;0.045 16 ~ 18 10 ~ 14 2 ~ 3 316L &#;0.03 &#;1.00 &#;2.00 &#;0.03 &#;0.045 16 ~ 18 10 ~ 14 2 ~ 3 410 &#;0.03 &#;1.00 &#;1.00 &#;0.03 &#;0.040 11 ~ 13.5 &#;0.6 &#; 416 &#;0.15 &#;1.00 &#;1.25 &#;0.15 &#;0.060 12 ~ 14 &#;0.6 &#; 17-4 ph &#;0.07 &#;1.00 &#;1.00 &#;0.03 &#;0.040 15.5 ~ 17.5 3 ~ 5 &#; &#;0.03 &#;1.00 &#;2.00 &#;0.03 &#;0.040 21 ~ 24 4.5 ~ 6.5 2.5 ~ 3.5

Stainless Steel Investment Casting Process

1. Wax Model Making & Assembly
Once the mold is ready, inject wax material into the mold cavity, then take out the wax model from the mold after cooling. Repair some appearance defects of wax models, such as slot, wax injection nozzle, flow pattern, etc. After inspection wax models, weld them to the casting system one by one to form a assembly, which looks like a tree.

2. Shell Building
Shell making process is a whole silica sol process, namely dip the assembly into good colloidal silica coating, sprinkle with fire-resistant sand, dry and harden shell under certain temperature,thus to form dense refractory coating surface outside the surface of wax models, and then repeat the step 5-6, finally form a certain strength and refractoriness of silica sol shell.

3. Dewaxing
Dewaxing is a process in which the wax inside the shell is melted by high temperature steam and then drained out, resulting in a cavity that can be poured into the mold.

4. Pouring
Melt stainless steel ingots into liquid status under a certain high temperature, then pour the liquid into the shell and cool under room temperature. After solidification, knock out the blacks and clean sand.

5. Cutting, Grinding & Surface Finishing
Cut the stainless steel casting blanks from assembly one by one, remove the sprue gate by grinding machine and smooth the surface by various surface finishes, such as shot blasting, sand blasting, electropolishing, mirror polishing, etc.

6. Inspection
After finishing production, inspection is also an indispensable process before delivery. The inspection of stainless steel castings includes dimensional inspection, defects inspection and material inspection. Only qualified products can be shipped to customers.

Why Stainless Steel Casting? What Are The Benefits?

• Affordable Tooling: Tooling is the basic step to start stainless steel casting process. Although the machining accuracy and material of tooling plays an important role of the final casting quality, the tooling of stainless steel is relatively affordable compared with other forming processes.
• Flexible design: Investment casting can cast out stainless steel products in different sizes and weights, so the design of cast stainless steel parts is very flexible. Stainless steel casting allows parts with minimun 3mm thickness and weights ranging from 0.05kgs-80kgs. Besides, stainlesss steel castings with complex structures are also castable.
• Close Tolerance: The dimensional accuracy of stainless steel investment casting can meet ISO CT5-CT6 level. Such close tolerance can ensure stainless steel castings with less or no maching.
• Good Surface: Even after shot blasting, the surface of stainless steel castings is very smooth and looks bright. And people will never worry about stainless steel castings will get rust with the time flys.
• High Production Efficiency: Stainless steel casting is a fast and repeatable process, so the production efficiency is very high, and no matter it is large or small volume, it can all meet.

Post Treatments

Heat Treatment: Solution Treatment

Solution treatment is a kind of heat treatment process in which stainless steel castings are heated to a high temperature and maintained constant temperature in the single-phase zone, so that the excess phase is fully dissolved into the solid solution and then cooled rapidly, so as to obtain the su-saturated solid solution. The purpose of solution treatment is mainly used to elimate the internal stress and improve the mechanical properties of cast stainless steel components, which will be easier to operate post machining.

Unlike heat treatment for other steel investment castings, solution treatment is the only heat treatment method used after stainless steel investment casting process. And we suggest heat treatment process especially for those stainless steel castings to be post machined, as the hardness of stainless steel castings is high, which is difficult to machine, and solution treatment will reduce the hardness effectively!

Post Machining

Investment casting is preferred to produce cast stainless steel parts mainly because it can creat near net shape products, even without secondary machining. But due to the limitations of stainless steel investment casting, this casting process can not creat net shape parts in most cases when there is a higher size accuracy and higher surface finish requirement. In this condition, post machining is operated to remove excess material by grinding, milling, drilling, etc. CNC machining is the most precise machining process, while the cost is high.

To serve our customers better, CFS has its machining capability to supply machined stainless steel castings for our customers when there is such requirement. With in house machining, we can do the inspection timely and solve problems in the shorest time. In addition, the machining cost is ideal compared with outsourced factory.

Surface Finish

For stainless steel castings, there are several surface finish methods to improve its appearance, including shot blasting, sand blasting, electropolishing, mirror polishing, powder coating, etc.

Shot blasting: The most common and cost-optimal surface finish method to remove mill scales, burrs. It is the process to smooth stainless steel castings by the grinding of small steel balls in shot blasting machine.

Sand blasting: The process of cleaning the surface of stainless steel castings by the impact of high speed sand flow. The surface is more smooth than that of sand casting, while the cost is higher.

Electropolishing: A technique in which stainless steel castings are used as the anode for electrolysis in an appropriate electrolyte to selectively remove its rough surface and improve its surface smoothness. The surface is a bit shinning after electropolishing.

Mirror Polishing: Like its name, it is the manual polishing process operated with grinding wheel, and the surface will looks very shinning like a mirror, which is most time costing surface finish method. And due to its high requirement, the cost is highest compared with other surface finish ways.

Powder Coating: A surface treatment method for spraying plastic powder onto stainless steel castings. Like painting, there are different colors selected.

Stainless Steel Casting Applications

For metal castings requiring corrosion resistance and high strength, stainless steel casting is an ideal choice. The stainless steel investment casting process is used to create components for a range of industries including aerospace, petrochemical, medical, automotive, and food and dairy. Some of the parts and components commonly produced through stainless steel casting include:

For more custom precision lost wax castinginformation, please contact us. We will provide professional answers.

• Valve bodies
• Pumps
• Housings
• Gears
• Bushings
• Brackets
• Arms
• Handles
• Marine equipment
• Medical devices