Designing tubing components demand considerations of strength, load, performance, and other critical factors. An experienced engineer meticulously plans out each part of their design to meet the needs of the required part. 

But before you get started, it’s a good idea to answer ten essential design questions to ensure the best result. 

1. What is the usage/application?

Explaining the details about the usage of the tubing will be critical to producing a component that suits your end needs.

For example, hydraulic cylinders are a good example of the type of part that is often made from a specially designed tube. It’s a part often used in applications like mining truck struts, telescoping cylinders, and scrap metal processing shears.

Depending on the overall design, it may require additional foundry expertise including secondary processes to make it economical to produce. 

What is the usage?
The Spuncast foundry in Watertown, Wisconsin, has a diverse catalog of capabilities for producing severe service applications such as hydraulic cylinders that demand high performance and no room for error.

2. Is it for a new or existing product?

This is a critical consideration because OEM (original equipment manufacturer) parts are required to be an exact replacement to what was originally used.

The fit on OEM parts is 100% guaranteed to the end-user and is usually more expensive than an aftermarket alternative because they are produced by the original manufacturer.

Aftermarket parts require the same high-quality standard of the original part and must meet the specifications of the existing product which is often achieved by a careful analysis of the needed material and design. 

Greg Whitman, Vice President of Spuncast centrifugal foundry, says that aftermarket replacement parts can offer greater convenience, selection, and better costs, but it’s critical to get it right. 

The quality of an aftermarket part needs to meet the required performance of the original part.

“The quality of an aftermarket part, in particular, needs to meet the required performance of the original part,” he said. “Centrifugal casting is a good solution for manufacturers looking for an aftermarket tubing component because of the flexibility and strength of the alloy material we use and the fact that we start hollow which means fewer material costs overall.”

Is it for a new or existing product?
A foundry engineer analyzes the existing design and material specifications of a needed aftermarket replacement part.

3. What are your budget considerations?

Of course, costs are going to be important in the decision making process. In order to produce your part and take full advantage of the production cost efficiencies of the centrifugal casting process, the foundry needs to know all the requirements upfront.

The material used is only one determinate in its price. It’s essential to understand the additional variables and their impact on price like:

  • Product complexity
  • Surface finish
  • Dimension tolerance

Understanding the relative importance of each factor influencing the casting process gives you a good idea of the total cost and how it applies to the end product.

The experience and the setup of the foundry itself are also another big determinate in price. A well-established foundry will have hundreds of dies that can be reused which will save you time and money. 

What are your budget considerations?
An established foundry has hundreds of molds with a large selection of sizes available to choose from.

Andy Ruble, a Metallurgist at Spuncast, advises manufacturers to find a foundry that has the capacity to be flexible, especially for creating parts where they may be adhering to a tight budget but still need very specific dimensions.

“We often have a die or a mold that will work, and if we don’t have the exact size, we may be able to cut off the extra and then remelt it again for use with a different part,” he said.

4. What size and quantity do you need?

The size and quantity of your part may limit where your component can be made, which is why it’s a crucial detail you need to explain to your foundry. Most foundries have some equipment limitations on one or the other (or sometimes both).

Size includes the length and the OD (outside diameter) of your tube design. A foundry’s capability to meet your specifications will be determined by the molds they have available. 

What size and quantity do you need?
A well-established foundry often acquires hundreds of varying size and shape molds that can produce a variety of tubing products.

Foundry methods like cutting shorter parts to be cast in multiples and then cut to desired lengths from a single casting is a common practice that gets around some of the limitations if they exist. It requires less metal and produces less waste while improving production cost-efficiency.

The efficiency of the process may also be influenced by quantity. Some foundries are simply not set up to produce low-volume castings, and that means production cost-efficiency may go up in that case.

Finding a foundry that can accommodate high or low volume will allow flexibility and originality in design. By being able to create a single prototype or place a large order of a familiar part all in the same place maximizes efficiency and shortens the supply chain. 

5. Do you know what material you want to use? 

In any casting process, the metal starts with a combination of raw materials. The process involves using the best combination of those materials to meet the requirements of your application and following the ASTM (American Society for Testing and Materials) chemical requirements.

Before your metal can be chosen and taken from raw materials to a finished product, you’ll need to get specific on its usage because the optimal material will ultimately be decided based on that.

Do you know what material you want to use?
A reliable alloy guide contains an overview of the well-known physical, mechanical and chemical properties of your choice of metals.

Narrow down your choices by using a good alloy guide (often provided by the foundry) and answering the following questions:

  • What stresses and strains will your product need to stand up to?
  • What other chemicals or materials will be involved? 
  • What are the functional and aesthetic requirements?

Consider the ideal characteristics for your specific application and contrast them with the available choices. Your foundry will be able to help you determine the best alloy combination.

6. What are the lead time and scheduling requirements?

How fast do you need your parts? Some processes can turn around first parts very quickly, while high-volume production tooling and setup could take longer. The timing relies on a few things like:

  • Amount of setup required
  • Material availability
  • Engineering involvement
  • Part complexity
  • Testing requirements
  • Secondary processes requests

Ultimately it boils down to how your chosen foundry does business and how they prioritize customer communication. A reliable foundry will do everything possible to stick to a schedule you can count on and let you know as soon as possible if there will be any delays.

“It’s about the conversations and taking the time to set up a good relationship. That comes from working with the customer, staying in contact, and following up on any issues that may arise,” said Joe Ferch, Business Development Manager, Spuncast. 

7. How thick will the walls need to be?

Changing the diameter and thickness of your tubing design can lead to differences in strength and flexibility and is a crucial part of the design.

The wall thickness of metal casting is controlled by the amount of material added during the pouring phase.

The North American Die Casting Association (NADAC) explains that controlling the wall thickness during the casting process reduces thin cast sections, thereby increasing the manufacturability of the part.

How thick will the walls need to be?

Tubing designs must meet the stresses and conditions of its intended routine operation as well as consider any unusual load conditions that may occur. It also needs to be able to withstand common stresses and have protection against corrosion.

In centrifugal casting, the centrifugal force assures uniform wall thickness and extremely close concentricity that can be further enhanced by surface machining.

What are your cast or machining tolerances?

Cast or machining tolerance refers to dimensional accuracy and the amount of permitted variance in the dimension of any given part.

During the design phase, setting a maximum and minimum dimensional limit is crucial. Those limits set the unwanted but acceptable deviation from the desired dimensions.

It’s an essential specification to consider because when they are not achieved, you may end up with:

  • Wasted material
  • Additional machining
  • Impaired product function

Of course, different materials and processes involve different standards. It often depends on what processes and material will be used and your unique part’s requirements and specifications to set up accurate tolerances.

What are your cast or machining tolerances?
Cast and/or machine tolerances vary depending on the material and product’s application.

In the end, misjudging cast or machining tolerances impacts the cost and quality of the component. So, it’s important to work with a foundry that is experienced with the many processes and details that need to be considered.

9. Will your finishing requirements need any secondary processes?

Most foundries can perform additional production operations to meet the overall finishing requirements of most components. But, they need to be made aware of that before manufacturing begins.

Our secondary processes allow us what the application needs.

Typical secondary processes include:

metal testing

Metal testing is used to determine the material’s mechanical characteristics such as strength, hardness, tensile, yield, and elongation. Other tests evaluate chemical characteristics like composition or residue analysis or corrosion resistance for conditions like humidity or saltwater.


heat treating

Heat treating extends the life of the manufactured components by improving the metal’s physical properties with a controlled heating and cooling process. Heat treatments will vary based on metal type and the mechanical properties that are required for the parts’ function.


CNC machining

CNC machining eliminates process variation by removing large amounts of metal fast and also can selectively remove an exact amount for a near-final shape. It’s a process that allows manufacturers to work at a much faster pace and still deliver the same high standard of products.

10. Will you require engineering support?

Foundry engineering support is a service that can benefit more complex projects. Technical assistance or additional service is especially common when developing new products.

The foundry can provide the needed help with component design, material information, metallurgy, secondary processes, and troubleshooting.

Engineer support offers a solid plan that can save you time and money while:

  • Validating the reliability of your design 
  • Checking casting tolerances and material applications
  • Providing expertise in process capabilities
  • Speeding up the overall process from design to build

Large quantity casting projects, in particular, will benefit from assistance in planning the production. Often, an engineer will start with a prototype to establish the most efficient method and critical factors involved.

Planning along with the needed engineer support means any subsequent runs and secondary processes, such as machining, will run smoothly.

Working with an experienced foundry

Designing a tubing component is a multi-step process requiring diversified expertise. Working closely with a dedicated centrifugal casting foundry during the design phase will ensure you get a better product and better lead times.

With over 45 years of experience, Spuncast can help through every stage of the process, from material selection to production.