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Investment Castings for Defense Manufacturing

It takes precision-engineered components to meet the challenging performance criteria required for today’s advanced military systems, and investment castings are often the ideal manufacturing solution for aerospace and defense applications. 

Investment casting offers a wide range of benefits, such as the ability to produce complex shapes with thin walls and excellent surface finish. Investment casting is a highly repeatable process and castings are accurate to tight tolerances with a high level of internal soundness, meeting stringent X-ray and NDT requirements. Investment casting can be used with a broad range of materials, such as armor steel, stainless steel, aluminum, nickel, and cobalt alloys.

Furthermore, investment casting eliminates the risk of defects in welds by enabling component consolidation. Investment casted parts also need less machining than those cut from billet or bar, and controlled solidification can optimize grain structure for improved mechanical properties. With the growing demand for high-strength lightweight parts, investment casting is the process of choice for today’s military OEM’s designing housings, mounts, brackets, latches, chassis and engine components.

There are several factors to consider when designing and specifying investment castings for military applications. In this blog, we will cover four major items. 

Materials

aluminum investment casting part

Material selection and heat treatment parameters are keys to determining the mechanical properties of the cast part, such as mass, strength, fatigue resistance, and thermal expansion. Specific strength is often a key selection criterion, as using more low-density material can reduce overall mass.

Solidification behavior and grain structure are also factors in material selection for defense castings. With investment casting, it’s possible to regulate solidification through local thickness variations in the ceramic shell, which raises or lowers strength.

Some of the most widely used alloys in military investment casting are:

  • Aluminum, mainly grades like A356 and A357
  • Stainless steel, including 17-4 PH
  • Carbon steel
  • Armor steel
  • Nickel-based alloys and Cobalt-based alloys

Design & Precision

For parts destined for manufacture by investment casting, design involves more than creating prints of the final geometry.

First, detailed 3D models are created with advanced CAD programs that enable visualization of every feature and integration with mating parts of an assembly. Then, computer-aided engineering (CAE) tools are used to investigate how the design will perform under expected and extreme conditions. This can include analysis of fluid dynamics and responses to thermal and mechanical loads.

The design process also involves building the patterns that will form the mold cavity. These patterns must include allowances for shrinkage of both the wax and the materials used for the part. The final shape and thickness of the shell determine cooling rates, which may also be modeled for optimization.

Once part geometry is determined, physical models are often helpful for assessing fit with other parts. This can be achieved by 3D printing representative parts in either plastic or metal. These printed parts may also be suitable for some testing, depending on how close they are to the desired final part.

Quality Control

Casting receiving CMM inspection

With defense castings, it’s important to focus on quality from the start instead of sorting good from bad after they’ve been made. This is achieved by operating a rigorous quality management system (QMS) that’s independently certified to national and international standards.

Despite the tight control a QMS provides over every process, inspection is still needed to verify conformance to specifications and the complete absence of defects. These inspections include dimensional checks, surface visual inspection, and sub-surface inspection using techniques like computer radiography and penetrant testing.

Regulatory Compliance

Defense contractors are well aware of the mission-critical nature of their products and the extensive umbrella of regulations and quality standards that govern them. For companies making military castings, the list includes:

  • DFARS: Department of Defense (DoD) procurement processes are detailed in The Defense Federal Acquisition Regulation Supplement. This creates a level playing field for every business supplying the DoD.
  • ITAR: The International Traffic in Arms Regulations are designed to prevent the export of U.S. technology to nations with which the U.S. does not have good relations. Companies making products for the military register with the Directorate of Defense Trade Controls (DDTC) and commit to following all relevant rules relating to technology transfer.
  • CMMC 2.0: This framework developed by the DoD ensures contractors and subcontractors with natural security information pass qualifying cybersecurity requirements. The new model, improved from its former CMMC 1.0, establishes three levels for contractors, with Level 1 being the lowest and Level 3 being the highest. 
  • AMS-2175: Probably the most essential standard for any foundry supplying military castings, AMS-2175, formerly known as MIL-STD-2175, specifies nondestructive testing methods and inspection criteria for metal castings.
  • NADCAP: Short for National Aerospace and Defense Contractors Accreditation Program, NADCAP certification covers manufacturing and inspection processes used in aerospace and defense. It’s intended to give buyers confidence that their products will be produced to the highest standards of quality.
  • AS9100: This is a form of the ISO9001 standard for quality management tailored to the needs of aerospace and defense contractors. Additional requirements cover aspects of manufacturing such as traceability and stopping counterfeit parts from entering the supply chain.

Get Precision Military Castings From Barron Industries

Certifications and standards are important when sourcing defense-related products, but so is the supplier’s experience. Casting is a complex process, and it takes a high level of expertise to ensure that cast components are defect-free.

Barron Industries combines over 100 years of experience with advanced technologies to produce the highest-quality military investment castings. Our many certifications and accreditations, including NADCAP,  AS9100, and CMMC 2.0, only speak to the rigor with which we manage every process and material to ensure our customers receive exactly what they need.

In addition to investment casting, we provide several in-house processes like 5-axis CNC machining, NADCAP-certified non-destructive testing and welding, Rapid Prototyping, and complete assembly, thus allowing Barron to reduce costs, compress lead times, and provide our customers with a single-source solution.

Contact Barron Industries today to learn more about our defense casting experience or to request a project quote.